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Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements

Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements. Rudolf Bötticher www.rudolf-boetticher.de . Motivation. Assess whether EFG with FSI and MMALE is possible for *MAT_SOFT_TISSUE . Compare the results with standard elements. Assess whether EFG is more robust.

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Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements

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  1. Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements Rudolf Bötticher www.rudolf-boetticher.de 

  2. Motivation • Assess whether EFG with FSI and MMALE is possible for *MAT_SOFT_TISSUE. • Compare the results with standard elements. • Assess whether EFG is more robust. Result will be: EFG is a luxury hourglass control ! 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_SOFT_TISSUE 1.4,1.4,1.4 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 5434a: always use the newest version for consistency and efficiency! TSSFAC NADV METH CTYPE DIREC PFAC ILEAK www.rudolf-boetticher.de

  6. AET=4 ELFORM=11 *EOS_GRUENEISEN bulk modulus *MAT_NULL *MAT_SOFT_TISSUE *EOS_IDEAL_GAS outflow www.rudolf-boetticher.de

  7. *MAT_SOFT_TISSUE • reinforced Mooney-Rivlin rubber C1=C2= 5 MPa K= 5 GPa (PR=0.4998) reinforcement in tension C5=500 MPa B-direction www.rudolf-boetticher.de

  8. 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 other codes may be better www.rudolf-boetticher.de

  9. Initial shortening of time step prevents intrusion *CONTROL_TIMESTEP ,,,,,222 *DEFINE_CURVE 222 www.rudolf-boetticher.de

  10. default *HOURGLASS 1,1,.00001 DIREC=3 PFAC=0.1 www.rudolf-boetticher.de

  11. near incompressibility and mm dimensions require tiny time step RI HG6 EFG no implicit, no time step split between tissue/ALE domain, no mass scaling! K=5 GPa www.rudolf-boetticher.de

  12. RI HG6 EFG FSI, MMALE dependent on time step! TSSFAC=0.25 www.rudolf-boetticher.de

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

  14. ELFORM=1 *HOURGLASS,6 EFG EFG performance lack: 10% elements switched, CPU time +15% 971: *SECTION_SOLID_EFG 1,41 1.4,1.4,1.4,,,3,2 www.rudolf-boetticher.de

  15. Conclusions • FSI simulations with MMALE and *MAT_SOFT_TISSUE EFG solids are possible in LS-DYNA. • EFG is superior in hourglass prevention for tricky cases. • Time step dependence of FSI needs further investigation! www.rudolf-boetticher.de

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