Hello everyone! I would like to ask you if there is a way to calculate the in-plane principal stresses of a shell element. These stresses are given at the results of the .odb file, but I am writing a VUMAT subroutine and I want to find these stresses at each material point and use their value in the calculations inside VUMAT while the model is 'running'. I used the utility routine VSPRINC, but the results are not equal neither to the max, mid, min principal stresses, nor to the max, min in-plane principal stresses that I read at the .odb file. Any suggestions? Thanks in advance!