Dear Dr.Bergstorm,

Thank you for your time, I am trying to model HDPE PE-100 temperature dependent behavior under compression and tension as a hyperelastic material. I have conducted tensile and compression tests and tried to curve fit the combined data (uniaxial) to abaqus hyperelastic models, however, the only stable model is marlow, which does not accept both compression and tenisle data except for trusses, beams, and rebars.

Therefore, I have tried defining the uniaxial test data in Abaqus using the tensile test data and the biaxial data using the equibiaxial tension data which is the same as the compression test data (but positive), using the equivalency of stress state mentioned in abaqus manual (abaqus 6.14 , 22.5.1 hyperelasticity). Moreover, I tried fitting the test data with all the strain energy potentials functions in Abaqus (Ogden (N=1 to N=6), Polynomial (N=1 & 2), Reduced polynomial (N=1 to N=6), etc..), However, I did not get any good fit plus the fact that most of the fits were unstable. Finally, I tried the free two week version of Mcalibration software to get a good and stable fit for my data but with no luck.

I currently do not know what to do in order to obtain a stable and good hyper-elastic fit for both my tensile and compression test data in Abaqus. I really appreciate any help.

Thanks and sorry for the long post.