I am modelling a foam structure using the Hyperfoam model in abaqus. I have two different parts. One being a solid cube and another being a solid cube with a spherical hollow inside of it. Both has same property(hyperfoam,viscoelastic) and the same boundary conditions(They are restricted in all 3 diplacement and rotation at the bottom and is pressed by a plate on the top to compress the foam to a certain strain level.)
However, I run into a few problems with my model. When I increase the compression strain to more than ~35%, the model with the spherical hollow in it fail to converge. However, the solid model would still converge at strain level of 90%. Abaqus says too many attempts made in this step. I tried increasing the number of increments and reducing the max increment step time in the Step Module in abaqus but nothing seems to work.
The other problem that I face is when i try to plot the stress-strain of the two models. I average the von mises stress and nominal strain of the elements that are on the surface that is being pressed. WHen i do this, i get the correct strain level for the solid cubic model (eg if i compressed it to 2 unit of length, i get the strain data up to 2 unit of length). However, for the cubic with spherical hollow, the strain rate of each elements are different. They vary from 0 to the unit length that I specify. Hence, when I get the average of the strain data, the strain is usually smaller than what I specify.
I would appreciate some assistance and guidance on the issues that I am facing. Thanks in advance for your time 🙂