Many times is enough modeling the linear behaviour of the material in our simulations, but other times is mandatory defining the plastic behaviour to get a realistic stress distribution.
First problem that those of us dedicated to finite element is define this behaviour. Not always is easy get that information and many times we take the values from plastic constituve laws such as Hollomon's law, but these laws are not generalized and are not valid for all materials. Also, they are not valid for full plastic strains range.
To do this task easier, I developed a plug-in which has implemented different plastic laws. Two of them are based in a iterative process adjust the parameters for fitting the FEM results with experimental data and to be able to get the full range of plastic strains.
Here is the link about how the plug-in works.
If you are interested in this plug-in or to develop a custom plug-in, don't hesitate to contact me.