anisomat.for

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      SUBROUTINE anisomat(SSEANISO,DANISO,DISO,K1,K2,KDISP,I4,I1)
C>     ANISOTROPIC PART : ISOCHORIC SEF AND DERIVATIVES
      IMPLICIT NONE
      include 'PARAM_UMAT.INC'
C
      DOUBLE PRECISION SSEISO,DANISO(4),DISO(5)
      DOUBLE PRECISION K1,K2,KDISP,I4,I1
      DOUBLE PRECISION DUDI1,D2UD2I1,SSEANISO
      DOUBLE PRECISION E1,EE2,EE3,DUDI4,D2UD2I4,D2DUDI1DI4,D2DUDI2DI4
C
      dudi1=diso(1)
      d2ud2i1=diso(3)
C      
      e1=i4*(one-three*kdisp)+i1*kdisp-one
C
      sseaniso=(k1/k2)*(dexp(k1*e1*e1)-one)

      IF(e1.GT.zero) THEN
C
      ee2=dexp(k2*e1*e1)
      ee3=(one+two*k2*e1*e1)
C
      dudi1=dudi1+k1*kdisp*e1*ee2
      d2ud2i1=d2ud2i1+k1*kdisp*kdisp*ee3*ee2
C      
      dudi4=k1*(one-three*kdisp)*e1*ee2
C
      d2ud2i4=k1*((one-three*kdisp)**two)*ee3*ee2
      
      d2dudi1di4=k1*(one-three*kdisp)*kdisp*ee3*ee2
      d2dudi2di4=zero


C
      ELSE
      dudi4=zero
      d2ud2i4=zero
      d2dudi1di4=zero
      d2dudi2di4=zero

      d2ud2i1=zero
C
      END IF
      !FIRST DERIVATIVE OF SSEANISO IN ORDER TO I1
      daniso(1)=dudi4
      !FIRST DERIVATIVE OF SSEANISO IN ORDER TO I2
      daniso(2)=d2ud2i4
      !2ND DERIVATIVE OF SSEANISO IN ORDER TO I1
      daniso(3)=d2dudi1di4
      !2ND DERIVATIVE OF SSEANISO IN ORDER TO I2
      daniso(4)=d2dudi2di4
C
      diso(1)=dudi1
      diso(3)=d2ud2i1
C
      RETURN
      END SUBROUTINE anisomat