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Comparison of EFG and Standard Elements for the Rubber Membrane in a Biomedical Valve in LS-DYNA 970.5434 Rudolf Bötticher www.rudolf-boetticher.de.

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Presentation on theme: "Comparison of EFG and Standard Elements for the Rubber Membrane in a Biomedical Valve in LS-DYNA 970.5434 Rudolf Bötticher www.rudolf-boetticher.de."— Presentation transcript:

1 Comparison of EFG and Standard Elements for the Rubber Membrane in a Biomedical Valve in LS-DYNA Rudolf Bötticher

2 Dresden, www.rudolf-boetticher.de Motivation Assess whether EFG with FSI and MMALE is possible. Compare the results with standard elements. Assess whether EFG is more robust.

3 Dresden, www.rudolf-boetticher.de EFG is easy! *CONTROL_EFG $ in 970 EFG and (dormant) IMPLICIT cards are not tolerated $ in the same deck $ implicit and axisymmetric EFG not implemented! *SECTION_SOLID_EFG 5,41 $ the non-default bigger support helps to have consistent $ EFG simulations for *MAT_MOONEY-RIVLIN_RUBBER 1.5,1.5,1.5

4 Dresden, www.rudolf-boetticher.de MM-ALE is easy, if you got a working deck to refine! *ALE_MULTI-MATERIAL_GROUP Proceedings

5 Dresden, www.rudolf-boetticher.de FSI: Tweaking of *CONSTRAINED_LAGRANGE_IN_SOLID TSSFAC NADV METH CTYPE DIREC PFAC ILEAK 3854, 5434 and newer beta versions deliver different results for identical decks!

6 Dresden, www.rudolf-boetticher.de *MAT_MOONEY-RIVLIN_RUBBER *EOS_GRUENEISEN ELFORM=11 *MAT_NULL *EOS_IDEAL_GAS AET=4

7 Dresden, www.rudolf-boetticher.de Why LS-DYNA for this problem? Curiosity Code is at your disposal Expect the same efficiency as for parallel crash simulation Rely on the advanced material modeling CFX may be better

8 Dresden, www.rudolf-boetticher.de Membrane covered with null shells Filling with *MAT_VACUUM

9 Dresden, www.rudolf-boetticher.de CTYPE=4 CTYPE=5 DIREC=3 PFAC=0.1

10 Dresden, www.rudolf-boetticher.de A=500MPa A=100MPa PR=0.49 near incompressibility and mm dimensions require tiny time step no implicit, no time step split between rubber/ALE domain, no mass scaling!

11 Dresden, www.rudolf-boetticher.de 5831 beta version delivers different results. However, problem not solved. FSI not robust against artificial shortening of time step. No difference between EFG and standard elements.

12 Dresden, www.rudolf-boetticher.de Robustness It proves difficult generating an extreme situation where EFG works but standard elements do not! EFG may be superior preventing hourglass modes.

13 Dresden, www.rudolf-boetticher.de EFGELFORM=1 *HOURGLASS,6 EFG performance lack: 10% elements switched, CPU time +20%

14 Dresden, www.rudolf-boetticher.de Conclusions FSI simulations with MMALE and structural EFG solids are possible in LS- DYNA. Here no real advantage of EFG over standard elements. EFG may be better in hourglass prevention. Time step dependence of FSI needs further investigation!


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