General Mechanical

General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

Hyperelastic material simulation issue

    • Przemysław Oborowski

      TAGS: #membrane, #fabric, #contact, #nonlinear, #hyperelastic, #rubber, #Mooney, #Rivlin, #axisymmetric, #2D

      I'm trying to do the 2D axisymmetric simulation of the membrane shown in the picture below:

      The simulation is divided in 2 steps
      1. 0-0.5s  -> initial pressing bu the contacts (ramped effect)
      2. 0.5s-1.5s -> Yellow element displacement for 0.7mm down, which squezes the membrane further.

      Here is a mesh used in the last trial (TRI6, QUAD 4), but I've already tried multiple variants of meshing:

      The problem occurs around 1.33s/1.5s and it seems, that it is connected to the nodes sticking to the rigid surface.

      More movies available under the link:

      The contact is defined as below (place, where the the possible problem occured, marked with arrow):

      Simulation setup:

      Max. Newon-Rapson residual was located here:

      Error (similar for all elements):

      Rubber properties:

      Could You please help me in this issue? :)

      Thank You in advance for support!

    • John Doyle
      Ansys Employee

      Below are a few tips to try: 

      1. Drop midside nodes.  The linear shape functions can sometimes offer better stability.  
      2. Consider a coarser mesh.  Not too coarse, but slighly larger elements might be less suceptible to element distortion errors, since their integration points are not so close to the boundary.
      3. Switch back to Aug Lagrange and reduce the contact stiffness.
      4. Use many more substeps.
      5. If the above tips do not help, consider adding Nonlinear Adaptive Meshing.
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