Thirteenth Engineering Mechanics Symposium · Thirteenth Engineering Mechanics Symposium 5 Preface The Graduate School on Engineering Mechanics, a joint initiative of the Eindhoven

Thirteenth Engineering Mechanics Symposium 28 - 29 October 2010 De Werelt, Lunteren

Graduate School on Engineering Mechanics c/o Eindhoven University of Technology PO Box 513, building W-hoog 4.133 5600 MB Eindhoven NL Tel.: +31 40 2478306 Fax: +31 40 2447355 E-mail: [email protected] http://www.em.tue.nl

Colophon: Editor: R.A.M.F. van Outvorst Publication date: September 2010 Notice: An electronic version of this brochure will be available at: http://www.em.tue.nl

Thirteenth Engineering Mechanics Symposium 3

Contents

Preface 5

1. Program 7

2. Koiter Lecture and Introduction to the Workshops 11

3. Introduction Presenters and Abstracts of Presentations 19

4. Survey of Poster Presentations 45

4 Thirteenth Engineering Mechanics Symposium


Preface The Graduate School on Engineering Mechanics, a joint initiative of the Eindhoven and Delft Universities of Technology and the University of Twente, organizes on an annual basis the Engineering Mechanics Symposium. The aim of this symposium is to stimulate the communication and the exchange of information with respect to ongoing research in the field of Engineering Mechanics. To achieve this, the program contains a koiter lecture by a leading expert in the field, topical sessions in relation to the selected research program of the graduate school, poster presentations of actual research projects by PhD-students and a meeting of the senior academic staff. The Thirteenth Engineering Mechanics Symposium takes place October 28-29, 2010 at De Werelt in Lunteren. In the opening session, Prof. Herbert Mang from Vienna University of Technology will present a koiter lecture entitled: COMPUTATIONAL ENGINEERING MECHANICS – elucidating general features of materials and structures Furthermore, four workshops are organized that partly run plenary and partly run in parallel. Topics of this year’s workshops are:

MuST/Multiscale Organized by Prof. René de Borst (TU/e, main organiser), Prof. Bert Sluys (TUD), Prof. Stefan Luding (UT)

Optimization Organized by Dr. Bert Geijselaers (UT, main organiser), Dr.ir. Pascal Etman (TU/e) and Dr. M. Abdallah (TUD)

Mathematical and numerical solution methods Organized by Prof. Harald van Brummelen (TU/e, main organiser), Prof. Mark Peletier (TU/e).

Energy Organized by Prof. Daniel Rixen (TUD) The workshop organizers provide plenary introductions on the trends and challenges of the workshops. Two of those plenary introductions have been included in the morning program on the first symposium day, whereas the other two have been included in the morning program of the second symposium day. Next, two of the actual workshops have been scheduled to run in parallel on the first symposium day, whereas the other two have been scheduled to run in parallel on the second symposium day. Each workshop consists of two parts, separated by a break. Each part consists of 2 presentations by AIOs/postdocs. The duration of each of the AIO/postdoc presentations is 20 minutes and followed by 10 minutes of discussion. For the best AIO-presentation within each workshop a prize will be awarded. Winners will be announced directly before the closing of the symposium on Friday, October 29. Additionally, there are two poster discussion sessions in which PhD-students participating in the Graduate School on Engineering Mechanics present their current research project. In relation to these presentations a contest is organized in which a jury selects the best three contributions. This year’s members of the jury are: Dr. ir. Frederic Blom (NRG), Dr. Sergio Turteltaub (TUD), Dr. Yves Bellouard (TU/e), Dr. ir. Timo Meinders (UT). Winners will be announced directly before the closing of the symposium on Friday, October 29. On Friday, October 29 a meeting of the senior academic staff participating in Engineering Mechanics takes place. This report contains more detailed information on the Thirteenth Engineering Mechanics Symposium. Included are the following sections:

Section 1: Detailed program of the symposium

Section 2: Abstracts of the koiter lecture and introduction to the workshops

Section 3: Abstracts of presentations in the workshops and a short introduction of the presenters

Section 4: Survey of poster presentations



1 PROGRAM

This section contains the detailed program of the Thirteenth Engineering Mechanics Symposium. Information on the koiter lecture and introductions to the sessions are presented in section 2. Abstracts of the presentations can be found in section 3.



Program Thirteenth Engineering Mechanics Symposium

Thursday, 28 October 2010

10.00-10.30 Registration and Informal get-together Room Azië

10.30-12.40 Opening Session Room Afrika

10.30-10.40 Opening of the Symposium by Prof. Marc Geers

10.40-11.40 Koiter lecture: "Computational Engineering mechanics - elucidating general features of materials and structures" by Prof. Herbert Mang

11.40-12.10 Trends and challenges in “MuST/Multiscale” by Prof. René de Borst

12.10-12.40 Trends and challenges in “Optimization” by Dr. Bert Geijselaers

12.45-13.45 Lunch

13.50-14.50 Workshops 1 and 2, part A

Workshop 1: Room Afrika MuST/Multiscale

Workshop 2: Room Amerika Optimization

Vinh Phu Nguyen (TUD) Computational homogenization for cohesive crack modelling

Laura Del Tin (TUD) Handling of stress constraints in topology

optimization

Faisal Irzal (TU/e) A two-scale approach for propagating cracks in a fluid saturated porous material

Attila Nagy (TUD) Isogeometric design optimisation of anisotropic composite shells

14.50-15.50 Poster Discussion Session l: Room Azië Presentation of current research projects, carried out by PhD students and Postdocs participating in Engineering Mechanics

15.50-16.20 Break

16.20-17.20 Workshops 1 and 2, part B

Workshop 1, cont’d Room Afrika MuST/Multiscale

Workshop 2, cont’d: Room Amerika Optimization

Erica Coenen (TU/e) A multi-scale oddity: unifying homogenization and localization

Alexandre Paternoster (UT) Actuators for Smart Applications.

Johan Hol (UT) Multiscale friction modeling for sheet metal forming

Maria Rudnaya (TU/e) Derivative-free optimization for focus and

astigmatism correction

17.30-18.30 Poster Discussion Session II: Room Azië Presentation of current research projects, carried out by PhD students and Postdocs participating in Engineering Mechanics

18.30-19.00 Informal reception

19.00-22.00 Dinner & historical lecture Prof. Fred van Keulen

22.00-24.00 Bar


Program Thirteenth Engineering Mechanics Symposium

Friday, 29 October 2010

09.00-10.00 Plenary Session Room Afrika

09.00-09.30 Trends and challenges in “Mathematical and numerical solution methods” by Prof. Mark Pelletier / Prof. Harald van Brummelen

09.30-10.00 Trends and challenges in “Energy” by Prof. Daniel Rixen

10.00-11.00 Workshops 3 and 4, part A

Workshop 3: Room Afrika Mathematical and numerical solution methods

Workshop 4: Room Amerika Energy

Patricio Rosen Esquivel (TU/e) Flow in Corrugated Pipes

Casper T. Bolsman (TUD) Flapping wing actuation using resonant compliant mechanisms - An insect-inspired design

Wijnand Hoitinga (TUD) Goal-oriented adaptive methods for a Boltzmann-type equation

Pieter. H. de Jong (UT) Power harvesting in a helicopter lag damper

11.00-11.30 Break

11.30-12.30 Workshops 3 and 4, part B

Workshop3, cont’d: Room Afrika Mathematical and numerical solution methods

Workshop 4, cont’d: Room Amerika Energy

Pooria L. Pahlavan (TUD) Wavelet-based Spectral Finite Element Method for Simulation of Elastic Wave Propagation

Sven N. Voormeeren (TUD) Hybrid Dynamic Substructuring in Wind Turbine Engineering

Vitaliy Ogarko (UT) A hierarchical approach for contact detection in highly polydisperse granular systems and how to find the optimal parameters

A. Can Altunlu (UT) Nano energy for the benefit of Macro energy

12.35-12.50 - Announcement of winning contributions in the AIO/Postdoc Presentation contest and in the Poster contest - Closure

12.50-13.50 Lunch

14.00-15.30 Assembly of Project Leaders EM Room Amerika

16.00-20.00 Meeting of EM Advisory Board De Lunterse Boer


2 KOITER LECTURE

and

INTRODUCTION TO THE WORKSHOPS

This section contains abstracts of the Koiter Lecture by Prof. Herbert Mang and Introductions to the workshops “MuST/Multiscale”, “Optimization”, “Mathematical and numerical solution methods”, and “Energy” by the session organizers.



Koiter Lecture

COMPUTATIONAL ENGINEERING MECHANICS – elucidating general features of materials and structures

Herbert A. Mang

Institute for Mechanics of Materials and Structures, Vienna University of Technology, Karlsplatz 13/202, A-1040 Vienna, Austria, [email protected]

Key Words: Structural stability, Multiscale mechanics, Wood, Concrete

Introduction. Computational Mechanics has become a mature scientific discipline with great impact on engineering, in general, and on civil engineering in particular. Herein, current challenges in this wide field that constitute the nucleus of the research efforts of the Institute for Mechanics of Materials and Structures at the Department of Civil Engineering of Vienna University of Technology are explored. On the one hand, these challenges refer to the behavior of complex structures built up by simple materials in the linearly elastic domain and to the wish of theoretical identification of general features of loss of structural stability including the initial postbuckling behavior. On the other hand, a great challenge lies in the complexity of the material behavior. This challenge is met through resolving the material into its micro and nanostructures, including consideration of chemical reactions at the respective scales. Accordingly, sensitivity analysis of the buckling and initial postbuckling behavior of structures, including a steel bridge, and multiscale analyses of wood and concrete will be presented. The part of the lecture that is devoted to stability analysis is also meant to be an hommage to Prof. W.T. Koiter after whom this lecture was named.

Methods. At the structural scale, a new (necessary and sufficient) condition for bifurcation buckling from a membrane stress state will be presented. With the help of Koiter’s initial prebuckling analysis it will be shown that zero-stiffness postbuckling representing a specific form of transition from imperfection sensitivity to insensitivity in the course of sensitivity analysis of the initial postbuckling behavior requires such a state of stress. At the material (microstructural) scale, random and periodic homogenization schemes will be used to represent the hierarchical organizations of wood and concrete. These models rest on “universal” properties of elementary material constituents, be they cellulose, hemicellulose, lignin, and water in the case of wood, and cement, water, hydrates, and aggregates in the case of concrete. Complementing the classical realm of elasticity, the presentation will also comprise material strength and fluid transport. Results and Conclusions. Among the conclusions drawn from sensitivity analysis of the initial postbuckling are the imperfection sensitivity of hilltop buckling and the imperfection insensitivity of zero-stiffness postbuckling. This analysis is viewed as a step in the direction of better understanding the reasons for specific modes of the initial postbuckling behavior of elastic structures and of its interplay with the prebuckling behavior. This will help to improve the design of structures with favorable buckling and postbuckling characteristics. At the material (microstructural) scale, remarkably, the complex failure characteristics of materials such as wood and concrete can be traced back to one dominant, simple failure characteristics of a single nanoscaled component: lignin in wood, and hydrates in concrete. At the same time, the overall strength characteristics are strongly influenced by the water content in the materials. In civil engineering problems, the water content may change significantly because of drying in wood and of hydration and dehydration in concrete.


Workshop 1

Multi-scale Simulation Technologies

René de Borst Eindhoven University of Technology

Bert Sluys Delft University of Technology

Stefan Luding University of Twente

Multi-scale technologies are quickly becoming a new paradigm in many branching of science, including in simulation-based engineering. This also holds true for computational mechanics, where multi-scale approaches are among the most important strategies to further our understanding of the behavior of engineering and biomedical materials. Indeed, this understanding and the tools that are being developed in multi-scale computational mechanics greatly assist the engineering of new materials. In multi-scale analyses an ever greater resolution is sought at ever smaller scales. In this manner it is possible to incorporate the physics more properly and therefore, to construct models that are more reliable and have a greater range of validity at scales that are relevant in engineering. When resolving smaller and smaller scales, discontinuities and the discrete nature of matter become more and more important. Moreover, non-mechanical effects, like magneto-electro-chemical fields, humidity and temperature, can cause non-negligible effects, and often have to be considered as well. In this lecture, we will give a concise classification of multi-scale computational methods. Next, we will present examples of research projects that focus on multi-scale analyses in Eindhoven, Delft and Twente.


Workshop 2

Optimization

H.J.M. Geijselaers1, L.F.P. Etman

2, M. Abdallah

3

1University of Twente

2Eindhoven University of Technology

3 Delft University of Technology

The development of computational methods for optimization gained momentum in the second half of

the previous century. Almost as soon as the finite element method became available as a tool for

analysis of structures and systems, researchers tried to combine it with already available methods for

optimization.

In this talk a short introduction to optimization problem formulation and solution is given. Some

historical achievements are mentioned. An overview of current research is given with reference to

activities in the graduate school Engineering Mechanics.

The contributions to the session are briefly introduced.


Workshop 3

Mathematical and numerical solution methods

Harald van Brummelen1,2

and Mark Peletier2

1

Eindhoven University of Technology, Department of Mechanical Engineering, Multiscale Engineering Fluid Dynamics Section (MEFD), P.O. Box 513, 5600 MB Eindhoven

2

Eindhoven University of Technology, Department of Mathematics and Computer Science, Centre for Analysis, Scientific computing and Applications (CASSA), P.O. Box 513, 5600 MB Eindhoven Phone +31-(0)40 2475470, e-mail:

[email protected]

Mathematical models and techniques play a fundamental part in many branches of research of the various groups within the Engineering Mechanics research school. Most of the research in the EM groups bears an application-oriented character, befitted to the embedding of the groups in engineering departments. A notable exception is provided by the Centre for Analysis, Scientific computing and Applications (CASA), which is embedded within the Department of Mathematics and Computer Science at TU/e. In addition to the Scientific Computing chair, CASA encompasses the Applied Analysis and Variational Methods chairs, which provides CASA with a rather unique signature within the Engineering Mechanics community. The mathematical and numerical topics treated within the various EM groups include:

Finite-element methods and isogeometric techniques

Reduced-order modelling

Molecular dynamics and discrete-element methods

Numerical and theoretical homogenization

Variational methods

Theory and application of PDEs

Numerical solution techniques for coupled problems

However, this list is certainly non-comprehensive.

In the presentation, we will provide an overview and an attempt at classification of various research directions within the theme “mathematical and numerical solution methods”.


Workshop 4

Energy

D.J. Rixen

Dpt. of Precision and Microsystem Engineering, Delft Univ. Tech., Mekelweg 2, 2628 CD Delft, The Netherlands

phone +31 (0)15 278 1523, e-mail [email protected]

Energy is at the heart of the challenges our society is facing in this modern era. How to provide energy to portable systems? How to find enough energy to fuel the economical growth? What energy for developing countries that do not have access to expensive oil? Is it possible to still keep our living standard and not exhausting the energy resources or producing dramatic climate changes? Engineering mechanics, as one of the fundamental fields of modern engineering has a major role to play in the energy challenges we must tackle to render our world sustainable, safe and enjoyable. Think about the energy that can be saved by optimizing materials and structures. Better materials and better designs can significantly reduce the weight and increase the life-time of products, thereby reducing the energy needed to use and produce them. The better integration of structures, actuators and control allows optimizing complex systems (such as wind-turbines, cars, ….), creating new opportunities for highly efficient systems. Powering portable or implantable systems is a field that requires novel paradigms in order to harvest energy from external motion or from small heat sources for instance. Autonomous systems open new applications in the biomedical world, but also in fancy gadgets we all love to have. In the presentation we will summarize the work done in the different groups of the Engineering Mechanics school on those topics. We will reflect on what other researches in the world are going on to come up with innovative solutions to the energy challenge.

mailto:[email protected]



3 INTRODUCTION PRESENTERS

AND

ABSTRACTS OF PRESENTATIONS

This section contains abstracts of presentations at the Thirteenth Engineering Mechanics Symposium. Abstracts are in alphabetic order on the (first) author. Abstracts of the keynote lecture and an introduction to the workshops are presented in section 2.



Short Introduction speakers at the 13th Symposium of the Graduate School on Engineering Mechanics (in alphabetic order)

Abstract title: Nano energy for the benefit of Macro energy Workshop: Energy Altunlu, A.C. (Can) University of Twente, Faculty of Engineering Technology Advisor: Prof.dr.ir. A. de Boer Co-advisor: Dr.ir.P.J.M. van der Hoogt

Biography and description of research: Can Altunlu is a second year PhD student at University of Twente in the Structural Dynamics and Acoustics Group. He started his research in September 2009. He holds a M.Sc. degree (2009) from Koc University and B.Sc. degree (2007) from Istanbul Technical University, Istanbul, Turkey. The structural integrity, durability and reliability of the critical components of gas turbine engines for power generation govern the safety of power plants. Fatigue, creep and fatigue/creep interaction are the main damage mechanisms of the plant type gas turbine engines due to the operation at elevated temperatures under variable stresses. The thermo-acoustic instabilities in combustion systems cause high sound pressure levels resulting in vibration of the structure. It is essential to predict the residual lifetime and evaluate the damage of the liner material. The objective of the research project is the life assessment due to the limit cycles of thermo-acoustic oscillations in gas turbine combustors that is motivated by the need for lean combustion technologies and reducing emissions. The research is supported by the EC in the Marie Curie Actions – Networks for Initial Training, under call FP7-PEOPLE-2007-1-1-ITN, Project LIMOUSINE with project number 214905.

Abstract title: Flapping wing actuation using resonant compliant mechanisms - An insect-inspired design Workshop: Energy Bolsman, C.T. (Caspar) Faculty of 3ME, Department of precision and Microsystems engineering (PME), Delft University of Technology Advisor: Prof.dr.ir. F. van Keulen Co-advisor: Dr.ir. J.F.L. Goosen

Biography and description of research: Working on the development of flapping wing Micro Air Vehicles (MAVs), Caspar started his PhD in November 2005 within the structural optimization and computational mechanics group. He will defend his thesis in October 2010. His research is part of the Atalanta program. This program aims at the development of an artificial miniature flying sensor platform (insect/butterfly). This artificial insect is a demonstrator for the design and control of complex and adaptable systems. The overall program includes all components required for such a device, such as sensors, actuators, data management in distributed systems, power storage and management. This project aims at the development of the actuation (flying) mechanism. Focus is on efficient lift production and the minimization of energy usage by making use of resonant properties.


Abstract title: A multi-scale oddity: unifying homogenization and localization Workshop: MuST/Multiscale Coenen, E.W.C. (Erica) Department of Mechanical Engineering, Eindhoven University of Technology Advisor: Prof.dr.ir. M.G.D. Geers. Co-advisor: Dr.ir. V.G. Kouznetsova

Biography and description of research: Erica Coenen is an M2i PhD researcher working in the group of prof. Marc Geers (Mechanics of Materials), in Mechanical Engineering Department of TU/e. Her PhD project started in January 2007 and is on the development and application of a new multi-scale method to model damage and localization of ductile materials. The motivation for this project is that the design of metal products and forming operations is continuously challenged by demands for costs reduction, environmental regulations, new design trends etc. This, combined with the increased utilization of advanced materials, e.g. high-strength steels and aluminium alloys, requires reliable predictions of the manufacturability and (residual) product properties after forming. Also in material separation processes, such as cutting and blanking, the trajectory of process induced cracks determines the quality of the final product, and therefore need to better understood.

Abstract title: Handling of stress constraints in topology optimization Workshop: Optimization Del Tin L. (Laura) Department of Mechanical Engineering, Eindhoven University of Technology Advisor: Prof. Dr. ir. F. van Keulen

Biography and description of research: Laura Del Tin took her PhD from the University of Bologna on model order reduction techniques for electrically driven microsystems in 2007. Since then, she is working on different aspects of modeling, simulation and optimization of microsystems and mechanical structures. Her present work focuses on the study of stress constraints in topology optimization of industrial mechanical components.

Other participants: The work presented is in collaboration with Femto Engineering and ASML, as part of the Microned project AP2.10.


Abstract title: A two-scale approach for propagating cracks in a fluid saturated porous material Workshop: MuST/Multiscale Irzal, F. (Faisal) Department of Mechanical Engineering, Eindhoven University of Technology Advisor: Prof.dr.ir. R. de Borst. Co-advisor: Dr.ir. J.J.C. Remmers, Dr.ir. J.M.R. Huyghe.

Biography and description of research: Faisal Irzal joined the Numerical Method in Engineering group in Eindhoven University of Technology as a PhD researcher in May, 2009, after graduating as Mathematic for Industry post-master program at Stan Ackermans Institute at the same university. Having background in applied mathematics gives advantage for him to deal with the complexity of his current project that concerns about the propagating cracks in porous material. The aim of this project is to extend the existing approach for 2D-propagating cracks in porous material such that it can tackle the geometrically nonlinear behaviour. The model will further be implemented using finite element method by exploiting the partition-of-unity property of finite element shape functions.

Abstract title: Power harvesting in a helicopter lag damper Workshop: Energy Jong de, P. H. (Pieter) University of Twente, Faculty of Engineering Technology, Structural Dynamics and Acoustics Advisor: Prof. dr. ir. A. de Boer Co-advisor: Dr. ir. R. Loendersloot

Biography and description of research: Pieter begun work as a PhD student at the University of Twente in February 2009, following an MSc. degree obtained mid-2008. His PhD work is focused on harvesting energy from ambient vibrations in a helicopter rotor within the framework of the European Clean Sky project. Although the obtained power output is not directly of any use towards ‘greening’ a helicopter the indirect benefits are extensive. Active condition monitoring helps for instance in replacing rotor blades when they are truly at the end of their life as opposed to replacing un-instrumented blades at a time which is based on a very conservative lifetime calculation. Local processing can also be performed and the information may be transferred to the helicopter chassis wirelessly or through a single data link. Local processing reduces the number of links required, greatly simplifying the electronic aspects of rotor design.


Abstract Title: Multiscale friction modeling for sheet metal forming Workshop: MuST/Multiscale Hol, J University of Twente, Faculty of Engineering Technology Advisor: Prof.dr.ir. J. Huétink Co-advisor: Dr.ir. T. Meinders EM research theme: Applied Mechanics

Biography and description of research: M2i PhD researcher Johan Hol is working at the University of Twente since July 2009. Research is performed on advanced friction modeling in cooperation with the industrial partner Corus and the Surface Technology and Tribology group at the University of Twente. The motivation of his project arises from the automotive industry where simulations of sheet metal products are everyday practice. An accurate forming analysis can however only be made if, amongst others, the material behavior and friction conditions are modeled accurately. In the majority of simulations still a simple Coulomb friction model is used which does not include the influence of important parameters such as pressure, punch speed or deformation of the sheet material. The objective of his project is to provide an improved macroscopic friction model including microscopic dependencies.

Abstract title: Goal-oriented adaptive methods for a Boltzmann-type equation Workshop: Mathematical and numerical solution methods Hoitinga, W. (Wijnand) Department of Aerospace Engineering and Department of Mechanical, Maritime and Materials Engineering, Delft University of Technology Advisor: Prof.dr.ir. R. de Borst. Co-advisor: Prof. dr. ir. E. H. van Brummelen

Biography and description of research: Wijnand Hoitinga started his Ph.D. research in the Engineering Mechanics group of Professor René de Borst at the Aerospace Engineering Department of Delft University of Technology in June 2006, with Harald van Brummelen as his advisor. He works within the MicroNed consortium on "Optimal-adaptive computational methods for discrete/continuum problems in MEMS." Many things have changed since the start of the project: Professor de Borst became dean of the Mechanical Engineering Department at TU/e and van Brummelen became chair of Multiscale Engineering Fluid Dynamics section at TU/e. Wijnand is currently a guest in the Precision and Microsystems Engineering group of Professor Fred van Keulen at TU Delft. Over the past years Wijnand has worked on the Boltzmann equation. The Boltzmann equation describes flow problems in the transitional molecular/continuum regime. Because the Boltzmann model is (6+1)-dimensional, its computational approximation is a daunting challenge. An important result of Wijnand's work has been the development of a (2+1)-dimensional Boltzmann-type model, which serves to test new numerical techniques. Wijnand has developed a discontinuous Galerkin finite-element method for the model problem. In addition, he has developed a goal-adaptive refinement method for the model problem, thus creating the first goal-adaptive method for a Boltzmann-type equation.


Abstract title: Isogeometric design optimisation of anisotropic composite shells Workshop: Optimization Nagy, A. P. (Attila) Aerospace Structures and Computational Mechanics Chair Faculty of Aerospace Engineering Delft University of Technology Advisor: Prof. Zafer Gürdal Co-advisor: Dr. Mostafa M. Abdalla

Biography and description of research: Since early 2007 Attila Nagy pursuits his PhD at the Faculty of Aerospace Engineering in Delft. His main research focuses on the development of a non-uniform B-spline based isogeometric design optimisation framework with special emphasises on Cosserat media typically used to model slender/thin-walled structures in aerospace and automotive applications. Shape optimal design and structural sizing has been integrated in a multilevel design scheme that can be directly applied on the conserved computational geometry while exploiting superior numerical properties of the isogeometric approach. Formulating commonly employed strength and manufacturing constraints in a variational sense adds an additional compound to the framework and seamlessly blends into the underlying analysis environment. The research aims to perform shape design and stiffness tailoring of anisotropic composite shells in a simultaneous fashion

Abstract title: Computational homogenization for cohesive crack modeling Workshop: MuST/Multiscale phenomena Nguyen, V.P. (Phu) Faculty of Civil Engineering and Geosciences, Delft University of Technology Advisor: Prof.dr.ir. L.J. Sluys Co-advisor: Dr.ir. M. Stroeven

Biography and description of research: Vinh Phu Nguyen started his Ph.D in the Computational Mechanics group at the faculty of Civil Engineering and Geosciences of TUD of July 2007. The goal of his PhD is to devise a computational homogenization scheme for quasi-brittle softening materials. His current research involves the multiscale simulation of cohesive crack propagation in quasi-brittle heterogeneous solids. The existence of representative volumes for a class of softening materials undergoing localized damage has been numerically proved. A computational homogenization scheme for cohesive crack modelling in which the underlying microstructure is taken into account has been developed. Extension of the proposed scheme to mixed-mode crack growth problems as well as reducing the computational cost involved are in progress.


Abstract title: A hierarchical approach for contact detection in highly polydisperse granular systems and how to find the optimal parameters

Workshop: Mathematical and numerical solution methods

Ogarko, V.A. (Vitaliy)

University of Twente, Faculty of Engineering Technology

Advisor: Prof.dr.ir. S. Luding; Co-advisor: Dr.ir. A.R. Thornton

Biography and description of research: Vitaliy Ogarko is a PhD student of the Multi Scale Mechanics group at the University of Twente. His PhD project concerns the development of hierarchical data structures for the micro-macro transition, coupling of different fields, and coarsening or refinement. The scientific challenge is to understand systems with strongly different particle sizes with gas-, fluid-, and solid-like behavior at the same time. This involves multi-physics, micro-systems, (moving) interfaces and multi-field problems in general. More specific, such systems occur in grinding or comminution and transport of particulate systems – before and during processing of modern, high-performance materials (ceramics, metals, plastics, etc.).

As most recent achievement, he developed an algorithm for setting the optimal parameters (the number of hierarchies and cell sizes) for his hierarchical grid broad phase contact detection method for arbitrary particle size distribution functions. Other participants: This research is supported by the Dutch Technology Foundation STW, which is the applied science division of NWO, and the Technology Programme of the Ministry of Economic Affairs (10120).

Abstract title: Wavelet-based Spectral Finite Element Method for Simulation of Elastic Wave Propagation Workshop: Mathematical and numerical solution methods Pahlavan, P. L. (Pooria) Department of Aerospace Structures, Delft University of Technology Advisor: Prof.dr. Z. Gürdal Co-advisor: Ir. C. Kassapoglou

Biography and description of research: Pooria L. Pahlavan is a PhD student of the research group “Aerospace Structures (AeS)” who started his project in August 2008. He received his BSc and MSc in Mechanical Engineering from Ferdowsi University of Mashhad, Iran. His current research area is structural health monitoring (SHM)” of thin-walled metallic and composite structures while the focus is on wave propagation-based methods. As damage and material discontinuities affect the propagation of ultrasonic waves in the structure viewed as the waveguide, interpretation of the changes in the structure response with which the existence and characteristics of the damage can be quantified is of substantial importance. Effective simulation of high-frequency wave propagation and reliable damage identification algorithms are the main targets of his PhD project.


Abstract title: Actuators for Smart Applications. Workshop: Optimization Paternoster, A (Alexandre) Advisors: Prof. A. de Boer, prof. R. Akkerman.

Biography and description of research: Alexandre Paternoster is a PhD student at the University of Twente in the Structural Dynamics and Acoustics Group since February 2009. His research subject is on actuators systems for shape morphing applications. The objective is to develop such a system for rotorblades in order to enhance the performance of rotorcraft transportation. The performance and stability of a helicopter in forward flight is defined by how much it is possible to alleviate the lift unbalance between the helicopter’s sides as it moves forward. The Gurney flap is a shape morphing concept which improves the lift and the stall behavior when it is needed. Actuators technologies were selected to fit the requirements of deploying the Gurney flap depending of the control strategies considered. This research includes the design and testing of a mechanism that will connect the actuator technology selected with the Gurney flap. Other participants: This project is part of Green RotorCraft Intergrated Technology demonstrator which is a section of Clean Sky Europoean Join Technology Initiative.

Abstract title: Flow in Corrugated Pipes Workshop: Mathematical and Numerical Solution Methods Rosen Esquivel, P.I. (Patricio) Centre for Analysis and Scientific Computing CASA, Department of Mathematics, Eindhoven University of Technology Advisor: Prof.dr. R.M.M. Mattheij Co-advisors: Dr. J.H.M. Ten Thije Boonkkamp, Dr. J.A.M. Dam

Biography and description of research: Patricio Rosen started his PhD. research in October 2008. His project is related to the cryogenic industry and to complex flows in general. The main concern is the construction of lower dimensional models (nodal, or 1D models) as an alternative of performing full 3D CFD methods, for simulating flow transport in components of the cryogenic industry. These lower dimensional models, should be adequate for their use in the simulation of a network of interconnected process components. The main effects to be captured are those generated on the flow by the wall shape, some other possible factors to study are: wall heat transfer, non-stationary wall, transitional flow and phase-transition. Patricio Rosen studied actuarial science and mathematics in the National Autonomous University of Mexico (UNAM). He received a double M.Sc. (cum laude) degree in industrial mathematics from the University of Kaiserslautern and the Eindhoven University of Technology, where he is currently completing his PhD studies in the Department of Mathematics and Computer Science, in the field of fluid dynamics.


Abstract title: Derivative-free optimization for focus and astigmatism correction Workshop: Optimization Rudnaya, M.E. (Maria) Eindhoven University of Technology, Department of Mechanical Engineering Advisor: Prof.dr. R.M.M. Mattheij Co-advisor: Dr. J.M.L. Maubach

Biography and description of research: Maria Rudnaya joined the Centre for Analysis, Scientific computing and Applications (CASA) at the Department of Mathematics and Computer Science of the TU/e as a PhD researcher in October 2007. The ultimate goal of the research project is to automate the electron microscope's controls, in order to get in-focused, astigmatism-free images without the aid of the user. The work is carried out as a part of the Condor project at FEI Company under the responsibilities of the Embedded Systems Institute (ESI). This project is partially supported by the Dutch Ministry of Economic Affairs under the BSIK program.

Abstract title: Hybrid Dynamic Substructuring in Wind Turbine Engineering Workshop: Energy Voormeeren, S.N. (Sven) Department of Mechanical Engineering, Delft University of Technology Advisor: Prof.dr.ir. D.J. Rixen

Biography and description of research: Sven Voormeeren is a PhD student at Delft University, working in the group of Engineering Dynamics. Since april 2008 he is working on a collaborative project between Siemens Wind Power and Delft University, developing and implementing dynamic substructuring techniques for dynamic analysis of wind turbines. In wind turbine engineering, there is a trend towards ever larger and more optimized designs. This inherently leads to more pronounced structural dynamic effects and coupling of local (component) dynamics with the global dynamics can occur. However, traditional aero-elastic codes used in wind turbine engineering are unable to predict these effects. To overcome this, the paradigm of dynamic substructuring is used to develop a more detailed, yet efficient dynamic analysis tool.


Nano energy for the benefit of Macro energy

A. C. Altunlu, Peter van der Hoogt, André de Boer

Faculty of Engineering Technology, Section Applied Mechanics, University of Twente,

P.O. Box 217, 7500 AE Enschede, The Netherlands

e-mail: [email protected]

The structural integrity, durability and reliability of the critical components of gas turbine engines for (macro) energy generation govern the safety of power plants; therefore the total lifetime must be accurately predicted. Fatigue, creep and fatigue/creep interaction are the main damage mechanisms of the plant type gas turbine engines due to the operation at high temperatures under variable stresses. Fatigue failures are caused by high cycle fatigue (HCF) and low cycle fatigue (LCF). The damage mechanisms are responsible for the fatigue life spent until crack initiation and for crack propagation. The thermo-acoustic instabilities in combustion systems cause high sound pressure levels resulting in vibration of the structure. It is important to predict the lifetime and evaluate the damage of the liner material in the way of achieving a lean combustion and reducing emissions in gas turbines. The proposed lifetime prediction method consists of a synergy between damage evolution and crack propagation theories. The total life prediction of combustion liners has been examined in two stages. The first stage is the life assessment of the liner structure until the smallest crack length for physically small cracks is satisfied. Subsequent stage is the thermal displacement analysis to predict the residual life of the crack by calculating the localized temperature fields at the crack tip due to the plastic work done. The plastic deformation ahead of the crack front prior to fracture has been simulated by the fracture mechanics based analysis in the EPFM (Elastic-plastic Fracture Mechanics) domain. The crack tip field intensity has been examined by means of the linear-elastic fracture parameter stress intensity factor (KI) and the capability of the analysis has been extended with the J-Integral, which is a path-independent line integral, describing the strain (nano) energy release rate used for modeling plasticity at the crack tip. The stability of the crack has been predicted by comparing the fracture parameter KI with the fracture toughness KIC of the material under Mode I loading propagating crack for a ductile material. Subsequently, JI has been calculated and compared with JIC to determine the crack extension. The analysis procedure has been repeated for each crack length increment until the final crack length was achieved. This paper describes a methodology to obtain strain and stress distribution around the crack tip for the second stage of the total life prediction approach. This method enables to predict a stable mode I crack growth and concludes by highlighting the importance of the damage evolution of the propagating crack tip for the residual life prediction of a component and future prospects on the method.


Flapping wing actuation using resonant

compliant mechanisms

An insect-inspired design

C.T. Bolsman

Dpt. of Precision and Microsystem Engineering, Delft Univ. Tech., Mekelweg 2, 2628 CD Delft, The Netherlands

e-mail [email protected]

The realization of a wing actuation mechanism for a flapping wing micro air vehicle requires a move away from traditional designs based on gears and links. An approach inspired by nature’s flyers is better suited. For flapping flight two wing motions are important: the sweeping and the pitching motion.

The current design is set up to exploit resonant properties, as exhibited by flying insects, to reduce the energy expenditure and to provide amplitude amplification for the wing sweeping motion. In order to achieve resonance, a significantly compliant structure has to be incorporated into the design. The structure used for elastic storage is a ring-type structure which is combined with a compliant amplification mechanism to realize the wing sweeping motion. After initial sizing, prototype structures are analyzed. Based on the initial analysis, the structures are realized to be tested later. For lift production, timing of the wing pitching motion is of paramount importance. A compliant pitching hinge is introduced to obtain passive pitching motion.

The wings are analyzed independent of the structure and consequently tuned. The objective is to reproduce a reference motion based on insect kinematics by using a coupled quasi-steady aerodynamic and mechanical model. The wings are realized and consequently tested to judge if manufactured wings reflect the predicted performance. The wings are coupled to the ring-based thorax to test the performance of the assembled structure. Significant lift is produced, in the order of the weight of the structure, while kinematic patterns present during resonant actuation show accurate reproduction of predicted wing motion. The combination of the ring-based structure and compliant wing pitching mechanism shows that simple lightweight structures can be used to obtain both large amplitude wing sweeping motion and passive pitching motion in an energy efficient manner.

Ring-based four winged prototype, without actuator. Compliant hinges indicated in red.



A multi-scale oddity: unifying homogenization and localization

Erica Coenen, Varvara Kouznetsova and Marc Geers

Eindhoven University of Technology, Department of Mechanical Engineering,

Section Materials Technology, P.O. Box 513 , 5600 MB Eindhoven, NL.

phone:+31 40 247 5169, email: [email protected]

Simultaneously with the increased utilization of complex materials, the demand for multi-scale

modeling has increased. Computational homogenization schemes are based on the solution of two

nested boundary value problem for the macro-and microscale. These techniques are very powerful

and versatile, especially in the applications where overall material properties are influenced by applied

strain paths and microstructural evolution.

Computational homogenization relies on microstructural volume elements (MVEs) which are locally

representative for the microstructure. Strain localization inevitably limits the concept of classical

homogenization.

Figure: Damage and strain localization within a microstructural volume element limits the

concept of representativety and thus of classical homogenization.

In this work, an innovative multi-scale framework has been developed, which correctly upscales the

effect of microscale damage on macroscale fracture. The new scheme, divides the microscopic

deformation into a bulk and localization type of deformation. The macroscopic continuum is enriched

with a cohesive discrete crack, which lumps the microstructural strain localization and the residual

load carrying capacity. This overcomes the limitation of classical schemes and enables structural

analyses beyond the point of strain localization and up to the point of fracture.

Classical

homogenization

New multi-scale

framework


Handling of stress constraints in

topology optimization

L. Del Tin, A. Verbart, M. Langelaar, F. van Keulen

Delft University of Technology

Topology optimization of structures subjected to stress constraints is of great industrial interest. However, while the use of topology optimization for the solution of problems with volume or compliance constraints is an established procedure, the handling of stress constraints still poses some issues. Various techniques proposed in literature to address these problems will be introduced and compared, for both density-based and level set topology optimization. In particular, the role of the different parameters involved in the optimization will be analyzed and the performance of different methods evaluated for different design problems.


A two-scale approach for

propagating cracks in a fluid saturated porous material

F. Irzal, J.J.C. Remmers, J.M.R. Huyghe, R. de Borst, K. Ito

Numerical Methods in Engineering Eindhoven University of Technology,

Faculty of Mechanical Engineering P.O. Box 513, 5600 MB Eindhoven, The Netherlands

phone: +31 40 247 2271, e-mail: [email protected]

Abstract

This research focuses on the fracture that may occur in intervertebral discs. The intervertebral disc,

which lies between adjacent vertebrae in the spine, serves as a shock absorber, load distributor,

spacer and flexibility provider to the spine. The presence of damage in the discs, e.g. cracks, faults and

shear bands, can obviously change their physical behaviour of the disc which may affect its capacity of

absorbing and transmitting load. This, in turn may cause severe lower back pain on human body.

An extension to a finite strain framework of a two-scale numerical model for propagating cracks in

porous material [1, 2] is proposed to model the fracture on intervertebral discs with in combination

with a hyperelastic material response. In the model, a crack is described as a propagating cohesive

zone by exploiting the partition-of-unity property of finite element shape functions *3+. At the

microscopic scale, the flow in the cohesive crack is modeled as viscous fluid using Stokes equations

and averaged over the cross section of the cavity. The governing equations are derived for the

momentum and the mass for a fluid saturated porous medium, which are assumed to hold on the

macroscopic scale. The weak formulations are derived for this model and calculated under total

Lagrangian formulation. The resulting discrete equations are non-linear due to the the cohesive crack

model, the geometrical nonlinear effect and non-linearity of the coupling terms. A Crank-Nicholson

scheme takes care of the time integration of the system.

References [1] F. Kraaijeveld, et al. , Engng. Fracture Mech., 2009. [2] J.Rethoré, et al., Arch Appl Mech75: 595-606, 2006. [3] J.J.C. Remmers, et al., Comp. Mech. 31(1), 2003.


Power harvesting in a helicopter lag damper

P. H. de Jong, A. de Boer, R. Loendersloot, P. J. M. van der Hoogt

Institute of Mechanics, Processing and Control – Twente (IMPACT) Section Structural Dynamics and Acoustics, University of Twente

P.O. Box 217, 7500 AE Enschede, The Netherlands phone +31 53 4893605, email [email protected]

The European Clean Sky project is oriented towards ‘greening’ aircraft. One of the contributions of the University of Twente is in the field of rotor craft and this work discusses the application of power harvesting techniques in the rotor. The desire to instrument rotors places more requirements on rotor design and electrical / data connections with the chassis. To simplify electrical systems local processing and even wireless applications are considered. Locally generating power for these systems further simplifies the electrical infrastructure in the rotor resulting in stand-alone smart rotor blades. Power harvesting using piezo electric materials is investigated within the rotor system, in particular the lag damper. This component dampens in-plane motion of the blades preventing phenomena such as ground and air resonance. Due to the characteristic of the damper normal flight conditions lead to a load profile which resembles a step function. An 8.15m radius blade is considered which leads to an excitation of ±9kN at 4.2Hz. Using Simulink and Simscape simulations are performed on optimized piezo stacks installed in series with the lag damper. Various electric circuits are considered which vary in complexity and passive or active operation. Up to 7.4W of power can be harvested from the specified blade using the most advanced circuit and the given flight condition. During simulations various crucial design aspects were discovered as well. These aspects strongly influence power output and are to be addressed in the detailed future design of a prototype. The harvested energy from the simulation is sufficient to allow for instrumentation of the blade, local processing and wireless transmissions. The design can also be down-scaled to tailor the power output to the energy requirements of the instrumentation.



Multiscale friction modeling for sheet metal forming

J. Hol*, M.V. Cid Alfaro**, T. Meinders***, J. Huétink***

* Materials innovation institute (M2i), P.O. box 5008, 2600 GA Delft, the Netherlands

e-mail: [email protected] ** Corus Research Centre, P.O. box 10000, 1970 CA IJmuiden, the

Netherlands *** University of Twente, Faculty of Engineering Technology, chair

of Forming Technology, P.O. box 217, 7500 AE Enschede, the Netherlands

Keywords: friction modeling, asperity contact, real contact area, ploughing, adhesion, coefficient of friction Abstract: The automotive industry uses Finite Element (FE) software for formability analyses to reduce the cost and lead time of new vehicle programs. In this respect, FE analysis serves as a stepping stone to optimize manufacturing processes. An accurate forming analysis of an automotive part can however only be made if, amongst others, the material behavior and friction conditions are modeled accurately. For material models, significant improvements have been made in the last decades, but in the majority of simulations still a simple Coulomb friction model is used. The Coulomb friction model does not include the influence of important parameters such as pressure, punch speed or deformation of the sheet material. Consequently, even using the latest material models, it is still cumbersome to predict the draw-in of a blank during large scale forming processes correctly. To better understand contact and friction conditions during lubricated sheet metal forming processes, experimental and theoretical studies have been performed in order to describe microscopic dependencies. On microscopic level, friction is due to adhesion between contacting asperities, the ploughing effect between asperities and the appearance of hydrodynamic friction stresses. The real area of contact, which depends on different flattening and roughening mechanisms, plays an important role in characterizing friction. However, micro models encompassing these mechanisms are generally regarded as too cumbersome to be used in large scale simulations. In this presentation, an advanced friction model is proposed which couples the most important friction mechanisms. Based on statistical parameters a fast and efficient translation from micro- to macro modeling is included. A general overview of the friction model is presented and the translation from micro to macro modeling is outlined. The development of real area of contact is described by the flattening models proposed by Westeneng [1]. The effect of ploughing and adhesion on the coefficient of friction is described by the friction model of Challen & Oxley [2]. The implementation of these models in FE codes is discussed and the feasibility of the advanced macroscopic friction model is shown by a full scale sheet metal forming simulation. FE simulations on micro-scale have been performed in order to validate the flattening models included in the friction model. References: [1] A. Westeneng (2001), “Modelling of Contact and Friction in Deep Drawing Processes”, PhD

thesis University of Twente, ISBN 90-365-1549-1 [2] J.M. Challen and P.L.B. Oxley, “An explanation of the different regimes of friction and wear

using asperity deformation models”, Wear, 53:229–243, 1979


Goal-oriented adaptive methods for a Boltzmann-type equation

Wijnand Hoitinga

Delft University of Technology, Department of Mechanical, Maritime and Materials

Engineering and Department of Aerospace Engineering, Mekelweg 2, 2628 CD, Delft

Phone +31-(0)15 2781518, e-mail: [email protected]

In flow modeling, one has access to three different types of models, notably, the molecular model, the Boltzmann model and the continuum models (e.g. the Navier-Stokes equations). What model to choose depends on the Knudsen number; see figure 1. For Knudsen between, say, 0.01 and 10, the Boltzmann model provides an accurate flow description. The Boltzmann model is given by an integro partial-differential equation that describes the evolution of a one-particle probability-density function. For d spatial dimensions, the Boltzmann equation is set on a 2d+1 dimensional domain, where the +1 accounts for time dependence. On account of the high-dimensional setting, the construction of numerical approximations to the Boltzmann equation is a daunting challenge. The restricted interest to particular quantities of interest in many engineering applications, combined with the complexity corresponding to the high-dimensional setting of the Boltzmann equation, indicates that enormous computational savings can be achieved by means of goal-oriented adaptive finite-element methods. In goal-adaptive methods, a computational model with minimal complexity is generated for one particular output functional. To test goal-adaptive strategies for the Boltzmann equation, we have developed a 1D (d=1) prototype of the Boltzmann equation that exhibits the essential features of the higher dimensional counterparts. For this simplified Boltzmann model we have developed a goal-adaptive discontinuous Galerkin finite-element method. Our numerical results illustrate that goal-adaptive indeed provides a very powerful technique for the Boltzmann equation.

∞_ Knudsen _ 0

Figure 1 Hierarchy of flow models


Isogeometric design optimisation of anisotropic composite shells

A. P. Nagy1*

, M. M. Abdalla1

, Z. Gürdal1

1

Aerospace Structures and Computational Mechanics Chair, Delft University of Technology, Kluyverweg 1, 2629 HS Delft

The Netherlands, *Corresponding author: [email protected]

KEYWORDS: isogeometric analysis, NURBS, stiffness tailoring, multilevel shape design, manufacturing

constraints

ABSTRACT Thin-walled composite shells, typically modeled as inextensible one-director Cosserat continua during

the design phase, are of particular importance in aerospace and automotive applications. Based on

the recently introduced isogeometric analysis, simultaneous structural sizing and shape optimization

of multi-layered Kirchoff-Love shells is proposed. Adaptation of identical geometric representations

for both design and analysis eliminates repetitive conversions between computer aided and facet

based geometries traditionally used in finite element analysis. The presented design framework

employs non-uniform rational B-splines. Shape changes can be represented by altering both spatial

location of the control points and the associated weights. Sizing variables defined at the control points

are interpolated by the same spline basis functions. Analytical evaluation of consistent discrete

sensitivities is emphasized that significantly improves the performance of the optimisation process.

While sizing should reflect local stress states, shape design is preferably pursued on a global level.

Thus, a multilevel approach is utilised, where shape design is performed on a coarser mesh. Projecting

the shape design sensitivities bridge the gap between different levels. Finally, both structural

constraints and manufacturing requirements are addressed within the design formulation.


Computational homogenization for cohesive crack modelling

Vinh Phu Nguyen

Delft University of Technology, Faculty of Civil Engineering and Geosciences, Structural Mechanics Section, P.O. Box 5048, 2600 GA Delft

phone: +31 15 278 3436, e-mail: [email protected]

This research project aims at devising a computational homogenization method, which is objective with respect to finite element discretizations of the coarse scale/fine scale models and to the fine scale model dimension. The method is applied to softening quasi-brittle materials. These materials have a random heterogeneous microstructure that undergoes localized damage such as concrete. The concept of RVE for quasi-brittle softening materials has been revisited in [2] in which we developed a new averaging technique coined the failure zone averaging scheme . The basic idea of the scheme is to do the averaging over a propagating damaged zone, rather than over the entire fine scale domain. By doing so, we have been able to obtain homogenized initially rigid cohesive laws which are independent of fine scale model size which allows us to state that an RVE exists for softening materials when averaging towards a coarse scale cohesive law. Departing from the results presented in [2], we have devised a computational homogenization based multiscale crack framework in [3]. The basic ingredients of the method are as follows. The coarse scale model is a homogeneous elastic solid (with effective properties computed in a pre-processing step by means of conventional homogenization theory) containing a cohesive crack (modelled by Partition-of-Unity Finite Element Method, PUFEM). The behavior of that cohesive crack is coming from finite element computations performed on a fine scale model. In the fine scale model, all heterogeneities are explicitly meshed and failure of microstructural constituents is modelled by a non-local continuum damage model. The coarse-fine scale coupling is done in the spirit of the multilevel finite element framework which is better known as

FE2

methods [4]. Two drawbacks associated with conventional homogenization theory applied for softening materials are eliminated in the proposed multiscale crack framework. This presentation will focus on the existence of an RVE for softening materials and the proposed homogenization based multiscale crack model. Numerical examples including a comparison with a direct numerical simulation (DNS) are given to demonstrate the performance of the method.

Reference

[1] I.M. Gitman, H. Askes, L.J. Sluys. Representative volume: existence and size determination, Engineering Fracture Mechanics 74(16) (2007) 2518-2534.

[2] V.P.Nguyen, O. Lloberas-Valls, M. Stroeven, L.J. Sluys. On the existence of representative volumes for softening quasi-brittle materials-A failure zone averaging scheme, Computer Methods in Applied Mechanics and Engineering, 2010. In Press, Corrected Proof.

[3] V.P.Nguyen, O. Lloberas-Valls, M. Stroeven, L.J. Sluys. Homogenization based multiscale crack modelling: from micro diffusive damage to macro cracks, Computer Methods in Applied Mechanics and Engineering, 2010. Submitted.

[4] F. Feyel A multilevel finite element method (Fe2) to describe the response of highly non-linear structures using generalized continua, Computer Methods in Applied Mechanics and Engineering, 192 (2003) 3233-3244.


A hierarchical approach for contact detection in highly

polydisperse granular systems and how to find the optimal

parameters

V. Ogarko and S. Luding

Multi Scale Mechanics/TS, Faculty of Engineering Technology, University of Twente, 7500 AE, Enschede, The Netherlands.

[email protected]; [email protected]; http://msm.ctw.utwente.nl

Collision detection is a basic computational problem arising in systems consisting of many objects, particles or atoms. It is fundamental to many applications, including computer games, physically based simulations of metals, concrete and other engineering materials.

The Discrete Element Method (DEM) is a very enticing simulation technique for computing the motion of a large number of objects, e.g., particles in granular media [1]. Since such large numbers, like millions of particles, imply a long computation time, for realistic systems, high performance computing is mandatory. The performance of the computation relies on several factors, which include the physical model, on the one hand, and the contact detection algorithm used on the other. Different contact detection mechanisms such as grids, trees, Delaunay triangulation and spatial sorting are analyzed [2, 3].

The single-level grid-based contact detection methods (i.e. Linked Cell [2]) are straightforward, widely used and perform well for similar sized objects; but, they are unable to deal with particles of greatly varying sizes, like for example in concrete. If the particles within the system are polydisperse, i.e., their sizes differ, the size of a single grid would have to conform to the largest particle existing in the system. Fortunately, this size problem can effectively be addressed by the use of multi-level (hierarchical) data structures, such as hierarchical grids [4].

In this study, we describe a robust algorithm for contact detection, which has computational complexity and memory consumption both O(N) , for particles widely distributed in size [4]. The multi-scale hierarchical approach presented allows us to simulate highly polydisperse systems without loss of performance, while the hash table storage approach allows us to simulate large (or even unbounded) systems, e.g., with inhomogeneities due to clustering, without the memory overhead associated with storage of the data structure. The cell size at each hierarchy level can be selected independently and this allows setting it up in an optimal way according to the particles size distribution (PSD) function.

We analyzed theoretically and confirmed with DEM simulations how to choose the optimal parameters (cell sizes, hierarchy levels) for arbitrary PSD in order to get best performance. The time performance is measured for the realistic particles systems with different numbers of particles, different polydispersity and different volume fraction for the 2D and 3D cases.

[1] S. Luding, Introduction to Discrete Element Methods: Basics of Contact Force Models and how to perform the Micro-Macro Transition to Continuum Theory, EJECE (Alert Course Lecture, Aussois), 785-826 (2008). [2] B. Muth, M.-K. Muller, P. Eberhard and S. Luding. Collision Detection and Administration Methods for Many Particles with Different Sizes. In: Wills B. editor. Proceedings of MEI (minerals engineering international). Brisbane, Australia; 2007. p. 1–18. [4] V. Ogarko, S. Luding. Fast, robust and memory efficient collision detection algorithm for granular media simulations with different sizes. (In preparation, 2010).

http://msm.ctw.utwente.nl/


Wavelet-based Spectral Finite Element Method for Simulation

of Elastic Wave Propagation

Pooria L. Pahlavan

Delft University of Technology, Faculty of Aerospace Engineering,

Department of Aerospace Structures, Kluyverweg 1, 2629 HS Delft, the Netherlands. Phone: +31 (0)15 2787308, Email: [email protected]

Damage detection systems in structural health evaluation predominantly seek changes in the structure response with which the existence and characteristics of the damage can be quantified. One of the most significant classes of these systems is based on the fact that damage and material discontinuities affect the propagation of elastic waves in the structure viewed as the waveguide. While small-sized damage is only sensitive to high frequency waves, the h-method Finite Elements with a Newmark time-integration scheme is known to be inefficient in terms of computational cost and accuracy. Also p-method Finite Elements e.g. Spectral Element method does not bring a drastic improvement in terms of accuracy. On the other hand, the classical approach for dealing with wave propagation problems employs transformed domains in order to let the assumed solution satisfy the governing wave equations as closely as possible. For 2D and 3D waveguides, this class of solution methods reduces the problem to a 1D equation by transforming the spatial coordinates as well as the time. However, handling geometrical complexities and imposing boundary conditions to the model for the spatial transformation is either numerically inefficient or limited to periodic BCs confining the method to certain applications. In this study, by taking advantage of the unique properties of the WT without encountering the spatial transformation hardships, a third way is suggested by adopting a Finite Element approach in the transformed domain. The novel super-convergent wavelet-based spectral FEM (SWFEM) with superior approximation properties has been developed to solve the elastic wave equation in membrane-type structures. In the 2D WSFEM, having computed the exact values of the connection coefficients and derivative operators of Daubechies compactly supported wavelets over a finite interval, the in-plane wave equation of the 2D structure has been temporally transformed. Then, the transformed elastodynamic equations have been decoupled using an eigenvalue analysis. Since no exact solution is available for a general loading and boundary condition, a Finite Element formulation has been implemented. However, contrary to the classical FEM, shape functions in the introduced SWFEM are functions of the wave numbers obtained from the temporal approximation. As the name suggests, the FE formulation of the problem being derived in the transformed domain converges very quickly with fewer DOFs compared to the conventional FEM. Note that using the compactly supported wavelets, the temporal discretization is also done with drastically fewer sampling points compared to Newmark integration scheme. This substantially reduces the total number of DOFs in the time-space domain. Moreover, the equations associated with these discrete points are decoupled and can be solved in parallel. More details about the method can be found in [1].

Reference [1] L. Pahlavan, C. Kassapoglou, Z. Gürdal. “Wavelet-based Finite Element Method for Crack Detection in Plate Structures”. The 9th World Congress on Computational Mechanics. Sydney, Australia, 2010.


Actuators for Smart Applications.

Alexandre Paternoster, Andre de Boer, Richard Loendersloot and Remko Akkerman.

Engineering Technology, Universiteit Twente

Actuator manufacturers are developing promising technologies which meet high requirements in performance,

weight and power consumption. Those technologies are offering bright perspectives in the industry, providing

feasible solutions for the actuation of smart systems with active control. Conventionally, actuators are

characterized by their displacement and load performance. This hides the dynamic aspects of those actuation

solutions. Work per weight performed by an actuation mechanism and the time needed to develop this

mechanical energy are by far more relevant figures. Constraints on the time, weight and power required can

easily be added in order to find the optimal weight or power efficient actuator for the application investigated.

This process has been applied to an active flap (so-called Gurney flap) on a helicopter rotor blade with which the

lift/drag ratio can be changed. Actuation time constraints have been applied to investigate the various

technologies available for active concepts. The focus on this study is on the feasibility of active control of Gurney

flaps integrated within a smart rotor blade. The main part was the estimation of the energy required to deploy a

Gurney flap within an active control scheme and finding an optimal solution regarding the performance desired,

the power available and manufacturing constraints. Active control for rotor blades requires an actuation faster

than the blade passing frequency to be able to improve the aerodynamic performances of the blade. The

conclusions are highly depending on the time constraints. The best actuators according to that selection are stack

actuators in this example. The Gurney flap application shows the effectiveness of the actuator selection

procedure based on dynamic performance per weight. The generic nature of the procedure allows to use it for a

wide range of applications.


Flow in Corrugated Pipes

P. I. Rosen Esquivel

Eindhoven University of Technology, Department of Mathematics, Centre for Analysis and Scientific Computing CASA, P.O. Box 513, 5600 MB Eindhoven

phone +31-(0)40-2473162, e-mail [email protected]

The effect of wall shape in the friction factor of a forced flow through pipes or hoses is of interest in many applications. Several numerical and experimental studies have shown that the contribution of wall shape on the flow is not trivial even in the laminar case. The friction factor in corrugated pipes has been found to differ from the classical Moody diagram which presents the laminar friction factor as independent of wall roughness. Available CFD computation techniques allow to predict flows in arbitrary geometry, based on these computations, the friction factor can be calculated, but this kind of procedures can become prohibitively expensive in terms of calculation time. In this talk we discuss a method for estimating the pressure losses for laminar forced flow in axially symmetric pipes with varying radius. The approach is based on an analytic expression for the friction factor, obtained after integrating the Navier-Stokes equations and an asymptotic expansion for the flow field. Examples for the validation of the method are presented. References: [1] Rosen Esquivel, P.I., ten Thije Boonkkamp, J.H.M., Dam, J.A.M., Mattheij, R.M.M. “Efficient estimation of the friction

factor for forced laminar flow in axially symmetric corrugated pipes”. In Proceedings of 2009 ASME 3rd

Joint US-European Fluids Engineering Summer Meeting. FEDSM-ICNMM 2010-30378.


Derivative-free optimization for focus

and astigmatism correction

M.E. Rudnaya*, W. van den Broek**, R.M.P. Doornbos***, S.C. Kho*, R.M.M. Mattheij*, J.M.L. Maubach*

*CASA, Eindhoven University of Technology, 5612AZ, Eindhoven, +31-40-247-31-62, [email protected]

**EMAT, University of Antwerp, Belgium

***Embedded Systems Institute, Eindhoven, The Netherlands

Electron microscopy is a powerful research tool. Nowadays electron microscopy still requires an expert operator in order to manually obtain in-focus and astigmatism-free images. Both the focus and the two-fold astigmatism have to be adjusted regularly during the image recording process. Possible reasons are for instance the instabilities of the environment and the magnetic nature of some samples. For the next electron microscopy generations the manual operation has to be automated. One of the reasons is that for some applications the high level of repetition severely strains the required concentration. Therefore, a robust and reliable simultaneous autofocus and two-fold astigmatism correction algorithm is a necessary tool for electron microscopy automation. The problem of automated focus and astigmatism correction in electron microscopy is at least a three-parameter problem (one focus and two astigmatism parameters). The evaluation function is an image recording with a further computing of an image quality measure. The image quality measure reaches its optimum, when an image has the highest possible quality, i.e. the microscopic parameters are at optimal focus and astigmatism. Thus, the optimization goal is to maximize the image quality measure in a three-parameter space. Computations determining an image quality measure costs much less time than an image recording. Therefore, and also because repeated recordings can damage or destruct the sample, it is needed to optimize the focus and astigmatism with just a few recordings. The optimization is further made difficult due to the recording’s noise and the absence of analytical derivative information. Calculating (approximately) derivatives with finite differences would dramatically increase the amount of necessary image recordings, and is therefore not discussable. For electron microscopy we present an automated application for simultaneous focus and two-fold astigmatism correction based on the image quality measure and derivative-free optimization [1]. The approach proved to work both for simulated images and in a real-world application on a scanning transmission electron microscope. The speed and accuracy of it are comparable to those of a human operator. The Nelder-Mead simplex method and the Powell interpolation-based trust-region method are discussed and compared for a real-world application running on a scanning transmission electron microscope [2].

References

[1] M.E. Rudnaya, W. van den Broek, R.M.P. Doornbos, R.M.M. Mattheij, J.M.L. Maubach. Autofocus and two-fold astigmatism correction in HAADF-STEM. Casa-report 10-09, Eindhoven University of Technology, 2010. http://www.win.tue.nl/analysis/reports/rana10-09.pdf.

[2] M.E. Rudnaya, S.C. Kho, R.M.M. Mattheij, J.M.L. Maubach. Derivative-free optimization for autofocus and astigmatism correction in electron microscopy. In Proc. 2nd International Conference on Engineering Optimization, 2010.

Acknowledgment

This work has been carried out as a part of the Condor project at FEI Company under the responsibilities of the Embedded

Systems Institute (ESI). This project is partially supported by the Dutch Ministry of Economic Affairs under the BSIK program.

We kindly acknowledge D.Langsweirdt (Technical University of Leuven), N.Venema (Technolution) for the assistance with

software developmet; S.Sluyterman, M.Otten (FEI), S. van Loo (ESI) for their useful comments and suggestions.


Hybrid Dynamic Substructuring in Wind Turbine Engineering

S.N. Voormeeren and D.J. Rixen

Delft University of Technology, Faculty of Mechanical Engineering,

Section Engineering Dynamics, Mekelweg 2, 2628 CD Delft, Netherlands

Phone : +31-(0)15-2781881, e-mail: [email protected]

Being one of the most abundant sources of renewable energy, wind power has the potential to play a major role in a sustainable future energy supply. However, to be truly competitive with conventional sources the cost of wind energy must be further reduced. To achieve this, wind turbines are getting ever larger and more optimized. Hence, efficient and accurate determination of the wind turbine’s structural dynamics is crucial. Traditionally the global dynamic behaviour of a wind turbine is analyzed using so-called aero-elastic codes. In addition to the structural properties, these codes model the aero-, hydro- and controller dynamics. For certification purposes, thousands of load cases need to be evaluated. To keep computation times acceptable these models must therefore be relatively coarse. Due to the design optimization of wind turbines, components can start to exhibit local dynamic behaviour, increasing loading up to a level that can cause failure. However, due to their relatively few degrees of freedom, the aero-elastic models are often not capable of predicting these local effects. To overcome these problems, a more detailed structural dynamic analysis tool is being developed based on the paradigm of dynamic substructuring (DS) [1]. The DS methodology consists in performing dynamic analysis of a complex system in a component-wise fashion. First, the system is decomposed in components (substructures). Then discrete dynamic models (often finite element models) are created for the components, which are subsequently assembled to obtain the complete dynamic model. This approach allows recognizing local dynamic problems more easily, combining modelled and measured components, and sharing substructure models from different project groups. By combining this component-wise approach with model reduction techniques a very powerful dynamic analysis tool can be created, combining both accuracy and efficiency. Although the concept of DS has been around already for some decades [2], it has not yet become a standard tool in dynamic analysis. The aim of this project is therefore to try and further develop the DS methodology through theoretical extensions and implement the methodology in the wind turbine engineering practice.

In this presentation we will give an overview of the work done in this PhD project. Furthermore, we will go into some detail regarding the component model reduction methods and the efficient updating of the reduction bases for use in a design process.

References [1] S.N. Voormeeren, P.L.C. van der Valk & D.J. Rixen. Practical Aspects of Dynamic Substructuring in Wind Turbine

Engineering. Proceedings of the 28th

International Modal Analysis Conference, Jacksonville, 2010 [2] D. de Klerk, D.J. Rixen, & S.N. Voormeeren. General Framework for Dynamic Substructuring: History, Review and

Classification of Techniques. AIAA Journal, 2008, 46, 1169-1181


4

SURVEY

of

POSTER PRESENTATIONS This section contains a survey of poster presentations of actual PhD-projects within the Graduate School Engineering Mechanics. Furthermore, poster presentations are available through:

http://www.em.tue.nl



Survey of Poster Presentations Thirtheenth EM Symposium

Nr. Last name First name Univ. Title poster

01 Ahmed Awais TUD A Discontinuous, Geometrically Non-linear Solid-Like-Shell Element

02 Altunlu Can UT Life assessment of combustion liners by fracture mechanics approach

03 Ayas Can TU/e Climb assisted glide in passivated crystals

04 Beers, van Paul TU/e A grain boundary interface model in strain gradient crystal plasticity

05 Beex Lars TU/e Multiscale mechanics of atomistic crystals

06 Bergers Lambert TU/e Design of an in-situ SEM sub-microN tensile tester

07 Boer Steven UT Efficient modeling of a large stroke elastic mechanisms using beam and superelements

08 Boustheen Allwyn TU/e Layered modular polymeric later structured µ-valve

09 Burgt, van de Yoeri TU/e Close-loop control of a laser assissted carbon nanotube growth process for interconnects in flexible electronics

10 Cloots Rudy TU/e Multi-scale mechanics of traumatic brain injury

11 Coenen Erica TU/e A multi-scale oddity: unifying homogenization and localization

12 Del Tin Laura TUD Stress constraints in density-based optimization

13 Dijk, van Nico TUD The influence of design interpolation on structurral responses in topology optimization

14 Dogge Michael TU/e Mechanics of phase boundaries in multiphase steel

15 Drenth Emiel UT Lifetime assessment of PVC gas and water pipes using micro-indentation

16 Ertürk Isa TU/e Strain gradient crystal plasticity modeling of particle strengthened alloys

17 Grouve Wouter UT Mandrel peel test for tape placement

18 Guido, de Samuele UT Surrogate modelling for structural optimitzation

19 Haanappel Sebastiaan UT Constitutive modelling of UD reinforced thermoplastic laminates

20 Hilkhuijsen Peter UT Plasticity in stainless steel and TRIP steel

21 Hoitinga Wijnand TUD Goal-oriented adaptivity for a Boltzmann-type equation

22 Hol Johan UT Friction modeling on multiple scales

23 Hosseini Saman TU/e Numerical simulation of failure mechanisms in composites

24 Irzal Faisal TU/e A two-scale approach for propagating cracks in a fluid saturated porous material

25 Javani Joni Hamid Reza TU/e Stable three dimensional crack initiation/propagation based on adaptive meshing

26 Jong, de Pieter UT Power harvesting in a helicopter

27 Karupannasamy Dinesh Kumar UT Friction modeling for sheet metal forming (SMF) on multiple scales

28 Kolluri Murthy Naga TU/e Experimental characterization of full cohesive zone law using miniature mixed mode bending setup

29 Krijgsman Dinant UT A local contitutive model with anisotropy for homogeneous 2D biaxial deformation modes

30 Kuipers Erwin UT Development of new method for the measurement of sound absorption

31 Mandapalli Prtihvi TUD Multiphysics computational modelling of damage in heterogenous materials under impact loading

32 Martinez Lopez Alejandro UT Effect of bending on formality limit curves

33 Matteucci Marco TU/e A reconfigurable superparamagnetic bead filter for microfluidic detection of bio-material

34 Meijaard Jacob UT Modeling of anisotropic beams

35 Neggers Jan TU/e Global digital image correlation for full field strain maps of bulged membranes

36 Nguyen Phu TUD Computational homogenization for cohesive crack modelling

37 Niazi Muhammed UT Plasticity induced anisotropic damage modeling for forming processes

38 Ooijevaar Ted UT Vibration based structural health monitoring of composite structures

39 Opstal, van Timo TU/e Airbag-deployment simulations

40 Pahlavan Pooria TUD Wavelet-based spectral finite element method for simulation of elastic wave


propagation

41 Paternoster Alexandre UT Actuators for smart rotorblades

42 Perdahcioglu Semih UT Multi-phase steels and phase transfromations

43 Pina Juan Carlos TU/e Thermal expansion and elastic mismatch in thermo-mechanical behaviour of cast iron

44 Pizzocolo Francesco TU/e Experimental validation of the numerical model for the crack propagation in poroelastic media

45 Poh Leong Hien TU/e A scale transition plasticity theory - from crystal to continuum

46 Quak Wouter UT An adaptive methods & forming processes

47 Ravanan Mahmoud UT Material characterization of PVC water pipes by means of nonlinear ultrasound

48 Rodriguez Natalia UT Friction modeling in cluding viscoelastic anisotropic material behaviour

49 Rudnaya Maria TU/e Derivative-free optimization for focus and astigmatism correction

50 Samimi Mohammad TU/e A self-adaptive cohesive zone model for interfacial delamination

51 Saputra O TUD Moving particle with thermal gradient in microfabricated fluidic device

52 Schutte Arjan UT An implicit and explicit solver for comtact problems

53 Shabir Zahid TUD The role of cohesive law parameters on intergranular crack propagation in brittle polycrystals

54 Shroff Sonell TUD Non-matching Meshes- Mortar method

55 Starkov Konstantin TU/e Variable structure production control method for a line of N Manufacturing machines

56 Stelt, van der Arnoud UT Alloying and caldding of advanced AI-alloys employing friction stir welding

57 Tabak Umut TUD Irca, iterative reduced correction algorithm for vibroacoustics

58 Talebian Mojtaba TUD Multidomain numerical tools for environmental impact assessment and monitoring of CO2 sequestration

59 Valefi Mahdiar UT High temperature tribology study of CuO doped TZP

60 Valk, van der Paul TUD Structural dynamics of offshore wind turbine foundations

61 Voormeeren Sven TUD Dynamic substructuring as analysis tool in wind turbine engineering

62 Vossen Bart TU/e Multi-scale analysis of cohesive interfaces

63 Weerathunge Kdawathagedara

Saumya TUD Multi-scale modeling of damage in heterogenous materials under impact loading

64 Wiebenga Jan Harmen UT Robust optimization of forming processes

65 Winogrodzka Agnieszka UT Motion in vacuum by elastic mechanisms and tribology

66 Woldman Martijn UT Abrasive wear of military platforms

67 Yadegari Sourena TUD Coupled thermomechanical analysis of transformation-induced plasticity in multiphase steels

68 Yaqoob Muhammad Adeel

UT Positioning accuracy in vacuum: effects of friction

69 Yazdchi Kazem UT Determination of the size of the representative volume element for random fibrous media

70 Zwieten, van Dirk TU/e Observer design for networks and distributed control

Graduate School on Engineering Mechanics c/o Eindhoven University of Technology PO Box 513, building W-hoog 4.133 5600 MB Eindhoven NL Tel.: +31 40 2478306 Fax: +31 40 2447355 E-mail: [email protected] http://www.em.tue.nl

Documents

Thirteenth Engineering Mechanics Symposium · Thirteenth Engineering Mechanics Symposium 5 Preface The Graduate School on Engineering Mechanics, a joint initiative of the Eindhoven