ABAQUS UMAT子程序详解： isotropic elasticity & plasticity with J2 flow...

 SUBROUTINE UMAT(STRESS,STATEV,DDSDDE,SSE,SPD,SCD,
     1 RPL,DDSDDT,DRPLDE,DRPLDT,STRAN,DSTRAN,
     2 TIME,DTIME,TEMP,DTEMP,PREDEF,DPRED,MATERL,NDI,NSHR,NTENS,
     3 NSTATV,PROPS,NPROPS,COORDS,DROT,PNEWDT,CELENT,
     4 DFGRD0,DFGRD1,NOEL,NPT,KSLAY,KSPT,KSTEP,KINC) 
C
      INCLUDE 'ABA_PARAM.INC'        
C
      CHARACTER*80 MATERL    !定义MATERL为80字节的字符型变量
      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),
     4 DFGRD0(3,3),DFGRD1(3,3)
C
      DIMENSION EELAS(6),EPLAS(6),FLOW(6)
      PARAMETER (ONE=1.0D0,TWO=2.0D0,THREE=3.0D0,SIX=6.0D0) 
      DATA NEWTON,TOLER/10,1.D-6/ 
C
C -----------------------------------------------------------
C     UMAT FOR ISOTROPIC ELASTICITY AND ISOTROPIC PLASTICITY 
C     J2 FLOW THEORY
C     CAN NOT BE USED FOR PLANE STRESS
!本UMAT子程序适用于各向同性的弹塑性变形，采用J2流动法则，
!不能用于计算平面应力实例
C -----------------------------------------------------------
C     PROPS(1) - E     
C     PROPS(2) - NU
C     PROPS(3) - SYIELD
C     CALLS AHARD FOR CURVE OF SYIELD VS. PEEQ

!杨氏模量E ，泊松比NU，和屈服应力SYIELD分别储存在PROPS(1)，
!PROPS(2)和PROPS(3)中
!由函数AHARD可以得到屈服应力(SYIELD)相对于等效塑性(PEEQ)的曲线
C -----------------------------------------------------------
C
      IF (NDI.NE.3) THEN    
!当NDI (正应力数不等于3说明该算例属于平面应力类，输出如下提示信息）        
         WRITE(6,1)
 1       FORMAT(//,30X,'***ERROR - THIS UMAT MAY ONLY BE USED FOR ',
     1          'ELEMENTS WITH THREE DIRECT STRESS COMPONENTS')
      ENDIF
C
C     ELASTIC PROPERTIES !材料的弹性属性
C
      EMOD=PROPS(1)  !将杨氏模量值赋给EMOD
      ENU=PROPS(2)   !泊松比值赋给ENU
      IF(ENU.GT.0.4999.AND.ENU.LT.0.5001) ENU=0.499  
!当泊松比等于0.5, 定义ENU=0.499
      EBULK3=EMOD/(ONE-TWO*ENU)  !3倍的体积模量 3K
      EG2=EMOD/(ONE+ENU)        !2倍的剪切模量 2G
      EG=EG2/TWO                !G  剪切模量
      EG3=THREE*EG              ! 3倍的剪切模量 3G
      ELAM=(EBULK3-EG2)/THREE    !λ
C
C     ELASTIC STIFFNESS  定义弹性本构矩阵DE
      
C
      DO 20 K1=1,NTENS
        DO 10 K2=1,NTENS
           DDSDDE(K2,K1)=0.0  !先将矩阵DDSDDE清零