C
C User subroutine VFRIC 
      subroutine vfric (
C Write only - 
     *     fTangential, 
C Read/Write - 
     *     statev,
C Read only - 
     *     kStep, kInc, nContact, nFacNod, nSecNod, nMainNod,
     *     nFricDir, nDir, nStateVar, nProps, nTemp, nPred, numDefTfv, 
     *     jSecUid, jMainUid, jConSecid, jConMainid, timStep, timGlb,
     *     dTimCur, surfInt, surfSec, surfMast, lContType,
     *     dSlipFric, fStickForce, fTangPrev, fNormal, frictionWork,
     *     shape, coordSec, coordMain, dircosSec, dircosN, props,
     *     areaSec, tempSec, preDefSec, tempMain, preDefMain )
C
      include 'vaba_param.inc'
C
      dimension props(nProps), statev(*), 
     1     dSlipFric(nDir,nContact),
     2     fTangential(nFricDir,nContact),
     3     fTangPrev(nDir,nContact),
     4     fStickForce(nContact), areaSec(nSecNod),
     5     fNormal(nContact), shape(nFacNod,nContact), 
     6     coordSec(nDir,nSecNod), coordMain(nDir,nMainNod), 
     7     dircosSec(nDir,nContact), dircosN(nDir,nContact),
     8     jSecUid(nSecNod), jMainUid(nMainNod),
     9     jConSecid(nContact), jConMainid(nFacNod,nContact),
     1     tempSec(nContact), tempMain(numDefTfv),
     2     preDefSec(nContact, nPred),
     3     preDefMain(numDefTfv, nPred)
C
      character*80 surfInt, surfSec, surfMast 
      parameter ( zero = 0.d0, one = 1.d0, half = 0.5d0 )
C     
      dTimCurInv = one / dTimCur	
      do kcon = 1, nContact
        xMu = props(1) + props(2) * tempSec(kcon) * half
        xMuInv = one / xMu
        slipRate = dSlipFric(1,kcon) * dTimCurInv         
        fTangential(1,kcon) = -slipRate*areaSec(kcon)*xMuInv
      end do
      if ( nDir .eq. 3 ) fTangential(2,kcon) = zero
*
      return
      end