1!
2!     CalculiX - A 3-dimensional finite element program
3!              Copyright (C) 1998-2021 Guido Dhondt
4!
5!     This program is free software; you can redistribute it and/or
6!     modify it under the terms of the GNU General Public License as
7!     published by the Free Software Foundation(version 2);
8!
9!
10!     This program is distributed in the hope that it will be useful,
11!     but WITHOUT ANY WARRANTY; without even the implied warranty of
12!     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13!     GNU General Public License for more details.
14!
15!     You should have received a copy of the GNU General Public License
16!     along with this program; if not, write to the Free Software
17!     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18!
19      subroutine creep(decra,deswa,statev,serd,ec,esw,p,qtild,
20     &  temp,dtemp,predef,dpred,time,dtime,cmname,leximp,lend,
21     &  coords,nstatv,noel,npt,layer,kspt,kstep,kinc)
22!
23!     user creep routine
24!
25!     INPUT (general):
26!
27!     statev(1..nstatv)  internal variables
28!     serd               not used
29!     ec(1)              equivalent creep at the start of the increment
30!     ec(2)              not used
31!     esw(1..2)          not used
32!     p                  not used
33!     temp               temperature at the end of the increment
34!     dtemp              not used
35!     predef             not used
36!     dpred              not used
37!     time(1)            value of the step time at the end of the increment
38!     time(2)            value of the total time at the end of the increment
39!     dtime              time increment
40!     cmname             material name
41!     leximp             not used
42!     lend               if = 2: isotropic creep
43!                        if = 3: anisotropic creep
44!     coords(1..3)       coordinates of the current integration point
45!     nstatv             number of internal variables
46!     noel               element number
47!     npt                integration point number
48!     layer              not used
49!     kspt               not used
50!     kstep              not used
51!     kinc               not used
52!
53!    INPUT only for elastic isotropic materials:
54!     qtild              von Mises stress
55!
56!    INPUT only for elastic anisotropic materials:
57!     decra(1)           equivalent deviatoric creep strain increment
58!
59!
60!     OUTPUT (general):
61!
62!     decra(5)           derivative of the equivalent deviatoric
63!                        creep strain increment w.r.t. the von Mises
64!                        stress
65!
66!     OUTPUT only for elastic isotropic materials:
67!     decra(1)           equivalent deviatoric creep strain increment
68!
69!     OUTPUT only for elastic anisotropic materials:
70!     qtild              von Mises stress
71!
72      implicit none
73!
74      character*80 cmname
75!
76      integer leximp,lend,nstatv,noel,npt,layer,kspt,kstep,kinc
77!
78      real*8 decra(5),deswa(5),statev(*),serd,ec(2),esw(2),p,qtild,
79     &  temp,dtemp,predef(*),dpred(*),time(2),dtime,coords(*)
80!
81      qtild=(1.d10*decra(1)/dtime)**0.2d0
82      decra(5)=5.d-10*dtime*qtild**4
83!
84      return
85      end
86