超弹性材料UMAT子程序实现

*USER SUBROUTINES
      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,NSTATEV,PROPS,NPROPS,COORDS,DROT,PNEWDT,
     4 CELENT,DFGRD0,DFGRD1,NOEL,NPT,LAYER,KSPT,KSTEP,KINC)
C
INCLUDE 'ABA_PARAM.INC'
C     
      REAL Et, Stress_Max, EkEk

       CHARACTER*8 CMNAME
       DIMENSION STRESS(NTENS),STATEV(NSTATEV),
     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 Et(3),Stress_Max(3,3),EkEk(1),DFGRDM1_INV(3,3),En(3),
     5 TEMP(1),DTEMP(1),DFGRDP(3),DFGRDM1(3, 3),DFGRDM0(3, 3),
     6 CBAR(3,3),DDSDDE_Max(6,6)
C
      DIMENSION BBAR(6),DISTGR(3,3)
C
      PARAMETER(ZERO=0.D0, ONE=1.D0, TWO=2.D0, THREE=3.D0, FOUR=4.D0)
C
C ----------------------------------------------------------------
C    UMAT FOR COMPRESSIBLE NEO-HOOKEAN HYPERELASTICITY
C    CANNOT BE USED FOR PLANE STRESS
C ----------------------------------------------------------------
C    PROPS(1) - C10
C    PROPS(2) - D1

C    PROPS(3) - EPSILON
C    PROPS(4) - En(1)/abs(En)
C    PROPS(5) - En(2)/abs(En)
C    PROPS(6) - En(3)/abs(En)
C    PROPS(7) - DFGRDP(1,1)
C    PROPS(8) - DFGRDP(2,2)
C    PROPS(9) - DFGRDP(3,3)
C ----------------------------------------------------------------
C
C   Read Material PROPERTIES
C
      C10=PROPS(1)
      D1 =PROPS(2)
      EPSILON=PROPS(3)
      
C
C   Read The Prestretch
C      
      do J=1,3
      DFGRDP(J)=0
      end do  
           
      IF (KSTEP==1) then
      DFGRDP(1)=exp(log(PROPS(7))*time(2)) 
      DFGRDP(2)=exp(log(PROPS(8))*time(2))
      DFGRDP(3)=exp(log(PROPS(9))*time(2))
      else
      DFGRDP(1)=PROPS(7) 
      DFGRDP(2)=PROPS(8)
      DFGRDP(3)=PROPS(9)