SUBROUTINE fric_coef (fCoef, fCoefDeriv, nBlock, nProps,nTemp, 
     $     nFields, iData, rData, surfInt, surfSec, surfMain,props, slipData,
     $     pressure, tempAvg, fieldAvg)
c
      include 'aba_param.inc'
c
      dimension fCoef(nBlock,2), 
     *   fCoefDeriv(nBlock,20,2),
     *   props(nProps),
     *   slipData(nBlock,*),
     *   pressure(nBlock),
     *   tempAvg(nBlock), 
     *   fieldAvg(nBlock,nFields)
c
      integer*4 iData(*)
      real*8 rData(*)
c
c
c    Offset parameters to various integer quantities in iData(*)
c
      parameter( i_ifc_KStep   = 1,
     *           i_ifc_KInc    = 2,
     *           i_ifc_Kit     = 3,
     *           i_ifc_Node    = 4,
     *           i_ifc_nStateV = 5,
     *           i_ifc_nFDir   = 6)
c
c    Offset parameters to various real quantities in rData(*)
c
      parameter( i_rfc_TimStep = 1,
     *           i_rfc_TimGlb  = 2,
     *           i_rfc_DTimCur = 3,
     *           i_rfc_Drot    = 4,
     *           i_rfc_StateV  = 8)
c
c   Offset parameters of slipData
c
      parameter( i_SD_SlipRateMag  = 1,
     *     i_SD_SlipRate1    = 2,
     *     i_SD_SlipRate2    = 3,
     *     i_SD_SlipEq       = 4,
     *     i_SD_Slip1        = 5, 
     *     i_SD_Slip2        = 6,
     $     n_SD_Length       = 6)
c
c   Offset parameters of friction derivatives                  
c
      parameter( i_fDer_SlipRateMag  = 1,
     *     i_fDer_Pressure     = 2,
     *     i_fDer_Temperature  = 3,
     *     i_fDer_SlipRate1    = 4,
     *     i_fDer_SlipRate2    = 5, 
     *     i_fDer_SlipEq       = 6,
     *     i_fDer_Slip1        = 7,
     *     i_fDer_Slip2        = 8)
c
      character*80 surfInt, surfSec, surfMain
!
      real*8 cslip1, cslip_lat
      real*8 fax, sax, flat, slay
      parameter (afrac=0.05d0)
!
      nFDir     = iData(i_ifc_nFDir)
      cslip1  = slipData(1,i_SD_Slip1)
      cslip2 = slipData(1,i_SD_Slip2)
c      
      fax   = props(1)
      sax   = props(2)
      flat  = props(3)
      slay  = props(4)

c ******  Friction in the 1-Direction
      IF (abs(cslip1).LE.sax) THEN
        fCoef(1,1) = fax * abs(cslip1/sax)
        if (cslip1 .lt. -afrac*sax) then
           fCoefDeriv(1,i_fDer_Slip1,1) = -fax/sax
        else if (cslip1 .gt. afrac*sax) then
           fCoefDeriv(1,i_fDer_Slip1,1) = fax/sax
        else
           fCoefDeriv(1,i_fDer_Slip1,1) = cslip1*fax/(afrac*sax*sax)
        end if
      ELSE
        fCoef(1,1) = fax
      END IF

c ******  Friction in the 2-Direction
      IF (abs(cslip2).LE.slay) THEN
       	fCoef(1,2) = flat * abs(cslip2/slay)
        if (cslip2 .lt. -afrac*slay) then
           fCoefDeriv(1,i_fDer_Slip2,2) = -flat/slay
        else if (cslip2 .gt. afrac*slay) then
           fCoefDeriv(1,i_fDer_Slip2,2) = flat/slay
        else
           fCoefDeriv(1,i_fDer_Slip2,2) = cslip2*flat/(afrac*slay*slay)
        end if
      ELSE
       	fCoef(1,2) = flat
      END IF
!
      if (iData(i_ifc_Node) .eq. 21) then
c         write(7,*) 'nfdir',nFDir
c         write(7,*) 'slip1',slipData(1,i_SD_Slip1)
c         write(7,*) 'slip2',slipData(1,i_SD_Slip2)
c         write(7,*) 'props',props(1),props(2),props(3),props(4)
c         write(7,*) 'f1',fCoef(1,1)
c         write(7,*) 'f2',fCoef(1,2)
c         write(7,100) iData(i_ifc_Node),cslip1,cslip2,fCoef(1,1),fCoef(1,2)
      end if

 100  format ('SL Node:',i7,' Cslip:',2(1x,e14.6),' mu_1,mu_2:',2(1x,e14.6))
      return
      end