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VISCOELASTIC UMAT

Submitted by supandanane on
research

Hello every body,

 

I am looking for VISCOELASTIC UMAT code based on Maxwell or Kelvin elements. If someone can help me with it.

 Regards

Frank Richter

 

 For the Maxwell model you find it in my PhD thesis

"Upsetting and Viscoelasticity of Vitreous SiO2: Experiments, Interpretation and Simulation"

http://opus.kobv.de/tuberlin/volltexte/2006/1179/





The
Kelvin-Voigt model can be derived in an analogous manner. The code is
underneath. I have the derivation written up as a pdf document; but this
thing here does not allow me to upload it. Disclose your e-mail adress,
then I can send it to you.



Good luck



Frank



--------------------------------------------------------



      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,KSTEP,KINC)

C

      INCLUDE 'ABA_PARAM.INC'

C

      CHARACTER*80 CMNAME

      DIMENSION STRESS(NTENS),STATEV(NSTATV),

     1 DDSDDE(NTENS,NTENS),

     2 DDSDDT(NTENS),DRPLDE(NTENS),

     3 STRAN(NTENS),DSTRAN(NTENS),TIME(2),PREDEF(1),DPRED(1),

     4 PROPS(NPROPS),COORDS(3),DROT(3,3),DFGRD0(3,3),DFGRD1(3,3)

C

C

      INTEGER i, j

      REAL Y, n, eta

      REAL lambda, thetalambda, mu, thetamu

      REAL A, B, C, D, F, G

C

      REAL, DIMENSION(NTENS,NTENS):: DDSDE

      REAL, DIMENSION(NTENS,NTENS):: DDSDS

      REAL, DIMENSION(NTENS):: SIGold

C

      Y = PROPS(1)

      n = PROPS(2)

      eta = PROPS(3) ! shear viscosity

C

      lambda = Y*n/((1.0d0+n)*(1.0d0-2.0d0*n))

      mu = Y/(2.0d0*(1.0d0+n))

      thetalambda = 3.0d0*eta/Y

      thetamu = eta/mu

C

      A = lambda*(1.0d0 + thetalambda/DTIME) +

     1    2.0d0*mu*(1.0d0 + thetamu/DTIME)

      B = lambda*(1.0d0 + thetalambda/DTIME)

      C = lambda + 2.0d0*mu

      D = lambda

      F = 2.0d0*mu*(1.0d0 + thetamu/DTIME)

      G = 2.0d0*mu

C

      DO i = 1,NTENS

        DO j = 1,NTENS

          DDSDDE(i,j) = 0.0d0

          DDSDE(i,j) = 0.0d0

          DDSDS(i,j) = 0.0d0

        END DO

      END DO

C

C DEFINE TENSOR COEFFICIENTS RELATED TO NORMAL STRESSES

C

      DO i = 1,NDI

         DO j = 1,NDI

            DDSDDE(i,j) = B

            DDSDE(i,j) = D

            DDSDS(i,j) = 0.0d0

         END DO

         DDSDDE(i,i) = A

         DDSDE(i,i) = C

         DDSDS(i,i) = -1.0d0

      END DO

C

C DEFINE TENSOR COEFFICIENTS RELATED TO SHEAR STRESSES

C

      DO i = NDI+1,NTENS

       DDSDDE(i,i) = F/2.0d0

       DDSDE(i,i) = G/2.0d0

       DDSDS(i,i) = - 1.0d0

      END DO

C

C STORE PRESENT STRESS STATE IN ARRAY SIGold

C

      DO i= 1,NTENS

        SIGold(i) = STRESS(i)

      END DO

C

C UPDATE STRESSES

C

      DO i = 1,NTENS

        DO j = 1,NTENS

          STRESS(i) = STRESS(i) + DDSDDE(i,j)*DSTRAN(j) +

     1                DDSDE(i,j)*STRAN(j) +

     2                DDSDS(i,j)*SIGold(j)

        END DO

      END DO

C

      RETURN

      END

------------------------------------------
Ruhr-University
Bochum
Germany

Tue, 07/03/2012 - 18:08 Permalink
Cleary

Dr. Richter,

I realize this forum post is many years old, but I would be supremely interested in viewing the PDF derivation for your Kelvin-Voigt model. I am a graduate student at California Polytechnic State University, and your PhD work has been fundamental to my thesis and as well as the work of my peers. 

Would it still be possible to get this from you? 

Thank you,

Austin C.

accummin [at] calpoly [dot] edu

Sun, 05/03/2015 - 17:17 Permalink
sergkuznet

Hi Frank! Thank you for sharing your UMAT code here. I just started working on the viscoelastic material and will need to implement a nonlinear anisotropic viscoelastic material in UMAT. Your code seems to be a great start. You mentioned above the pdf write up for derivation. I was wondering if you may share it and your PhD thesis, the ilnk above doesn't work? My email is sergkuznet [at] hotmail.com

Thank you!

Wed, 09/06/2017 - 01:55 Permalink