*HEADING
 : EXPONENTIAL DECAY FRICTION (1 SLIP DIR, LAGRANGE MULTIPLIER)
*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
*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
*SURFACE INTERACTION,NAME=CI1
 1.0,
*FRICTION, EXPONENTIAL DECAY, LAGRANGE
 0.3, 0.1, 4.0
*GAP CONDUCTANCE
 10.0,0.
 10.0,1.
*SURFACE INTERACTION,NAME=CI2
 1.0,
*FRICTION, ROUGH
*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
*NODE PRINT, FREQ=0
*OUTPUT,FIELD,FREQ=0
*NODE OUTPUT
*EL PRINT, FREQ=0
*OUTPUT,FIELD,FREQ=0
*ELEMENT OUTPUT
*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)
**                                                           
** Given:    P=300.0, Tau=85.0
** Results:  mu=0.3
**           Tcrit=90   --> "Sticking"
**
*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
 2,1,85.0
 2,2,-300.0
 4,2,-300.0
*OUTPUT,FIELD,FREQ=1
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN1,MASTER=RS1
CSTRESS,CDISP
*CONTACT PRINT, F=99, 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,-300.0
 4,2,-300.0
*END STEP
**
** STEP 5: CHANGE FRICTION AND APPLY SHEAR FORCE
**
** Given:    P=300.0, Tau=-145.0
** Results:  mu=0.5,  Tcrit=150.0   "sticking"
**
*STEP, NLGEOM
 CHANGE FRICTION TO AN ISOTROPIC MODEL
*STATIC
 .1,1.0
*CHANGE FRICTION, INTERACTION=CI1
*FRICTION, EXPONENTIAL DECAY, TEST DATA, LAGRANGE
 0.5, 
 0.3, 0.2
 0.2,
*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,-145.0
 2,2,-300.0
 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,-300.0
 4,2,-300.0
*END STEP
**
** STEP 7: RESET THE FRICTION MODEL TO THE ORIGINAL MODEL
**         AND APPLY A SLIP 
**
*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,-300.0
 4,2,-300.0
*END STEP
**
** STEP 8: CHANGE FRICTION FOR ROD 2
**
*STEP, NLGEOM, AMP=STEP
 CHANGE FRICTION FOR ROD 2
*STATIC
 ,1.0
*CHANGE FRICTION, INTERACTION=CI1
*FRICTION, LAGRANGE
 0.0,
*CHANGE FRICTION, INTERACTION=CI2
*FRICTION, EXPONENTIAL DECAY, TEST DATA, LAGRANGE
 0.3, 0.0
 0.1, 0.2
*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: APPLY A SLIP ON ROD 2
**
*STEP, NLGEOM
 APPLY SLIP ON ROD 2
*STATIC
 .1,1.0
*BOUNDARY, OP=MOD, AMP=AMP1
 4,1,1,1.0
*CONTACT PRINT, F=99, SLAVE=CN2, MASTER=RS1
*OUTPUT,FIELD,FREQ=1
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=CN2,MASTER=RS1
CSTRESS,CDISP
*END STEP