VUMAT error

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VUMAT error

siree_gogineni
Hello all,

I have written a VUMAT for 3 element maxwell model.When i try to run it with a simple model I get a warning message as follows

"A material defined in user subroutine VUMAT must be defined as purely elastic (using the initial elastic modulus) at the beginning of the analysis (stepTime=0). This is an informative message. It does not necessarily indicate that user subroutine VUMAT is incorrectly defined".

The analysis terminates due to excessive element distortion.Is it because i did not define the material as purely elastic at time step=0 ?
Please let me know

Thanks
Sireesha


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Re: VUMAT error

teeper07
You need a linear elastic material definition to initialize the solution. Try something like this:
 

 C     ******************************************************************
 C     ------------ INITIALIZE MATERIAL AS LINEARLY ELASTIC--------------
 C     ******************************************************************
 C
       twoG = two * g0
       lmda = k0 - twoG * oneThrd
 C
       IF (totalTime.EQ.0.0) THEN
 C
          DO k = 1,nblock
             trace = strainInc(k,1) + strainInc(k,2) + strainInc(k,3)
             stressNew(k,1) = stressOld(k,1) + twoG*strainInc(k,1) +
      $                       lmda*trace
             stressNew(k,2) = stressOld(k,2) + twoG*strainInc(k,2) +
      $                       lmda*trace
             stressNew(k,3) = stressOld(k,3) + twoG*strainInc(k,3) +
      $                       lmda*trace
             stressNew(k,4) = stressOld(k,4) + twoG*strainInc(k,4)
             stressNew(k,5) = stressOld(k,5) + twoG*strainInc(k,5)
             stressNew(k,6) = stressOld(k,6) + twoG*strainInc(k,6)
          END DO
 C
          RETURN
 C
       END IF
 C