[Solved] VUMAT EXAMPLES for Hyperelastic materials

I am not sure what is causing your element distortions. Can you try with a single element and just apply a uniaxial load?

Abaqus/Explicit expects the stresses to be returned in a co-rotational coordinate system. You can achieve this by either calculating the Cauchy stress based on the deformation gradient and then rotating the stress, or you can achieve the same effect (but more efficiently) if you simply calculate the stress using the left Cauchy-Green tensor U.

-Jorgen

Thank you, Jorgen.

For your prompt reply and advice. I realized that material properties contribute to the excessive distortion. There is a pair of properties that work well for both the inbuilt and the VUMAT producing similar results whereas others only  work for the inbuilt model but not VUMAT.

I am working on understanding more about this and improving the model.

Thank you so much.