SUBROUTINE FRIC(LM,TAU,DDTDDG,DDTDDP,DSLIP,SED,SFD,
     1     DDTDDT,PNEWDT,STATEV,DGAM,TAULM,PRESS,DPRESS,DDPDDH,
     2     SLIP,KSTEP,KINC,TIME,DTIME,NOEL,CINAME,SLNAME,
     3     MSNAME,NPT,NODE,NPATCH,COORDS,RCOORD,DROT,TEMP,
     4     PREDEF,NFDIR,MCRD,NPRED,NSTATV,CHRLNGTH,PROPS,NPROPS)
C                    
      INCLUDE 'ABA_PARAM.INC'
C                    
      CHARACTER*80 CINAME,SLNAME,MSNAME
      DIMENSION TAU(NFDIR),DDTDDG(NFDIR,NFDIR),DDTDDP(NFDIR),
     1     DSLIP(NFDIR),DDTDDT(NFDIR,2),STATEV(*),
     2     DGAM(NFDIR),TAULM(NFDIR),SLIP(NFDIR),
     3     COORDS(MCRD),RCOORD(MCRD),DROT(2,2),TEMP(2),
     4     PREDEF(2,*),TIME(2),PROPS(NPROPS)
C                    
      PARAMETER(ZERO=0.0D0,PRECIS=1.D-14,XKS=1.D6,RAUMTEMP = 20)
      REAL WERTE
      DATA WERTE/105, 110, 115, 
     120, 125, 130, 135, 140, 
     145, 150, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 
     &0.35, 0.3, 0.25, 0.2/
      DIMENSION WERTE(2, 10)
C                    
C     IMPLEMENTATION OF COULOMB
C     FRICTION USING PENALTY METHOD
C     
C     VARIABLES USED:
C        XMU   = COEFFICIENT OF FRICTION
C        GCRIT = CRITICAL ELASTIC SLIP
C        STIFF = ARTIFICIAL STIFFNESS
C        GAMMA = TOTAL SLIP
C        STATEV(1) = ELASTIC SLIP
C        TAUCRIT   = CRITICAL FRICTIONAL STRESS
C                    
C
C
C
      IF (LM .EQ. 2) THEN
C
C                       GAP IS OPENED AT START
C                       OF THE CURRENT INCREMENT
C                       
         IF (XMU .LE. PRECIS) RETURN 
      END IF
C                    
      LM    = 0
C
C    ABGLEICH VON OBERFLAECHENTEMPERATUR TEMP(2) MIT TABELLARISCH HINTERLEGTEN WERTEN  
C
      IF (TEMP(2) .EQ. RAUMTEMP) THEN
      XMU = 0.7
      RETURN
      ELSE
      DO LV1 = 1,10
      IF (TEMP(2) .EQ. WERTE(LV1,1)) THEN
      XMU = WERTE(LV1,2)
      RETURN
      ENDIF
      ENDDO
      RETURN
      ENDIF
      GCRIT = 5*CHRLNGTH
C                    
C                    CHECK IF PRESSURE IS NON-POSITIVE
C                    
      IF (PRESS .LE. ZERO) THEN
         STATEV(1)   = ZERO
         GAMMA       = DGAM(1)
         IF (XMU .LE. PRECIS) THEN
            DDTDDG(1,1) = ZERO
            DDTDDP(1)   = XMU*GAMMA/GCRIT
         ELSE
            DDTDDG(1,1) = XKS
            DDTDDP(1)   = ZERO
         END IF
         TAU(1)      = ZERO
         DSLIP(1)    = ZERO
         RETURN
      ELSE
C                       
C                       COMPUTE FOR CRITICAL STRESS
C                       AND ARTIFICIAL STIFFNESS
C                       
         TAUCRIT = XMU*PRESS
         STIFF   = TAUCRIT/GCRIT
      ENDIF
C                    
C                    COMPUTE FOR THE TOTAL SLIP
C                    AND FRICTIONAL SHEAR STRESS
C                    
      GAMMA = STATEV(1) + DGAM(1)
      TAU(1) = STIFF*GAMMA
C                    
C                    CHECK IF THE FRICTIONAL STRESS
C                    EXCEEDS THE CRITICAL STRESS
C                    
      IF (ABS(TAU(1)) .LT. TAUCRIT) THEN
C                       
C                       BEHAVIOR REMAINS ELASTIC
C                       
         STATEV(1)   = GAMMA
         DDTDDG(1,1) = STIFF
         DDTDDP(1)   = XMU*GAMMA/GCRIT
         DSLIP(1)    = ZERO
      ELSE
C                       
C                       BEHAVIOR IS PLASTIC
C                       
         TAU(1) = SIGN(TAUCRIT,GAMMA)
         STATEV(1)   = TAU(1)/STIFF
         DDTDDG(1,1) = ZERO
         DDTDDP(1)   = SIGN(XMU,GAMMA)
         DSLIP(1)    = GAMMA - STATEV(1)
      ENDIF
      RETURN
      END