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Question

I use the simple isotropic elastic material in uniaxial tension as an example. First the isotropic elastic behavior is directly coded inside the UMAT subroutine and it works fine below (OK.for).

Now I coded the isotropic elastic behavior in a separate subroutine (see “mymodel” in NOTOK.for below) and then let UMAT call mymodel subroutine. However it doesn’t work and after printing out the parameter (C) when calling/after-calling mymodel subroutine, it shows that the parameter (C) is not updated in UMAT after calling mymodel subroutine. This is strange because FORTRAN passes parameters by adresses so the parameter should be automatically updated in UMAT.

Could anyone help to check the problem? All files (includinng Abaqus .inp) are given below. Thanks very much!

OK.for

      subroutine umat(stress,statev,ddsdde,sse,spd,scd,
     1 rpl,ddsddt,drplde,drpldt,
     2 stran,dstran,time,dtime,temp,dtemp,predef,dpred,cmname,                       
     3 ndi,nshr,ntens,nstatv,props,nprops,coords,drot,pnewdt,
     4 celent,dfgrd0,dfgrd1,noel,npt,layer,kspt,jstep,kinc)
     
      include 'aba_param.inc'
      
      character*80 cmname
      dimension C(6,6)
      dimension stress(ntens),statev(nstatv),
     1 ddsdde(ntens,ntens),ddsddt(ntens),drplde(ntens),
     2 stran(ntens),dstran(ntens),time(2),predef(1),dpred(1),
     3 props(nprops),coords(3),drot(3,3),dfgrd0(3,3),dfgrd1(3,3),
     4 jstep(4) 
     
 
      E=3.5e9
      XNU=0.346
      
      XK=E/3.0/(1.0-2.0*XNU)
      G=E/2.0/(1+XNU)
      
      C=0.0
      C(1,1) = XK+4.0/3.0*G
      C(2,2) = C(1,1)
      C(3,3) = C(1,1)
      C(4,4) = G
      C(5,5) = G
      C(6,6) = G
      C(1,2) = XK-2.0/3.0*G
      C(1,3) = C(1,2)
      C(2,3) = C(1,2)
      C(2,1) = C(1,2)
      C(3,1) = C(1,2)
      C(3,2) = C(1,2)     
      

      print '("C=")'
      print *,C   
      ddsdde=C

       DO i=1, NTENS
       DO j=1, NTENS
           STRESS(j)=STRESS(j)+DDSDDE(j, i)*DSTRAN(i)
       END DO
       END DO     

      print '("ddsdde=")'
      print *,ddsdde

      end

NOTOK.for

      subroutine umat(stress,statev,ddsdde,sse,spd,scd,
     1 rpl,ddsddt,drplde,drpldt,
     2 stran,dstran,time,dtime,temp,dtemp,predef,dpred,cmname,                       
     3 ndi,nshr,ntens,nstatv,props,nprops,coords,drot,pnewdt,
     4 celent,dfgrd0,dfgrd1,noel,npt,layer,kspt,jstep,kinc)
     
      include 'aba_param.inc'
      
      character*80 cmname
      dimension C(6,6)
      dimension stress(ntens),statev(nstatv),
     1 ddsdde(ntens,ntens),ddsddt(ntens),drplde(ntens),
     2 stran(ntens),dstran(ntens),time(2),predef(1),dpred(1),
     3 props(nprops),coords(3),drot(3,3),dfgrd0(3,3),dfgrd1(3,3),
     4 jstep(4)
     
     
  
      call mymodel(C)
      print '("C=")'   ! here output extremely large and random numbers, different from C above
      print *,C   
      ddsdde=C

       DO i=1, NTENS
       DO j=1, NTENS
           STRESS(j)=STRESS(j)+DDSDDE(j, i)*DSTRAN(i)
       END DO
       END DO     

      print '("ddsdde=")'
      print *,ddsdde

      end 
      
 
      
      subroutine mymodel(C)
      
      dimension C(6,6) 
      
      E=3.5e9
      XNU=0.346
      
      XK=E/3.0/(1.0-2.0*XNU)
      G=E/2.0/(1.0+XNU)
      
      C=0.0
      C(1,1) = XK+4.0/3.0*G
      C(2,2) = C(1,1)
      C(3,3) = C(1,1)
      C(4,4) = G
      C(5,5) = G
      C(6,6) = G
      C(1,2) = XK-2.0/3.0*G
      C(1,3) = C(1,2)
      C(2,3) = C(1,2)
      C(2,1) = C(1,2)
      C(3,1) = C(1,2)
      C(3,2) = C(1,2)
      
      print '("C=")'     ! output C correctly here
      print *,C   

      end

test.inp

*Heading
** Job name: matrix Model name: Model-1
** Generated by: Abaqus/CAE 6.14-1
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**
** PARTS
**
*Part, name=Part-1
*End Part
**  
**
** ASSEMBLY
**
*Assembly, name=Assembly
**  
*Instance, name=Part-1-1, part=Part-1
*Node
      1,           1.,           1.,           1.
      2,           1.,           0.,           1.
      3,           1.,           1.,           0.
      4,           1.,           0.,           0.
      5,           0.,           1.,           1.
      6,           0.,           0.,           1.
      7,           0.,           1.,           0.
      8,           0.,           0.,           0.
*Element, type=C3D8
1, 5, 6, 8, 7, 1, 2, 4, 3
*Nset, nset=_PickedSet2, internal, generate
 1,  8,  1
*Elset, elset=_PickedSet2, internal
 1,
** Section: Section-1
*Solid Section, elset=_PickedSet2, material=MAT0
,
*End Instance
**  
*Nset, nset=_PickedSet4, internal, instance=Part-1-1, generate
 5,  8,  1
*Elset, elset=_PickedSet4, internal, instance=Part-1-1
 1,
*Nset, nset=_PickedSet5, internal, instance=Part-1-1, generate
 1,  4,  1
*Elset, elset=_PickedSet5, internal, instance=Part-1-1
 1,
*End Assembly
** 
** MATERIALS
** 
*Material, name=MAT0
*Depvar
     12,
*User Material, constants=1
0.,
** ----------------------------------------------------------------
** 
** STEP: Step-1
** 
*Step, name=Step-1, nlgeom=NO, inc=2
*Static, direct
0.5, 1., 
** 
** BOUNDARY CONDITIONS
** 
** Name: BC-1 Type: Displacement/Rotation
*Boundary
_PickedSet4, 1, 1
_PickedSet4, 2, 2
_PickedSet4, 3, 3
_PickedSet4, 4, 4
_PickedSet4, 5, 5
_PickedSet4, 6, 6
** Name: BC-2 Type: Displacement/Rotation
*Boundary
_PickedSet5, 1, 1, 0.01
** 
** OUTPUT REQUESTS
** 
*Restart, write, frequency=0
** 
** FIELD OUTPUT: F-Output-1
** 
*Output, field, variable=PRESELECT
** 
** HISTORY OUTPUT: H-Output-1
** 
*Output, history, variable=PRESELECT
*End Step

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Danh mục

Abaqus umat calls my other subroutine but it doesn’t work