Is there a default umat when no user material is declared

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1

Hi.
Is there a “baseline” umat that is used if no *USER MATERIAL card is declared? I want to change the plasticity criterion there to Mises/Barlat/Hill or something else. Can you say if its possible? Maybe if you have such umat you can share it with me?

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umat_user.f has only the heading/template, but you can find some built-in umats in the source code: Code search results · GitHub

According to Makefile, we have:

  • umat_abaqus.f
  • umat_abaqusnl.f
  • umat_abaqusnl_total.f
  • umat_aniso_creep.f
  • umat_ciarlet_el.f
  • umat_compression_only.f
  • umat_def_plas.f
  • umat_elastic_fiber.f
  • umat_ideal_gas.f
  • umat_johnson_cook.f
  • umat_lin_el_corot.f
  • umat_lin_iso_el.f
  • umat_main.f
  • umat_single_crystal_creep.f
  • umat_single_crystal.f
  • umat_tension_only.f
  • umat_undo_nlgeom_lin_el.f
  • umat_undo_nlgeom_lin_iso_el.f

Also, check the TFEL/MFront library as it includes Barlat plasticity, for instance.

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One ABAQUS related baseline UMAT example to change the plasticity criterion you can find on Github from Barlats group. You can easily adopt it for ccx: In the Fortran UMAT code comments you will find how they use the 2nd user material parameter to decide which plasticity criterion should be used during the analysis run:

C PROPS(2): OPTIONS FOR YTELD FUNCTION MODEL
C 1- VON_MISES
C 2- HILL 1948
C 3- YLD2000_2D [1]
C 4- YLD2004_18P [7]

Example: Your inp file controls with the 2nd value below the *USER MATERIAL card which criterion will be used. Below example (bold highlighted value of 2.) selects the Hill criterion for the analysis:

*MATERIAL, NAME=ABAQUSNLYOON_BARLAT
*Density
7.8e-09,
*Depvar
70,
** PROPS(2): OPTIONS FOR YTELD FUNCTION MODEL:
** 1- VON_MISES
** 2- HILL 1948
** 3- YLD2000_2D [1]
** 4- YLD2004_18P [7]
*User Material, constants=40
5., 2., 5., 2., 2., 3e-05, 197360., 0.33
7284., 1040., 0.135, 0.436, 0., 0., 0., 0.
0., 0., 177960., 57.02, 3., 3., 100., 150.
0.5, 0.9, 8., 0.788, 65., 1.22, 18., 6.
1.02736, 0.939644, 0.962783, 0.983882, 0.986196, 0.939192, 0.98523, 1.01359

Remark: I would not recommend to use above plasticity criterion option 3. (=YLD2000_2D) as the 2D ccx element types are expanded to 3D! For any Barlat related criterion I would selection option 3 (YLD2004_18P) with an inp model consisting of solid elements.

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Thanks for the reply’s guys. I’ll try your suggestions.

5

Hello, i have a question regarding mfront. I generated some libraries but it isnt working, it just stops on 1st iteration. i tried to move it to some folders like usr/local/lib tried to export it to LD_LIBRARY_PATH but to no succes. Can you say how you do that? or maybe link some guide on that matter?