LS Dyna

LS Dyna

UMAT mesh dependency

    • Pratik Ganorkar


      I have a user defined material model and it gives similar results when highly meshed and single element  stress strain testing outputs in tensile, compression and shear.

      But, when I do a  low velocity impact on that material with spherical steel ball on surface of plate made up of the user defined material, then the force-displacement graphs are mesh dependent, with fine mesh acting more softly compared to coarse mesh which acts more hard.  The results are expected to be mesh dependent. What could be the possible reasons for mesh dependencies?

      Please share your knowledge with me.

      Pratik Ganorkar (

      MTech, Mechanical Engineering, IIT Goa

    • Armin Abedini

      Hi Pratik,

      Do you incorporate plastic deformation in your analysis? If yes, plastic localization is a mesh-dependent phenomenon and may be the source of mesh dependency in your model.

    • Andreas Koutras
      Ansys Employee


      If there is damage and softening in the material model, its fracture energy will need to be regularized to account for the element size. There are plenty of references on this online. 

    • Pratik Ganorkar

      Hi Armin and Andreas,

      Thank you for your response. It has helped me solve the problems.

      Thank you very much

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