*HEADING
: SIMPLE CONTACT, TUBE-TUBE INTERFACE WITH INTERNAL CONTACT  [ITT21]
*NODE
1,0.,0.
5,10.,0.
11,0.,0.
13,4.,0.
*NGEN,NSET=OUT
1,5
*NGEN,NSET=IN
11,13
*ELEMENT,TYPE=B21
1,1,2
11,11,12
*ELGEN,ELSET=OUTER
1,4
*ELGEN,ELSET=INNER
11,2
*BEAM SECTION,SECT=PIPE,ELSET=OUTER,MATERIAL=STEEL
.25,.05
*BEAM SECTION,SECT=PIPE,ELSET=INNER,MATERIAL=STEEL
.18,.03
*ELSET,ELSET=BEAMS
INNER,OUTER
*MATERIAL,NAME=STEEL
*ELASTIC
30E6,.3
*ELEMENT,TYPE=ITT21,ELSET=INTERFAC
21,12
22,13
*INTERFACE,ELSET=INTERFAC
.02, 
*SLIDE LINE,ELSET=INTERFAC,TYPE=LINEAR
1,2,3,4,5
*BOUNDARY
1,1
1,2
1,6
11,1
11,2
11,6
**
*STEP,NLGEOM,INC=20
Step 1 - MOVE NODE 5 IN -Y DIRECTION
*STATIC
0.5,1.
*CONTROLS,PARAMETERS=FIELD,FIELD=DISPLACEMENT
5.0E-3, 
*BOUNDARY
5,2,2,-1.0
*PRINT,CONTACT=YES
*EL PRINT
S,E
*NODE PRINT
U,RF
*OUTPUT, FIELD, FREQ=5
*ELEMENT OUTPUT
S,E
*NODE OUTPUT
U,RF
*END STEP
**
*STEP,NLGEOM,INC=20
Step 2 - MOVE NODE 5 IN +Y DIRECTION
*STATIC
.1,1.
*BOUNDARY
5,2,2,2.0
*PRINT,CONTACT=YES
*END STEP