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[Amrith Mariappan]

Link to my umat49v and Keyword files

Hello,

 

I'm experiencing an issue with coupling a user-defined material (UMAT49V) to an equation of state in LS-DYNA R16.1. The EOS pressure array pc(i) accessed via common/eosdloc/ remains zero throughout the simulation, even though the configuration appears correct.

 

Environment:

- LS-DYNA Version: R16.1-182-g5848067bc5 (MPP, Windows 10, Intel Fortran 19.0)

- Material: *MAT_USER_DEFINED_MATERIAL_MODELS (MT=49)

- EOS: *EOS_GRUNEISEN (EOSID=1)

 

Configuration:

My material card is set up with:

- IEOS = 1 (EOS coupling enabled)

- NHV = 12 (reserved 4 slots for EOS as per manual)

- PART card references both MID=1 (UMAT) and EOSID=1 (EOS)

 

In my UMAT49V subroutine, I access the pressure via:

text

  common/eosdloc/pc(nlq)

  ...

  p_eos = pc(i)

text

 

Observed Behavior:

- Debug prints show pc(i) = 0.0 for all cycles

- The UMAT is being called (deviatoric stresses compute correctly)

- Time stepping is working (4347 cycles completed)

- Elements are deforming (strain increments are non-zero)

 

What Works:

- MAT_010 (*MAT_ELASTIC_PLASTIC_HYDRO) with the SAME *EOS_GRUNEISEN card works correctly and produces non-zero pressure

- This confirms the EOS card itself is valid

 

Question:

Is the common/eosdloc/pc() mechanism supported for *MAT_USER_DEFINED_MATERIAL_MODELS in R16.1? The manual (Appendix A, section on user materials with EOS) states that I should:

1. Set IEOS=1

2. Reserve first 4 history variables for EOS

3. Access pressure via pc(i)

 

I've done all three, but pc(i) never gets populated. Is there a compilation flag, additional include file, or different approach needed for user materials to access EOS pressure in R16?

 

Workaround Consideration:

Would implementing the EOS in dyn21ueos.f (using ueos41) instead of relying on external *EOS_GRUNEISEN cards be more reliable for user material coupling?

 

Any guidance would be greatly appreciated. I can provide the full keyword file and UMAT code if needed for troubleshooting.

 

Thank you,

Amrith