Hi,
I am trying to find the derivative of vonMises (sigma_vm) stress square wrt to stress, is the following correct ?:
d(sigma_vm**2)/d(sigma)
= 2 * sigma_vm * d(sigma_vm)/d(sigma)
= 2 * sigma_vm* 3 * S_ij / (2 * sigma_vm) (where Sij is the deviatoric stress tensor);
finally leading to the expression of RHS as: 3*S_ij
Is this correct or am I missing something ?