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Comparison of EFG and Standard Elements for the Rubber Membrane in a Biomedical Valve in LS-DYNA 970.5434

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 . Motivation. Assess whether EFG with FSI and MMALE is possible. Compare the results with standard elements.

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Comparison of EFG and Standard Elements for the Rubber Membrane in a Biomedical Valve in LS-DYNA 970.5434

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

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

  3. 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 www.rudolf-boetticher.de

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

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

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

  7. 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 www.rudolf-boetticher.de

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

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

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

  11. 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. www.rudolf-boetticher.de

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

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

  14. 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! www.rudolf-boetticher.de

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