*HEADING
: SIMPLE CONTACT TEST, SMALL SLIDING, CPS6M
** CONTACT FEATURES TESTED:
**    *CONTACT INTERFERENCE, *FRICTION, *CHANGE FRICTION (mu=0 and mu=0.3)
**      BOTH FRICTION STEPS ARE PERTURBATION STEPS
*RESTART,WRITE, FREQ=4
**
*NODE
1,1.,
3,2.,
9,2.,1.2
7,1.,1.2
5,1.5,.6
11,0.,1.
13,3.,1.
15,1.5,2.
19,3.,3.
17,0.,3.
*NGEN,NSET=BOT
1,3
*NGEN
3,9,3
7,9
1,7,3
11,13
13,19,3
11,17,3
*NGEN,NSET=TOP
17,19
*ELEMENT,TYPE=CPS6M,ELSET=BOT
1,1,3,7,2,5,4
2,3,9,7,6,8,5
*ELEMENT,TYPE=CPS6M,ELSET=TOP
3,11,13,17,12,15,14
4,13,19,17,16,18,15
**
*SOLID SECTION,ELSET=BOT,MATERIAL=MAT
*SOLID SECTION,ELSET=TOP,MATERIAL=MAT
*MATERIAL,NAME=MAT
*ELASTIC
1.E5,.3
*SURFACE INTERACTION,NAME=SLIDE
 1., 
*FRICTION
0., 
*surface,NAME=BOTS
2,S2
*surface,NAME=TOPS
3,S1
*CONTACT PAIR,INTERACTION=SLIDE, SMALL SLIDING
BOTS,TOPS
*BOUNDARY
BOT, 1,2
TOP, 1,2
**
** step 1: Shrink fit with *CONTACT INTERFERENCE.
** 	   Establish base state.
**
*STEP,INC=20,NLGEOM
*STATIC
0.2,1.,0.2,0.2
*CONTACT INTERFERENCE, SHRINK
BOTS,TOPS
*EL FILE
S, 
*NODE FILE
U, 
*CONTACT FILE,SLAVE=BOTS,MASTER=TOPS
*CONTACT PRINT,SLAVE=BOTS,MASTER=TOPS
*PRINT,CONTACT=YES
*ENDSTEP
**
** step 2: slide to the right w/o friction, linear perturbation
**
*STEP,PERT,NLGEOM
*STATIC
*BOUNDARY,OP=MOD
BOT,1,1, 0.1
*EL FILE
S, 
*NODE FILE
U, 
*CONTACT FILE,SLAVE=BOTS,MASTER=TOPS
*CONTACT PRINT,SLAVE=BOTS,MASTER=TOPS
*PRINT,CONTACT=YES
*ENDSTEP
**
** step 3: change surface friction
**
*STEP,NLGEOM
*STATIC
1.0,1.0
*CHANGE FRICTION,INTERACTION=SLIDE
*FRICTION
0.3, 
*ENDSTEP
**
** step 4: slide to the left w/ friction, linear perturbation
**
*STEP,NLGEOM,PERT
*STATIC
*BOUNDARY
BOT,1,,-0.1
*EL FILE
S, 
*NODE FILE
U, 
*CONTACT FILE,SLAVE=BOTS,MASTER=TOPS
*CONTACT PRINT,SLAVE=BOTS,MASTER=TOPS
*PRINT,CONTACT=YES
*ENDSTEP