Simulation Driven Innovation 1

Falling Object Protective Structure (Fops) Testing

Abstract

This paper highlights the Importance of Simulation Driven product design approach. The efficient simulation tools like Altair HyperMesh,

HyperCrash and Radioss coupled with engineering Knowledge can effectively assist the designers in achieving the desired compliance, especially in

the field of Product Design wherein the physical tests are mandatory for the compliance certification. The use of simulation can help the designers to

achieve the desired Time, Cost and Weight Optimization without compromising over the Structural Integrity.

Introduction As a new product design group we belong to the SANDVIK Surface Mining segment. The activities involved are the Concept Design and Proto Building using the engineering knowledge and Simulation tools. During the Proto stage the process Time, Cost and the weight optimization activities are undertaken.

At SANDVIK Surface Mining and construction of FOPS CAB is designed to fit in range of Blast hole Drills. The CAB structural members call for a reasonable protection from falling objects like tree, rocks, small concrete blocks, hand tools, etc.

Avinash B Assistant Manager, Design

SANDVIK ASIA Pvt,Ltd #25/26, Abshot Layout

Sankey Road Cross Bangalore-560 052

Siddaram P.Horti Senior Design Engineer SANDVIK ASIA Pvt,Ltd #25/26, Abshot Layout

Sankey Road Cross Bangalore-560 052

Naresh Rao M. Design Engineer

SANDVIK ASIA Pvt,Ltd #25/26, Abshot Layout

Sankey Road Cross Bangalore-560 052

Figure 1: Blast Hole Drill Figure 2: Operator Cab

Simulation Driven Innovation 2

The Falling Object Protective Structure, FOPS (Level-II energy requirement) compliance was tested in accordance with the ISO 3449 2005-09 and Deflection Limiting volume (DLV) with ISO 3164 DLV.

Figure 3: Level II energy requirement curve The Deflection Limiting Volume (DLV) is the orthogonal approximation of large, seated male operator wearing normal clothing and a hard hat. The protective properties of the FOPS system shall be evaluated according to the ability of the cab or protective structure to resist the Impact. The FOPS shall completely cover and overlap the vertical projection of DLV. DLV shall not be entered by any part of the protective structure under the first or subsequent Impact of the test object. In addition to the Impact requirements, there are material requirements for ensuring that the FOPS has meaningful resistance to the brittle fracture. The structural steel material selection will be done in accordance with 6.3 of ISO 3449:2005(E).

DROP OBJECT WEIGHT 226.8 KgFALLING HEIGHT 5.23 mDIAMETER OF THE DROP TARGET 400 mm

DROP OBJECT WEIGHT 226.8 KgFALLING HEIGHT 5.23 mDIAMETER OF THE DROP TARGET 400 mm

Simulation Driven Innovation 3

Process Methodology The Cab is made up of structural steel comprising of tube, angle and plates. The top members are HVAC (Heating Ventilation and Air-conditioning) cover and the Roof. The HVAC cover is bolted onto the roof and covers the Heating Ventilation and Air-conditioning unit. The HVAC cover and the roof shall act as FOPS.

Figure 4: showing the HVAC cover and roof

FE Idealization

The structural members like tubes, angles and plates were idealized using the 2D shell elements. The stringent quality aspects were maintained to get good quality mesh especially on the roof structure and the HVAC cover, which are the targets of drop load.

Figure 5: FE model

HVAC Cover

HVAC Cover Roof

Drop object as master

Roof as slave

DLV of Operator

Simulation Driven Innovation 4

The drop object was Idealized using Hexahedral elements. The overall structure is quad and Hex dominent.

Table 1: Quality Criteria

Sl.NO Quality criteria Value Units 1 Warpage <10 2 Aspect ratio 5 3 Jacobian 0.8 4 Min angle for quad >40 5 Max angle for quad <140 6 Min angle for tria >20 7 Max angle for tria <120 8 Min element size >2 mm 9 Max element size <10 mm

Material model and deck creation

Table 2: Material models for the structural members

Sl.NO Components Material Card Material Yield stress

(Mpa) 1 Plates M1_Elast ASTM Steel 345 2 Tubes M1_Elast ASTM Steel 315 3 Angles M1_Elast ASTM Steel 315

Contact selection Multiusage type7 is used to define the contact between the drop object and the cab Roof. The roof is considered as slave and the drop object as master component. Calculation To bring down the computation time, the falling height 5230mm (5.23m) is reduced to 5mm.The Initial velocity for the reduced distance of 5mm hence computed using the formula-1.

V2 = 2gh 1 Where, V = Velocity g = Acceleration due to gravity, 9.81 m/sec2

h = Height of fall

Table 3: Input parameters

Sl.NO Input Parameters Value Units 1 Actual drop height 5.23 m 1 Weight of drop object 226.8 Kg 2 Simulation Drop height 0.0005 m 3 Initial velocity 10.1293 m/sec

Simulation Driven Innovation 5

Results & Discussions

Figure 6: Deformation Tendency Figure 7: Deformation Tendency

The Physical test conducted on Proto using the Level-II energy requirement resulted in the measurement which is astoundingly proximate to the already measured deformation got from RADIOSS Explicit solver. The post drop test deformation on the cab roof measured 44.45 mm of permanent set and whereas the post simulation deformation measurement resulted in 52.5 mm. A variation of 15% in the deformation value of Simulation and the Actual Drop test was observed. The energy absorption of the target structure after the simulation corresponds to 11250 Joule. It has been also found that the DLV was not violated by the instantaneous or permanent deformations found from both simulation and Drop Test. Benefits Summary As the testing system falls under the category of destructive testing, the proto design calls for the fusing of Engineering knowledge & Simulation. A Simulation driven product design approach prior to Physical test with effective usage of Altair HyperWorks products viz, HyperMesh and RADIOSS proved to be effective in achieving the desired compliance for FOPS and also avoided excess time and cost over run Challenges The FE idealization of such structure is cumbersome and time consuming. The quality of mesh for the above stated application should be maintained with utmost care to ensure the credibility of the simulation output. As the work undertaken was a very new assignment for us, the help documents provided by Altair were not specific to the nature of the job. It took some time for us to key in the right approach. Future Plans With the newly acquired skill with the Altair Products, the present process will be fine tuned to achieve better Simulation output. Apart form FOPS testing, the scope will be extended to optimize the structure for Rollover Protective Structure (ROPS) and Tip Over Protective structure (TOPS).

Simulation Driven Innovation 6

Conclusions The physical drop test is essential for the certification of the protective structures which involve human life. The simulation tools can be used during the concept stage of the Cab design. The actual certification cannot be obtained only on the basis of simulation results. The non-violation of DLV (Deflection Limiting Volume) can only be certified followed by a Physical drop test. It is seldom possible to extract much data out of the destructive test which makes it difficult for the designers to study the structural behavior in detail under the Impact loads. The use of efficient simulation tools like Altair products like Radioss will enable the designers to study and understand the structure response under the above Impact loads.

ACKNOWLEDGEMENTS

Sincere thanks to Mr. Shib Bhowmik, President, SMC and Mr. Anantha K S, Associate Vice President, for their continued support and encouragement. Also would like to thank Mr.Ravi B, General Manager, Design, who patiently spent a lot of time in discussing every small aspects of the FOPS assignment.

Thanks to Altair team who supported us throughout the project span and took all the extra effort to enable us in better understanding the Altair products.

REFERENCES [1] ISO 3449:2005(E) [2] ISO 3164:1992(E) [3] MACHINE DESIGN DATABOOK BY McGraw-Hill