3 PROJECT RECOMMENDATIONS FOR FISCAL Y 2006 · TABLE 3-1 Project Recommendations for Fiscal Year 2006 ... Impact Test which is not amenable to quantitative structural ... compressive,

PROJECT RECOMMENDATIONS FOR FISCAL YEAR 2006

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3 PROJECT RECOMMENDATIONS FOR FISCAL YEAR 2006

Table 3-1 lists the projects proposed for the 2006 program. Detailed descriptions of each project follow below. Every project recommended by the SSC is considered to be of significant potential value to the marine industry. TABLE 3-1 Project Recommendations for Fiscal Year 2006

Number Project Title Page

06-01 Fracture Toughness of Marine Structural Steels 2 06-02 Assessment of A Hull Failure Scenario 6 06-03 Feasibility, Conceptual Design and Optimization of a Large Composite Hybrid Hull 13 06-04 Experiments in Wave Basin to Arrive at te Wave Bending Moments 16 06-05 Reliability-Based Fast Hull Optimization Methodology for High Speed Multi-Hull Vessels 19 06-06 Reliability-Based Design Optimization of Damaged-Tolerant Primary Ship Hull Structure 22 06-07 Data Mining for Predicting Corrosion Growth in Ship Structure 25 06-08 Weight Optimized Design of Non Primary Ship Structural Components 28 06-09 Structural and Fire Performance Characteristics of Composite Materials Fabricated with

Polyurethane Resins Subjected to UL1709 Fire Testing 31

06-10 Structural and Fire Performance Characteristics of Composite Materials Fabricated with Polyurethane Resins

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06-11 Welding Distortion Analysis of Hull Blocks Using Equal Load Method Baseds on Inherent Strain 41 06-12 Review and Update USCG SSC Website Case Studies 44 06-13 Strength and Fatigue Testing of Composite Patches for Ship Plating Fracture Repair 47 06-14 SSC Impact Study 55 06-15 Development of Certification and Design Guidelines of Composite Ship Structures Subjected to

Low Velocity Impact 60

06-16 Vehicle Deck Strength Study for the Marine Industry 64 06-17 Importance of Fabrication and Detailing 68 06-18 Machinery Mount and Foundation Design 72 06-19 Significance of Constraint Effects on Fracture Resistance Design 75 06-20 Nondestructive Fracture Toughness Characterization of Grade A Steels 78 06-21 Identification of Local and Global Modal Interactions in Stiffened Ship Panel Structures at Pre and

Post Buckled States 81

06-22 Optimization of Fatigue Life and Structural Performance of Marine Structures 89 06-23 Reliability –Based Performance Assessment of Damaged Ships 95 06-24 Fracture Toughness of Marine Steels at Various Loading Rates (05-09) 101 06-25 Quantification of Peening Effect – Can it be Accounted for in Design (05-12) 104 06-26 Shakedown of Residual Stresses During the Service Life of a Ship Structure Welded Detail (05-11) 106 06-27 Estimate of Thickness Stress Profiles & Peak Stresses from Shell Element FE Models (05-13) 109 06-28 Response of Ship Structure Containing Cracks: Load vs. Displacement Control (05-14) 112 06-29 Estimation of Weld Hydrogen Cracking Delay Time (05-19) 116

RESEARCH RECOMMENDATIONS FOR FY 2006

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06-01 Fracture Toughness of Marine Structural Steels Submitted by: Harold S. Reemsnyder

1.0 OBJECTIVE.

1.1 Develop a database for the fracture toughness of base metal, weld-metal, and heat-affected-zones of marine structural steels to be used in the damage tolerance analysis of marine structures.

2.0 BACKGROUND.

2.1 Criteria for fracture-resistant design, fatigue-damage repair, and damage tolerance and structural integrity analyses require laboratory-generated elastic-plastic fracture-toughness data from fracture-mechanics-based tests, e.g., J-integral or crack-tip opening displacement (CTOD). Such data, gathered over a range of temperatures, thicknesses, chemistries, thermo-mechanical processing, and welding parameters for marine steels, will serve as input to the “SSC 409 Guide to Damage Tolerance Analysis of Marine Structures” and “SSC 430 Fracture Toughness of a Ship Structure.” A previous project, “Marine Structural Steel Toughness Data Bank,” SSC-352, focused on the development of a data bank that included the then-available (1990) values of Charpy V-notch impact energy, critical initiation (JIc), nil-ductility transition temperature (NDTT), and dynamic tear (DT) energies for 12 structural steels. However, these data are of limited value for damage tolerance and structural integrity analyses. Such analyses require more general elastic-plastic fracture-toughness data such as the J-integral (not limited to plane-strain fracture toughness) or CTOD.

2.2 To achieve the full intent of the project, it will be necessary to define the available

data and the extent of the additional work required before any testing should be undertaken. This will require a Phase I program to gather the existing data and identify gaps, followed by a Phase II program of data generation if needed. Owing to the nature of testing required to obtain elastic-plastic toughness data, any Phase II program will be a focused effort aimed at the most critical data gaps, rather than an attempt to cover the missing toughness properties of all or many materials. This work would also aim to complement but not duplicate other parallel programs.

2.3 Hull fractures still plague the industry, e.g., Lake Carling et al. However, the only

fracture characterization of hull steels generally available is the Charpy V-Notch Impact Test which is not amenable to quantitative structural integrity analysis. Indeed, many hull fractures are occurring in Grade A steels for which a Charpy criterion is not given in the rules for building and classing steel ships. The assessment of structural reliability will be enhanced through the use of fracture-mechanics-based analysis that recognizes the reserves of elastic-plastic fracture toughness that exist in materials after crack initiation. Conservatism in design


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and material selection can be reduced through better knowledge of material properties.

3.0 REQUIREMENTS.

3.1 Scope

3.1.1 To achieve the full intent of the project, it will be necessary for the Contractor to define the available data and the extent of the additional work required before any testing should be undertaken.

3.1.2 In the Phase I program, the Contractor will gather the existing data and

identify gaps, followed by a Phase II program of data generation if needed.

3.1.3 Owing to the nature of testing required to obtain elastic-plastic toughness data, any Phase II program will be a focused effort aimed at the most critical data gaps, rather than an attempt to cover the missing toughness properties of all or many materials.

3.1.4 This work would also aim to complement but not duplicate other parallel

programs.

3.2 Tasks. (Identify the tasks to carry out the scope of the project).

3.2.1 The contractor shall investigate the data bank of “Marine Structural Steel Toughness Data Bank,” SSC-352, and determine the applicability of those data to fracture-mechanics-based damage tolerance analysis.

3.2.2 The contractor shall gather available fracture toughness data for base

metal, weld-metal, and heat-affected-zones of marine and similar steels that are not included in SSC-352. The first priority is applicable base plate and weldment data.

3.2.3 The Contractor shall organize the available fracture toughness data for

base metal, weld-metal, and heat-affected-zones of marine steels as input to the “Guide to Damage Tolerance Analysis of Marine Structures” developed in SSC project SR-1374.

3.2.4 The Contractor shall identify the data needed to fill in gaps, e.g., grades,

thicknesses, welding processes and parameters.

3.2.5 If concluded to be necessary, the Contractor shall design a program to obtain such data over a two-year period.

3.3 Project Timeline. See Enclosure (x).


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4.0 GOVERNMENT FURNISHED INFORMATION.

4.1 Standards for the Preparation and Publication of SSC Technical Reports. 5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).

5.1 The Contractor shall provide quarterly progress reports to the Project Technical Committee, the Ship Structure Committee Executive Director, and the Contract Specialist.

5.2 The Contractor shall provide a print ready master final report and an electronic

copy, including the above deliverables, formatted as per the SSC Report Style Manual.

5.3 The Contractor shall provide, if concluded to be necessary, the design of a program

for Phase II to gather those data required to fill the gaps identified in Phase I.

6.0 PERIOD OF PERFORMANCE.

6.1 Project Initiation Date: date of award. 6.2 Project Completion Date: 12 months from the date of award.

7.0 GOVERNMENT ESTIMATE. These contractor direct costs are based on previous

project participation expenses.

7.1 Project Duration: x months.

7.1.1 Phase I: 12 months. ($68,000.00) 7.1.2 Phase II: 24 months. (58,000.00)

7.2 Total Estimate: $

7.2.1 Phase I: 900 labor hours. 7.2.2 Phase II: 2000 labor hours.

7.3 The Independent Government Cost Estimate is attached as enclosure (x).

8.0 SOLE SOURCE JUSTIFICATION INFORMATION.

8.1 Company Selected for Sole Source Contract Award.

BMT-Fleet Technology Limited.


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8.2 Basis for Sole Source Contract Award.

8.2.1 BMT-Fleet Technology Limited has demonstrated their high level of professionalism and competence to assemble, synthesize, analyze, and present fatigue and fracture data in previous Ship Structure Committee Projects SR-1358 “Optimized Design Parameters for Welded TMCP Steels,” SR-1374 “A Guide to Damage Tolerance Analysis of Marine Structures,” SR-1386 “Short Course on Fatigue and Fracture Analysis of Ship Structures” and “Fatigue Resistant Detail Design Guide for Ship Structures,” SR-1384 “Crack-Arrest Toughness of Steel Weldments,” and SR-1429 “Fracture Toughness of a Ship Structure.”

9.0 SUGGESTED CONTRACTING STRATEGY.

9.1 Contracting strategy.


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06-02 Assessment of A Hull Failure Scenario Submitted by: S.Petinov, Strength of Materials,

St.Petersburg State Polytechnic University

1.0 OBJECTIVE. 1.1. The reviews of in-service damages indicate that fatigue cracks may reach considerable

sizes, frequently in relatively short periods of service, resulting from operation in severe sea conditions and insufficient accessibility to the affected details. These cracks endanger the hull integrity since undetected they can turn into unstable phase. Even relatively slow, they can change the boundary conditions of the adjacent plate elements affected by the in-plane, combined, compressive, bending and shear stresses. As a result of crack growth and development of free edges of plate elements, the buckling conditions may be attained for such elements, resulting in further decrease of stiffness of hull structure. In case of insufficiently redundant structures, e.g. in wing tanks of single-skin tankers, this process may be menacing to the structural integrity through redistribution of stresses between main frames in a cargo compartment, development of “secondary” overstressed zones and new fatigue and buckling-affected components until the hull girder stiffness would drop down. In case of bulk carriers with single side structure the development of damage to hull structure initiated by fatigue cracks, e.g. in side frame bracket connections, can be different from the above, however, the consequences of propagation of the bracket cracks into the side shell may not be only the flooding of the cargo compartment. This mechanics of structural failure is more implied than clearly documented. A study of succession and interaction of mechanisms of failure constituting a feasible scenario of hull failure is needed and the development of methodology of assessment of pre-catastrophic conditions of hull structures as well.

2.0 BACKGROUND. 2.1. In fatigue design and in procedures of assessment of residual life of hull structural details,

in particular, when insufficiently redundant structures are considered, the allowable and critical states of damage are not clearly defined yet. Partly this is because the fatigue design procedures based on the S-N curves concept do not imply a physical definition of damage, a crack size, and partly because the modeling of the final phase of structural failure is a complicated procedure with uncertain interaction of mechanisms of structural damage. Also, the final phase may be seen a process specific for a particular type of structure and particular combination of service conditions. Respectively, the implied analysis of the process of failure may be regarded a provisional procedure of a limited value.

2.2. The current approaches to sub-critical portion of life of hull structures typically include analysis of fatigue crack initiation and sub-critical growth, usually based on assumption of elastic behavior of the structure and of a particular affected segment of the structure. The


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critical condition of the structure when the stable crack propagation turns into the accelerated stage, is assessed using the Feddersen-Morozov type criterion, e.g. the Failure Assessment Diagram [8.1]. The latter allows the two feasible developments of the failure scenario: one suggests onset of plastic deformation in a sizable part of structure because of reduction of crossection of affected details which turns into a “plastic collapse”, and another is associated with transition of fatigue process into the unstable phase defined by either of, linear or non-linear fracture mechanics criteria, such as KIc, Jic. Apart from the recent “Kurdistan” case [8.2], mostly several historical examples may be regarded favorable in the sense of above criteria ([8.3], [8.4], etc.). Scarce casualties with barely documented details of failure succession, e.g. the suggested mechanics of failure of bulk-carriers described by Ferguson [8.5], feasible explanation of bulk-carrier casualties by cracking of side shell, flooding of cargo compartment and failure of transverse bulkheads given by D.Liu [8.6] may be regarded favorable for the more common type of scenario. Also, fragmentary evidence allows suggesting a serious role in failure scenario of buckling and post-buckling deformation of stiffened panels of transverse frames initiated due to growth of fatigue cracks and sequential weakening of boundary conditions of panels. Post-buckling deformation of side frame panels occurring with the wave passage over affected part of structure, in its turn, makes feasible initiation of low-cycle fatigue in buckle hollows, resulting in progressive fracture of structural components and development of following fracture origins leading to catastrophic hull failure.

2.3. The known and implied succession and interaction of mechanisms of failure constituting a feasible scenario of hull failure should be analyzed, first even for particular ship structure and assumed loading conditions. The implicit simulation of failure scenario can be realized based rather on a laboratory test of a scale structure where several mechanisms of failure might be observed. Although it is not assumed in the present project because of uncertainty of operational conditions, complications involved in tracing of initial and secondary cracks in welded components, the project is aimed at development of methodology of analysis of structural failure which is seen a well-timed issue. It should be a necessary component in ship and offshore structural design, in particular, of structures with limited redundancy: modeling of feasible scenario of failure can be used as indicator of insufficiently reliable elements which should be re-designed. Also it can be applied to assess the efficiency of carried out and planned repair, to assess the reliability of ship structures in service, when the critical locations can be well-developed and the loading history would become essentially definite.

3.0 REQUIREMENTS. 3.1. Scope.

The scope of the project would be the numerical simulation of structural failure of a bulk carrier cargo compartment structure comprised of the following parts:

3.1.1 Assessment of primary crack growth and of corresponding changeover of

stiffness of affected assembly and hull girder components; considering of other than fatigue mechanisms of failure triggered by crack propagation in affected region


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3.1.2 Assessment of the order and mechanisms of damage to the hull part under the scope and evaluation of a sub-critical phase criterion

3.1.3 Representation of the damage evolution as a time-dependent process and

development of recommendations for establishing the allowable and critical phases of the process of structural failure

3.1.4 Recommendations for the future works aimed at feasible generalization of

the methodology

3.2 Tasks. The work would consist of the following principal tasks:

3.2.1. Selection of a representative bulk carrier hull structure with known – even fragmentary

– damage records and designing of a global FE model of the representative hull part (a cargo block) and of local FE models of structural details where fatigue cracks are likely to initiate and grow

3.2.2. Evaluation of statistical parameters of the wave loads (bending moments and hydrodynamic pressure distribution) in formats of the long-term distribution necessary for fatigue damage assessment in initial phase, until the stiffness of structure remains insignificantly affected. Also, statistical parameters of wave loads components would be estimated within a short-term scheme (a stationary sea state), a feasible condition for hull structure damage development into a pre-catastrophic phase

3.2.3. An analysis of crack initiation and growth would be carried out until – and if - the

conditions for other than fatigue mechanisms of damage would be attained. In dependence on the stress conditions of affected structural component the material plasticity would be taken into account in the crack propagation assessment. The wave and inertia loads would be considered in format of long-term distribution of load components. Correlation between load components would be allowed

3.2.4. The further analysis of structural damage would be carried out taking into account

changes of stiffness of the structure due to the crack extensions and feasible buckling of cracked panels, redistribution of stresses, initiation and evolution of secondary damages until the pre-catastrophic phase would develop. The loads would be considered in format of intensive correlated stationary processes (short-term distribution format)

3.2.5. The components of structural failure would be presented as the time-dependent

process, as it is being done to display the progress of fatigue damage in the form of crack growth vs load cycles diagram. This would allow to trace the role of individual components in structural damage and failure, to introduce the necessary changes into structural details responsible for “channeling” the mechanisms of failure. Also, it


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would facilitate establishing the allowable and critical phases of damage in hull structures. The respective recommendations would be given.

3.3 Project Timeline. See Enclosure (a). 4.0 GOVERNMENT FURNISHED INFORMATION.

4.1 Standards for the Preparation and Publication of SSC Technical Reports would be strictly followed

5.0 DELIVERY REQUIREMENTS.

5.1 Quarterly progress reports would be provided to the Project Technical Committee, the Ship Structure Committee Executive Director, and the Contract Specialist.

5.2 The Contractor shall provide a print ready master final report and an electronic copy,

including the above deliverables, formatted as per the SSC Report Style Manual. 6.0 PERIOD OF PERFORMANCE.


7.0. Time, Cost and Man-hour ESTIMATE.

7.1 Project Duration: 14 months. 7.2 Total Estimate: $ 58,139 7.3 The Cost Estimate is attached as enclosure (b).

8 REFERENCES.

8.1. Yee, RD, Malik, L, Basu, R and Kirkhope, K (1997) Guide to Damage Tolerance Analysis of Marine Structures. SSC Report 402, Ship Structure Committee 8.2. Waite, J (2004) Marine Casualty Investigation. Engineering Integrity, Vol.15, pp. 22-26, January 8.3. The Design and Methods of Construction of Welded Steel Merchant Vessels (1947) SSC, Final Report of a Board of Investigation 8.4. Acker, HG (1953) Review of Welded Ship Failures. SSC Report 63, Ship Structure Committee 8.5. Ferguson, JM (1991) Bulk Carriers - The Challenge. Lloyd's Register of Shipping


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8.6. Liu, D (2001) Structural Safety of Ships. Proceedings, 8th International Symposium PRADS-2001. Shanghai. Vol. I, pp.13-21 8.7. Petinov, S, Polezhaeva, H and Morozova, A (1993) Reserves of Fatigue Damaged Redundant Structures. Proceedings, International Conference on Fracture ICF-8, 2, Kiev 8.8. Petinov, S, Polezhaeva, H and Frumen, A (1997) A Post-Accident Study of a Tanker Structural Damage. “Ship Technology Research / Schiffstechnik”, Vol.44, No.3 8.9. Petinov, S (2000) Life-Cycle Fatigue Reliability of Ship Structures: An Integrated Approach. Proceedings, International Congress SIM-OUEST, B, November. Nantes, France 8.10. Petinov, S (2000) Life-Cycle Reliability of Ship Structures: A Proposed System. «Journal of Ship Research», Vol.44, No.1 8.11. Petinov, S (2003) Fatigue Analysis of Ship Structures. Backbone Books, NJ


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Enclosure (a)

October January April July October January ID Task Name

1 Article I. SSC Project

2 Project Start 3 Develop Work Plan 4 Approval of the Work

Plan

5 Review of Literature 6 QPR 1 7 Develop FE Model

of a Cargo Compartment and Wave Loads

8 Deliverable 9 QPR 2 10 Fatigue Process

Analysis

11 Deliverable 12 QPR 3 13 Failure Progress of

Structure Simulation until Onset of Critical Phase

14 QPR 4 15 Develop the Failure

Diagram

16 QPR 5 17 Final Report 18 QPR 6 19 Project Complete

Section 1.01 “Assessment of a Hull Failure Scenario”

(a)


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Enclosure (b)

Article II. Project cost estimate

1. Direct labor cost (Project adviser, 2 FE analysts, 1 wave loads expert, 2 fatigue analysts

and 1 senior student) - $37,500 2. Fringe (Government established labor tax) – 26.2% of the direct labor cost, $9,825

3. Other direct costs (Travel, expendables) - $5,000

4. Subtotal: $52,325

5. Overhead (University established): 0.1 of the total project cost - $5,814

6. Total cost: - $58,139

Note: The detailed description in the form advised by SSC to be submitted if the project would be accepted


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06-03 Feasibility, Conceptual Design and Optimization of a Large Composite Hybrid Hull

Submitted by: Alaa E. Mansour University of California, Berkeley

1. Objective

To study the feasibility of an advanced hybrid hull design for large ships. The main concept is to design a 3-D space frame made of steel to resist the global (primary) load and a composite material to act as a watertight barrier and resist local pressure (secondary and tertiary loads).

2. Background

2.1 The use of composite sandwich laminates in ship construction has rapidly grown in the recent years. But these composites have been used only in construction of small ships.

2.2 Many of the problems of the joints between sandwich laminates can be overcome by using a hybrid hull concept [8.2]. The latest developments in the joints between steel to sandwich laminates have opened up ways to use the Steel to resist global hull bending, shear and torsion and sandwich laminates to resist local pressure and act as a watertight barrier [8.3].

2.3 ONR has recently funded a project on conceptual design of a hybrid hull at the University of California at Berkeley (ONR/N00014-03-1-0656) titled “Advanced Hull Design using Composite Material”. The sandwich material used in the project, consisted of glass fiber reinforcement as skin and foam as core. This particular combination of skin and core has been studied and experimented in [8.3].

3. Requirements

3.1 Scope

3.1.1 The Contractor shall conduct a feasibility study of the use of hybrid hull in large ships, at least as large as a steel cruiser ship of length 160 m., beam 15 m., and molded draft 7 m.

3.1.2 The Contractor shall identify the problems encountered in designing the hull including issues related to stiffening of the composite barriers to increase its stiffness and the joints between the steel frame and the composite barriers.

3.1.3 The Contractor shall address the feasibility of the applicability of the hybrid concept to large ships.

3.1.4 The Contractor shall address the advantages and disadvantages of the new concept and the benefits of the new hybrid design.

3.2 Tasks


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3.2.1 The Contractor shall establish a preliminary design of a large hybrid hull based on the concept stated under ‘Objective’. The hull characteristics should be at least as large as a steel cruiser ship of length 160 m., beam 15 m., and molded draft 7 m.

3.2.2 The Contractor shall construct a finite element model and subject it to the most important load cases in order to investigate the interaction between the primary steel structure and the secondary composite material within the primary steel frame. The loads shall be established using a sea keeping program and the ABS Rules.

3.2.3 The contractor shall analyze the finite element analysis results and make sure that the stress levels in the primary steel frame and secondary composite material are within prescribed stress levels.

3.2.4 The Contractor shall then optimize the design using a reliability-based analysis. The safety indices should be at least as large as the parent steel ship in order to ensure adequate safety.

3.2.5 The Contractor shall report results of the research program.

3.3 Project Timeline

4. Government Furnished Information

Final Report format - SSC Report Style Manual 5. Delivery Requirements


5.2 The Contractor shall provide the finite element model, loads and results. 5.3 The Contractor shall provide reliability indices of both the parent ship and the new

hybrid design.

Task / Month 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 181. Preliminary Design

2. Finite Element Analysis

3. Reliability Analysis

4.Optimization based on Reliability

5. Assessment of results and feasibility of concept

6. Conclusions

7. Quarterly reports and Final report


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5.4 The Contractor shall provide the optimized hybrid hull preliminary design. 5.5 The Contractor shall provide a statement regarding the feasibility of applying the new

concept to large ships and the advantages and disadvantages of the new design. 5.6 The Contractor must deliver all raw and condensed information developed during the

project to SSC. 5.7 The Contractor shall provide a print ready master final report and an electronic copy,

including the above deliverables, formatted as per the SSC Report Style Manual. 6. Period of Performance


7. Time and Cost Estimate

7.1 Project Duration: 18 months. 7.2 Project Man-hour: 2000 hours

7.3 Total Estimate: $ 100,000

8. References

8.1 Advanced Hull Design using Composite Material, Presentation, ONR / N00014-03-1-0656, November 2005, University of California at Berkeley.

8.2 Design Guide for Marine Applications of Composites, SSC-403, Jan 1997. 8.3 Design and Testing of Joints for Composite Sandwich / Steel Hybrid Ship Hulls by Jun

Cao and Joachim L. Grenestedt, July 2003 (to be published).

8.4 Test of a redesigned glass-fiber reinforced vinyl ester to steel joint for use between a naval GRP superstructure and a steel hull by Jun Cao and Joachim L. Grenestedt (to be published).

8.5 Response Analysis of Dynamically Loaded Composite Panels, Hans Jorgen Riber’s

Dissertation Thesis, Technical University of Denmark, June 1997.


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06-04 Experiments In Wave Basin To Arrive At The Wave Bending Moments Submitted by S. Surendran, Indian Institute of Technology Madras, India

1.0 OBJECTIVE. Data sets on section modulus requirement on hull forms like VLCC’s and modern container ships are less available than other ship types. Using scaled down models in a wave basin, the measurements of the bending moments at top and bottom of midship under various steepness and forward speeds can be carried out. Tests can be done for fully loaded conditions and if required for partly loaded conditions. Waves and winds corresponding to any sea states can be generated in the laboratory. 1.1 Establishing strength criteria of various types of new generation hulls 1.2 Examining reasons for global and local failures 1.3 Generating set of data to validate various analysis methods. Eg. Paik J K and Anil Kumar T (2003) 2.0 BACKGROUND. 2.1 Ultimate limit state considerations concentrate on the reliability of ship structure. As trial data is rare for modern hull forms, the same can be generated using scaled down models. 2.2 Accidents continue to happen despite great care taken by designers and builders. It is seen that the unified formula by IACS (International association of classification society) is not sufficient for determination of wave bending moments and section modulus of ships. More data using model tests need to be generated to design new generation hull forms. 2.3 Available theory and experimental results are not very useful for design of new generation hull forms used for commercial transportation in the sea. Infrastructure systems, like wave basin facilities should be efficiently utilized for generating data on wave bending moments and other sea keeping aspects of ships. 2.4 Analysis techniques when combined with laboratory results may lead to better conclusions.

2.2 The net bending moment due to waves, forward speed effect, torsion(severe for container ship), slamming and impact loads, etc. will be measured for ship models under fully loaded and ballast conditions

3.0 REQUIREMENTS. Scope. 3.1.1 Any alternate required hull forms may be suggested if the proposal does not cover the desired type. Model making, model loading, model instrumentation, and taking measurements during the experiment are the critical phases. Models are to be fabricated in fiber reinforced plastic and are to be controlled remotely in the wave basin. The Contractor shall conduct an assessment on the wave bending moments by conducting experiments in wave basin for various sea states and forward speeds of ships under fully loaded and ballast conditions.


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3.1.2 The Contractor shall identify the required bending moments and hence the section modulus at midships and structural distribution at the midship. This will be done for three types of ships. The Contractor shall address requirement of bending moment values for realistic short term conditions of ship operation. The data based on ‘Sea keeping standards for cruiser stern ships ‘(SNAME, 1975 authored by Theodore A. Loukakis et al)are not adequate to arrive at the modern hull forms discussed in the objective. The deck or the bottom of the vessels are subjected to bending moments and such total hull girder moments and hence forces are to be determined with better accuracy. The extreme panels are subjected to maximum stress levels and fail first Authentic values of bending moments obtained from tests conducted in wave basins will give better results on the collapse of stiffened panels/structures at deck and bottom. Such values when used as input for packages based on FEM or nonlinear FEM methods, will give better results for the midship design of ships. 3.1.3 The contractor shall provide tables of non-dimensional wave heights, Froude numbers and bending moment response. Project Timeline. See Enclosure (I). 4.0 GOVERNMENT FURNISHED INFORMATION.

Standards for the Preparation and Publication of SSC Technical Reports 5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).


6.4 The Contractor shall provide print ready master final report. 6.5 The Contractor shall provide a print ready master final report and an electronic copy,


6.6 Project Initiation Date: date of award. 1st April 2006 6.7 Project Completion Date: 12 months from the date of award.

7.0 Time, Cost and Man-hour ESTIMATE. These contractor direct costs are based on previous project participation expenses.

Project Duration: 12 months. Project Man-hour: 4000 Total Estimate: $60, 000


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1.0 REFERENCES.

1.Paik J. K, & Anil Kumar Thayamballi ,Ultimate limit state design of steel plated structures, John Wiley & Sons Ltd , 2003 2.Paik J.K, A guide for the ultimate longitudinal strength assessment of ships., Marine technology Vol.41, , July 2004, pp.122-139. 3. Loukakis T. A & Chryssostomidis C, Seakeeping standard series for cruise stern ships, SNAME 1975,pp-67-127 4. Rutherford, S.E, Caldwell, J.B., Ultimate longitudinal strength of ships: a case study, SNAME Trans. 1990.


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06-05 Reliability-Based Fast Hull-Optimization Methodology for High-Speed Multi-Hull Vessels

Submitted by: [Martec Limited and BMA Engineering]

1.0 OBJECTIVE.

6.8 The objective of the proposed work is to develop methodologies and algorithms for optimizing the early-stage design and analysis of high-speed multi-hull ships. The methodologies and algorithms will encompass concurrent optimization of multi-hull vessel-payload capacity and structural integrity within a reliability-based framework that rationally accounts for system and operational uncertainties.

2.0 BACKGROUND.

2.1 The vast majority of US naval vessels are of relatively large mono-hull construction, with limited speed requirements. In recent years, there has been an increased desire for high-speed transit capabilities for enhanced naval operations. This has, in turn, led to increased interest in the application of multi-hull platforms for naval missions. This is due in part to the fact that multi-hull ships have the potential for superior high-speed performance. In addition, multi-hull ships offer potential advantages such as larger deck area per ton of displacement, and greater transverse stability. Other advantages of multi-hull vessels include a wide range of choices for reducing the wave-making resistance by exploiting arrangements of hull elements and varying hull forms, improved seakeeping performance over mono-hulls, better survivability in terms of added collision protection and damaged stability, signature reduction by exhausting between the side hulls rather than conventional main structure funneling, and flexibility to accommodate many propulsion plant arrangements.

2.2 The analysis and design of advanced multi-hull ships pose many new technical

challenges that are beyond the realm of conventional displacement mono-hull ship design. These ships are characterized by more complex geometric configurations and performance requirements. Due to the many complexities, there are significant uncertainties associated with the design, analysis, and operation of multi-hull vessels. These uncertainties could be associated with the environment, combat-related loading, hulls/sub-system interactions, and perhaps more importantly, the modeling of the system itself. Furthermore, only a limited database of experience currently exists for multi-hull vessels. Therefore, a reliable, robust, and accurate numerical simulation tool, with automated optimization capabilities to ensure a thorough search within a specified design space, is required for optimal design, performance, and safety analysis of multi-hull ships.


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3.0 REQUIREMENTS.

3.1 Scope. 3.1.1 The scope of the project includes: (a) review and summary of multi-hull

vessels and related design, analysis and computational tools; (b) development of deterministic- and reliability-based optimization algorithms for weight optimized multi-vessel design; (c) applications of the developed methods to typical multi-vessel configurations; and preparation of guidelines and report.

3.2 Tasks.

3.2.1 The contractor shall prepare and present a work plan for approval by the Project Technical Committee.

3.2.2 The contractor shall review the multi-vessel designs and associated design,

analysis and computational tools

3.2.3 The Contractor shall develop methodologies and algorithms for early state design of multi-hull ship structures

3.2.4 The Contractor shall develop fast algorithms that concurrent optimization

of multi-hull vessels, with weight reduction and structural integrity as optimization goals.

3.2.5 The Contractor shall investigate means of accounting for uncertainties

inherent in the system and loading conditions

3.2.6 The Contractor shall, in conjunction with the PTC, select suitable multi-hull vessel configurations and demonstrate the viability of the developed methodologies and algorithms

3.2.7 The contractor shall prepare guidelines and final report providing details

of the methodologies and the case studies. 4.0 GOVERNMENT FURNISHED INFORMATION.

4.1 Standards for the Preparation and Publication of SSC Technical Reports 5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).



21

5.2 The Contractor shall present a work plan at the kick-off meeting 2 weeks after contract award

5.3 The contractor shall, at the end of two quarters, present the methodologies for

multi-vessel design optimization

5.4 The contractor shall, at the end pf three quarters present the results of the validation and studies

5.5 The Contractor shall, at the end of eleven months provide a draft final report to

the PTC for review and comments 5.6 The Contractor shall provide a print ready master final report and an electronic




7.0 Time, Cost and Man-hour ESTIMATE. These contractor direct costs are based on

previous project participation expenses.

7.1 Project Duration: 12 months. 7.2 Total Estimate: $80,000


22

06-06 Reliability-Based Design Optimization of Damaged-Tolerant Primary Ship Hull Structures


1.0 OBJECTIVE.

1.1 The objective of the proposed work is to develop optimization methodologies and algorithms for damaged-tolerant design of the primary ship at the design stage. The methodologies and algorithms will encompass concurrent optimization of primary hull structure using various elastic, elastic-plastic and plastic models and structural integrity within a reliability-based framework that rationally accounts for system and operational uncertainties. Anticipated structural damages, such as fatigue and corrosion, and associated uncertainties should be incorporated into formulation.

2.0 BACKGROUND.

2.1 Traditional design of primary ship structures has relied upon a combination of engineering experience, sound judgment, and deterministic-based approaches such as working stress design (WSD). Anticipated structural damage to the primary structure, such as fatigue and corrosion, which consume a large portion of operational and maintenance cost, is usually incorporated into the design through an informal process of choosing the shapes, location and sizes of primary ship member’s components. Furthermore, although ship structure designers acknowledge the existence of uncertainties, engineers have dealt with the many uncertainties inherent in design aspects such as loading, material properties/behavior, and even failure modes through the use of suitable factors of safety. In recent years advances have been made in the development of structural optimization tool which will allow for automated search within a design space of alternate viable designs that can maximize strength and minimize weight. Recent developments over the past 10-15 years, however, have sought to improve the state-of-the-art in ship structural design by moving from WSD practices to reliability-based limit state design through the use of partial safety factors for the various load and strength parameters. Defined based on the ability to achieve target reliability levels (in terms of safety and functionality for a specified service life and operating environment), these factors permit a more rational and proportional account of inherent uncertainties and have lead to the development of the reliability-based load and resistance factor design (LRFD) approach. Further more the concept of damage tolerant design, where anticipated structural damage are incorporated in primary ship design at the design stage in order to minimize operational and maintenance cost has also be discussed. While the merits of each of the concept, structural optimization, reliability-based design and damage-tolerant design, have been presented for ship structural design, the potential benefits resulting from the combined application of these concept at conceptual and design stage have not been explored.


23

2.2 A methodology that seeks to amalgamate reliability-based design methods, damage-tolerant design, with structural optimization techniques, combining the robustness of each to produce an innovative approach to ship structural design which fully accounts for uncertainties inherent in the design process and facilitates a realization of the potential for weight reduction, cost savings, and improved design should be developed. The methodology should be have a reliable, robust, and accurate numerical simulation tool, with automated optimization capabilities to ensure a thorough search within a specified design space. The numerical optimization tool should have the flexibility of being used in a working stress design environment, reliability based design environment with or without damage-tolerance concepts.

3.0 REQUIREMENTS.

3.1 Scope. 3.1.1 The scope of the project includes: (a) review and summary of strength

models hull girder and related design, analysis and computational tools; (b) development of deterministic- and reliability-based concurrent optimization algorithms for weight and strength optimized damaged-tolerant hull girder design; (c) applications of the developed methods to typical hull-girder configurations such as single-hull double-hull, large naval and commercial vessels; and preparation of guidelines and report.

3.2 Tasks.

3.2.1 The Contractor shall prepare and present a work plan for approval by the Project Technical Committee.

3.2.2 The Contractor shall review the hull-girder designs and associated design,

analysis and computational tools

3.2.3 The Contractor shall develop methodologies and algorithms for early state damage-tolerant design of primary ship structures

3.2.4 The Contractor shall develop fast algorithms that can concurrently

optimize primary structures, with weight reduction, structural integrity, improved service life and maintenance cost minimization through damage-tolerance design, which accounts for the effect of corrosion and fatigue during the early design stage as optimization goals.

3.2.5 The Contractor shall investigate means of accounting for uncertainties

inherent in the system and loading conditions

3.2.6 The Contractor shall, in conjunction with the PTC, select suitable primary structures configurations, namely single hull, double-hull, multi-deck,


24

tanker and naval vessels and demonstrate the viability of the developed methodologies and algorithms





5.2 The Contractor shall present a work plan at the kick-off meeting 2 weeks after

contract award

5.3 The contractor shall, at the end of two quarters, present the methodologies for primary structure design optimization

5.4 The contractor shall, at the end pf three quarters present the results of the

validation and studies

5.5 The Contractor shall, at the end of eleven months provide a draft final report to the PTC for review and comments









25

06-07 Data Mining for Predicting Corrosion Growth in Ship Structures Submitted by: [Martec Limited and BMA Engineering]

1.0 OBJECTIVE.

1.1 The primary objectives of this study are the research, development and demonstration of a data mining methodology and framework whereby existing vessel corrosion data from multiple sources can be efficiently collected and formatted in a consistent manner to allow modeling of corrosion growth in marine vessels..

2.0 BACKGROUND.

2.1 Vessel ownership cost and vessel readiness are largely influenced by the cost of maintenance, a burden borne by ship owners and operators throughout the life of their vessels. Corrosion protection, mitigation, and repair are largely responsible for increased ownership costs and decreased readiness levels, and typically consume a significant portion of vessel owners’ annual maintenance budgets. Organic coatings are commonly used to protect metal components of marine vessels, in order to prevent corrosion of the components. However, over time, these coatings break down and corrosion will develop, potentially compromising a vessel’s structural integrity and readiness. As a result of past and present research by several organizations in the marine community, extensive laboratory and field data has been collected on coating breakdown and corrosion development for a variety of structures under diverse corrosive environments. Understanding and prediction of corrosion development aboard marine vessels requires judicious collection, assimilation, and analysis of this data (which may currently exist in a variety of formats). The use of data mining techniques such as regression analysis, artificial neural networks (ANN), data characterization, sensitivity analysis, graphical representation, etc. could prove invaluable during such an effort.

2.2 An innovative data-mining methodology that makes use of information in several

databases, in combination with data mining techniques that are consistent with the data types, is required to model corrosion growth in marine vessel. The would provide benefits such as improved assessment of the rate of corrosion growth in marine vessels under various operating environments, the overall goal of providing savings in vessel maintenance costs.

3.0 REQUIREMENTS.

3.1 Scope. 3.1.1 The scope of the project includes: (a) overview of marine vessel corrosion

databases; (b) overview of data mining methodologies; (c) development of data mining algorithms and tools for predict marine vessel corrosion propagation that is consistent with various databases; (d) applications of


26

the developed methods to selected commercial and naval vessel systems; and (e) preparation of guidelines and final report.

3.2 Tasks.


3.2.2 The Contractor shall perform an overview of various corrosion databases

and assess the nature of the corrosion data.

3.2.3 The contractor shall perform an overview of data mining techniques and assess their suitability for the available corrosion data.

3.2.4 The Contractor shall develop methodologies and algorithms to apply data

mining techniques for predicting corrosion growth in marine vessel components.

3.2.5 The Contractor shall, in conjunction with the PTC, select suitable naval

and commercial vessel components/systems and demonstrate the viability of the developed methodologies and algorithms





5.2 The Contractor shall present a work plan at the kick-off meeting 2 weeks after

contract award

5.3 The contractor shall, at the end of 6 months, provide overviews of the corrosion databases, data mining techniques and proposed approach.

5.4 The contractor shall, at the end of 9 months, present the developed data mining

methodologies and algorithms for predicting corrosion in marine vessels.

5.5 The contractor shall, at the end pf ten months present the results of the validation and studies


27










28

06-08 Weight-Optimized Design of Non-Primary Ship Structural Components


1.0 OBJECTIVE.

1.1 The objective of the proposed work is to develop optimization methodologies and algorithms for weight reduction of non-primary ship structural components. The methodologies and algorithms will be developed within a reliability-based framework to remove the conservatism associated with the design of these non-primary members.

2.0 BACKGROUND.

2.1 The design of non-primary ship structural components, such as hatches, doors, foundations, masts, has traditionally relied upon a combination of engineering experience and deterministic-based approaches such as working stress design (WSD). This often results in conservative designs that are not weight optimized. As the industry moves towards faster vessels with larger payload requirements, there is a need to minimize the weight of these non-primary components, without compromising operational safety and structural integrity. Although attempts are currently being made to achieve weight reduction by application of advanced composite materials for non-primary components, their design is still based on WSD with their associated conservatism. However, recent developments have sought to improve the state-of-the-art in ship structural design by moving from WSD practices to reliability-based limit state design through the use of partial safety factors for the various load and strength parameters. Defined based on the ability to achieve target reliability levels (in terms of safety and functionality for a specified service life and operating environment), these factors permit a more rational and proportional account of inherent uncertainties and have lead to the development of the reliability-based load and resistance factor design (LRFD) approach. Also, advances have been made in the development of structural optimization tools which will allow for automated search within a design space of alternate viable designs that can maximize strength and minimize weight. It is proposed that the effective reduction of weight of these components at the conceptual, design and even the operational stages will require a combination of reliability based design/analysis and advanced optimization techniques.

2.2 A methodology that seeks to amalgamate reliability-based design methods with

structural optimization techniques, combining the robustness of each to produce an innovative approach to ship structural design which fully accounts for uncertainties inherent in the design process and facilitates a realization of the potential for weight reduction, cost savings, and improved design should be developed. The methodology should be a reliable, robust, and accurate numerical simulation tool, with automated optimization capabilities to ensure a thorough search within a specified design space. The numerical optimization tool should


29

have the flexibility of being used in a WSD or reliability based design environment.

3.0 REQUIREMENTS.

3.1 Scope. 3.1.1 The scope of the project includes: (a) overview and selection of non-

primary components of interest and their associated design/analysis methods; (b) development of deterministic- and reliability-based concurrent optimization algorithms for weight optimized design; (c) applications of the developed methods to typical non-primary ship components, such as hatches, doors, foundations, masts, etc, and (d) preparation of guidelines and report.

3.2 Tasks.


3.2.2 The Contractor shall review the design, analysis and application of

selected non-primary ship structural components such as hatches, doors, foundations, masts, etc, and associated computational tools

3.2.3 The Contractor shall develop methodologies and algorithms for

deterministic and reliability based design optimization of selected non-primary components.

3.2.4 The Contractor shall, in conjunction with the PTC, select suitable non-

primary structural configurations, and demonstrate the viability of the developed methodologies and algorithms






30

5.2 The Contractor shall present a work plan at the kick-off meeting 2 weeks after contract award

5.3 The contractor shall, at the end of two quarters, present the methodologies for

non-primary structure design optimization

5.4 The contractor shall, at the end pf three quarters present the results of the validation and studies










31

06-09 Structural and Fire Performance Characteristics of Composite Materials Fabricated With Polyurethane Resins Subjected to UL1709 Fire Testing

Submitted by: John J. McMullen Associates

1.0 OBJECTIVE.

1.1 Perform testing to further quantify the performance of enhanced polyurethane resin systems when subjected to the requirements of the UL1709 fire testing standards.

1.2 Provide comparative strength data for polyurethane based composites with the enhanced resin

system to the baseline resin system that would be used for composite product not subjected to the severe demands of a pooling hydrocarbon fire (UL1709). All strength data shall be developed in accordance with appropriate standards.

1.3 Allow naval engineers and designers to consider the use of polyurethane based composite

materials to provide more competitive designs for applications requiring exposure to the UL1709 testing criteria.

2.0 BACKGROUND.

2.1 Polyurethane resin systems have recently undergone significant research and development and currently provide superior strength compared to composite material systems fabricated using the more traditional resin systems associated with the marine industry, i.e., polyester, vinylester and epoxy. This development includes consideration to satisfy the Fire, Smoke and Toxicity, (FST), requirements associated with fires on commercial ships. The improved polyurethane resins can be used in either pultruded products or those developed with procedures more typically found in today’s shipyards, i.e., VARTM and hand lay-up procedures.

2.2 In addition to these commercial requirements, the US Navy requires that any material used as

a Fire Zone boundary on a surface combatant be able to satisfy the more stringent requirements of the testing standards presented in UL1709, a test that simulates a fire due to pooled hydrocarbon fuels, and is more severe than the commercial tests. As such, polyurethane based composites must satisfy these criteria for USN surface combatant application. This will reduce topside weight and increase survivability of the vessel.

2.3 With the increasing use of composite materials on many current and future US Navy surface

combatants, quantifying the behavior of polyurethane based composites for this application could provide for weight savings and increased survivability compared to other resin based composite systems. Superior strength and FST properties of polyurethane based composites for non-UL1709 applications have already been demonstrated compared to composite materials that use polyester, vinylester or epoxy resins.

2.4 Significant experience in both the DDX and LCS programs, along with the LPD 17 Main

Mast, has led to the recognition that there is good opportunity to advance the state of the art of composite materials for naval through the expanded use of polyurethane based composite materials.


32

3.0 REQUIREMENTS.

3.1 Scope.

3.1.1 The Contractor shall use existing data from applicable small scale tests to predict

results from the UL1709 tests, which require production of large scale test specimens. The Contractor shall use accepted procedures for the extrapolation of results from small scale to large scale to help predict satisfactory results from the large scale UL1709 tests and minimize cost and time associated with actual UL1709 testing.

3.1.2 The Contractor shall fabricate 3 test specimens to be prepared for shipping and

testing in accordance with UL1709 procedures at a third party test facility.

3.1.3 The Contractor shall report on the results of the tests conducted under the UL1709 conditions.

3.2 Tasks.

3.2.1 The Contractor shall obtain a copy of the UL1709 test standard and define the criteria applicable to test specimens for polyurethane based composite qualification.

3.2.2 The Contractor shall develop a Test Plan. The Test Plan shall include a

preliminary phase that uses existing data and results from previous tests typically used to predict large scale performance. The results of these tests shall be extrapolated to the criteria of UL1709 using accepted procedures. The results of the extrapolations shall help predict UL1709 results and be used to alter the resin systems prior to execution of the large scale tests required for UL1709.

3.2.3 The Contractor shall develop test specimens for UL1709 based on the results of

the preliminary efforts using the small scale tests results. The test panels/specimens shall be shipped to the third party test facility for execution of the testing. The Contractor shall supervise and witness the UL1709 testing or otherwise verify the adequacy of the test facility.

3.2.4 The Contractor shall provide the details for increased costs and any process

requirements for the enhanced resin system that successfully satisfies the UL1709 criteria.

3.3 Project Timeline. See Enclosure (1).


4.1 Standards for the Preparation and Publication of SSC Technical Reports 5.0 DELIVERY REQUIREMENTS.


33

5.1 The Contractor shall provide quarterly progress reports to the Project Technical Committee,

the Ship Structure Committee Executive Director, and the Contract Specialist. 5.2 The Contractor shall provide a copy of the Test Plan to the PTC prior to implementation. The

PTC can provide review and comment to the Test Plan but all modifications shall be agreed upon between the Contractor and the PTC prior to final modification.

5.3 The Contractor shall provide the results of the preliminary small scale extrapolation effort to

predict large scale results prior to fabrication of the test panels/specimens for the UL1709 testing.

5.4 The Contractor shall provide drawings of the UL1709 test specimens prior to testing.

5.5 The Contractor shall provide all test results from the test facility along with an assessment of

their performance relative to the UL1709 criteria. 5.6 The Contractor shall provide a print ready master final report and an electronic copy,



7.0 Time, Cost and Man-hour ESTIMATE. These contractor direct costs are based on previous


7.1 Project Duration: 12 months. 7.2 Project Man-hour: 7.3 Total Estimate: $

Section 2.01 ENGINEERING HRS

RATE SUB

TOTALSenior Materials Engineer 460 85 39100 Senior Materials Test Engineer 200 85 17000 Management 100 112 11200

Section 2.02 CLERICAL SUPPORT TOTAL HRS 760

TRAVEL AND OTHER DIRECT COST (includes contractor travel for periodic meetings with SSC and to meet with software producers) 35000


34

TOTAL

ESTIMATE 102300

8.0 REFERENCES.

8.1 Reference.


35

Structural and Fire Performance Characteristics of Composite Materials Fabricated With Polyurethane Resins Subjected to UL1709 Fire Testing

Enclosure (1)

Timeline of Deliverables

Deliverable Frequency Date Expected

Project Progress Reports Quarterly The 10th of the following month

Provide copy of Test Plan to PTC for review and comment

One time deliverable 2 months from date of contract award

Provide a report detailing the extrapolation efforts predicting large scale results using small scale test results.

Article III. One time deliverable

4 months from date of contract award

Article IV. Provide drawing of the test specimen.

Article V. One time deliverable


Article VI. Provide a report that details the results of all UL1709 testing including an assessment of the performance relative to the acceptance criteria of UL1709. Report shall include cost and process considerations for the successful resin system.

Article VII. One time deliverable


Article VIII. Draft Final Report Article IX. One time

deliverable 11 months from date

of contract award Article X. Final report Article XI. One time


of contract award


36

06-10 Structural and Fire Performance Characteristics of Composite Materials Fabricated With Polyurethane Resins

Submitted by: John J. McMullen Associates

1.0 OBJECTIVE.

1.1 Educate designers and engineers along with owners and operators to the significant increases in the strength and Fire, Smoke and Toxicity (FST) properties of composite materials using polyurethane resins.

1.2 Provide comparative strength and FST data for polyurethane based composites to those

fabricated with the traditional resins used in the marine industry; polyester, vinylester and epoxy. All data has been developed in accordance with appropriate standards.

1.3 Provide a single reference that contains significant, up-to-date data on the strength and FST

properties of various composite materials commonly used in the marine industry.

1.4 Allow commercial and naval designers to consider the use of polyurethane based composite materials to provide more competitive designs for applications ranging from the entire hull girder of high speed vessels to local structural applications such as deckhouses, portable dunnage, railing and walkway/access systems.

2.0 BACKGROUND.

2.1 Composite materials used in the marine industry have traditionally been fabricated using either polyester, vinylester or epoxy resin, depending on the requirements of the finished product. A significant amount of research and development has recently gone into the use of polyurethane resins as the matrix medium for composite materials. This has resulted in products with superior strength and FST, (Fire Smoke & Toxicity), characteristics compared to the same product fabricated with the traditional polyester, vinylester or epoxy resins. The improved polyurethane resins can be used in either pultruded products or those developed with procedures more typically found in today’s shipyards, i.e., VARTM and hand lay-up procedures.

2.2 The US Navy is currently considering the use of composite materials for application to future

surface combatants in unprecedented quantity. Many of these applications include topside, manned spaces where the use of polyurethane based composites will reduce the amount of material required for the design due to its increased strength and FST properties. This will reduce topside weight and increase survivability of the vessel.

2.3 Significant experience in both the DDX and LCS programs, along with the LPD 17 Main

Mast, has led to the recognition that there is good opportunity to advance the state of the art of composite materials for both naval and commercial applications through the expanded use of polyurethane based composite materials.


37

3.0 REQUIREMENTS.

3.1 Scope.

3.1.1 The Contractor shall identify the relevant standards currently used for commercial and naval applications of composite materials for both strength and FST.

3.1.2 The Contractor shall provide all the relevant strength and FST information

typically required to substantiate the use of composite materials in structural applications of commercial craft and US Navy surface combatants.

3.1.3 The Contractor shall define a structural system, i.e., a deckhouse, to be designed

using the strength properties for composite materials using each of the four resin systems investigated through this project, i.e., polyurethane, polyester, vinylester and epoxy.

3.1.4 The Contractor shall determine the weights and costs associated with each

structural system designed using composite materials with polyurethane, polyester, vinylester and epoxy resin systems.

3.2 Tasks.

3.2.1 The Contractor will provide two lists of all strength and FST design and testing standards currently used for application of composite materials. One list shall address the standards used in the commercial marine industry and the second shall address the standards for application to US Navy surface combatants. Each list will include full definition of the testing procedures and objectives, along with pass/fail criteria, as applicable.

3.2.2 The Contractor shall perform a literature search and provide the database of

strength and FST information that supports the use of composite materials in accordance with the standards defined above. The strength and FST data shall be provided for composite materials using each of the resin systems investigated by this project, i.e., polyurethane, polyester, vinylester and epoxy. The data shall be obtained for E-Glass, S-Glass and Carbon fiber reinforcement, as available. Any missing data shall be identified. This project does not propose any testing to obtain missing data identified through this task.

3.2.3 As part of the literature search the Contractor shall also provide relevant data not

defined by specific standards such as fatigue performance, ballistic and fragmentation performance, impact and damage tolerance, corrosion, etc.

3.2.4 The Contractor shall define a representative structural system to be designed

using composite materials. The structural system shall, at a minimum, represent a typical superstructure. Loads and boundary conditions shall be defined as part of the system, which shall then be designed using a composite materials system based on each of the four resin systems compared in this project.

3.2.5 Cost and weight data will be developed for each material systems developed

above.


38

3.3 Project Timeline. See Enclosure (1).


4.1 Standards for the Preparation and Publication of SSC Technical Reports 5.0 DELIVERY REQUIREMENTS.


5.2 The Contractor shall provide two lists of design and testing standards used for marine

applications of composite materials for 1) Commercial and 2) US Navy applications.

5.3 The Contractor shall provide the database of strength and FST information for composite materials using polyurethane, polyester, vinylester and epoxy resins in conjunction with E-Glass, S-Glass and Carbon fiber reinforcement.

5.4 The Contractor shall provide graphical representation of the strength and FST information in

the database for ease of comparison between the different resin and reinforcement systems.

5.5 The Contractor shall provide a drawing that defines the structural system to be developed using each of the four resin systems investigated by this project. The drawing shall include the full extent of the system to be designed, load cases to be applied to the various components of the structural system, load combinations that need to be considered and boundary conditions to be assumed for analysis.

5.6 The Contractor shall, upon completion of the structural designs, provide four separate

drawings, one for each of the solutions developed for the respective resin systems. Structural detail typical for a preliminary design shall be included in the drawings. Other advantages/disadvantages inherent with any of the particular material systems shall also be discussed. This shall include fabrication and lifetime maintenance considerations as well as physical attributes of the material system.

5.7 The Contractor shall provide the weight and cost estimates associated with the materials for

each structural design. 5.8 The Contractor shall provide a print ready master final report and an electronic copy,



7.0 Time, Cost and Man-hour ESTIMATE. These contractor direct costs are based on previous


7.1 Project Duration: 12 months.


39

7.2 Project Man-hour: 7.3 Total Estimate: $

Section 11.01 ENGINEERING HRS

RATE SUB

TOTALMaterials Engineer 280 68 19040 Structural Engineer 240 75 18000 Structural Designer 80 58 4640 Management/Quality Assurance 120 108 12960

TOTAL HRS 720 TRAVEL AND OTHER DIRECT COST (includes contractor travel for periodic meetings with SSC and to meet with software producers) 1200

TOTAL

ESTIMATE 55840

8.0 REFERENCES.

8.1 Reference.


40

Structural and Fire Performance Characteristics of Composite Materials Fabricated With Polyurethane Resins

Enclosure (1)

Timeline of Deliverables

Deliverable Frequency Date Expected

Project Progress Reports Quarterly The 10th of the following month

Provide two lists of design and testing standards

One time deliverable 2 months from date of contract award

Provide the database of strength and FST information for composite materials with all four resin systems.

Article XII. One time deliverable


Article XIII. Provide graphical representation of strength and FST data.

Article XIV. One time deliverable


Article XV. Provide a drawing that defines the loads, boundary conditions and extent of the structural system to be designed.

Article XVI. One time deliverable


Article XVII. Provide four separate drawings representing the structural design solution using each of the four resin systems. Include inherent advantages and disadvantages associated with each material regarding fabrication and lifecycle maintenance.

Article XVIII. One time deliverable


Article XIX. Provide weight and cost estimates for the materials associated with each design solution.

Article XX. One time deliverable


Article XXI. Draft Final Report Article XXII. One time


of contract award Article XXIII. Final report Article XXIV. One time


of contract award


41

06-11 Welding Distortion Analysis of Hull Blocks using Equivalent Load Method Based on Inherent Strain

Submitted by : [Prof. Chang Doo Jang, Dept. of Naval Architecture & Ocean Engineering,

Seoul National University]

1.0 OBJECTIVE. 1.1 The objective of the present work is to develop an efficient analysis method that

can predict the welding distortion of ship hull blocks considering the fabrication sequences, phase transformation of steel and free convection. Considering that the shape of a block is complex and various types of welding distortions are combined, the analysis method should satisfy the following requirements.

1.1.1 The analysis method should be capable of considering the various modes of welding distortions such as longitudinal/transverse shrinkage and longitudinal/transversal bending simultaneously. 1.1.2 The analysis should reflect the change of structural stiffness according to the fabrication stages. 1.1.3 The analysis should reflect the change of phase transformation of steel by material properties 1.1.4.1 The efficiency of calculation time and cost should be guaranteed

considering the complexity of hull block shapes.

1.2 My research group has carried out the studies on this problem by using the equivalent load method based on inherent strain, and successfully developed the welding distortion simulator for stiffened panels. This method could consider the variation of shape and stiffness of a fabricating block and, therefore, simulate the effect of assembly sequence on the final distortion quantitatively.

1.3 Since it requires experimental data of only simple specimen, this approach can be

utilized in the estimation of welding distortion of curved blocks which has more complex shapes. So, the present work is mainly focused on curved blocks to accomplish the simulation of welding deformation for whole ship hull blocks.

2 BACKGROUND. 2.1 Nowadays, most commercial and naval ships are constructed by block building

method in shipyards. The blocks which constitute the ship hull are built in a series of production process, and transferred to the pre-erection area for the preparation works including the correction of distortion. The distortion of a block is inevitably induced by welding and is accumulated according to the sequential fabrication process.

2.2 As the block erection step accounts for about one-third of the whole shipbuilding process, the accuracy of a block's shape and size has a close relation with the overall efficiency of production in shipyard. To increase the precision of fabrication, the welding distortion and the exact distortion margin at every fabrication stage should be estimated to meet the allowable tolerances of ship hull blocks.


42

2.3 Most workmen like to weld downward direction, but in large blocks, there must be so many curved plates. Therefore welding direction should be changed according to plate normal direction. Heated surface by welding would be cooled by air free convection which is influenced by slope. The cooling speed would change the portion of transformed phases which have other material properties. It means that welding distortion would occur differently according to normal direction. Newly developed inherent strain method for line heating deformation can reflect phase transformation, so that the method is strongly recommended to welding distortion analysis.

3 REQUIREMENT

3.1 Scope 3.1.1 Development of welding distortion simulator 3.1.2 The simulator deals with a block unit. 3.1.3 The block can contain curved plates. 3.1.4 The methodology considers phase transformation.

3.2 Tasks 3.2.1 Development of equivalent load method based on inherent strain 3.2.2 Welding distortion experiment according to poses 3.2.3 Welding distortion experiment of curved plate 3.2.4 Verification of the developed method 3.2.5 Block modeling for welding distortion analysis 3.2.6 Welding distortion analysis considering assembling process

4 GOVERNMENT FURNISEHD INFORMATION. 5 DELIVERY REQUIREMENT.

5.1 Quarterly progress reports will be provided to the Project Technical Committee. 5.2 Each report will consist of a print ready master and an electronic copy.

6 PERIOD OF PERFORMANCE. 6.1 Project Initiation Date : 01/01/2006 6.2 Project Completion Date : 12 months from the date of award.

7 Time, Cost and Man-hour ESTIMATE. 7.1 Project Duration : 12 months. 7.2 Project Man-hour : 4(people) 3(hours) 250(days) = 3000(Man-hour) 7.3 Total Estimate : 90,000 $ (=3000(Man-hour) 30($/hour))

8 REFERENCES.

8.1 C. D. Jang, H. S. Ryu and C. H. Lee, Prediction and Control of Welding Deformations in Stiffened Hull Blocks using Inherent Strain Approach, Proc. of 14th ISOPE, Vol. 4, 2004.

8.2 C. D. Jang, Y. S. Ha and D. E. Ko, An Improved Inherent Strain Analysis for the Prediction of Plate Deformations Induced by Line Heating Considering Phase Transformation of Steel, Proc. of 13th ISOPE, 2003.


43

8.3 C. D. Jang and C. H. Lee, Prediction of Welding Deformations of Ship Hull Blocks, Journal of Ship and Ocean Technology, Vol. 7, No. 4, pp. 41-49, 2003. 12

8.4 C. D. Jang, H. K. Kim and Y. S. Ha, Simulation of Plate Bending by High Frequency Induction Heating, Journal of Ship Production, pp. 234-244, 2002. 12.

8.5 C. D. Jang, C. H. Lee and D. E. Ko, Prediction of welding deformations of stiffened panels, Journal of Engineering for the Maritime Environment, Vol. 216, No. M2, pp. 133-143, 2002. 12.


44

06-12 Review and Update USCG SSC Website Case Studies Submitted by: JMS Naval Architects & Salvage Engineers

1.0 OBJECTIVE. 1.1 JMS proposes to review and update the technical content and presentation of the

educational case studies section of the SSC website. JMS will obtain input from organizations and institutions involved in teaching and/or communicating structural issues related to safety and life at sea and other SSC mission objectives.

2.0 BACKGROUND. 2.1 JMS developed the educational case studies section of the SSC website

http://www.shipstructure.org/case_studies.shtml in April 2000. The goal of the site is to increase appreciation of structural issues that are unique to the shipbuilding industry and provide a forum for the dissemination of information to universities and practicing naval architects. However, the website has not been updated in 5 years. Particular “failure” incidents are continuing, form a predictable pattern in some cases, and further, seem preventable in various ways.

3.0 REQUIREMENTS. 3.1 Scope

3.1.1 JMS will conduct an assessment of the current website case studies for errors and omissions pertaining to the existing content itself and any links that may no longer be working. Some out of date material and dead links have been discovered already after a quick review. It would also be useful to add links to full papers or additional information where there are none currently. JMS will add any additional content that has been developed since the original website development.

3.1.2 JMS will obtain input from organizations and institutions involved in teaching and communicating structural issues related to safety and life at sea and other SSC mission objectives, for suggestions for new case studies and other website improvements. These organizations will also be polled on how useful the site is and if they are using or referring their students to it or if they have adopted the information included there as part of their curricula.

3.1.3 JMS will work with the SSC POC to review the findings of the poll/interviews and make selections of the suggested improvements and suggested new case studies to incorporate into the website.

3.1.4 The following case studies are examples of the technical issues that may be applicable to the educational case studies section of the SSC website:

• MSC CARLA, a containership that was midbody lengthened, failed and broke in two in the modified area.


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• Examination of the oil tanker PRESTIGE that failed and broke in two off the coast of Spain.

• Structural failures of SWATH vessels

• Double hulling of existing, older single hull tank barges. Some recurring stress fractures and structural weakening have been discovered and repaired repeatedly on some designs.

• Patterns in bulker designs that are repeatedly leading to failures. Over one hundred bulkers have failed over the past decade resulting in over 300 lives lost.

3.1.5 JMS will review the current case studies and any new case studies for ways to better illustrate the more difficult to understand concepts with visuals such as better line illustration, photographs, or 3-dimensional animations.

3.2 Tasks.

3.2.1 Identify and contact industry and academic representatives

3.2.2 Modify existing cases studies

3.2.3 Based on feedback from industry and academic contacts, select candidate studies to be reviewed by SSC POC.

3.2.4 Implement studies selected by SSC. Cases will include: Background, Summary, Details, Results, Acknowledgements, and Links. Photos, sketches, and animation will be included as appropriate.

3.2.5 JMS will provide a print ready master final report and an electronic copy of all the new and any modified website content, including text, graphics, animations and instructions, ready to be formatted by the SSC website.

4.0 GOVERNMENT FURNISHED INFORMATION. 4.1 Standards for the Preparation and Publication of SSC Technical Reports

5.0 DELIVERY REQUIREMENTS.


5.2 JMS will provide a print ready master final report and an electronic copy of all the new and any modified website content, including text, graphics/animations and instructions, ready to be formatted by the SSC website, formatted as per the SSC Report Style Manual, as appropriate.

6.0 PERIOD OF PERFORMANCE. 6.1 Project Initiation Date: date of award.

6.2 Project Completion Date: 6 months from the date of award.


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7.0 Time, Cost and Man-hour ESTIMATE. These contractor direct costs are based on previous project participation expenses.


7.2 Project Man-hour: 300

7.3 Total Estimate: $25,000

8.0 REFERENCES. JMS Background Material


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06-13 Strength and Fatigue of Composite Patches for Ship Plating Fracture Repair

Submitted by: Dale G. Karr1 and Anthony Waas2

1Department of Naval Architecture and Marine Engineering, University of Michigan, Ann Arbor, MI 2Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI

1.0 OBJECTIVE.

1.1 It is the objective of this research to explore and experimentally validate the use of composite patches for preventing crack growth and extending the lifetime of aluminum and steel ship structures. A composite patch works as a crack arrestor by decreasing the stress in the area of the crack tip. Load is shed from the base plate through an adhesive layer to the composite patch. In addition, the added constraint of the composite patch can prevent these cracks from coalescing into a larger crack. Analytical capabilities exist for predicting the effectiveness of the composite patch configuration, but such analyses demand specific idealizations and assumptions that must be validated experimentally in order for this technology to be used in practice. Our proposed project seeks to develop this technology as a useful and reliable tool for aluminum and steel ship plating fracture repair and to foster its industrial acceptance and implementation.

2.0 BACKGROUND.

2.1 Repeated loading may result in the initiation of cracks in ship structure from fatigue. In particular, repeated loading in areas of stress concentrations leads to fatigue cracks that can grow to critical lengths and result in catastrophic structural failure of components and hull plating. Increased attention to maintenance and corrosion control is therefore particularly important for vessels designed with thinner plating afforded by higher-strength steels. Examples include the hull-structure cracking observed in Trans-Alaska Pipeline Service (TAPS) tankers [1,2,3]. 2.2 An important consideration is the determination of critical crack length for a given hull material in order to assess potential for catastrophic failure [4,5]. Once cracking is detected, weld repairs may be conducted and structural modifications may be introduced. These approaches may solve the immediate problem temporarily but too often they move the initiation point for the crack to a new location. A solution is to lower the stress levels caused by load-induced conditions or structural imperfections so that fatigue crack initiation and growth are either prevented entirely or deferred for an acceptable amount of additional service life. The composite patch serves to do just that: reduce the stress intensity level. The reduction in stress intensity reduces substantially the crack growth rate. If it is assumed that microcracks or flaws already exist and the patch is placed in an area of high stress or an area where cracks will likely develop, the composite patch can prevent these cracks from growing or coalescing into larger cracks.


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2.3 Composite patches have been proven effective in other industrial applications. In contrast to other repair methods, repairs carried out with composite patches are completed faster, exhibit good fatigue resistance, do not cause stress concentrations, result in low added weight, and are economically attractive [6,7]. In the aerospace community, composite patches are an “effective technique for improving fatigue life and maintaining high structural efficiency” [7,8]. It has been reported that high patch modulus materials attached to an aluminum base plate is a useful technique where surface preparation has enabled the development of adequate adhesive strength [7]. Aircraft components repaired with a composite patch have exhibited an 84% reduction in the stress intensity factor and a 1000% increase in the fatigue life [8]. Composite materials have also been used to rehabilitate steel bridges. Such repairs resulted in a 113% increase in the strength of damaged girders [9].

2.4 As in other industries, general use of composites in the marine industry is on the rise. Limited work in the marine field has been conducted with aluminum vessels [10]. Generally speaking, analytical and numerical studies of adhesively bonded composite patches used as crack arrestors have been investigated for cracked sheets and plates [11-16] and in particular within the context of ship structure repair [17,18]. The previous work by Edwards and Karr [17] and by Bone et al. [18] forms the basis for the proposed project. This project will extend the previous work to include steel plating and to include testing the composite patches under fatigue conditions [19-22].

2.5 In the previous project by the investigators, 1/6th inch and 1/8th inch thick aluminum plates were used as base plates. The tests were conducted using 7075-T6 aluminum with both glass and graphite patches. Both pre-impregnated and wet lay-up processes were tested for comparison. Additionally, both single and double-sided patches were tested. The aluminum specimens were 12 by 12 inch plates with 2-inch edge cracks. For each test, the crack itself was first machined to a chevron or V-style notch and then fatigued until an initial crack was evident. After this, 4 by 4 inch unidirectional fiber composite patches were placed over the cracked area. The specimens were then tested by applying monotonically increasing load. With just one layer of glass fibers on a 1/8-inch thick plate, the maximum tensile load increases by almost 40%. Putting a layer of carbon fiber patch on both sides of the crack improves the maximum tensile load by almost 55%. These average results were achieved using only a small 1.5 hp vacuum pump for 8 hours, and a room temperature cure of 2 weeks. The primary mode of failure for the test specimens was delamination. Effects of various adhesive systems and additional layers of composite patching were studied. A summary of the load capacity for some 1/16th plates is shown below. Note that the arrow on the upper level test data points indicate that the plates failed by overall yielding rather than composite delamination; that is, the plate was restored to 100% of its pre-cracked capacity, a nearly three-fold increase in static strength. These experiments provide a good basis for further systematic testing for steel plates and fatigue testing.


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2.4 Of course elimination of all potential crack initiation sites or conditions in ship strutures is not practical, and that some dependence on other approaches must be available to preclude catastrophic failure. Major concerns are and will continue to be fitness for service during operation, where the effect of minor cracking is assessed; and life-extension considerations, where the effect of severe structural damage is assessed. When cracking of ship structure occurs during service, decisions must be made about repairs. Depending on circumstances, immediate repairs may or may not be necessary. Cracks that are load induced must be repaired or an alternative load path provided. Composite patch repairs may be completed rapidly, may exhibit vastly improved fatigue resistance, reduce rather than increase stress concentrations, have lower added weight than metal doublers, and are very cost effective. Thus these composite repairs have the potential as an efficient, economical, and expedient way to extend time between major structural repairs. Our previous studies indicate great promise for this approach in that static strengths of cracked metal plating can be substantially increased. However, such repairs for ship structure must also retain their integrity under repeated loading conditions, hence the need for verification in a fatigue-testing program.

3 REQUIREMENTS.

3.1 Scope.

3.2 The Contractor shall conduct an assessment of candidate adhesive systems for glass and carbon fiber composite patches to steel plating. 3.3 The Contractor shall identify the optimum composite adhesive systems for both aluminum and steel plating.


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3.4.1 The Contractor shall design and conduct static strength tests of these

systems to supplement existing findings for aluminum plating. 3.5 The Contractor shall conduct fatigue tests of the selected designs for composite

patching of pre-cracked plates.

3.5.1 Tasks and Timeline.

The project consists of two major complementary components: the numerical analyses and the experiments plus our documentation efforts. The major tasks are as follows, with milestone completion and estimated work hours. The work hours are combinations of the Investigators and student based on a total of 1000 hours for student work and 500 hours faculty. Portions of Professor Waas’ hours are included as Laboratory director and not charged to proposed project. Portions of Professor Karr’s hours are included in thesis supervision and not charged to the project.

3.5.2 The Contractor shall develop Finite Element Analyses for the steel plate systems to supplement the existing analyses of aluminum plates. Completion: 4 mo. from start date. (100 hours). 3.5.3 The Contractor shall analyze, using the Finite Element Software, the

aluminum and steel systems to predict crack growth and plate/patch failure. Completion: 6 mo. from start date. (150 hours).

3.5.4 The Contractor shall design candidate crack/plate/patch systems for

testing. Completion: 9 mo. from start date. (250 hours).

3.5.5 The Contractor shall develop experimental arrangement for the strength tests. The experiments will be conducted at the University of Michigan’s Composite Structures Laboratory (Section 9). Fixtures, such as that shown below and used in previous projects, will be designed and constructed. Completion: 12 mo. from start date. (200 hours).

3.5.6 The Contractor shall develop experimental arrangement for the fatigue

tests. Completion: 12 mo. from start date. (250 hours).

3.5.7 The Contractor shall perform strength and fatigue tests for the developed system designs. Completion: 22 mo. from start date. (450 hours).

3.5.8 The Contractor shall develop and deliver documentation of progress and

final results. Completion: 24 mo. from start date. (100 hours).


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4 GOVERNMENT FURNISHED INFORMATION.

4.1 Standards for the Preparation and Publication of SSC Technical Reports 5 DELIVERY REQUIREMENTS.


5.2 The Contractor shall provide a Peliminary Report on the Finite Element

Analyses, Initial Static Tests, and Fatigue Life Predictions of the proposed fatigue tests, within 14 months of start date.

5.3 The Contractor shall provide a print ready master final report and an electronic copy, including the above deliverables, formatted as per the SSC Report Style Manual.

6 PERIOD OF PERFORMANCE.

6.1 Project Initiation Date: date of award.

6.2 Project Completion Date: 24 months from the date of award.


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7 Time, Cost and Man-hour ESTIMATE.

These contractor direct costs are based on previous project participation expenses. Costs include one Graduate Student Research Assistant and faculty support for the project, and $20,000 (as cost sharing with the University) for purchases of fatigue testing equipment and supplies.


7.2 Project Man-hours: 1,500.

7.3 Total Estimate: $200,000.

8 REFERENCES.

1. U.S. Coast Guard Navigation and Vessel Inspection Circular No. 15-91, CH-1. 2. Sucharski, D. “Owner and Operators Viewpoint crude Oil Tanker Hull Structure

Fracturing: An Owner’s Perspective” In Prevention of Fracture in Ship Structure, Committee on Marine Structures, Marine Board, National Research Council, pp 87-124, 1997.

3. Report on the Trans-Alaska Pipeline Service (TAPS) Tanker Structural Failure Study, Office of Marine Study, Security and Environmental Protection, United States Coast Guard, June 25,1990.

4. Francis, P.H., Lankford, J. Jr., Lyle, F.F. Jr., “A Study of Subcritical Crack Growth in Steel Ships,” Ship Structure Committee Report No. 251, 1975.

5. Card, J.C. and Palermo, P.M., “Safeline for Ships”, In Prevention of Fracture in Ship Structure, Committee on Marine Structures, Marine Board, National Research Council, pp. 81-86, 1997

6. Jones R. and Smith W.R., “Continued Airworthiness of Composite Repairs to Primary Structures for Military Aircraft,” Composite Structures, Vol. 33, 1995, pp. 17-26.

7. Ong, C.L. and Shen, S.B., “The Reinforcing Effect of Composite Patch Repairs on Metallic Aircraft Structures,” International Journal of Adhesion and Adhesives, Vol. 12, No. 1, Jan 1992, pp. 19-2

8. Lena, M.R., Klug, J.C., Sun, C.T., “Composite Patches as Reinforcements and Crack Arrestors in Aircraft Structures,” Journal of Aircraft, Vol. 35, No. 2, Mar-Apr 1998, pp. 318-323.

9. Rajagopalan, G., Immordino, K.M., Gillespie, J.W. Jr., “Adhesive selection methodology for rehabilitation of steel bridges with composite materials”, Proceedings of the American Society for Composites 1996. Technomic Publ Co Inc, Lancaster, PA, USA. p 222-230, 1996.

10. Allan, R.C., Bird, J. and Clarke, J.D., “Overview: Use of Adhesives in Repair of Cracks in Ship Structures,” Materials Science and Technology, Vol. 4, No. 10, Oct 1988, pp. 853-859.

11. Aglan, HA, Gan, YX, Wang, QY, Kehoe, M. Design guidelines for composite patches bonded to cracked aluminum substrates. Journal of Adhesion Science and Technology, v 16, n 2, 2002, p 197-211.


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12. Belhouari M, Serier B, Bouiadjra BB. Computation of the stress intensity factors for repaired cracks with bonded composite patch in mode I and mixed mode. Composite Structures, v 56, n 4, June, 2002, p 401-406.

13. Rastogi N, Soni SR, Denney JJ. Analysis of bonded composite patch repaired metallic structures: An overview. Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference, v 2, 1998, AIAA-98-1883, p 1578-1588

14. Tsamasphyros GJ, Kanerakis GN, Karalekas D, Rapti D, Gdoutos EE, Zacharopoulos D, Marioli-Raga ZP. Study of composite patch repair by analytical and numerical methods. Fatigue and Fracture of Engineering Materials and Structures, v 24, n 10, October, 2001, p 631-636

15. Qin M, Dzenis YA. Analysis of single lap adhesive composite joints with delaminated adherends. Composites Part B: Engineering, v 34, n 2, March, 2003, p 167-173.

16. Chung KH, Yang, WH, Cho MR. Fracture mechanics analysis of cracked plate repaired by composite patch. Key Engineering Materials, v 183 (I), 2000, p 43-48.

17. Edwards, M. and Karr, D.G. "Analysis of Composite Patches for Ship Plating Fracture Repair," Ship Technology Research/Shiffstechnik, Vol. 46, No. 4, pp. 231-237, 1999.

18. Bone, J. "Testing of Composite Patches for Ship Plating Fracture Repair," 2003, M.S. Thesis, University of Michigan. Also presented at the SNAME Annual Meeting, October, 2003, San Fransisco, CA.

19. Rao VV, Singh R, Malhotra SK. Residual strength and fatigue life assessment of composite patch repaired specimens. Composites Part B:Engineering, v 30, n 6, 1999, p 621-627.

20. Kam, T.Y., Tsai, K.C., Chu, K.H., Wu, J.H., “Fatigue Analysis of Cracked Aluminum Plates Repaired with Bonded Composite Patches,” AIAA Journal, Vol. 36, No. 1, 1998, pp. 115-118.

21. Wang CH, Rose LRF, Baker AA. Modelling of the fatigue growth behaviour of patched cracks. International Journal of Fracture, v 88, n 4, 1998, p L65-L70.

22. Wang QY, Pidaparti RM. Static characteristics and fatigue behavior of composite-repaired aluminum plates. Composite Structures, Vol. 56, pp 151-155, 2002.

9 FACILITIES REQUIRED

9.1 Existing office space, computer equipment, state of the art software packages and laboratory facilities will used throughout the project duration at no charge to the project. The experiments will conducted at the University of Michigan Composite Structures Laboratory. The Composite Structures Laboratory was established in 1988 by the Department of Aerospace Engineering. Its activities involve research and training of graduate and undergraduate students in the Static and Dynamic Behavior of Structures made of advanced composite materials. During the last decade, the NASA Langley Research Center, the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Office, the Department of Energy, the National Science Foundation, and the Ship Structures Committee have funded


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research projects. In addition, funds have also been received from various industries, most notably the big three automakers and their allied industrial partners, the Automotive Composites Consortium. Most activities of the laboratory are conducted in the FXB Aerospace Building and spans several laboratory rooms designed for different types of experiments. Collectively, these rooms cover an area of approximately 2300 square feet.

9.2 Several servo hydraulic testing frames are available for mechanical characterization

of composite structures. These include a large capacity (100k lbf. force-50k inch.lbf. torque) MTS tension-torsion combined loading test frame, a small capacity tension-torsion pneumatically driven test frame(3k lbf capacity), a biaxial planar loading frame (50k lbf capacity), a 10k lbf screw driven Riehle test frame, two miniaturized table top compression-tension loading frames (range from 1 lbf – 50klbf.), a Charpy impact hammer, an instrumented drop tower facility, a 12x6 pneumatically isolated optical table, a Kodak high speed digital camera(1k frames/sec.), and a CORDIN high speed variable framing rate camera(20 frames/microsecond). These loading devices are supplemented by state of the art data acquisition systems and several additional optical devices for interferometric measurements and speckle photographic measurements. The laboratory also has several load cells spanning a broad range of load capacities, displacement measuring mechanical and optical transducers. A temperature and pressure controlled press for manufacturing flat laminates and several ovens are available for coupon level manufacturing of composites. A well equipped optical and scanning electron micrography laboratory is available for users of the composite structures laboratory. Students training in the laboratory have access to a campus wide network of powerful workstations and personal computers for computational work.


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06-14 Impact Study Submitted by: Columbia Research Corporation

1.0 OBJECTIVE.

1.1 The purpose of this proposed study is to promote the value of the Ship Structure Committee (SSC) and identify clear and traceable links between the work sponsored, supported and published by the SSC, and how this work is utilized and/or incorporated into commercial and military enterprises, to include shipbuilding designs or practices, and/or incorporated into industry standards. It is proposed that a comprehensive survey be developed, and then widely distributed to the variety of organizations that both support SSC and access SSC sponsored work. These organizations will include class societies, standards organizations, the US Navy, US Coast Guard, MARAD, Military Sealift Command, domestic and international shipbuilders, and academia. These organizations will be queried regarding their knowledge and awareness of SSC work, and how they utilize/incorporate SSC sponsored products into their end products. This survey will request the citation of specific examples so as to more concretely identify the influence of SSC sponsored work within the shipbuilding industry. These results will provide guidance as to where future resources should be directed to best meet industry needs, while offering evidence of specific industry applications and impact of SSC work to provide justification for ongoing and future funding requests.

2.0 BACKGROUND.

2.1 The goal of the SSC is “to enhance the safety of life at sea, promote technology and education advancements in marine transportation, and to protect the marine environment.” This is accomplished through extensive research, professional collaboration, testing efforts, and associated studies/reports, which are posted on the SSC web site for public access. Inclusion of these findings by classification and safety organizations is at their own discretion.

2.2 The extent to which the SSC’s findings are utilized within and across the shipbuilding

industry is not readily identifiable, making it difficult to quantifiably measure added value and justify future SSC funding requests.

3.0 REQUIREMENTS.

3.1 Scope.

3.1.1 Phase I: Survey and Initial Report:

3.1.1.1 In cooperation with SSC members, the contractor shall identify and develop a comprehensive list of builders, class societies,


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government organizations, standards organizations, educational institutions, and contracting firms that may have benefited from SSC work.

3.1.1.2 Simultaneously, the contractor shall develop a comprehensive

survey that seeks to identify specific examples whereby SSC sponsored work is utilized and/or incorporated by these organizations into their own work. Ultimately, the survey will seek to identify quantifiable benefits provided to the organization.

3.1.1.3 A initial survey for wide dissemination to the aforementioned

organizations will be developed, and will be aimed at gathering information on previously sponsored work and knowledge of the SSC. The purpose of the initial study is to target an audience for the comprehensive survey.

3.1.1.4 A survey for posting on the SSC website will also be developed,

and will be aimed at how current and future users of the SSC website apply SSC sponsored work.

3.1.1.5 The Ship Structure Committee Website Trends data will be

analyzed in an effort to determine the primary customers of the SSC.

3.1.1.6 The contractor shall contact and solicit the comprehensive survey

to those identified to better understand what influence and impact these SSC and findings have had on ship safety and structure in their organization. The comprehensive survey, developed by the contractor and in cooperation with SSC, shall query their awareness, utilization, and impact of SSC work and shall be user specific where pertinent. The survey should include awareness, utilization, and impact of SSC work. Portions of the survey should include, but not be limited to, acquisition, design, construction, maintenance and inspections, technology, materials, production techniques, fatigue and fracture resistance, loading criteria and hull monitoring. The survey should cover all aspects of previous SSC reports and possible incorporation into organization work processes.

3.1.1.7 The Contractor shall produce an initial report of findings

describing the impact of SSC work including but not limited to the areas of: specifications, technical manuals, standards, acquisition programs, academia, and congressional inquiries. This will be used to support a possible industry briefing or conference in September 2005


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3.1.1.8 A consortium may be held to invite prevalent ship structure experts from around the world to discuss SSC reports and their impact. This may be couple with the September 2005 conference.

3.1.2 Phase II: Final Report

3.1.2.1 Based on a final analysis of all survey results and findings of the industry conference, a Final Report shall be delivered that includes but is not limited to the following: • Quantifiable benefits of SSC sponsored work across industry. • Strategies to effectively communicate these benefits to

sponsoring activities in order to sustain and potentially increase funding to SSC.

• Focus areas for future SSC sponsored efforts

3.1.2.2 The following items should be discussed when describing the impact of the SSC • Specifications • Technical Manuals • Standards/Rules/Guidance Notes • Acquisition Programs • Classes • Congressional Inquiries

3.1.2.3 The final report should include a breakdown of impact by: • Shipyard • Country • International Region • Topic (material, design, construction, maintenance, etc) • Industry (commercial shipping, high speed ferry, academia,

offshore, naval, etc.) • Ratio of value to industry against SSC investment

(Cost/Benefit)

3.2 Tasks.

3.2.1 The Contractor shall obtain all possible users of SSC reports and findings from SSC along with contact information.

3.2.2 These users shall be surveyed with regards to SSC influence as it has and

continues to have on ship structure design and safety. 3.2.3 The Contractor shall collect, organize, analyze, and report all findings to

the SSC.



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4.1 Standards for the Preparation and Publication of SSC Technical Reports. 5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).

5.1 The Contractor shall provide quarterly progress reports to the Project Technical Committee, the SSC Executive Director, and the Contract Specialist.

5.2 The Contractor shall provide a work plan for approval within two weeks of contract

start. 5.3 The Contractor shall provide a print ready master final report and an electronic copy,

including the above deliverables, formatted as per the SSC Report Style Manual or other mutually agreeable format, as may be dictated by the findings of this study.


6.1 Project Initiation Date: date of award. 6.2 Project Completion Date: It is envisioned that this project will be completed in 2

distinct phases.

Phase I: 5 months from the date of award. Phase II: 10 months from date of award.

7.0 GOVERNMENT ESTIMATE. These contractor direct costs are based on previous



7.2.1 Phase I: $50,000 / 5 months 7.2.2 Phase II: $30,000 / 2 months

7.3 The Independent Government Cost Estimate is attached as enclosure (x).

8.0 REFERENCES.

8.1 Design Guidelines for Doubler Plate Repairs of Ship Structures SSC 03-12 N00024-01-D-7016, Delivery Order 009 08 September 2003 through 07 March 2005


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POC: Mr. Natale Nappi, (202)781-3700, [email protected] 9.0 SUGGESTED CONTRACTING STRATEGY.

It is suggested that this effort be contracted through a firm fixed price purchase

order, funded in two distinct phases.


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06-15 Development of Certification and Design Guidelines of Composite Ship Structures Subjected to Low Velocity Impact

Submitted by: Anteon Corporation / NSWCCD

1. OBJECTIVE.

The main objectives of this project are 1) development of certification and design guidelines of composite ship structures subjected to low velocity impact; 2) performance of an experimental study to understand the physics of impact failure mechanisms; and 3) demonstration of the applicability of using a predictive tool for designing an impact damage tolerable marine composite structures with a higher level of confidence. 2. BACKGROUND.

2.1 Motivation

Ship structures are subjected to low-velocity, low energy impact-induced damage during their service life caused by ice impact, grounding, dropping tools during maintenance operations, high pressure watering during the deicing, etc. The low velocity impact can generate fiber, matrix and/or delamination damage inside a fiber composite laminate, which may significantly reduce the in-plane strength. The fact that these impacts may take place without leaving any visible evidence on the surface of an impacted laminate makes it even more important to account for these loading cases in the design process. Both the structural mechanics and fracture mechanics based models cannot fully capture the impact damage evolution due to coexistence of continuum and discrete damage. The lack of fidelity of existing impact damage assessment tools has forced US navy to implement a costly and time consuming test-driven approach in designing the impact damage tolerable composite ship structures. The test-driven approach will severely limit the US Navy in exploration of new materials, designs, and fabrication techniques for the maximum impact resistance of a composite ship structural component.

2.2 Justification

The non-inspectable and hidden damage resulted from the low velocity impact has posed a great challenge in designing the damage tolerable composite ship structures. The use of a “knock-down” factor based on limited number of impact tests will result in the design of unknown risk. The added unnecessary weight will have a big impact on the payload, top speed, and operation range of a ship. The on-board impact damage assessment tool can assist in decision making regarding the continue operation or deport repair and maintenance action after an impact accident. The design approach will replace the test-driven certification process with a performance-driven design iteration. The design approach can be readily transitioned to the Navy and commercial industry for use in current, on-going and future composite impact design application.


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3. REQUIREMENTS.

3.1 Scope. (Identify the phases of the project).

The main scope of this program is to conduct a combined experimental and analytical study to explore the failure physics of a marine composite structure subjected to a low velocity impact and develop an impact damage assessment tool to capture the synergistic interaction of continuum and discrete damage during the damage progression. An extensive experimental program is currently initiated at the Naval Surface Warfare Center Carderock Division (NSWCCD) to study the effect of impact energy, the geometric parameters of an impactor on the composite panels with various thicknesses and lamination sequences. By leveraging this effort with the analytical/numerical development, a great deal can be accomplished under a given budget constraint.

3.1.1 The Contractor shall team with the US Navy (NSWCCD) to conduct a combined experimental and numerical study to capture the impact damage progression and its associated final rupture. The dynamic response of a testing article has to be analyzed under a given impact condition with and without the damage. The validated dynamic response model will be used to assist in experimental design, instrumentation, data collection, and damage characterization.

3.1.2 The Contractor shall develop an impact damage assessment model based on the observed failure mechanisms. Current structural mechanics based tool cannot fully capture the fracture process in composite structures subjected to the impact loading. Detailed finite element analysis characterizing multiple disbonding cracks is too complicated in terms of model generation, data interpretation and model validation to impact the usual design process for composite. An efficient and accurate numerical prediction model needs to be developed to 1) characterize initiation and propagation of a delamination failure; 2) capture micro-damage induced stiffness reduction; 3) ultimate failure strength for a given initial impact damage.

3.1.3 The Contractor shall demonstrate the accuracy and validity of the developed impact damage assessment tool by comparing the model prediction with the experimental data. After validating the tool, the contractor shall demonstrate how to apply the developed tool to determine the design allowable for a given impact scenario.

3.2 Tasks. (Identify the tasks to carry out the scope of the project). 3.2.1 Performance of Experimental Study on Impact Damage Quantification – The contract shall work closed with the Navy during the test set-up, test matrix identification, data correction, damage monitoring, and post-damage identification.

3.2.2 Development of Delamination Failure Model – Given the large scale of a typical ship structure, the contract shall develop a delamination initiation and progression model based on the shell element formulation. The model should capture the delamination initiation at an arbitrary location and the progression of multiple delamination damages in


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a typical laminated composite ship structures or composite sandwich structures. The delamination driving force need to be accurately quantified and a failure criterion need to be implemented to monitor the delamination failure.

3.2.3 Development of a Hybrid Discrete and Continuum Damage Model – Both the

delamination (discrete) and continuum (microcracking) damage will occur for a composite structure subjected to the low velocity impact. The contractor shall develop a hybrid damage evolution model to characterize the synergistic interaction between the microcracking induced stiffness reduction and the propagation of a delamination damage.

3.2.4 Validation of the Impact Damage Assessment Model – The contractor shall work

closely with the Navy in defining the test cases for the tool validation study. The purpose of this task is to demonstrate that the impact damage and its resulting ultimate strength of a composite structure can be predicted from material and failure data at its coupon level.

3.2.5 Tool Application for Designing Impact Damage Tolerable Structure – The

contractor shall apply the validated impact damage assessment tool to determine the design allowable for a composite structure. Given the design requirement associated with a potential impact incident, the design allowable will be computed using the tool and compared with an empirically based conventional design. By comparing with the design without the impact damage, a “knock-down” factor will be computed to show the additional requirement in safety margin once the impact needs to be considered in the design.


1) TASK Work Breakdown Schedule

1 2 3 4 5 6 7 8 9 10 11 12

Task 1. Experimental Characterization of Impact Response and Damage

Task 2. Development of a Delamination Failure Model

Task 3. Development of a Hybrid Damage Assessment Model

Task 4. Validation of Impact Damage Assessment Tool

Task 5. Tool Application and Design Allowable

Task 6. Final Report ∆


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4.1 Standards for the Preparation and Publication of SSC Technical Reports 5 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).






7 Time, Cost and Man-hour ESTIMATE. These contractor direct costs are based on


7.1 Project Duration: 12 months. 7.2 Project Man-hour: 1300 7.3 Total Estimate: $150,000

8 REFERENCES.

8.1 Simonsen, B.C. (1997) “Ship grounding on rock – II Validation and application”, Marine Structure, 10 (7), pp. 563-584.

8.2 Dyka, C.T. and R. Badaliance (1997) “Damage in mainre composites caused by shocking loading”, Composite Science and Technology, 58 (9), pp.1433-1442.

8.3 Nguyen, M.Q., S.S. Jacombs, R.S. Thomson, D. Hachenberg, and M.L. Scott (2005) “Simulation of impact on sandwich structures”, Composite Structures, 67 (2), pp. 217-227.

8.4 Elder, D.J., R.S. Thomson, M.Q. Nguyen, and M.L. Scott (2004) “Review of delamination predictive methods for low speed impact of composite laminates”, Composite Structures, 66 (1-4), pp. 677-683.

USSC Project Recommendation for FY 2006

Vehicle Deck Strength Study for the Marine Industry

Submitted by: Elliott Bay Design Group 1.0 UOBJECTIVE

1.1 The objective of this paper is to develop structural design guidance for vehicle decks on RO/RO and ferry type vessels. This discussion will provide the marine industry with a comprehensive engineering reference by compiling methods from lessons learned, current regulatory rule sets, traditional first principle calculations, finite element analysis, and additional design publications. The conclusions drawn from this comparison will provide research towards the development of a standard of care analysis method for the primary components of vehicle deck design.

2.0 UBACKGROUND 2.1 Many documented design methods exist for vehicle decks and each significantly

varies in methodology, assumptions, and resulting scantling selection. Recent experience has shown that following regulatory rules does not ensure desired deck design life for certain loading conditions. Special attention needs to be given to each deck structural component with respect to:

• Adequate vehicle load selection where the design reflects the worst case probable event(s) and realistic traffic volume

• Local deck panel deflection and plastic deformation • Deck stiffener selection and the use of longitudinal versus transverse

framing • Weld details and how vehicle traffic quantities relate to fatigue life for

various welding methods • Evaluation of different construction materials and alternative plate

stiffening concepts to minimize weight

2.2 Providing the marine industry with a consolidated set of design guidelines takes a necessary step towards defining a new standard of engineering design and addresses specific issues involved with vehicle deck structure.

2.3 Previous vehicle deck design experience and a comparison of the current available methods will provide trends in scantling selection and welding configurations to be included in this project.

3.0 UREQUIREMENTS 3.1 Scope

3.1.1 The Contractor (EBDG) will research existing vehicle deck design methods, the most current vehicle load applications, and discuss both successful and unsuccessful historical cases of vessel vehicle decks.

Vehicle Deck Guidelines for the Marine Industry Page 2 Submitted by Elliott Bay Design Group

3.1.2 The Contractor will conduct a design comparison using each researched method and identify areas requiring further investigation.

3.1.3 The Contractor will develop recommendations for design methodology for the primary structural components of vehicle decks towards developing an industry standard design practice.

3.1.4 The results of this project will be a comprehensive set of vehicle deck structural design guidelines for the marine industry. Portions of this work have the possibility of being incorporated into existing regulatory sets.

3.2 Tasks

3.2.1 Task 1 – Literature and Data Collection: The Contractor will research current regulatory design practices, available vehicle design load information, and industry design practices for vehicle decks.

3.2.2 Task 2 – Historical Survey: The Contractor will survey previous projects and obtain performance evaluations on vehicle decks structures currently in service for multiple vessel types. Performance evaluations will include the following information for each case:

• Description of vehicle traffic, construction materials, scantling arrangement, and welding or connection methods

• Design methodology used for each application • Any observed deck panel permanent deformation • Any observed local yielding of stiffeners, deck plate, or welds • Any observed excessive corrosion and possible causes • Any required repair history, if available • Any additional observations

3.2.3 Task 3 – Regulatory Design Methodology Comparison: The Contractor will carry out vehicle deck design calculations using available regulatory rules and guidelines for classed vessels. The Contractor will identify trends and demonstrate the most efficient design concepts for each vehicle deck component.

3.2.4 Task 4 – Alternative Design Methods: The Contractor will develop vehicle deck designs using finite element analysis, traditional first principal calculations, and additional available methodologies outside of the previously cited regulatory rules.

3.2.5 Task 5 – Documenting and Reporting: The Contractor will assemble observations and conclusions and provide vehicle deck design guidelines for industry reference. Guidelines will include suggestions for design approach to each vehicle deck component.

3.3 Project Timeline

3.3.1 The project can be completed within 8 months from the project initiation date. The following task breakdown indicates estimated hours for each item:

• Task 1 (Literature and Data Collection) – 80 Hours


• Task 2 (Historical Survey) – 160 Hours • Task 3 (Regulatory Design Comparison) – 60 Hours • Task 4 (Alternative Design Methods) – 100 Hours • Task 5 (Documenting and Reporting) – 80 Hours

4.0 UGOVERNMENT FURNISHED INFORMATION 4.1 Standards for the Preparation and Publication of SSC Technical Reports.

5.0 UDELIVERY REQUIREMENTS 5.1 The Contractor will provide quarterly progress reports to the Project Technical

Committee, the Ship Structure Committee Executive Director, and the Contract Specialist.

5.2 The Contractor will provide a draft outline of the paper prior to its assembly for review and comments by the Committee. This outline will include an abstract of the paper's intent and content topics to be discussed.

5.3 The Contractor will provide a print ready master final report and an electronic copy on CD-ROM (in either MS Word or Acrobat PDF media), including the above deliverables, formatted as per the SSC Report Style Manual.

6.0 UPERIOD OF PERFORMANCE 6.1 Project Initiation Date: date of award 6.2 Project Completion Date: 8 months from the date of award

7.0 UTIME, COST, MAN-HOUR ESTIMATE U 7.1 Duration: 8 Months 7.2 Man-Hour: 480 Total Hours 7.3 Total Estimate: $44,000 (Includes $5,000 for travel and reproduction expenses.)

8.0 UREFERENCES

8.1 Current American Bureau of Shipping Rules as they pertain to vehicle deck design.

8.2 Current DNV Rules as they pertain to vehicle deck design.

8.3 Current Lloyd's of London Rules as they pertain to vehicle deck design.

8.4 ANSYS, INC. – ANSYS Professional v9.0, an internationally recognized general-purpose structural finite element analysis program.

8.5 Young, Warren C., "Rourke's Formulas for Stress and Strain", McGraw –Hill, Inc., Sixth Edition, 1989.

8.6 American Institute of Steel Construction, Inc. - (AISC) Manual of Steel Construction, 9 P

thP Edition - Working Stress Design (WSD), 1989.

8.7 AASHTO LRFD Bridge Design Specifications, U.S., 3rd Edition (2004).

8.8 "Guide for Uniform Laws and Relations Governing Truck Size and Weight Among the WASHTO States", Western Association of State Highway and Transportation Officials, January 2000.

8.9 Hughes, Owen, "Ship Structural Design", The Society of Naval Architects and Marine Engineers, 1988.

8.10 Technical and Research Bulletin No. 2-14, "Design of Deck Plating and Hatch Cover Plating for Fork Lift Truck Loading", The Society of Naval Architects and Marine Engineers.



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06-17 Importance of Fabrication and Detailing Submitted by: [BMT Fleet Technology Limited]

1.0 OBJECTIVE.

1.1. The objective of this project is to develop a guidebook on the importance and the identification of fabrication and detailing practice that will improve quality / reduce vessel life cycle costs.

2.0 BACKGROUND.

2.1 While design Engineers and Naval Architects are trained or have reference materials that support their efforts to preclude premature ship structural or mechanical degradation (e.g. fatigue, fracture, corrosion), this information may not be as readily available to shipyard workers, supervisors or inspectors. Where information is available, it tends to be presented in terms of workmanship rules which do not provide the user with an understanding of the underlying reason for the requirement and thus in some instances may be difficult to interpret or apply.

2.2 It is important for shipyard workers, supervisors or inspectors to understand the

effects of fabrication and detailing practice since a significant proportion of structural or mechanical component failures may be directly attributed to these issues. By better impressing the reasoning for and importance of fabrication and detailing on non-design personnel may result in better ship fabrication and maintenance quality by having another level of quality assurance in the ship design / production process.

2.3 With increases in demand for and turnover in shipyard workers, supervisors or

inspectors and increasing turnover, the proposed fabrication and detailing guide may be useful as an element of a training program to help develop qualified personnel for these jobs. This training could be developed by individual employers or could be presented as an SSC sponsored event such as the short course on Fatigue and Fracture in Ship Structures [ref 1].

3.0 REQUIREMENTS.


3.1.1 The Contractor shall ensure that the guide to fabrication and detailing quality relates workmanship / inspection criteria to the structural strength or degradation mechanisms they address and provides a technically sound description of these relationships that would be understood by laymen.

3.1.1 The Contractor shall ensure that the guide to fabrication and detailing

quality is complete in its coverage of ship production issues.


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3.1.3 The Contractor shall ensure that the guide is supported by a literature bibliography of related work.


3.2.1 It is proposed that the project could be completed with the following

tasks: 3.2.1.1 Define ship production tasks and degradation mechanisms or

strength deterioration modes (failure modes or limit states) of interest. - The intent of this task is to define the scope of the guide and should be the focus of the project kickoff meeting. It is suggested that the guidance document include the following, however this will be open to discussion with the Technical Committee:

Ship Production Tasks

Degradation Mechanisms & Failure Modes

- Material Quality - Fatigue & Fracture - Fitup and Surface Prep

- Corrosion

- Structural Details - Structural Yielding - Joining - Buckling - Coating Application - Excessive Deflection, etc…

3.2.1.2 Review class and military workmanship rules - This review will

produce a listing of general inspection requirements and these items will be grouped in terms of their rationale and the production tasks they impact. For example: - Work surface cleanliness can be related to weld faults (Joining task) and or lack of paint adhesion (Coating Application task)

- Limits on distortion (Material Quality or Joining tasks) can be related to residual stress, fatigue, buckling or other structural issues.

3.2.1.3 Develop inspection and guidance notes for each ship production task – The goal of this task is to develop pictorial, qualitative or semi-quantitative descriptions of the issues of concern for each ship production task covering issues such as:

1) Material Quality (Receiving Inspection / Handling and Storage) - Base Materials - Joining Consumables - Coating Products

4) Joining -Weld Faults - Structural Faults - Joining Sequence

2) Fit-Up and Preparation - Alignment - Surface preparation

5) Priming and Paint Application - Coating Types - Application Practice


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3) Structural Detailing - Structural Continuity - Connection Types - Drainage - Material Combinations

It is expected that this task will involved shipyard and class society consultation to support the development of the desired information.

3.2.1.4 Develop guide to fabrication and detailing quality – In this task the t notes and data collected for each task in the guide will be assembled into a consistent and cohesive guide suitable for training.

3.2.1.5 This task will be used to develop a brief overview of a training course that could be offered using the guide as its basis.

3.2.2 The Contractor shall keep the project technical committee and contracting authority informed of the progress of the project at least on a quarterly basis.

3.3 Project Timeline. . Task Description Q1 Q2 Q3 Q4

1 Define ship production tasks and faults

2 Review rules and develop rationale 3 Collect and summarize ship

production tasks

4 Assemble fabrication and detailing guide

5 Develop course syllabus


4.1 Standards for the Preparation and Publication of SSC Technical Reports 4.2 Most of the technical data required for this program is available in the public

domain or can be readily obtained from Class. Therefore no specific government furnished information is required.

5 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).


5.2 The Contractor shall provide a brief training course syllabus, outlining the content

of a training course that could be offered based upon the work compiled in this report will be submitted.


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5.3 The Contractor shall provide interim progress reports and hold a kick off meeting, interim progress meeting and a final project presentation




6.1 Project Initiation Date: Jan 2006. 6.2 Project Completion Date: 12 months from the date of award.



7.1 Project Duration: 12 months. 7.2 Project Man-hour: approx 400 7.3 Total Estimate: approx $50,000

8 REFERENCES.

8.1 BMT Fleet Technology Limited, “Short Course on Fatigue and Fracture in Ship Structures”, Prepared and presented on behalf of the US Ship Structure Committee.


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06-18 Machinery Mount and Foundation Design Submitted by: [BMT Fleet Technology Limited]

1.0 OBJECTIVE.

1.0 The objective of this project is to develop a guide on the design and analysis of machinery mounts and foundations.

2.0 BACKGROUND.

2.1 Improperly designed or installed machinery mounts and foundations can introduce vibration into surrounding structure resulting in issues from excessive noise to premature mechanical wear or fatigue failure. A significant proportion of failures on a ship are related to mechanical system vibration issues due to ill tuned systems operating near their natural frequency or inadequate isolation.

2.2 While a wide range of technical papers, supplier manuals and text books (e.g. ref 1 -

4) exist on the subject, the design of machinery foundations is commonly treated with a less scientific approach than hull structure design. A Structural Engineer or Naval Architect may be tasked with hull structural design and may consider fatigue issues, however, often machinery foundations are designed by draftsmen based upon past experience and rules of thumb.

3.0 REQUIREMENTS.


3.1.1 The scope of the proposed contract is not to develop new analysis techniques or software, rather, to collect and describe appropriate design and analysis techniques in a similar fashion to that completed for fatigue, damage tolerance and finite element modeling [ref 5-7].

3.1.1 The Contractor shall conduct a literature review defining machinery foundation types and design approaches.

3.1.2 The Contractor shall provide a glossary of terminology and sample applications of the design techniques to demonstrate concepts.

3.1.3 The Contractor shall ensure that the guide is supported by a literature bibliography of related work.


3.2.1 It is proposed that the project could be completed with the following tasks:

3.2.1.1 Perform literature review to assemble reference materials describing the state of practice in machinery mount and foundation and design. This information will


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be compared with existing design standards and rules of thumb.

3.2.1.2 Perform a review of existing machinery mount and foundation types, as well as, resilient mount and machinery installation techniques. This information will be used to identify typical machinery installation materials and characteristics.

3.2.1.3 Prepare complete and self consistent machinery mount and foundation design methodologies. It is suggested that several methodologies will be presented to support differing design objectives and levels of complexity. For example, handbook (rule of thumb or hand calculation) versus detailed numerical analysis techniques are envisaged. Different design and analysis techniques will be needed for different foundation types or different levels of isolation/noise control.

3.2.1.4 Prepare worked examples implementing the proposed analysis/design techniques for realistic machinery foundation scenarios.

3.2.1.5 Prepare a final report documenting the work completed in this project.

3.2.2 The Contractor shall keep the project technical committee and

contracting authority informed of the progress of the project at least on a quarterly basis.

3.3 Project Timeline.

Task Description Q1 Q2 Q3 Q4 1 State of design practice literature

review

2 Collect information on machinery installation techniques and materials

3 Develop deign and analysis techniques

4 Prepare and complete design examples

5 Prepare Final Report


4.1 Standards for the Preparation and Publication of SSC Technical Reports 4.2 Most of the technical data required for this program is available in the public

domain or can be readily obtained from Class. Therefore no specific government furnished information is required.


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5.2 The Contractor shall provide interim progress reports and hold a kick off meeting,

interim progress meeting and a final project presentation 5.3 The Contractor shall provide a print ready master final report and an electronic



6.1 Project Initiation Date: Jan 2006. 6.2 Project Completion Date: 12 months from the date of award.



7.1 Project Duration: 12 months. 7.2 Project Man-hour: approx 500 7.3 Total Estimate: approx $70,000

8 REFERENCES.

8.1 William Kauffmann, "Don't Gamble on Machinery Foundations", 2 pages – 1973 8.2 W.K. Newcomb, "Principles of Foundation Design for Engines & Compressors"

(Ingersoll-Rand), 7 pages – 1951 8.3 "Basic Vibration & Vibration Isolation Theory" by Unisor Machinery Installation

Systems, 11 pages - mid 1980s 8.4 Suresh Arya, Michael O'neill and George Pincus, "Design of Structures and

Foundations for Vibrating Machines," Published by Gulf Publishing Company, 1979, 1981. ISBN no. 0-87201-294-8. Library of Congress Catalog Card No. 78-56171.

8.5 Glen, et. al. “Fatigue Resistant Detail Design Guide for Ship Structures”, BMT Fleet Technology Limited for SSC, Report 405.

8.6 Glen, et. al. “Guide to Damage Tolerance Analysis of Marine Structures”, BMT Fleet Technology Limited for SSC, Report 409.

8.7 Basu, et. al, “Guidelines for Evaluation of Ship Structural Finite Element Analysis”, MIL Systems for SSC, Report 387.


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06-19 Significance of Constraint Effects on Fracture Resistance Design Submitted by: BMT Fleet Technology Ltd

1.0 OBJECTIVE.

1.1 Assess the level of conservatism of using standard 3-point bend fracture toughness data in membrane/tension loaded situations.

2.0 BACKGROUND.

2.1 Criteria for fracture-resistant design, damage tolerance and structural integrity analyses require laboratory-generated elastic-plastic fracture-toughness data from fracture-mechanics-based tests, e.g., J-integral or crack-tip opening displacement (CTOD). Such data is commonly available from standard “deep-notched” 3-point bend specimen geometries. Such geometry and loading result in high-constraint at the crack tip. By contrast, structural loading situations, in the presence of flaw, such as fatigue cracks, are often subjected to primarily membrane loading. The latter produces low constraint at the crack tip and therefore the “driving force” for crack extension is reduced compared to a high-constraint loading..

2.2 The above situation leads to conservative defect acceptance criteria when using

fracture-resistant design methodologies such the use of the failure assessment diagram (FAD). A reduction in the level of conservatism may reduce maintenance costs and system downtown. This study is proposed to examine the conservatism of using fracture toughness parameters from standard high-constraint, small-scale tests.

3.0 REQUIREMENTS.

3.1 Scope

3.1.1 To achieve the full intent of the project, it will be necessary for the Contractor to select material suitable for the testing program.

3.1.2 The Contractor will perform the necessary laboratory tests.

3.1.3 The Contractor will analyze the test results and compare them with elastic-

plastic defect assessment procedures to generate an understanding of the level of conservatism when using high-constraint fracture toughness data.


3.2.1 Task 1: A background document will be prepared highlighting the effects of constraint on fracture assessment procedures and methodologies for


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addressing constraint effects in both testing and elastic-plastic fracture mechanics criteria.

3.2.2 Task 2: The contractor shall review material property fracture toughness

data with the objective of selecting two materials for the program and design a test matrix. The materials used will be typical of those employed in ship structure applications. SSC members and steel manufacturers will be solicited for the materials.

3.2.3 Task 3: Fracture toughness specimens will be machined and testing will be

carried out on base metal in accordance with ASTM standards to generate high-constraint fracture toughness values. Testing will be completed at a singletwo test temperature and QS loading rate. CTOD values and J-resistance curves (for situations leading to ductile crack extension) will be obtained for the materials. 10 to 126 tests are planned for each material to ensure that the potential variability in fracture toughness is captured and evaluated in the project.

3.2.4 Task 4: A set of wide plate tests will be conducted using the same

materials to generate low-constraint fracture toughness values for comparison with the data generated in Task 3 using the same test temperatures and loading rates as the small-scale specimens. These tests will be more representative of a membrane dominated loading scenario in a large structure. A minimum of 6 tests will be conducted for each material to ensure that the potential variability in fracture toughness is captured and evaluated in the project.

3.2.5 Task 5: The fracture toughness values will be used to illustrate the relative

level of conservatism when using a high-constraint fracture toughness value with an elastic-plastic fracture assessment criteria (i.e. BS7910 Level 2 FAD).

3.2.6 Task 6: Restraint correction factors proposed by various standards will be

reviewed and the Task 5 results will be revisited to evaluate the performance of these factors.

3.3 Project Timeline.

3.3.1 The project will take approximately 9 months to complete from the date awarded.


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4.1 Final report from the contractor. 4.2 Material for the Preparation and Publication of SSC Technical Reports.

5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).


5.2 The Contractor shall provide a print ready master final report and an electronic copy,

including the above deliverables, formatted as per the SSC Report Style Manual.

5.3 The Contractor shall provide, if concluded to be necessary, the outline for the next Phase of the Program.





7.1 Project Duration: 9 months. 7.2 Project Man-hour: 650 7.3 Total Estimate: $55,000

8.0 REFERENCES.

8.1 Reference.

8.1.1 SR-1374 “A Guide to Damage Tolerance Analysis of Marine Structures,” 8.1.2 SR-1386 “Short Course on Fatigue and Fracture Analysis of Ship

Structures” 8.1.3 SR-1429 “Fracture Toughness of a Ship Structure.”


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06-20 Nondestructive Fracture Toughness Characterization of Grade A Steels

Submitted By: BMT Fleet Technology Limited 0.0 OBJECTIVE.

0.1 The objective of this project is to determine if fracture toughness properties for in-service Grade A materials can be estimated from nondestructive material characterization.

1.0 BACKGROUND.

1.1 Fracture control plans for welded structures such as ships usually call for, directly or indirectly, adequate resistance to crack propagation in the base material.

1.2 Much of the world’s commercial shipping fleet is built from steel grades without a toughness requirement. Many recent maritime disasters have resulted in catastrophic failures and these are most likely to cause loss of life or major pollution, as seen in the FLARE, the ERICA, and recently Lake Carling.

1.3 Some work on this area has been performed by Lloyds Register as reported in a publication that summarizes the Grade A steel from steel mills around the world do meet the requirements to avoid brittle fracture based on Charpy transition temperature. However, fast fracture still appears to take place.

1.4 Along with an understanding of the structural loads and structural configuration, a key element of damage tolerance analysis or defect criticality assessment is knowledge of the resistance of the materials to fracture expressed in terms of fracture toughness. Vessels having structural steels that do not meet toughness requirements would have a higher risk of brittle fracture events.

1.5 Removing samples to determine fracture toughness through destructive testing is expensive and may be impractical in many situations. The ability to quantify toughness properties nondestructively will enable engineers to ensure operational safety based on realistic material property data rather than using overly conservative estimates. The data will help in carrying out reliable fitness-for-purpose analyses of flaws found in service, and thus lead to cost-effective structural integrity maintenance practices.

2.0 REQUIREMENTS.

2.1 Scope.

2.1.1 The Contractor will collect samples of 20 Grade A steels and carry out the required testing program to generate the material properties to nondestructively characterize the materials. These properties include:


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• Microstructural information (pearlite volume fraction, grain size and inclusion content)

• Material hardness • Chemical composition

2.1.2 Base metal Fracture toughness testing will be performed for each of the 20 materials. Six tests will be conducted for each material to gauge the potential variability in the toughness properties. Testing will be conducted at one test temperature and one strain rate, which will be decided upon in conjunction with the project steering committee.

2.1.3 Trends between the material properties and fracture toughness values will be evaluated. Grade A steels data, if available, will also be sought from literature and similar trends between material properties and fracture toughness values will be sought.

2.1.4 The results will be documented in a final report. As a minimum the project will generate a materials property database for Grade A steels especially fracture toughness properties for the samples obtained.

2.2 Tasks.

2.2.1 Task 1 – Material Collection: The contractor will solicit SSC members, steel producers and shipyards to obtain 20 samples of Grade A steel.

2.2.2 Task 2 – Nondestructive Characterization: The material property testing program will be designed and implemented to obtain the nondestructively measured material properties.

2.2.3 Task 3 – Mechanical Testing: Tensile testing will be conducted to obtain the mechanical properties of the materials.

2.2.4 Task 4 – Fracture Toughness Testing: Fracture toughness testing will be carried out on each of the steel samples.

2.2.5 Task 5 – Data Correlation: Trends between the nondestructive material properties and the fracture toughness data will be investigated.

2.2.6 Task 6 – Reporting: The final report issued by the Contractor will include a database of the material property data and correlations.

2.3 Project Timeline. The project could be completed within one calendar year. Tasks 1 to 4 will be completed in the first eight months and Tasks 5 and 6 completed in the remaining four months.


4.1 Final Report. 4.2 Database of material properties.


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5.2 The Contractor shall provide a print ready master final report (paper copy and on

3.5” diskette or CD-ROM in MS Word format) including the above deliverables.

5.3 In the final report, the Contractor will identify any gaps in data correlations and propose a methodology for addressing these gaps if possible.


6.1 Project Initiation Date: As early as January 2006

6.2 Project Completion Date: 12 months from the date of award. 7 GOVERNMENT ESTIMATE. These contractor direct costs are based on previous





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06-21 Identification of Local And Global Modal Interactions In Stiffened Ship Panel Structures At Pre And Post-Buckled States

Submitted by

Ioannis T. Georgiou (*) Science Applications International Corporation (SAIC)

McLean, Virginia 22100

1.0 OBJECTIVE

1.1. The objective of this research effort is to compute and characterize systematically the physical mechanisms causing local and global interactions among buckling and vibration modes of stiffened plates under various combinations of boundary loads. In particular, it will be determined how the modal characteristics of vibration change as a state of buckling instability of a pre loaded configuration is approached when varying load parameters. These interactions will be extracted from finite element dynamics as changes of the modal characteristics of vibration and quantification of energy transfer among vibration and buckling modes.

1.2. To accomplish the above objective, the response of prototypical (1) rods and arches, and

(2) stiffened plate and shell structures compressed at their boundaries and specified interior points will be computed with high accuracy by nonlinear finite element algorithms. The high resolution finite element simulations will be processed by the method of Proper Orthogonal Decompositions for multi-field structural dynamics. This approach will allow the identification, from available numerical databases, of the mechanisms causing interaction among buckling and vibration modes of statically pre loaded stiffened structures.

2.0 BACKGROUND 2.1. Even in biological structures, we encounter stiffened structures with quite involved

geometric complexity. Stiffened plate and shell structures fail globally and locally, in not well understood complex ways, when loaded by boundary and interior forces that compress and shear them. Failures appear first as a local and/or global buckling instability of a static loaded configuration and then as plastic flow, or even total failure, like rapid or progressive fracture. Physically, the buckled modes originate as instabilities of statically preloaded (compressed globally or locally) states. Vibrations about pre and post buckled states are accompanied by strong interactions among the various displacement fields of a stiffened structure. This is so since the static deformed state couples by creating nonlinear geometric nonlinearities the deformation fields.

2.2. A lot of effort has been devoted to determine the physical mechanisms causing local and

global buckling in stiffened plates and shells. In some efforts, linear models are used.


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These modes have limited predictability. Several analytic methods, such as the hybrid modal / FT method [1] and [3], have been used to study stiffened structures in recent papers. Reference [6] deals with the dynamic instability of stiffened plates. It uses a finite element approach. The system is linear. Analytic methods deal with linearized systems and small nonlinear regular perturbations of the linear systems.

2.3. The study of nonlinear modal interaction of local and global instabilities is of

considerable significance for optimal design of plates and shells. The low order models, such as the linear ones and their small perturbations, have limited predictability. The statically compressed and sheared stiffened plate is a nonlinear coupled dynamical system. A realistic approach towards understanding dynamic interactions in stiffened structures, which have by design complex domains with complex geometry, is one that involves modeling methods of nonlinear mechanics, such as nonlinear finite elements, which Nonlinear finite elements have been used to study several important issues in stiffened plates. Interaction between the lateral buckling of a stiffener and the buckling of the plate is an important issue [2, 3]. Amplitude modulation is a key feature of interactive buckling [12]. Another important dynamic phenomenon in stiffened structures is localization of vibration. Vibration localization may be very harmful or beneficial. Ship decks are plates stiffened with stiffeners. The misplacement of stiffeners can cause vibration localization. How will vibration localization affect buckling in dynamic load?

2.4. The local and global interaction of buckling modes has been studied mostly for static

cases. The vibrations that will occur about the preloaded state must be analyzed by using a model that is fully nonlinear. The case that is of great interest is the case where the static load in the boundaries is not uniform. The static deformation will not be uniform. For this case we would like to explore the coupled vibrations that will start under a uniform later pressure, in pulse form, of sinusoidal form.

2.5. A preloaded stiffened paned is dynamical systems which is coupled and depending on

the magnitude of the boundary compressive and shearing forced may contain multiple unstable states. The dynamics are complicated in time and space. The dynamics may activate only a few degrees of freedom. The dynamics may be analyzed if the characteristics of these degrees of freedom are known. At this time no analytic method exists to compute these degrees of freedom. These degrees of freedom can be computed provided that we know the dynamics. Indeed, this is possible by employing a nonlinear finite element algorithm based on the modern theory of rational mechanics. There exist many commercial finite element codes that provided a very accurate simulation of the dynamics.

2.6. The method of Proper Orthogonal Decompositions has been recently advanced by the

author and co-workers to analyze the vibrations of arbitrary spatial nonlinear rods, shells, and 3D thick beams and blocks [18-26]. POD is a well known technique from the beginning of this century. It has been applied to many fields in engineering science. Recently it is being developed for modal analysis of coupled nonlinear structural dynamics.


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2.7. The POD method provides a systematical way to analyze the finite element

computational dynamics of nonlinear structures. The POD analysis could identify the normal modes of vibration of a nonlinear vibratory system.

2.8. One of the novel results about the technique of Proper Orthogonal Decomposition is the

fact, that from one finite element simulation, we can determine an optimum set of Proper Orthogonal Decomposition modes as well as their energy contend. These modes can be used to derive optimal reduced models. Under certain conditions, these modes coincide with the normal modes of vibration of the system. The use of POD to analyze finite element simulations is a current topic of intensive research.

The focus of this research recommendation is to determine how the interaction evolves dynamically as the bucking instability is approached. The interaction will be measured by the amount of energy that is transferred from some modes to other modes to form localized modes. Also it will be determined how the energy of the pre loaded configuration is gradually transferred to other modes. Such an understanding of energy transfer in modal interaction before instability onsets will be very useful. Measuring energy transfer can be used as a monitoring tool to determine when we are close to a buckling state. Impact of the this research recommendation: The nonlinear finite element analysis combined with the powerful data processing technique of POD will provide a systematic methodology that will give the necessary tools to better understand the genesis of buckled states in stiffened panes with any boundaries and any loads. A better understanding can be accomplished by the derivation of reduced models for stiffened plates of complex geometries. The reduced models can be obtained by presenting the dynamics with the POD modes. These modes are optimum. Thus the reduced models will be optimal. If the load on the boundaries is not uniform, the static deformation will no be uniform. There will be regions where we have localized stress concentration. This will involve some wave lengths. So the vibration that will be caused by time varying loads will cause complex interactions between different time scales. The processing of the dynamics with POD will give results about the coupling of vibrations. Motivating Example: POD reveals the interactions and energy transfer in pre compressed nonlinear rods Figure 1 show an elastic rod restricted to deform in the plane. The free dynamics of the rod is exited by a blast load distributed uniformly over the transverse direction. Figure 2 compares the distribution of the auto-correlation energy for the free dynamics with a zero compressing load and a non-zero compressing load. The remarkable result is that the compressed rod has a totally different “energy” distribution than the non compressed rod. This reveals the strong interaction of the first buckled state and the nonlinear vibration normal modes. Figure 3 reveals the energy transfer form the mode that will become unstable at the first buckling load. The dynamics is simulated with a high performance finite element code for geometrically exact nonlinear models for elastic rods.


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P

Figure 1 – A geometrically exact elastic rod compressed axially by a point load at the left boundary.

Figure 2 – Auto-correlation energy spectrum for a compressed (red) and non compressed geometrically exact elastic rod. Vertical axis: fraction of auto-correlation energy. Horizontal axis: number of POD mode in motion.


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3.1.3 The contractor shall address the issue of modal interactions of stiffened plates and shells at pre and post buckled static states from the point of view of nonlinear coupled dynamical systems by means of Proper Orthogonal Decomposition processing of high resolution finite element simulations.

3.2 Tasks

3.2.1 The vibrations of thin and thick straight rods and arches under compressive static loads will be computed by a finite element model, which is available, for geometrically exact rods. The vibrations about pre buckled and post buckled states will be analyzed by the method of Proper Orthogonal Decompositions. The geometrically exact rod will function as a prototypical system for the development of POD tools to analyze the computational dynamics of stiffened structures under compressive loads and moments. 3.2.2 Extra fine finite element models will be generated for a series of prototypical stiffened plate and shell structures with regular shapes (rectangular, circular, elliptic). The stiffeners will be arranged in elementary ways. For various simple and combined compressive loads, the vibrations caused by lateral blast loads and harmonic loads will be computed by a nonlinear finite element procedure. For this purpose the commercial code ABACUS, which is available, will be used. The modal structure of the vibrations about various pre loaded states will be determined systematically with the method of Proper Orthogonal Decompositions.

3.2.3 Extra fine finite element models will be generated for a series of prototypical


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6.0 PERIOD OF PERFORMANCE 6.1 Project Initiation Date: 10-1-2005

6.2 Project Completion Date: 3-31-2007

7.0 Time, Cost and Man-hour ESTIMATE These contractor direct costs are based on previous project participation expenses.

7.1.1. Project duration: 18 months 7.1.2. Projected man hour: 1453 7.1.3. Total Estimate: 99,999

8.0 REFERENCES [1] L. Ji, B. R. Mace, R. J., 2004, “A hybrid mode/Fourier-transform approach for estimating the vibrations of beam-stiffened plate systems,” Journal of Sound and Vibration 274 (2004) 547-565. [2] Wein-Wen, “Buckling behavior of stiffened laminated plates”, International Journal of Solids and Structures 39(2002), 3039-3055. [3] Long-yuan Li, “buckling of stiffened plates and design of stiffeners,” International Journal of Pres. Ves. & Piping 74 (1997), 177-187. [6] Srivastava, A.KL., Datta, P. K., and Sheikh, “Dynamic Instability of stiffened plates subjected to non-uniform harmonic in-plane edge loading,” Journal of Sound and Vibration 262 (2003) 1171-1189. [12] Srinivasan S., Zeggane, M., “Stiffened plates and cylindrical shells under interactive buckling,” Finite Elements in Analysis and Design 38 ( 2001) 155-178. Author and Co-worker Publications on Proper Orthogonal Decomposition in Structural Dynamics and Acoustics [18] Georgiou I.T., Sansour J. 1998. Analyzing the Finite Element Dynamics of Nonlinear in-plane rods by the method of Proper Orthogonal Decomposition. Computational Mechanics, New Trends and Applications, S. Idelshom, E. Onate and E. Dvorkin (Eds.), CIMNE, Barcelona, Spain.

[19] Georgiou I.T., Schwartz I.B. 1999. Dynamics of Large Scale Coupled Structural-Mechanical Systems: a Singular Perturbation - Proper Orthogonal Decomposition Approach, SIAM Journal on Applied Mathematics Vol 59: 1178-1207.

[20] Georgiou, I. T, 2005, “On Proper Orthogonal Decompositions for One-Dimensional Coupled Structural Dynamics: Characterization of Coupled Vibrations of Nonlinear Rods” (submitted)


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[21] Georgiou, I. T., 2004, “Advanced proper orthogonal decomposition tools: using reduced models to identify normal modes of oscillation and slow invariant manifolds in the dynamics of a nonlinear rod,” Journal of Nonlinear Dynamics (in print).

[22] Georgiou I.T., Papadopoulos C.I., Servis D.P., Applying Proper Orthogonal Decomposition Tools For Modal Identification Of Coupled Structural-Acoustic Dynamic Fields, Proceedings of the ASME / IMECE 2004 Congress, Anaheim, California, USA, November 13-19, 2004.

[23] Georgiou, I. T., 2004, “Identification of Normal Modes of Vibration of Coupled Infinite-Dimensional Systems,” Proceedings of Euromech 475 Colloquium on Normal Modes of Vibrating System, June 6-9, 2004, Frejus, France.

[24] Papadopoulos C.I., Georgiou I.T., “Proper Orthogonal Decomposition in the Frequency Domain to Characterize Coupled Structural-Acoustical Systems,” Submitted for presentation to the 3rd M.I.T. Conference on Computational Fluid and Solid Mechanics Cambridge, Massachusetts, USA, June 14 - 17, 2005, (Ed. K.J. Bathe).

[25] Georgiou I.T., Sansour C., “Characterizing the spatio-temporal complexity of forced vibrations of nonlinear planar rods,” Fifth EUROMECH Nonlinear Dynamics Conference (ENOC-2005), Eindhoven, The Netherlands, August 7-12, 2005

[26] Papadopoulos C.I., Georgiou I.T., “Proper orthogonal decomposition analysis towards spatio-spectral structural-acoustic field identification,” Accepted for presentation to the Sixth European Conference on Structural Dynamics (EURODYN 2005), Paris, France, September 4-7, 2005.

Optimization of Fatigue Life and Structural Performance of Marine Structures

Submitted by: Altair Engineering, Inc. 1.0 OBJECTIVE

1.1. The objective of this project is to study the impact of state-of-the-art structural design optimization technology of Altair® OptiStruct® [1] on 1.1.1. improving fatigue life of ship structure AND

1.1.2. improving ship’s structural performance such as overall longitudinal bending strength, WHILE

1.1.3. reducing ship’s weight

A design process based on OptiStruct technology can yield designs that are significantly better than those obtained using the FEA and optimization tools that are currently used in the marine industry.

2.0 BACKGROUND 2.1. Current Process. The design optimization processes currently used in the marine industry

can be classified into following two broad categories:

2.1.1. Design Verification. In this classification a design engineer would use technology such as Finite Element Analysis (FEA) to estimate structural performance. Improvements in performance are achieved by manually changing the design and verifying the performance improvement using FEA analysis. This process of trial-and-error is used within the allocated resources to obtain the best possible design. With this process, design improvements are limited by (i) available resources, especia lly time, and (ii) ability of engineers to develop design concepts.

2.1.2. Design Refinement using Optimization. In this classification a design engineer would start with an existing design and parameterize it using one or more tools. He would then use an FEA-based optimization tool for evaluating and improving the design iteratively by varying design parameters. A good enginer would use this process effectively by starting with multiple design concepts. This process essentially replaces the trial-and-error approach of the previous section with a software-driven mathematical optimization. It typically yields better results than those obtained using a trial-and-error process. The scope of this process is again limited by the (i) initial design concepts, (ii) design parameters that are set up, and to a lesser degree (iii) available resources.

2.2. OptiStruct Design Process. The OptiStruct design process adds a step of concept design generation to the design process outlined in Section 2.1.2. The details of the proposed process are as follows.

2.2.1. Concept Design Generation. This step involves generating design concept without an initial design. OptiStruct only needs (i) the definition of a package space, which is the physical volume that the design has the freedom to occupy, and (ii) the structural performance criteria such as structural stiffness and natural frequencies of vibration. Given these input, OptiStruct yields an optimized structural topology that can be used as a starting design concept. This is best explained using a simple example.

Consider a case where a structure will be simply supported at the two bottom corners of the rectangle, and has a single vertical load to support at the top of the rectangle (Figure 1a). The structure is allowed to occupy any part of the rectangle. For this design topology optimization yielded a design concept shown in Figure 1b. This is a truss structure that we know from years of engineering to be the best topology for carrying such loads. However, topology optimization gave this design starting with simply a rectangular design space; i.e. there was no initial design. One can now take this concept to create the starting design, and further refine it using size and shape optimization.

Figure 1a. Rectangular Design Space Figure 1b. Topology Design Concept

Figure 2. Design of an Airbus A380 leading nose droop edge rib

Optimization technology has helped design a wide range of products. Figure 2 shows a rib structure for Airbus A380 leading droop nose designed using the proposed design process [2]; i.e. (i) concept design, followed by (ii) design refinement. Figure 3 shows the hardware of a rib built. A total of 500 Kg mass savings was achieved for the 13 ribs (Figure 4) designed using OptiStruct.

Figure 3. Rib Prototype Figure 4. A380 Leading Droop Nose Ribs

2.3. OptiStruct History. The pioneering research in topology optimization came from Martin Bendsoe and Noboru Kikuchi [3]. It was expanded further by Alejandro Diaz and Noboru Kikuchi [4]. The technology was adopted and productized by Altair [5] as OptiStruct. It received Industry Week’s Technology of the Year Award in 1994 [6].

2.4. Why Fund This Project? Design engineers in many different industries have benefited immensely from the optimization technology of OptiStruct. It is used in designing minimum weight structures that satisfy the prescribed performance criteria. Alternately, it is used for enhancing structural performance while maintaining the mass of the structure. Many design engineers have achieved both the mass savings as well as performance enhancements by applying OptiStruct in designing their products.

The mathematics and physics of design problems are identical irrespective of the industry. Hence, marine industry can benefit the same way from OptiStruct as other industries have. At the same time, each industry brings its own unique engineering and business challenges. Those can be addressed only by attempting to solve challenging design problems. This project should be funded to benchmark application of OptiStruct in designing marine structures.

3.0 REQUIREMENTS 3.1. Scope . Applying new technologies to any industry poses its own unique challenges. Designs

in each industry are guided by many factors such as materials, manufacturing processes, robustness requirements, etc. The purpose of this research is to determine the potential benefits of using OptiStruct in designing marine structures. This will be done as follows.

3.1.1. Work With the Current Constraints. While OptiStruct often challenges the existing design and manufacturing processes, generally a class of design problems exists where OptiStruct can be used within the existing design guidelines. A significant mass savings and marked performance improvement can be achieved on those designs. The industry can start seeing immediate benefit of this technology without a major change in the design and manufacturing process. This is the minimum benefit of this project.

3.1.2. Stretch the Envelope. The marine industry has used available technical knowledge to establish effective guidelines and best practices for designing marine structures. In order to meet challenges of future, these guidelines and practices should remain dynamic and change as new knowledge and technologies are gained. It is not the

objective of this project to establish immediate changes to current best practices. The scope here will be limited to studying the feasibility of making such changes. This will be done by solving a set of design problems with a varying degree of deviation from the current design guidelines. Benefits of resulting designs will be evaluated against its impact on the existing processes. This task will answer some questions and raise some more, which may lead to further studies. This task will bring benefits that will range form immediate to long-term in timing.

3.2. This project will be divided into the following tasks.

3.2.1. Identify design problems . Contractor will identify a set of problems that are in line with the scope of project described in the previous section. We foresee choosing three problems:

a. A design problem that will not extensively affect the current manufacturing and design guidelines; e.g. structure that connects rudder to the hull.

b. A design problem that would bring some immediate benefits, and would lead to additional benefits by modifying the design process

c. A design problem that could lead to significant benefits by making changes in the design process

3.2.2. Define performance requirements. This step will involve:

a. Collecting the necessary geometry and/or finite element models b. Compiling load cases

c. Defining the scope of structural analysis

3.2.3. Establish baseline performances.

a. Build FE models for the existing designs

b. Perform structural analyses

c. Establish the baseline performance

3.2.4. Concept design generation a. Determine available package space and build the corresponding FE models

b. Set up and run OptiStruct to obtain design concepts

c. Interpret design concepts

3.2.5. Develop initial designs a. Create CAD models of the designs generated in the previous task

3.2.6. Refine the designs a. Build FE models for the new designs

b. Set up and run structural optimization to refine the designs c. Assess performance of the final design

3.2.7. Compare performance improvements a. Compare performances of optimized and baseline designs

b. Assess the impact of OptiStruct design process on the current design and manufacturing processes

3.2.8. Publish a report. This report will contain

a. comparison of performances of optimized and baseline designs b. a discussion on impact of OptiStruct design process on the existing best

practices

c. recommendations for future investigations

4.0 GOVERNMENT FURNISH INFORMATION 4.1. Standards for the Preparation and Publication of SSC Technical Reports.

5.0 DELIVERY REQUIREMENTS 5.1. The Contractor shall provide quarterly progress reports to the Project Technical Committee,

the Ship Structure Committee Executive Director, and the Contract Specialist. 5.2. The contractor shall provide a print ready master final report and an electronic copy,

including the above deliverables, formatted as per the SSC Report Style Manual.

6.0 PERIOD OF PERFORMANCE 6.1. Project Initiation Date: Within 2 weeks after the Date of Award 6.2. Project Completion Date: 6 months after project initiation

7.0 TIMIMNG COST AND MAN-HOUR ESTIMATE 7.1. Project Duration: 6 months

7.2. Project Man-hours: 1,200 7.3. Total Estimate: $120,000

8.0 REFERENCES 8.1. Altair OptiStruct: http://www.altair.com/software/hw_os.htm.

8.2. Application of Topology, sizing and shape optimization methods to optimal design of aircraft components http://www.uk.altair.com/press/a380_release.htm.

8.3. Bendsoe, M.P, Kikuchi N: Computer Methods in Applied Mechanics and Engineering; (1988).

8.4. Diaz A.R., Kikuchi N: International Journal of Numerical Methods in Engineering (1992).

8.5. Altair Engineering, Inc.: www.altair.com.

8.6. Industry Week; Technology & Innovation; 1994 Technologies of the Year; http://www.industryweek.com/research/techandinn/techprofiles94.asp.

9.0 JUSTIFICATION FOR SOLE SOURCING Altair Engineering, Inc. is uniquely qualified for executing this project. Altair has adopted this technology from its inception, and Altair continuously enhances the capability and functionality of OptiStruct. No other product offers the breadth and depth that compares with OptiStruct’s. Altair has limited experience in designing marine structures. Hence, Altair plans to team up with a leading ship design company, such as BMT, that will provide the necessary product knowledge and expertise.

Altair has also executed a large number of optimization projects in our Product Design Consulting Business Unit. We have a large pool of highly qualified design and CAE engineers who can apply this technology in a very efficient manner to any design problem. This will ensure that the project will be completed with the least possible cost to the sponsors of this project. Finally, Altair understands that there are always challenges of taking this technology to a new industry. We have done pioneering work using this technology in many industry; e.g. the Airbus example of Section 2.2.1. It is very important to have this understanding in order to execute this project.

In conclusion, Altair brings a combination of software, project execution and business expertise that no other company can equal. Combining this with a partner with the expertise in designing marine products would provide a truly unique qualification for executing this project. Hence, it will be appropriate to sole source this project to Altair.


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06-23 Reliability-Based Performance Assessment of Damaged Ships Submitted by: Dr. Paul E. Hess III (NSWCCD),

Dr. Yongchang Pu, Dr. Hoi-Sang Chan, and Professor Atilla Incecik University of Newcastle Upon Tyne,

Prof. Purnendu K. Das

Universities of Glasgow and Strathclyde,

1.0 OBJECTIVE.

1.1 The objective of the proposed research is to develop a reliability-based analysis procedure for determining survivability, recoverability and operability of damaged ships, adopting a systematic approach. The wave excitation loads will be predicted by a non-linear method. The experimental study will compare the results obtained from the prediction with those obtained from measurements. The ultimate hull girder strength of damaged ships will then be evaluated considering effects of horizontal bending moment and shear. The reliability of damaged ships will be estimated, and a reliability-based decision format will be developed for damaged ships.

2.0 BACKGROUND.

2.1 A large number of ship accidents continue to occur despite the advances in navigation systems. So it is very important to ensure an acceptable safety level for damaged ships. In 1995-2000, 1336 ships were lost, with 6.6 million gross tonnage cargo loss and 2727 people reported killed or missing (Lloyd’s Register, 2000).

Conventional design, assessing an adequate structural strength in intact condition, does not necessarily guarantee an acceptable safety margin in damaged conditions. However, when a ship is damaged the operators need to decide the immediate repair actions by evaluating the effects of the damage on the safety of the ship using residual strength assessment procedure. International Maritime Organization (IMO) has therefore proposed an amendment, which states: ‘All oil tankers of 5000 tonnes deadweight or more shall have prompt access to computerized, shore-based damage stability and residual structural strength calculation programs.’ Pioneer research work in this area has assessed: residual strength of damaged ships and offshore structures (Smith and Dow, 1981); simplified method for assessing residual strength of hull girders of damaged ships (Qi, et al 1999); use of the section modulus to indicate the residual strength of damaged ships (Wang, et al 2002). Other papers also discuss residual strength of damaged ships, but all these studied the ultimate vertical bending moment capacity without considering the effect of horizontal bending moment, and the torsion and critical load case were not evaluated. Hence, the assumption was that the worst load case was vertical bending moment, and that horizontal bending moment and torsion are negligible, which may only be valid for intact ships. The floating condition of a damaged ship is normally quite different from its intact condition, and the worst load case could be quite different from its intact condition, e.g. the most critical condition of a damaged Ro-Ro ship is in quartering seas (Chan, et al, 2001).


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This project will provide ship owners and operators with needed tools and processes for improved decision-making in the operation of conventional existing ships as well as lightweight, high-performance, littoral combat craft given degradation or damage to the ship structure. Damage mechanisms include collision, corrosion, fatigue cracking, and combat.

Recognizing the urgent need of this research, Office of Naval Research (ONR) has decided to partially sponsor the project since July 2004 for two years. The present project proposal is to apply for SSC sponsorship to complement ONR funding.

2.0 REQUIREMENTS.

2.1 Scope.

3.1.1 The Contractor shall conduct experimental investigation of wave-induced hydrodynamic loading on a damaged ship so that these results could be used to validate the theoretical model and to provide model uncertainties for reliability analysis.

3.1.2 The Contractor shall carry out reliability analysis of a damaged ship so this will form the basis for developing reliability-based decision-making procedure.

3.2 Tasks.

The major tasks proposed in this project are as follows:

3.2.1 Task 1: Experimental Investigation of wave-induced hydrodynamic loading on a damaged ship. Participants: UNew and NSWCCD; Time: 20 months

A segmented model of ships will be constructed. The model, which will have a damaged compartment, will be equipped with load and pressure gauges to measure global vertical and horizontal bending moment, shear forces and torsion at two stations, and local pressures inside the damaged compartment. The motion responses will be measured in six degrees of freedom with a Sellspot system. The model will be tested in a number of regular waves and irregular sea states.

Tools for predicting the hull girder loading of a damaged ship under asymmetric loading has been developed at University of Newcastle, but requires validation through measurements and improvement/enhancement. The experimental results will be correlated with those of theoretical models, which are developed in the project sponsored by ONR. In addition the model uncertainty, which is defined as the ratio of experimental results to predicted results, of the numerical method will be calculated.

As pointed out in the previous sections, the worst load case of a damaged ship could be quite different from its intact condition. The most critical load case will be determined through proper strength assessment, which is one of the main tasks in Task 2. The results of the model uncertainty and the different load scenarios will be passed on to the


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University of Glasgow & Strathclyde team for strength assessment and reliability calculation.

3.2.2 Task 2: Reliability analysis of damaged ships Participants: UG&S and NSWCCD; Time: 20 months

Prediction of ultimate strength of damaged ships will be assessed by using a two-dimensional method (Smith and Dow, 1981), which provides reasonably accurate results and is suitable for being integrated in reliability analysis (ISSC,1997). As pointed out in the previous section, the existing studies neglect the effects of horizontal bending moment and torsion on the ultimate vertical bending capacity. In the proposed work, the effects of horizontal bending moment, shear forces, torsion and lateral load on vertical bending moment will be assessed. The cross-section of a ship will be divided into many elements, such as stiffened panels, unstiffened panels. The progressive loss of stiffness caused by buckling and post-buckling load-reduction in elements can be considered. The curvature of the hull girder is applied incrementally. For each increment, the corresponding strains in all the elements are calculated under the assumption that the cross-section plane will remain plane. The stress in each element will then be calculated from the stress-strain relation, which is predicted in advance by a non-linear analysis (Dow, 1980). The increment of bending moment of the cross-section can be obtained by integrating the stresses of all elements. In this way, the bending moment-curvature relationship of the cross-section is established. So the ultimate strength (maximum bending moment) of the cross-section is obtained.

When Smith’s method is applied to damaged ships, the damaged part of the ship is normally assumed being fully cut off. This simplified way to consider the effects of damage is quite conservative. To investigate the accuracy of Smith’s method in this case, a full non-linear explicit finite element code, ANSYS LS-DYNA, will be used to predict the extent of damage in a collision. The effects of assumed failure strain, friction coefficient, loading condition and the forward speed of the striking speed on the collision damage will be investigated. On the top of this analysis, another non-linear finite element analysis will be applied to predict the ultimate strength of the hull girder with the extent of damage determined in the above non-linear collision analysis. The results will be compared with Smith’s method.

The ultimate strength of hull girder will be compared with the extreme hull girder loads, which are predicted in Task 1, so that the safety margin for each load conditions can be evaluated, and the most critical load case can be determined.

A simulation-based reliability method and Smith’s method for predicting ultimate strength of hull girder will be integrated. Reliability of a damaged ship will be predicted.

3.2.3 Task 3: Write final report Participants: UNew, UG&S and NSWCCD; Time: 4 months


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4.1 Final Report Style Manual. See Enclosure (2). 5.0 DELIVERY REQUIREMENTS.


5.2 The Contractor shall provide a print ready master final report and an electronic copy, formatted as per the SSC Report Style Manual. In the report, the details of experimental results and their correlation with theoretical results shall be included. In addition the reliability of the damaged ship shall be reported.



3.2 Project Completion Date: 24 months from the date of award. 4.0 GOVERNMENT ESTIMATE.


4.2 Total Estimate: $US 100,000.

5.0 REFERENCES. Chan, H.S. (1992). Dynamic structural responses of a mono-hull vessel to regular waves. International Shipbuilding Progress 39, 287-315. Chan, H.S. (1993). Prediction of motion and wave loads of twin-hull ships. Marine Structures 6, 75-102. Chan, H.S. (1995). On the calculation of ship motions and wave loads of high-speed catamaran. International Shipbuilding Progress 42, 181-195. Chan, H.S., Incecik, A. and Atlar, M. (2001). Structural Integrity of a Damaged Ro-Ro Vessel. Proceedings of the second international conference on collision and grounding of ships, Technical University of Denmark, Lybgby, pp. 253-258.


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Das, P.K. and Dow, R. (2000). Hull Girder Reliability of a Naval Ship under Extreme Load, Journal of Ship Technology Research, Vol. 47, Germany, pp.186-196. Das, P.K., Mansour, A., Chen, H.H. and Spencer, J.(1997). A Deterministic and Probabilistic Fatigue Analysis of a Bulk Carrier Structure. Paper presented at OMAE 97 Conference, Yokohama, Japan, April. Das, P.K. and Zheng, Y. (2000). Cumulative Formation of Response Surface and its use in Reliability Analysis, Jnl of Probabilistic Engineering Mechanics, vol. 15, issue 4, pp309-315, Oct. Dow, R.S. (1980). N106C: A computer program for elasto-plastic, large deflection buckling and post-buckling behaviour of plane frames and stiffened panels. AMTE(S) R80726. Downes, J. and Pu, Y. (2002). Reliability Analysis of the Ultimate Hull Girder Strength of High Speed Craft. 1st International ASRANet Colloquium, 8-10th July 2002. Ferry-Borges, J. and Castenheta, M. (1971). Structural safety. Laboratoria Nacional de Engenhera Civil, Lisbon. Incecik, A. and Pu, Y. (2001). Deterministic and Probabilistic Assessment of FPSO Hull Girder Strength. the Eighth International Symposium on Practical Design of Ships and Other Floating Structures, Shanghai, China, September 16-21. ISSC, 1997. Ultimate Strength. Report of Committee III.1, International Ships and Offshore Structures Congress. Lloyd’s Register, 2000: World Casualty Statistics: annual statistical summary of reported loses and disposals of propelled sea-going merchant ships of not less than 100 GT. Maerli, A., Das, P.K. and Smith, S. (2000). A Rationalisation of Failure Surface Equation for the Reliability Analysis of FPSO Structures. Intl Shipbuilding Progress, vol. 47, no. 450, July 2000, pp215-225. Morandi, A.C., Das, P.K. and Faulkner, D. (1996). Finite Element Analysis and Reliability Based Design of Externally Pressurised Ring Stiffened Cylinders. Transactions of The Royal Institute of Naval Architects (RINA) Part B, vol. 138. Pu, Y., Das, P.K. and Faulkner, D. (1996). Structural system reliability analysis of SWATH ships. Engineering Structures, Vol. 18, No. 12, pp. 901-905. Pu, Y., Das, P.K. and Faulkner, D. (1997). Ultimate compression strength and probabilistic analysis of stiffened plates. Journal of Offshore Mechanics and Arctic Engineering, Vol. 119, No.4, pp. 270-275


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Pu, Y. Aryawan, I., Chan, H.S., Dunce, D., Mackie, G. and Incecik, A. (1998). Development of Generalised Design Methodology for Hull Girder Strength Assessment of Monohull FPSOs/FSUs’, final report for SHELL UK Exploration and Production, Nov., Qi, Enrong; Cui, Weicheng; Peng, Xingning; Xu, Xiangdong. (1999). Reliability assessment of ship residual strength after collision and grounding. Chuan Bo Li Xue/Journal of Ship Mechanics, v 3, n 5, (1999), p 40-46. Smith, C. and Dow, R., 1981. Residual Strength of Damaged Steel Ships and Offshore Structures. Journal of Constructional Steel Research, Vol. 1, No. 4, September. Wang, Ge; Chen, Yongjun; Zhang, Hanqing; Peng, Hua. ( 2002). Longitudinal strength of ships with accidental damages. Marine Structures, v 15, n 2, 2002, p 119-138.

6.0 SUGGESTED CONTRACTING STRATEGY.

9.1 The project is preferred to be contracted directly with individual members of the consortium separately.


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06-24 Fracture Toughness of Marine Steels at Various Loading Rates Submitted by: Harold S. Reemsnyder

2.0 OBJECTIVE.

2.1. Develop a database for the fracture toughness at various loading rates of base metal, weld-metal, and heat-affected-zones of marine structural steels to be used in the damage tolerance analysis of marine structures.

3.0 BACKGROUND.

3.1. The assessment of structural reliability will be enhanced through the use of fracture-mechanics-based analysis that recognizes the reserves of elastic-plastic fracture toughness that exist in materials after fatigue crack initiation and the effects of loading rate on toughness. Conservatism in design and material selection can be reduced through better knowledge of material properties.

3.2. The value of performing damage tolerance analysis in developing a cost effective

maintenance strategy or in determining a safe course of action once a flaw has been discovered in a ship structure is recognized. Criteria for fracture-resistant design, fatigue-damage repair, and damage tolerance and structural integrity analyses require laboratory-generated elastic-plastic fracture-toughness data from fracture-mechanics-based tests, e.g., J-integral or crack-tip opening displacement (CTOD). Such data, gathered over a range of temperatures, loading rates typical of marine service, thickness, chemistries, thermo-mechanical processing, and welding parameters for marine steels, will serve as input to “SSC 409 Guide to Damage Tolerance Analysis of Marine Structures” and “SSC 430 Fracture Toughness of a Ship Structure.” A previous project, SSC-352 Marine Structural Steel Toughness Data Bank, focused on the development of a data bank that included the then-available (1990) values of Charpy V-notch impact energy, critical initiation (JIc), nil-ductility transition temperature (NDTT), and dynamic tear (DT) energies for 12 structural steels. However, these data, by themselves, are of limited value for quantitative damage tolerance and structural integrity analyses. Such analyses require more general elastic-plastic fracture-toughness data such as the J-integral (not limited to plane-strain fracture toughness) or Crack-Tip Opening Displacement (CTOD).

3.3. To achieve the full intent of the project, it will be necessary to define and gather the

available fracture toughness data and identify gaps in that data to be filled by future fracture toughness testing. Strain rates for so-called quasi-static fracture tests can vary from 10-6 to 10-3 sec-1. Strain rates up to at least 10-2 sec-1 (typical of ship slamming) are possible with conventional closed-loop test systems and some might be able to achieve 10-1 sec-1. At strain rates on the order of 1 to 10 sec-1, typical of ship collision and shock, many correlations between fracture toughness tests and impact tests, e.g., Charpy V-notch, Drop Weight, etc., have been proposed and , after examination, might prove to be applicable. This work would also aim to complement but not duplicate other parallel programs. The assessment of structural reliability will be enhanced through the use of


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fracture-mechanics-based analysis that recognizes the reserves of elastic-plastic fracture toughness that exist in materials after crack initiation. Conservatism in design and material selection can be reduced through better knowledge of material properties.

4.0 REQUIREMENTS.

4.1. Scope. To achieve the full intent of the project, it will be necessary for the Contractor to gather the available fracture toughness data, at all loading rates, for marine steels and identify the gaps in that data.

4.1.1. This work would also aim to complement but not duplicate other parallel

programs.

4.2. Tasks.

4.2.1. Task 1 The Contractor shall investigate the data bank SSC-352 “Marine Structural Steel Toughness Data Bank,” and determine the applicability of those data to a load-rate-dependent fracture-mechanics-based damage tolerance analyses.

4.2.2. Task 2 The Contractor shall gather available fracture toughness data for base

metal, weld-metal, and heat-affected-zones of marine and similar steels that are not included in SSC-352. It is essential to establish the load-rates at which these data were determined. The first priority is applicable base plate and whole weldment data.

4.2.3. Task 3 The Contractor shall organize the available fracture toughness data for

base metal, weld-metal, and heat-affected-zones of marine steels as input to SSC-402 “Guide to Damage Tolerance Analysis of Marine Structures.”

4.2.4. Task 4 The Contractor shall identify the data needed to fill in gaps, e.g.,

grades, loading rates, thickness, welding processes and parameters.

4.3. Project Timeline. See Enclosure (x). 5.0 GOVERNMENT FURNISHED INFORMATION.

5.1.Final Report Style Manual. 6.0 DELIVERY REQUIREMENTS.

6.1. The Contractor shall provide quarterly progress reports to the Project Technical Committee, the Ship Structure Committee Executive Director, and the Contract Specialist.


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6.2. The Contractor shall provide a print ready master final report (paper copy and on 3.5” diskette or CD-ROM in MS Word format) including the above deliverables formatted as per the Final Report Style Manual.



6.2 Project Completion Date: 12 months from the date of award. 8.0 GOVERNMENT ESTIMATE. These contractor direct costs are based on previous project

participation expenses.


7.2 Total Estimate: $83,000.

7.2.1. 1100 labor hours.

8.0 SOLE SOURCE JUSTIFICATION INFORMATION.

8.1 Company Selected for Sole Source Contract Award. Fleet Technology Limited

8.2 Basis for Sole Source Contract Award.

8.2.1 BMT-Fleet Technology Limited has demonstrated their high level of professionalism and competence to assemble, synthesize, analyze, and present fatigue and fracture data in previous Ship Structure Committee Projects SR-1358 “Optimized Design Parameters for Welded TMCP Steels,” SR-1374 “A Guide to Damage Tolerance Analysis of Marine Structures,” SR-1386 “Short Course on Fatigue and Fracture Analysis of Ship Structures” and “Fatigue Resistant Detail Design Guide for Ship Structures,” SR-1384 “Crack-Arrest Toughness of Steel Weldments,” and SR-1429 “Fracture Toughness of a Ship Structure.”

9.0 Suggested Contracting Strategy. Enclosures: (1) Project Timeline (2) Final Report Style Manual (3) Independent Government Cost Estimate


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06-25 Quantification of Peening Effect - Can it be Accounted for in Design

Submitted By: [BMT Fleet Technology Ltd.]

1.0 OBJECTIVE.

1.1 Estimation of the Fatigue life Improvement by Hammer Peening on typical welded details. Is the life Improvement factor detail specific or generic?

2.0 BACKGROUND.

2.1 Weld fatigue life improvement techniques have been successfully applied in several industries. While there has been increasing interest in the application of such techniques to ship structures, at present there is a lack of guidance on the use of such techniques for design, construction and repair. Hammer peening has been considered to provide effective, repeatable benefits and significant performance improvements are possible for poor quality welds. 2.2 Hammer peening has been used with success for repairing side shell longitudinal/web frame connections on TAPS tankers where earlier fatigue cracking proved to be very expensive to repair on an annual basis. The design of the connections in the tanks at mid ships were modified, while hammer peening treatments were applied to the brackets elsewhere. It has been reported that the hammer peened connections have not experienced any cracking in three years whereas previously the cracking was occurring every year. Moreover, the hammer peening of a joint was reported to be ten times less expensive than the modified design. In an earlier SSC project (SSC -400/SR-1379), " Weld Detail Fatigue Life Improvement Techniques" a key recommendation was to perform systematic fatigue tests on standard details to which fatigue life improvement techniques have been applied and generate SN curves that can be used along side 'standard' SN curves. This exercise will allow us to determine whether LIF is detail specific or a general factor can be obtained for design usage.

3.0 REQUIREMENTS.

3.1 Scope 3.1.1 The Contractor shall identify and manufacture standard welded details. 3.1.2 The Contractor shall establish an experimental program where welds will

be hammer peened and fatigue tested to quantify the effect of hammer peening on fatigue life and compare the LIF of different welded details.


3.2.1 The Contractor shall identify the standard welded details.


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3.2.2 The Contractor shall establish fatigue life of the standard welded details.The contractor shall hammer peen the welded details and carry out fatigue tests to establish fatigue life. 3.2.3 The contractor shall evaluate the fatigue life improvement of each welded detail. 3.2.4 The contractor shall evaluate whether the life improvement factor can be generalized and accounted for in design calculations.

3.3 Project Timeline. 18 months


4.1 Final Report Style Manual. 5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).

5.1 The Contractor shall provide quarterly progress reports to the Project Technical Committee, the Ship Structure Committee Executive Director, and the Contract Specialist. 5.2 The Contractor shall document the standard welded details and the hammer peening procedure used 5.3 The contractor shall provide an assessment of the hammer peening procedure on fatigue life of different details and evaluate the feasibility of using the life improvement factors in design calculations. 5.4 The Contractor shall provide a print ready master final report (paper copy and on 3.5” diskette or CD-ROM in MS Word format) including the above deliverables formatted as per the Final Report Style Manual.


6.1 Project Initiation Date: date of contract award. 6.2 Project Completion Date: 18 months from the date of award.

7.0 GOVERNMENT ESTIMATE. These contractor direct costs are based on previous project participation expenses.

7.1 Project Duration: 18 months from the contract award. 7.2 Total Estimate: $ 130K

8.0 REFERENCES.


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06-26 Shakedown Of Residual Stresses During The Service Life Of A Ship Structure Welded Detail

Submitted By: BMT Fleet Technology Limited 1.0 OBJECTIVE.

1.1 The objective of the current program is to evaluate the relaxation (shakedown) of residual stresses in typical welded details in ship structures due to mechanical loading.

2.0 BACKGROUND.

2.1 Fatigue and fracture assessment standards or guides, such as BS 7910, recommend if the residual stresses are unknown for a welded detail then a residual stress of yield order magnitude should be assumed while carrying out fatigue and fracture evaluations. Residual stress measurements are not typically carried out either during ship fabrication or during its service life. Therefore, whenever there is a need to carry out damage tolerance analysis it is conservatively assumed that yield level residual stresses are present at the welded details.

2.2 The residual stresses may relax with time depending upon the magnitude and frequency of the applied loading. Therefore, as structures age the magnitude of residual stress remaining should decrease. It may be very conservative to assume the yield level residual stress and thus in many cases severely underestimate the life of a component and may result in undertaking unnecessary and costly maintenance initiatives.

3.0 REQUIREMENTS.

3.1 Scope.

3.1.1 The Contractor will carry out a literature review to collect data on residual stresses measured on typical welded connections (butt welds, fillet welds). Efforts will also be made to collect the residual stress data, if any, on ship structure details.

3.1.2 Literature Review will also be carried out to collect information on the relaxation of residual stresses with time due to cyclic loading.

3.1.3 If enough information on the magnitude of residual stresses is not available including the residual stress relaxation rates then a small experimental program will be carried out where up to three typical connections will be fabricated. The initial residual stresses will be measured. Fatigue testing will be carried out and residual stresses will be measured at the same locations at predetermined intervals, thus obtaining residual stresses relaxation curves for three connections each subjected to up to three different loading conditions.


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3.1.4 Analysis of the experimental results, numerical modeling and data collected from the literature will be used to develop a guidance note indicating reasonable means of considering variations in residual stress levels through the life of a ship structural detail when carrying out fracture evaluation. These techniques will be demonstrated through examples.

3.1.5 The results will be documented in a final report that could be used to support the existing fatigue design or fracture analysis manuals.

3.2 Tasks.

3.2.1 Task 1 – Literature Review: The Contractor will carry out a literature search and collect data on the magnitude of residual stresses and their relaxation during fatigue cycling.

3.2.2 Task 2 – Experimental Program: An experimental program will be developed that will include details of the simple welded connections that will be fabricated, welding procedures will be established, magnitude of loadings will be determined, and when and how to carry out the residual stresses will be established.

3.2.3 Task 3 – Fatigue Testing and Residual stresses Measurement: Fatigue testing of the welded connections will be carried out and residual stresses will be measured at the weld toes before and during the fatigue test at predetermined intervals.

3.1.4 Task 4 – Data Analysis: Fatigue testing data and the residual stress relaxation data will be evaluated. The focus of the analysis would be to evaluate whether a generalized procedure could be established so that if the approximate load history seen by a welded connection is known then a percentage of residual stress may have relaxed.

3.1.5 Task 5 – Reporting: The final report issued by the Contractor will include the results of the literature search, experimental program, data evaluation and a discussion on the impact of the initial residual stresses and their subsequent relaxation on fracture evaluation. Guidance will be provided on how to use this information for carrying out damage tolerance evaluation on ship structural details. The techniques developed in this project will be demonstrated through examples.

3.2 Project Timeline. The project could be completed within one calendar year. A breakdown of task durations would see Tasks 1 and 2 being completed in the first five months and Tasks 3 and 4 being completed in the second five months, leaving 2 months for reporting and review by the Technical Committee.


4.1 Final Report.


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5.2 The Contractor shall provide a draft outline of the final report for review. This outline will be used to indicate the scope and content of the report and be open to comment from the project technical committee.

5.3 The Contractor shall provide a print ready master final report (paper copy and on 3.5” diskette or CD-ROM in MS Word format) including the above deliverables.

5.4 In the final report, the Contractor will identify any gaps in the analysis and identify any further work that can be undertaken to address the gaps.


6.1 Project Initiation Date: date of the contract award.

6.2 Project Completion Date: 126

.


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06-27 Estimation of Through Thickness Stress Profiles and Peak Stresses from Shell Element FE Models (SSC)

Submitted By: BMT Fleet Technology Limited

1.0 OBJECTIVE.

1.1 Normally the determination of through thickness stress profiles and peak stresses is accomplished using detailed refined mesh FEA models with brick elements. The scope of this project will investigate the practicality of obtaining approximations of the stress profiles using shell elements without the need for detailed brick element submodeling. This approach could simplify the stress analysis required for stress-life, strain-life and fracture mechanics based fatigue life assessments for ship structures.

2.0 BACKGROUND.

2.1 If a family of hot spot stress versus fatigue life curves is available, hot spot stresses typically generated from FE models can be used in a manner similar to traditional S-N data to predict the fatigue life of a weldment. Unfortunately, data of this form is not readily available and difficult to generate. Additionally, hot spot stress is not applicable for other methods of fatigue life estimation, including strain-life and fracture mechanics based crack growth methods.

2.2 Peak stresses are often required for fatigue evaluation at the weld toe or weld root location. Peak stresses are generally comprised of membrane and bending stress components which cannot be obtained directly from shell element models in regions of local discontinuities like welded connections.

2.3 Estimation of the peak stress components from hot spot stresses is theoretically possible provided membrane and bending component stress concentration factors can be obtained to relate hot spot and peak stresses in the form of:

Membrane: mpeakm

t hsm

Kσσ

=

Bending : bpeakb

t hsb

Kσσ

=

2.4 The peak stress can then be estimated using the equation:

m m b bpeak hs t hs tK Kσ σ σ= +

3.0 REQUIREMENTS.

3.1 Scope.


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3.1.1 The Contractor will collect existing data and information for typical stress concentration factor solutions for the toe and/or root of various weld geometries.

3.1.2 Procedures will be developed to obtain peak stress estimates from hot spot

stresses for typical weldments. 3.1.3 The results will be documented in a final report which could be

incorporated into an existing fatigue design manual.

3.2 Tasks.

3.2.1 Task 1 - Literature / Data Collection and Review: The Contractor will gather publicly available information on membrane and bending stress concentration factor solutions for typical weldments and identify gaps in available data.

3.2.2 Task 2 – Generation of Stress Concentration Factors Database: The

information collected in Task 1 will be compiled into a database for use in this and future projects or incorporation into a fatigue design manual.

3.2.3 Task 3 – FE Modeling of Weldments: A series of shell element FE models

and 3D brick models will be generated for a set of typical structural details. The shell element models will be used to determine the hot spot stress membrane and bending components and the 3D models to determine the peak membrane and bending components.

3.2.4 Task 4 –Development of the Hot Spot Stress to Peak Stress Relationship:

The Contractor will use the results from Tasks 2 and 3 to generate a conversion methodology from hot spot stress components to peak stress components.

3.2.5 Task 5 – Reporting: The final report issued by the Contractor will include

the database of stress concentration factor solutions and instructions for converting between hot spot and peak stresses for typical weld geometries.

3.3 Project Timeline. The project could be completed within on calendar year. A

breakdown of task durations would see Tasks 1 and 2 being completed in the first four months and Tasks 3 and 4 being completed in the remaining eight months.


6.1 Final Report. 7.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).


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7.2 The Contractor shall provide a draft outline of the Guide for review prior to its

assembly. This outline will be used to indicate the scope and content of the guide and be open to comment from the project technical committee.

7.3 The Contractor shall provide a print ready master final report (paper copy and on 3.5”

diskette or CD-ROM in MS Word format) including the above deliverables.

7.4 In the final report, the Contractor will identify any gaps in available stress concentration factor solutions discovered during the literature review and propose a methodology for addressing these gaps.








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06-28 Response of Ship Structure Containing Cracks: Load vs.

Displacement Control Submitted By: BMT Fleet Technology Limited

1.0 OBJECTIVE. 1.1 The determination of local stresses in a structural detail of a ship is generally

accomplished using a submodeling approach in a linear-elastic finite element analysis (FEA). The complexity of the ship structure prevents the inclusion of all details of the structural geometry in the global FE model. Normally, stiffeners are represented using beam elements and openings are represented as rectangles even though they may actually have rounded edges to reduce stress concentrations. It is also impossible to use a mesh refinement detailed enough to generate accurate local stresses. A typical submodeling approach will work well to identify the local stresses in an undamaged structure, however, the introduction of cracks into an analysis can lead to problems in fatigue and fracture analysis depending upon whether the structure is under load or displacement control.

2.0 BACKGROUND.

2.1 The typical approach to submodeling uses a coarsely meshed global model to generate the local displacement response surrounding a detail from a load scenario applied to the global model. Displacements in the vicinity of the local detail of interested are then interpolated to the edges of a more refined submodel containing the necessary mesh refinement and structural detail to accurately identify the stress state.

2.2 The submodeling approach works well if the goal is just to identify the local stress state to determine the potential for crack initiation. However, if the goal is to determine the potential for crack growth and final fracture the submodeling approach may be inadequate in a redundant structure containing multiple load paths.

2.3 A previous project for the SSC (SR-1430, BMT Report 5359C-FR) identified the potential problem of using the typical submodeling approach when attempting to determine the stress intensity factor (SIF) solution for cracks introduced into local details. If the global model is not large enough and/or does not incorporate a crack then the local displacement field surrounding the detail where the crack is introduced may result in an underestimate of the SIF in a submodel containing the crack.


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2.4 Most handbook and weight function SIF solutions for cracks have as an underlying assumption that the cracked member is subjected to load control. The submodeling approach described above inherently results in the assumption that the detail is displacement controlled. The local crack tip stress intensity will be lower under a displacement controlled scenario than a load controlled scenario and as a result a non-conservative SIF may be estimated from the standard FEA submodeling approach.

2.5 On the opposite side of the spectrum, the standard SIF solutions generally assume that the cracked component is a single load path (i.e. load controlled) and do not account for redundancies elsewhere in the structure that may lead to load shedding under a local displacement controlled situation (i.e. multiple stiffeners sharing a load in a ship structure subjected to displacement controlled bending). In such cases, a load controlled assumption in a crack analysis can generate overly conservative SIF estimates and lead to shut down and maintenance sooner than actually required.

2.6 Some handbook correction factors do exist to attempt to correct for load versus displacement control in structures and guidance is also given in many references to try to reduce the impact of load vs. displacement controlled assumptions. However, the results of SR-1430 indicated that the handbook corrections do not always work as proposed.

2.7 An analysis of typical ship structures and local details is required to determine whether the load control or displacement control modeling assumptions are required to more accurately characterize the SIF solutions for fatigue crack and fracture analysis.

3.0 REQUIREMENTS.

3.1 Scope.

3.1.1 The Contractor will generate two global structural models (not full ship structures, but large sections) and consider a hog or sag load scenario for the structures, with (without crack tip elements) and without cracks.

3.1.2 Local submodels with cracks (incorporating crack tip elements) will be used to assess the impact of inclusion or exclusion of the crack in the global model.

3.1.3 Guidance on appropriate submodel sizes to reduce edge effects influencing the crack tip stress will also be provided.

3.1.4 The results will be documented in a final report which could be incorporated into an existing fatigue design or fracture analysis manual.


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3.2 Tasks.

3.2.1 Task 1 – Global Model Development: The Contractor will generate two global structural geometry models with and without cracks and subject the models to a hypothetical hog or sag load.

3.2.2 Task 2 – Submodel Development: Submodels will be developed for at least three locations in each structure. For each submodel location, two crack sizes and two modifications to the submodel dimensions will be considered for a total of 24 submodels.

3.2.2 Task 3 – Analysis of Submodel SIF Estimates: The 24 submodels will be used to generate SIF estimates for each global model/submodel configuration to determine the impact of each of the modeling variables.

3.2.3 Task 4 – Re-evaluation of Weight Function Solutions: A re-evaluation of the results based upon the weight function solutions generated in SR-1430 will be undertaken in light of the new information gathered.

3.2.4 Task 5 – Reporting: The final report issued by the Contractor will include the results of all modeling and a discussion of the impact of the various global model/submodel assumptions to provide appropriate guidance for generating SIF’s for ship structural details.

3.3 Project Timeline. The project could be completed within on calendar year. A breakdown of task durations would see Tasks 1 and 2 being completed in the first five months and Tasks 3 and 4 being completed in the second five months, leaving 2 months for reporting and review by the Technical Committee.


4.1 Final Report. 5.0 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).


5.2 The Contractor shall provide a draft outline of the final report for review. This outline will be used to indicate the scope and content of the report and be open to comment from the project technical committee.

5.3 The Contractor shall provide a print ready master final report (paper copy and on 3.5” diskette or CD-ROM in MS Word format) including the above deliverables.

5.4 In the final report, the Contractor will identify any gaps in the analysis and identify any further work that can be undertaken to address the gaps.


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6.0 PERIOD OF PERFORMANCE. 6.1 Project Initiation Date: As early as January 2006






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06-29 Estimation of Weld Hydrogen Cracking Delay Time Submitted By: BMT Fleet Technology Limited

1.0 OBJECTIVE

1.1 The objective of this program is to provide guidance on the maximum delay time for hydrogen cracks in multi-pass fillet and groove welds to ensure that final weld inspection is completed after the risk of cracking is over.

2.0 BACKGROUND.

2.2 A significant problem in welding steel is delayed hydrogen induced cold cracking. This form of weld cracking is most significant for high carbon equivalent steels including older high carbon steels and more modern high strength alloyed steels. Cracks of this type, as the name implies, form at low temperatures, below 150oC. They can form long after the weld has cooled to ambient temperature. This delay phenomenon can make it particularly difficult to schedule inspections intended to ensure structural integrity. Knowledge of the delay time to cold cracking and ability to manipulate it will enable design of cost effective/economic welding/fabrication procedures without any adverse impact on structural integrity.

2.3 BMT and Graville Associates have developed and continue to refine an engineering tool for multi-pass weld hydrogen management, which considers the hydrogen diffusion and delayed cracking phenomena. The current model considers a wide range of welding, environmental and material parameters influencing the risk of and delay time before hydrogen cracking

2.4 When dealing with base materials, weld metals and welding procedures that have the potential to produce hydrogen (delayed) cracking, a knowledge of the delay time to cracking is required to ensure that final weldment inspection occurs after the risk of hydrogen cracking has passed. This delay can range from hours to days depending on the welding procedure parameters and environmental conditions.

2.5 The delay in the occurrence of hydrogen cracking is due to the time required for the weld hydrogen to diffuse through the weldment to the crack initiation site. A large number of factors has been shown to influence the rate of hydrogen diffusion and thus the delay time for hydrogen cracking in multi-pass welds (welding process, material type, pre-heat, inter-pass time, pass sequence, and temperature, etc.). In general, hydrogen will diffuse from areas of high concentration (deposited weld metal) to locations of low hydrogen concentration (base metal, heat affected zone or the atmosphere). The rate at which hydrogen diffuses through a weldment is a function of primarily the material and its temperature, with higher temperatures promoting a higher rate of hydrogen diffusion. The increase in hydrogen diffusion rate with temperature is related to the utility of post weld heating to quickly drive off unwanted hydrogen. Research has also noted that hydrogen will preferentially diffuse to high stress areas, local stress concentrations such as weld root misalignment in a groove weld or a root gap in a fillet weld.


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3 REQUIREMENTS. 3.1 Scope

3.1.1 It is known that the development of a hydrogen crack requires a susceptible microstructure, the presence of hydrogen and a tensile stress. This has been demonstrated by many researches including BMT with the development of hydrogen cracking susceptibility curves that relate the micro-structural susceptibility (in terms of hardness) to hydrogen concentration and stress conditions promoting cracking. A sample susceptibility curve is given in Figure 1 and a horizontal line on this graph will illustrate that hydrogen cracking will manifest at lower hydrogen levels when the weldment is subjected to higher stress levels.

Figure 1: BMT Hydrogen Cracking Susceptibility Curve

3.1.2 Once the weld has been deposited and cooled to ambient conditions, the microstructure of the weldment and weld residual/shrinkage stresses do not change. Therefore, the formation of a delayed hydrogen crack requires that either the hydrogen concentration or applied load induced stress state at the crack initiation site changes. If the applied loading is assumed to remain constant, then the only factor that changes with time that would affect hydrogen cracking delay time is the hydrogen concentration at the initiation site. Therefore, it is proposed that the maximum delay time for hydrogen cracking could be estimated by considering the time to peak hydrogen concentration at the predicted initiation site in the weld metal and HAZ.

3.1.3 If a hydrogen crack has not formed at a site of interest when the local hydrogen concentration reaches its maximum value and the hydrogen embrittlement effect is maximized, then cracking will not occur unless there is an increase in applied loading or local material susceptibility. This general approach has been validated and applied to hydrogen cracking in pipeline in-service welds [ref 1] to demonstrate the effect of the environment, welding process, pre- and post-heat, pipe geometry and welding procedure on the time to cracking. For example, the time to peak hydrogen, cracking delay time for an in-service weld is shown in the figure below for a range of oil and gas pipeline product temperatures.


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-

10

20

30

40

50

60

70

80

90

-10 0 10 20 30 40 50 60 70Product Temperature (°C)

T

i

m

e

t

o

P

e

a

k

H

(

h

)

.

Gas t = 14mmGas t = 9mmGas t = 10mmGas t = 6mmGas t = 4mmLiquid t = 14mmLi qui d t = 9mmLiquid t = 10mmLi qui d t = 6mmLi qui d t = 4mmFigure 2: Sample Delay Times for Pipeline In-Service Welding 361.4 In general, changes in the applied loading after weld completion can be assumed to increase the applied load stress stat e and thus increase the potential for hydrogen cracking, since hydrogen cracking will manifest when a critical combination if applied and thus reduce the hydrogen cracking delay time. If the assumption that an increase in the applied loading (e.g., internal pressure) would increase the crack initiation site stress state holds true, then evaluating cracking delay time based upon a constant applied stress would develop a conservative hydrogen cracking delay time. 361.5 It is proposed that consideration of the time to peak hydrogen concentration as a surrogate for hydrogen cracking maximum delay time will be used in a four stage process to: - experimentally and numerically illustrate hydrogen cracking delay times for in-service welds, - additional validation of the existing BMT hydrogen diffusion analytic tools, - develop an inspection delay guidance note considering welding procedure and environment, and - demonstrate the guidance note application. 361.6 Experimentation will involve the use of hydrogen cracking delay time testing procedures that can be used to demonstrate the validity of the BMT hydrogen diffusion and delayed cracking model to fillet welds. Ultimately the BMT hydrogen diffusion and delayed cracking model will be used to simulate times to peak hydrogen in a range of in-service welding procedures to develop the desired


119

guidance note. The use of this guidance note will be demonstrated through sample applications.

3.2 Tasks

The proposed project scope of work will be completed with the support of previous development work supported by the Pipeline Research Council International amongst others. The work completed to satisfy the objective and scope outlined above would include the tasks outlined below including both fillet and groove welds. 3.2.1 Task 1 - Increase the numerical model validation base by experimentally measuring the delay time to cracking and hydrogen diffusion rates 3.2.2 Task 2 - Additional numerical model validation by estimation of hydrogen cracking delay times, 3.2.3 Task 3 - Development of an inspection delay guidance note considering welding procedure and environment, 3.2.4 Task 4 - Demonstrate the effect of local stress on hydrogen diffusion, 3.2.5 Task 5 - Development of hydrogen cracking susceptibility for low hydrogen concentrations, and 3.2.6 Task 6 - Project documentation and demonstration of the guidance note application.

3.3 Project Timeline. The project can be completed within an 12 month period.


4.1 Final Report Style Manual. 5 DELIVERY REQUIREMENTS. (Identify the deliverables of the project).


5.2 The Contractor shall provide a draft outline of the experimental plan for review prior to

experimentation. This outline will be used to indicate the scope and content of the experimental program and be open to comment from the project technical committee.

5.3 The Contractor shall provide a print ready master final report (paper copy and on 3.5”

diskette or CD-ROM in MS Word format) including the above deliverables formatted as per the Final Report Style Manual.




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6.2 Project Completion Date: 12 months from the date of award. 7 GOVERNMENT ESTIMATE. These contractor direct costs are based on previous



8 REFERENCES.

8.1 None. 9 SUGGESTED CONTRACTING STRATEGY.

It is proposed that a sole source award to BMT Fleet Technology Limited be considered based upon previous projects in the development of an understanding of the delayed cracking phenomena, delay time and the susceptibility of weldments. This work makes available to the US SSC the results of research in excess of US$350,000 in experimental and numerical modeling studies. This previous experience and data will be brought to the table to support the proposed project that is expected to have an additional budget of approximately US$350,000, with the SSC contribution being $70,000 and the remainder of the funds being provided by pipeline operators, PRCI, private industry and BMT in-house research dollars. BMT Fleet Technology Limited's past experience and preliminary development provide a level of confidence that the project can be successfully completed within the stated budget.

Documents

3 PROJECT RECOMMENDATIONS FOR FISCAL Y 2006 · TABLE 3-1 Project Recommendations for Fiscal Year 2006 ... Impact Test which is not amenable to quantitative structural ... compressive,