Real stress-real strain curve

Hey,

i have to verificate my simulationmodel with an one-element-test. For the one-element-test i need to plot the real stress and the real strain to build a stress-strain curve. I just found the possibility to plot the strain and the stress with the history plot in LS-Post, but they are not the real stress and strain. Can you help me please? I have a shell element. 

Thank you in advance!