*HEADING
SIMPLE  TESTS, SMALL SLIDING, CGAX8                          :--  
**RESTART,WRITE, FREQ=30
*NODE
1,1.,5.
2,1.5,5.
3,2.,5.
4,1.,7.5
5,2.,7.5
6,1.,10
7,1.5,10.
8,2.,10.
9,1.9,5.
10,2.4,5.
11,2.9,5.
12,1.9,7.5
13,2.9,7.5
14,1.9,10.
15,2.4,10.
16,2.9,10.
*ELEMENT,TYPE=CGAX8,ELSET=LEFTEL
1,1,3,8,6,2,5,7,4
*ELEMENT,TYPE=CGAX8,ELSET=RTEL
3,9,11,16,14,10,13,15,12
*ELSET,ELSET=SOLID
LEFTEL, RTEL
*NSET, NSET=LT_N
1,4,6
*NSET, NSET=RT_N
11,13,16
*SOLID SECTION,ELSET=SOLID,MATERIAL=SOLMAT
*MATERIAL,NAME=SOLMAT
*ELASTIC
30.E6,0.30
*SURFACE INTERACTION,NAME=SLIDE
 1., 
*FRICTION, ANISOTROPIC
0.1,0.2
*surface,NAME=LEFT
LEFTEL,S2
*surface,NAME=RT
RTEL,S4
*CONTACT PAIR,INTERACTION=SLIDE, SMALL SLIDING
LEFT,RT
*BOUNDARY
LT_N,1,2
LT_N,5,5
RT_N,1,2
RT_N,5,5
**
**    step 1  :  interference fit, (radial intereference)
**
*STEP, INC=20, NLGEOM
           SHRINK FIT
*STATIC 
0.1,1.,0.1,0.2
*CONTACT INTERFERENCE,SHRINK
LEFT, RT
*NODE PRINT, F=0
*EL PRINT, F=0
*OUTPUT,FIELD,FREQ=0
*ELEMENT OUTPUT
*OUTPUT,FIELD,FREQ=0
*NODE OUTPUT
*OUTPUT,FIELD,FREQ=50
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=LEFT,MASTER=RT
*CONTACT PRINT, SLAVE=LEFT , MASTER=RT, F=50
*ENDSTEP
**
**     step 2 : linear perturbation (about shrink fit); sliding upwards
**
*STEP,PERT,  NLGEOM
 PERT :- SLIDING UPWARDS
*STATIC
*BOUNDARY, OP=MOD
RT_N,2,,0.1
*NODE PRINT, F=0
*EL PRINT, F=0
*OUTPUT,FIELD,FREQ=0
*ELEMENT OUTPUT
*OUTPUT,FIELD,FREQ=0
*NODE OUTPUT
*OUTPUT,FIELD,FREQ=50
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=LEFT,MASTER=RT
*CONTACT PRINT, SLAVE=LEFT , MASTER=RT, F=50
*ENDSTEP
**
**     step 3 : linear perturbation (about shrink fit); twist 
**
*STEP, PERT, NLGEOM
  PERT: TWISTING
*STATIC
*BOUNDARY, OP=MOD
RT_N,5,,0.1
*OUTPUT,FIELD,FREQ=50
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=LEFT,MASTER=RT
*CONTACT PRINT, SLAVE=LEFT , MASTER=RT, F=50
*ENDSTEP
**
**     step 4: UNSYMM, linear perturbation, slide and twist
** 	          with shrink-fit base state.
**
*STEP,  PERT, NLGEOM, UNSYMM=YES
*STATIC
*BOUNDARY
RT_N,5,,0.1
RT_N,2,,0.1
*OUTPUT,FIELD,FREQ=50
*CONTACT OUTPUT,VARIABLE=PRESELECT,SLAVE=LEFT,MASTER=RT
*CONTACT PRINT, SLAVE=LEFT , MASTER=RT, F=50
*ENDSTEP
**
**       step 5: NLGEOM, UNSYMM, twist and sliding
**
*STEP, NLGEOM, UNSYMM=YES
*STATIC
0.1,1.0
*CONTROLS,PARAMETERS=FIELD
1.0E-6, 
*BOUNDARY
RT_N,2,,0.1
RT_N,5,,0.1
*ENDSTEP