SUBROUTINE HYPELA(D,G,E,DE,S,T,DT,MGENS,M,NN,LAYER,MAT,
     * MDI,MSHEAR)
       implicit real*8 (a-h,o-z)
       INCLUDE '../common/space'
       INCLUDE '../common/matdat'
       INCLUDE '../common/maters'
       INCLUDE '../common/els'
       INCLUDE '../common/concom'
       INCLUDE '../common/elmcom'
C       CALLED BY   THRUH
C* * * * * *
C
C     USER SUBROUTINE TO DEFINE YOUNG'S MODULUS AND POISSON'S RATIO
C     AS FUNCTION OF STRESS IN NON-LINEAR ELASTIC SMALL STRAIN
C     MATERIAL.
C
C     D        STRESS STRAIN LAW TO BE FORMED BY USER
C     G       CHANGE IN STRESS DUE TO TEMPERATURE EFFECTS
C     E        TOTAL STRAIN
C     DE       INCREMENT OF STRAIN
C     S        STRESS - SHOULD BE UPDATED BY USER
C     T        STATE VARIABLES
C     DT       INCREMENT OF STATE VARIABLES
C     NGENS    SIZE OF STRESS - STRAIN LAW
C     M        ELEMENT NUMBER
C     NN       INTEGRATION POINT NUMBER
C     LAYER    LAYER NUMBER
C     MAT      MATERIAL I.D.
C     NDI      NUMBER OF DIRECT COMPONENTS
C     NSHEAR   NUMBER OF SHEAR COMPONENTS
C
C* * * * * *
      DIMENSION E(1),DE(1),T(1),DT(1),G(1),D(NGENS,NGENS),S(1)
      DIMENSION DS(6),eo(22),so(22)
C  
C     THIS ROUTINE SET UP FOR PLANE STRESS ONLY
C
C     WARNING!!! THIS ROUTINE IS NOT SET UP FOR TEMPERATURE 
C                DEPENDENT PROPERTIES
C
C     ALL QUANTITIES ARE IN LOCAL SYSTEM DEFINED IN ORIENT
C
      data eo/0.0,0.25e-2,0.49e-2,0.74e-2,0.99e-2,0.0124,0.0148,
     1        0.0174,0.0198,0.02465,0.0295,0.03435,0.0392,0.04395,
     2        0.0487,0.05,0.055,0.06,0.065,0.07,0.075,0.08/
      data so/0.0,18720.,34059.,47000.,58500.,65280.,71000.,
     1        74786.,76350.,78592.,79567.,80541.,81516.,82491.,
     2  83465.,84000.,85000.,86000.,87000.,88000.,89000.,9e4/
      if((inc.ne.0).or.(m.gt.1)) goto 401
      write(6,994) eo
994   format(' strain data ' 8f10.4)
      write(6,993) so
993   format(' stress data ' 8f10.1)
401   continue
      I1=2*NOSLPS*(MAT-1)
      IESLX=I1+IESL
      IGSLX=I1+IGSL
      ISHRSX=I1+ISHRSL
C
C     DEFINE ELASTIC PROPERTIES
C     THESE COULD BE ORTHOTHROPIC WITH RESPECT TO PREFERRED ORIENTATION
C
      ET(1)=(so(2)-so(1))/(eo(2)-eo(1))
      et(2) = et(1)
      et(3) = et(1)
      XU(1)=0.3
      xu(2)=xu(1)
      xu(3)=xu(1)
      SHRMOD(1)= et(1)/(2*(1+xu(1)))
      shrmod(2)=shrmod(1)
      shrmod(3)=shrmod(1)
      if ((m.gt.1).or.(inc.gt.0)) goto 301
      write(6,996) et,xu,shrmod
996   format(' original data ',3e15.4)
301   continue
C
C     find current line segement
c
c   skip any calculation if inc = 0  or 1
       if (inc.eq.0)  goto 101
c   find equivalent strain
      estr = (e(1)**2+e(2)**2)
      if (estr .le. 0.0)  estr = 1e-6
      eeq = sqrt(estr)
      if ((m.eq.1).and.(inc.gt.1)) write (6,997) estr,eeq
997   format(' equivalent strain ', 2e10.4)
      do  78 i = 1,22
          if ((eeq.gt.eo(i)).and.(eeq.lt.eo(i+1))) then 
                       ii = i 
                       ij = i + 1
       if((m.eq.1).or.(m.eq.22))  write(6,1001) m,ii,ij
1001   format(' pointer on curve ', 3i5)
          else
               continue
      endif
78    continue
C
C     find current et young's modulus
c
      et(1) = (so(ij)-so(ii))/(eo(ii)-eo(ij))
      shrmod(1) = et(1)/(2*(1+xu(1)))
      et(2) = et(1)
      et(3) = et(1)
      shrmod(2)=shrmod(1)
      shrmod(3)=shrmod(1)
      if((m.eq.1).or.(m.eq.22)) then
      write(6,999) et,xu,shrmod
999   format(' calculated data ',3e15.4)
      else
       continue
      endif
C
C     FORM ELASTIC STRESS - STRAIN LAW
C
101   continue
      do 22 i=1,ngens 
        do 33 j=1,ngens
           D(i,j)= 0.0
33      continue
22    continue
      po = xu(1)
      AC = et(1)/(1-po**2)
      D(1,1)= ac
      D(2,1)= ac*po
      D(1,2)= ac*po
      D(2,2)= ac
      D(3,3)= shrmod(1)
      if((m.eq.1).or.(m.eq.22)) then
      write (6,998) ac,po,d
998   format(' ac,po and d matrix ',2e15.4,/,3f15.4,/,3e15.4,/,3e15.4)
      else
        continue
      endif
C
C     FORM INCREMENT OF STRESS
C
      CALL GMPRD(D,DE,DS,NGENS,NGENS,1)
C
C     ADD INCREMENTAL STRESS TO TOTAL STRESS
C
      CALL GMADD(S,DS,S,NGENS,1)
      RETURN
      END

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