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## Creep for isotropic materials (creep.f)

The user subroutine ``creep.f'' is made available to allow the user to incorporate his own creep law by selecting the keyword sequence *CREEP,LAW=USER in the input deck. The creep routine must return the creep rate and its derivative with respect to the Von Mises stress for a given Von Mises stress. The header and a description of the input and output variables is as follows:

          subroutine creep(decra,deswa,statev,serd,ec,esw,p,qtild,
         &  temp,dtemp,predef,dpred,time,dtime,cmname,leximp,lend,
         &  coords,nstatv,noel,npt,layer,kspt,kstep,kinc)
    !
    !     user creep routine
    !
    !     INPUT:
    !
    !     decra(1)           material name
    !     statev(1..nstatv)  internal variables
    !     serd               not used
    !     ec(1)              equivalent creep at the start of the increment
    !     ec(2)              not used
    !     esw(1..2)          not used
    !     p                  not used
    !     qtild              von Mises stress
    !     temp               temperature at the end of the increment
    !     dtemp              not used
    !     predef             not used
    !     dpred              not used
    !     time(1)            value of the step time at the end of the increment
    !     time(2)            value of the total time at the end of the increment
    !     dtime              time increment
    !     cmname             material name
    !     leximp             not used
    !     lend               not used
    !     coords(1..3)       coordinates of the current integration point
    !     nstatv             number of internal variables
    !     noel               element number
    !     npt                integration point number
    !     layer              not used
    !     kspt               not used
    !     kstep              not used
    !     kinc               not used
    !
    !
    !     OUTPUT:
    !
    !     decra(1)           equivalent deviatoric creep strain increment
    !     decra(2..4)        not used
    !     decra(5)           derivative of the equivalent deviatoric
    !                        creep strain increment w.r.t. the von Mises
    !                        stress
    !     deswa(1..5)        not used