I have created True stress vs True strain curve. It is also downward after yield strength. https://files.engineering.com/getfile.aspx?folder=e6b63230-7a78-4e1c-9456-e73af5503cde&file=Capture.JPG
I am using PP material for my projects. In stress strain curve of PP, Yield strength value 50 MPa and UTS value 20 MPa. Stress strain curve is downward after Yield value.
in this case How to load the plastic strain vs Stress curve for multi linear isotropic hardening...