What is the difference between "Maximum Principal Stress", "Maximum Principal Back Stress", "Maximum Principal Value of Stress", and "Major Principal Value of Stress"?
Major principal stress is the principal stress with maximum absolute value. For example, at an integration point, Sigma_1=-100, Sigma_2=-200 and Sigma_3=-300, major principal stress is -300. Maximum principal stress is the highest value, in this example -100.
The back stress tensor is relevant to viscoplasticity. Where the yield surface can shift if you use kinematic hardening.
I understood the connection between Maximum Principal Value of Stress and Major Principal Value of Stress. I also found the explanation in other posts using this example.
But what is the difference between Maximum Principal Stress and Maximum Principal Value of Stress?
If you have the "Principal Values of Stress" calculated by Marc and written to the Marc output file. Mentat will allow you to plot Maximum Principal Stress (or intermediate or minimum). Mentat is just sorting the values calculated by Marc.
The Maximum Principal Value of Stress is calculated in Mentat using the stress tensor. If you have other tensors written to the output file you will see "Maximum Principal Value of XXXX" in Mentat.
