Hi Lovisa
Why not create a 1 element cube model and run the three typical stress conditions (uniaxial tension, shear etc) for a range of stretch ratios and post process? The MAPDL solver does this behind the scenes when a hyperelastic material is present but will only show the results if the material is unstable (shows as a list of conditions & ranges that were unstable in the output file).
Mike
You are navigating away from the AIS Discovery experience