Hi,
I have a doubt in VUMAT if I calculate compliance tensor(as show in attached file) at each step and inverse it to obtain the constitutive tensor(Jacobian)and then multiply with strainInc to obtain stress increment.Similar to UMAT. Can I do this in VUMAT to calculate stressNew?.If no,why?.Then how?.
How to get stress rate as output in ABAQUS?
No, you will not update the Jacobian tensor, unless you pass the Di´ variables as a state variable and then update the Jacobian tensor.
For example, if you need to update your Jacobian tensor, you could do the following routine:
if (stateOld(km,6).lt.0) then
stateOld(km,6) = 0
end if
d1=0.0
d2=0.0
d6=0.0
E11r=1.0
E22r=1.0
d2_0=0.0
d6_0=0.0
flag = stateOld(km,6)
if (flag.gt.5) then
d1 = stateOld(km,1)
d2 = stateOld(km,2)
d6 = stateOld(km,3)
E11r = stateOld(km,4)
E22r = stateOld(km,5)
d2_0 = stateOld(km,8)
d6_0 = stateOld(km,9)
end if
C ***********************************************************
C CONSTITUTIVE LAW
C ***********************************************************
do 10 i=1,3
do 20 j=1,3
ddsdde(i,j) = 0.0;
20 continue
10 continue
ddsdde(1,1) = (E11*E11r*(1.0-d1)) / (1.0-(nu12*nu21)*(1.0-d2)*
1 (1.0-d1))
ddsdde(2,2) = (E22*E22r*(1.0-d2)) / (1.0-(nu12*nu21)*(1.0-d2)*
1 (1.0-d1))
ddsdde(2,1) = ((1.0-d2)*nu21*E11*E11r*(1.0-d1))/(1.0-(nu12*nu21)*
1 (1.0-d2)*(1.0-d1))
ddsdde(1,2) = ddsdde(2,1)
ddsdde(3,3) = G12*(1.0-d6)
c do 100 km = 1,nblock
C Stresses calculations
stressNew(km,1) = stressOld(km,1) +
1 ddsdde(1,1) * (strainInc(km,1)) +
2 ddsdde(1,2) * (strainInc(km,2)) +
3 ddsdde(1,3) * (strainInc(km,4))
stressNew(km,2) = stressOld(km,2) +
1 ddsdde(2,1) * (strainInc(km,1)) +
2 ddsdde(2,2) * (strainInc(km,2)) +
3 ddsdde(2,3) * (strainInc(km,4))
stressNew(km,3) = stressOld(km,3) + 0.0
stressNew(km,4) = stressOld(km,4) +
1 ddsdde(3,1) * (strainInc(km,1)) +
2 ddsdde(3,2) * (strainInc(km,2)) +
3 ddsdde(3,3) * (strainInc(km,4))
If I do not update the state variable 6 in the code, The Jacobian tensor will not be update in any step.
Regards
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