Abaqus issue: simulation fails when adding fat layer

[adamkilroy10]

Hi,

I am working on a 2D simulation to model the interaction between a wheelchair cushion and the user's leg when they sit on it. I created this model by tracing over an MRI scan of the leg in Fusion 360 and then importing into Abaqus. The simulation runs successfully when I model the leg with only one deformable layer and the bone. However, I want to model the leg with 2 deformable layers (muscle and fat). When I add this second layer, the simulation no longer works even if I set the 2 layers as the same material. I have attached a screenshot of the simulation working with one layer, and then how it looks with the 2 layers (which does not work).



Model setup

• 2D deformable leg model (imported from MRI scan tracing)
  • Bone (inner layer)
  • Muscle (middle layer)
  • Fat (outer layer)
  • Cushion

Boundary conditions

• Pressure load on top surface of bone
• Bottom surface of cushion fixed
• Bone displacement fixed downwards
• Tie constraints between each layer

Warnings/errors

• I get this warning for all the elements in the bone (I also get these warnings when the simulation works well with one tissue): Solver problem. Zero pivot when processing element BONE
• Error: Too many attempts made for this increment

If anyone has any ideas for this problem they would be greatly be appreciated, thanks!

 

[FEA way]

Are the layers modeled as separate parts ? It might be better to use a partition instead.