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Creep for anisotropic materials (ucreep.f)

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.



guido dhondt 2006-02-19