I am just curious, I came across a stress strain curve and I have attached the file for your reference. The red curve is the one where the material was loaded till failure. and the one in black is the cyclic unloading test results. I am just wondering, which material model would you start with for such a simulation. For example I would like to simulate a similar cyclic unloading test and interested to know the permanent deformation, so the unloading is important to me.
The [URL= https://polymerfem.com/content.php?78-three-network-model ]Three-Network Model[/URL] from the [URL= http://polyumod.com ]PolyUMod librar[/URL]y would work really well for that type of material.