identity_tensors.for

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      SUBROUTINE onem(A,AA,AAS,NDI)
C
C>      THIS SUBROUTINE GIVES:
C>          2ND ORDER IDENTITY TENSORS - A
C>          4TH ORDER IDENTITY TENSOR - AA
C>          4TH ORDER SYMMETRIC IDENTITY TENSOR - AAS
C
      IMPLICIT NONE
      include 'PARAM_UMAT.INC'
C
      INTEGER I,J,K,L,NDI
C
      DOUBLE PRECISION A(ndi,ndi),AA(ndi,ndi,ndi,ndi),
     1                 aas(ndi,ndi,ndi,ndi)
C
      DO i=1,ndi
         DO j=1,ndi
            IF (i .EQ. j) THEN
              a(i,j) = one
            ELSE
              a(i,j) = zero
            END IF
         END DO
      END DO
C
      DO i=1,ndi
         DO j=1,ndi
          DO k=1,ndi
             DO l=1,ndi
              aa(i,j,k,l)=a(i,k)*a(j,l)
              aas(i,j,k,l)=(one/two)*(a(i,k)*a(j,l)+a(i,l)*a(j,k))
           END DO
          END DO
        END DO
      END DO
C
      RETURN
      END SUBROUTINE onem