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)C INCLUDE 'ABA_PARAM.INC'C CHARACTER*80 CMNAME 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) double precision E,V,yield0,H,lamdba,G,STATEV double precision hydroStaticPressure,misesEqualStress double precision dEqualPlasticStrain double precision, DIMENSION(NTENS)::deviatoricStress INTEGER i,jC Elastic properties E = PROPS(1) V = PROPS(2) yield0 = PROPS(3) H = (PROPS(5)-PROPS(3))/(PROPS(6)-PROPS(4))
lamdba = E*V/((1+V)*(1-2*V)) G = E/(2*(1+V))
C Calculate the material jacobian matrix do i=1, NTENS do j=1, NTENS DDSDDE(i,j)=0 end do end do
do i=1,NDI do j=1,NDI DDSDDE(i,j)=lamdba end do DDSDDE(i,i)=lamdba+2*G DDSDDE(i+NDI,i+NDI)=G end do
C Calculate stress-try do i=1,NTENS do j=1,NTENS stress(i)=stress(i)+DDSDDE(i,j)*DSTRAN(j) end do end do
C Calculate hydroStaticPressure hydroStaticPressure=0 do i=1,NDI hydroStaticPressure=hydroStaticPressure+stress(i) end do hydroStaticPressure=hydroStaticPressure/3
C Calculate the deviatoricStress-try do i=1,NDI deviatoricStress(i)=STRESS(i)-hydroStaticPressure end do do i=1+NDI,NTENS deviatoricStress(i)=stress(i) end do
C Calculate misesEqualStress misesEqualStress=0 do i=1,NDI misesEqualStress=misesEqualStress+deviatoricStress(i)**2 end do misesEqualStress=sqrt(1.5*misesEqualStress)
C get the nth equalPlasticStrain from STATEV equalPlasticStrain=STATEV(1)
C Calculate the nth yield yieldn=yield0+H*equalPlasticStrain
if (misesEqualStress>yieldn) then dEqualPlasticStrain=(misesEqualStress-yieldn)/(H+3*G)
do i=1,NTENS deviatoricStress(i)=deviatoricStress(i)-3*G*dEqualPlasticStrain*deviatoricStress(i)/misesEqualStress end do
do i=1,NDI stress(i)=deviatoricStress(i)+hydroStaticPressure end do do i=1+NDI,NTENS stress(i)=deviatoricStress(i) end do else dEqualPlasticStrain=0 end if
STATEV(1)=equalPlasticStrain+dEqualPlasticStrain
RETURN END
