Dear all,
Recently, I have been working on the simulation of a pile-soil interaction with CEL method in Abaqus/Explicit. I simulate the sand with the Sand Hypoplasticity Model provided by Prof. Masin. And I use the VUMAT_UMAT Interface from Prof. Bienen.
However, When I call the Vumat.for file, two errors always appears:
Error 1: The option *user material,type=mechanical completely defines the material behavior. It can not be used with an option that defines part of a material`s behavior
Error 2: A material property that is not allowed with a user material has been specified
PS: The picture shows the error message and the sand constitutive model parameters setting.
I did not find a solution to these two errors on the Internet, so I ask for help. Any suggestion or comment will be appreciated.

user-material-3.png Depvar-2.png Elastic-1.png errors-0.png

  1. David Mašín
    David Mašín 3 months ago

    Hi Kunpeng, can you explain why you define also elastic material behaviour? All the material behaviour should be governed by vumat.

    • Kunpeng Wang Author
      Kunpeng Wang 3 months ago

      Hi Prof. Masin, if I delete elastic material behaviour, another error will be generated:
      ERROR in job messaging system: Error in connection to analysis
      There is also a warning message:
      A material defined in user subroutine VUMAT must be defined as purely elastic (using the initial elastic modulus) at the beginning of the analysis (stepTime=0). This is an informative message. It does not necessarily indicate that user subroutine VUMAT is incorrectly defined.
      This is similar to the problem Panpan Guo encountered:

  2. David Mašín
    David Mašín 3 months ago

    Hi Kunpeng, did you notice and activate this line in umat?

    c For use in ABAQUS EXPLICIT, activate the following line
    c if(kstep.eq.1 .AND. kinc.eq.1) testing=3

    testing==3 means that elasticity is activated for the initialisation step

    • Kunpeng Wang Author
      Kunpeng Wang 3 months ago

      Hi Prof. Masin,
      Yes, of course. This line is activated. But the problem still exists.

      • David Mašín
        David Mašín 3 months ago

        I see. This seems as a general problem of VUMAT usage, hope that someone using Abaqus explicit will be able to help.

  3. Mahdieh Masoudi
    Mahdieh Masoudi 3 months ago

    Hi Prof.Masin,

    Thank you for sharing the hypoplasty model.
    I would like to know that if the model (clay Hypoplasty) includes the large deformations and plastic strains, and can you guide me on how to define and declare values to parameters of the model inside the Abaques application.


    • David Mašín
      David Mašín 3 months ago

      Hi, please study “Mašín, D. (2015) Part 4: Determination of material parameters, PhD course “Hypoplasticity for Practical Applications” handouts [Presentation]”, it is awailable for download in SoilModels publication database. Regards David

  4. Mahdieh Masoudi
    Mahdieh Masoudi 3 months ago

    Thank you

  5. Britta Bienen
    Britta Bienen 3 months ago


    when using a umat or vumat, the following information needs to be included in the .inp file:
    *Material, name=Material-xyz
    *User Material, constants=integer_number

    The information you included above reads *User material, type=mechanical. Please also check that the number of material constants defined here match that in the umat/vumat.

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