*HEADING
 : COULOMB FRICTION (1 SLIP DIRECTION, ELASTIC SLIP FORMULATION)
*RESTART,WRITE,FREQ=0
*NODE, NSET=NALL
   1, 0., 0.
   2, 0., 1.
   3, 1., 0.
   4, 1., 1.
 100, 0., 0.
*ELEMENT,TYPE=B21,ELSET=BEAM
 1, 1,2
 2, 3,4
*BEAM SECTION,SECT=CIRC,ELSET=BEAM,MATERIAL=ELAS,TEMP=GRADIENTS
 0.564189584,
 0.,0.,-1.,
*MATERIAL,NAME=ELAS
*ELASTIC
 30.E6,0.3
*INITIAL CONDITION,TYPE=TEMPERATURE
   1, 20.0
   2, 20.0
*rigid body,analytical surface=RS1,REFNODE=100
*surface,TYPE=SEGMENTS,NAME=RS1
 START,-10.,0.
 LINE,10.,0.
*surface,type=node,NAME=CN1
 1,
*surface,type=node,NAME=CN2
 3,
*CONTACT PAIR,INTERACTION=CI1
 CN1,RS1
*CONTACT PAIR,INTERACTION=CI2
 CN2,RS1
**
** CONTACT INTERACTION 1 
**
** mu(p,t) = 0.005(t) + 2.5e-4*(p-100) with Tcrit = mu*p
**
** where   mu    friction coefficient
**         p     contact pressure ( 100 < p < 1100)
**         t     temperature      (   0 < t < 20)
**
*SURFACE INTERACTION,NAME=CI1
 1.0,
*FRICTION, TAUMAX=1000.0
 0.025, 0.0,  200.0, 0
 0.050, 0.0,  300.0, 0
 0.075, 0.0,  400.0, 0
 0.100, 0.0,  500.0, 0
 0.125, 0.0,  600.0, 0
 0.150, 0.0,  700.0, 0
 0.175, 0.0,  800.0, 0
 0.200, 0.0,  900.0, 0
 0.225, 0.0, 1000.0, 0
 0.250, 0.0, 1100.0, 0
 0.050, 0.0,  100.0, 10
 0.075, 0.0,  200.0, 10
 0.100, 0.0,  300.0, 10
 0.125, 0.0,  400.0, 10
 0.150, 0.0,  500.0, 10
 0.175, 0.0,  600.0, 10
 0.200, 0.0,  700.0, 10
 0.225, 0.0,  800.0, 10
 0.250, 0.0,  900.0, 10
 0.275, 0.0, 1000.0, 10
 0.300, 0.0, 1100.0, 10
 0.100, 0.0,  100.0, 20
 0.125, 0.0,  200.0, 20
 0.150, 0.0,  300.0, 20
 0.175, 0.0,  400.0, 20
 0.200, 0.0,  500.0, 20
 0.225, 0.0,  600.0, 20
 0.250, 0.0,  700.0, 20
 0.275, 0.0,  800.0, 20
 0.300, 0.0,  900.0, 20
 0.325, 0.0, 1000.0, 20
 0.350, 0.0, 1100.0, 20
*GAP CONDUCTANCE
 10.0,0.
 10.0,1.
**
** CONTACT INTERACTION 2 (ZERO FRICTION)
**
*SURFACE INTERACTION,NAME=CI2
 1.0,
*AMPLITUDE,NAME=AMP1
 0.0, 0.0, 0.2, 0.0625, 0.4, 0.1250, 0.6, 0.2500,
 0.8, 0.5, 1.0, 1.0
**
** STEP 1: ESTABLISH CONTACT (PRESCRIBED DISPLACEMENT)
**
*STEP, NLGEOM
 ESTABLISH CONTACT (PRECRIBED DISPLACEMENT)
*STATIC
 1.,1.
*BOUNDARY
 100,1,2,0.0
 100,6,6,0.0
 2,1,1,0.0
 2,2,2,-1.e-5
 2,6,6,0.0
 4,1,1,0.0
 4,2,2,-1.e-5
 4,6,6,0.0
*PRINT,CONTACT=YES
*OUTPUT,FIELD,FREQ=0
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN1,MASTER=RS1
*OUTPUT,FIELD,FREQ=0
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN2,MASTER=RS1
*CONTACT PRINT,F=0,SLAVE=CN1,MASTER=RS1
*CONTACT PRINT,F=0,SLAVE=CN2,MASTER=RS1
*END STEP
**
** STEP 2: ESTABLISH CONTACT (APPLY NORMAL PRESSURE = 300)
**
*STEP, NLGEOM
 ESTABLISH CONTACT (APPLY NORMAL PRESSURE = 300)
*STATIC
 1.,1.
*BOUNDARY,OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,1,1,0.0
 2,6,6,0.0
 4,1,1,0.0
 4,6,6,0.0
*CLOAD
 2,2,-300.0
 4,2,-300.0
*END STEP
**                           
** STEP 3: APPLY SHEAR FORCE  (Teq < Tcrit)
**         INCREASE PRESSURE FROM 300 to 450
**                                                           
** Given:    P=450.0, Ave. Temp=10.0, Tau=55.0
** Results:  mu=0.1375
**           Tcrit=61.87   --> "Sticking"
**           Elastic Slip = 0.0022
**
*STEP, NLGEOM
 APPLY SHEAR FORCE (Teq < Tcrit)
*STATIC
 .1,1.
*BOUNDARY,OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,6,6,0.0
 4,1,1,0.0
 4,6,6,0.0
*CLOAD, OP=NEW
 2,1,55.0
 2,2,-450.0
 4,2,-300.0
*OUTPUT,FIELD,FREQ=1
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN1,MASTER=RS1
CSTRESS,CDISP
*CONTACT PRINT,F=1,SLAVE=CN1,MASTER=RS1
*PRINT,CONTACT=YES
*END STEP
**
** STEP 4: REMOVE SHEAR FORCES 
**
*STEP, NLGEOM
 REMOVE SHEAR FORCES 
*STATIC
 .1,1.
*BOUNDARY,OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,6,6,0.0
 4,1,1,0.0
 4,6,6,0.0
*CLOAD, OP=NEW
 2,2,-450.0
 4,2,-300.0
*END STEP
**
** STEP 5: CHANGE FRICTION AND APPLY SHEAR FORCE
**         PRESSURE IS INCREASED TO 550.
**
** Given:    P=550.0, Ave. Temp=10.0, Tau=-100.0
** Results:  mu=0.2125, Tcrit=116.875
**           Elastic slip=0.0021
**
*STEP, NLGEOM
 CHANGE FRICTION TO AN ISOTROPIC MODEL
*STATIC
 .1,1.0
**
** NEW FRICTION MODEL FOR CONTACT INTERACTION CN1
**
** mu(p,t)=0.002(t) + 3.3e-4(p)                100 < p <= 500
** mu(p,t)=0.1650 + 0.002(t) + 5.5e-4(p-500)   500 < p <= 800
**                                              0 <= t <= 100
**
*CHANGE FRICTION, INTERACTION=CI1
*FRICTION
 0.0330, , 100.0,   0.0
 0.0660, , 200.0,   0.0
 0.0990, , 300.0,   0.0
 0.1320, , 400.0,   0.0
 0.1650, , 500.0,   0.0
 0.2200, , 600.0,   0.0
 0.3300, , 800.0,   0.0
 0.2330, , 100.0, 100.0
 0.2660, , 200.0, 100.0
 0.2990, , 300.0, 100.0
 0.3320, , 400.0, 100.0
 0.3650, , 500.0, 100.0
 0.4200, , 600.0, 100.0
 0.5300, , 800.0, 100.0
*BOUNDARY,OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,6,6,0.0
 4,1,1,0.0
 4,6,6,0.0
*CLOAD, OP=NEW
 2,1,-100.0
 2,2,-550.0
 4,2,-300.0
*END STEP
**
**  STEP 6: REMOVE SHEAR FORCES
**
*STEP, NLGEOM
 REMOVE SHEAR FORCES (2)
*STATIC
 .1,1.0
*BOUNDARY,OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,6,6,0.0
 4,1,1,0.0
 4,6,6,0.0
*CLOAD, OP=NEW
 2,2,-550.0
 4,2,-300.0
*END STEP
**
** STEP 7: RESET THE FRICTION MODEL TO THE ORIGINAL MODEL
**         AND APPLY A SLIP 
**         PRESSURE IS INCREASED TO 850.
**
** Given:   P=850, Temp=10.0, G_1=0.2
** Results: mu_1=0.2375
**          Tau=201.875
**
*STEP, NLGEOM
 RESET THE FRICTION MODEL TO THE ORIGINAL MODEL
*STATIC
 .1,1.0
*CHANGE FRICTION, RESET, INTERACTION=CI1
*BOUNDARY,OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,6,6,0.0
 2,1,1,0.2
 4,1,1,0.0
 4,6,6,0.0
*CLOAD, OP=NEW
 2,2,-850.0
 4,2,-300.0
*END STEP
**
** STEP 8: CHANGE FRICTION TO A SLIP VELOCITY DEPENDENT MODEL
**
*STEP, NLGEOM, AMP=STEP
 CHANGE FRICTION TO A SLIP VELOCITY DEPENDENT MODEL
*STATIC
 ,1.0
*CHANGE FRICTION, INTERACTION=CI1
*FRICTION
 0.0,
*CHANGE FRICTION, INTERACTION=CI2
*FRICTION
 0.2, 0.0, 100
 0.0, 2.0, 100
 0.4, 0.0, 500
 0.2, 2.0, 500
*BOUNDARY, OP=NEW
 100,1,2,0.0
 100,6,6,0.0
 2,1,1,0.0
 2,6,6,0.0
 4,1,1,0.0
 4,6,6,0.0
*CLOAD, OP=NEW
 2,2,-300.0
 4,2,-300.0
*CONTACT PRINT,F=0,SLAVE=CN2,MASTER=RS1
*OUTPUT,FIELD,FREQ=0
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN2,MASTER=RS1
*END STEP
**
** STEP 9: SLIP IN THE X DIRECTION WITH VARIABLE SLIP RATE
**
** Given:   P=300
** Results: mu_s=0.3 and mu_k=0.1
**          Tau=30.0     
**
*STEP, NLGEOM
 SLIP IN THE X DIRECTION WITH A VARIABLE SLIP RATE
*STATIC
 .1,1.0
*BOUNDARY, OP=MOD, AMP=AMP1
 4,1,1,1.0
*CONTACT PRINT,F=1,SLAVE=CN2,MASTER=RS1
*OUTPUT,FIELD,FREQ=1
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN2,MASTER=RS1
CSTRESS,CDISP
*END STEP