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Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements Rudolf Bötticher

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Presentation on theme: "Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements Rudolf Bötticher"— Presentation transcript:

1 Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG elements Rudolf Bötticher

2 Birmingham, 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 !

3 Birmingham, 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

4 Birmingham, MM-ALE is easy, if you got a working deck to refine! *ALE_MULTI-MATERIAL_GROUP Proceedings

5 Birmingham, FSI: tweaking of *CONSTRAINED_LAGRANGE_IN_SOLID TSSFAC NADV METH CTYPE DIREC PFAC ILEAK 5434a: always use the newest version for consistency and efficiency!

6 Birmingham, *MAT_SOFT_TISSUE *EOS_IDEAL_GAS AET=4 ELFORM=11 *EOS_GRUENEISEN bulk modulus *MAT_NULL outflow

7 Birmingham, *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

8 Birmingham, 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

9 Birmingham, Initial shortening of time step prevents intrusion *CONTROL_TIMESTEP,,,,,222 *DEFINE_CURVE 222

10 Birmingham, default *HOURGLASS 1,1, DIREC=3 PFAC=0.1

11 Birmingham, no implicit, no time step split between tissue/ALE domain, no mass scaling! RI HG6EFG K=5 GPa near incompressibility and mm dimensions require tiny time step

12 Birmingham, FSI, MMALE dependent on time step! RI HG6EFG TSSFAC=0.25

13 Birmingham, Robustness It proves difficult generating an extreme situation where EFG works but standard elements do not! EFG is superior in preventing hourglass modes.

14 Birmingham, EFGELFORM=1 *HOURGLASS,6 EFG performance lack: 10% elements switched, CPU time +15% 971: *SECTION_SOLID_EFG 1,41 1.4,1.4,1.4,,,3,2

15 Birmingham, 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!

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