The user subroutine ``ucreep.f'' is made available to allow the user to incorporate his own creep law in subroutine umat_aniso_creep. This is a viscoplastic material routine for elastically anisotropic materials. The viscoplasticity, however, is isotropic. The creep routine must return the Von Mises stress for a given equivalent creep strain rate. The header and a description of the input and output variables is as follows:
subroutine ucreep(amat,iel,iint,t1l,epini,ep,dtime,svm,dsvm) ! ! INPUT: ! ! amat: material name ! iel: element number ! iint: integration point number ! t1l: temperature ! epini: equivalent creep strain at the start ! of the increment ! ep: present equivalent creep strain ! dtime: time increment ! ! OUTPUT: ! ! svm: present Von Mises stress ! dsvm: derivative of the Von Mises true stress with respect ! to the present equivalent creep strain. ! Numerically: change the present equivalent ! strain with a small amount, calculate the amount ! of change this causes in the present Von Mises ! true stress, and divide the latter amount through the ! former amount.