*HEADING
 : CPS4 MODEL CHANGE VERIFICATION; DYNAMIC ANALYSIS
*NODE
 1,0.
 9,8.
41,0.,4.
49,8.,4.
*NGEN,NSET=BOT
 1,9,1
*NGEN,NSET=TOP
41,49,1
*NFILL,NSET=NALL
BOT,TOP,4,10
*ELEMENT,TYPE=CPS4
1,1,3,23,21
*ELGEN,ELSET=EALL
1,4,2,1,2,20,10
*ELSET,ELSET=REMOVE,GEN
2,4,1
12,14,1
*NSET, NSET=HOLDEM, GEN
5, 9, 1
25, 29, 1
45, 49, 1
*ELSET, ELSET=EOUT
1, 
*SOLID SECTION,MATERIAL=MAT,ELSET=EALL
1.,
*MATERIAL,NAME=MAT
*ELASTIC
207.00E12, 0.3
*DENSITY
7800.00,
*ELEMENT,TYPE=SPRING1,ELSET=SPR
101,21
*SPRING,ELSET=SPR
1, 
9.853813E6,
*NSET, NSET=XMOVE,GEN
1,41,20
45, 49,2
*NSET, NSET=SLIDE,GEN
1,9,1
*BOUNDARY
SLIDE,2,2
*ELSET,ELSET=left1
1,11
*surface, NAME=LEFT
left1,S4
*STEP, NLGEOM
Step 1: Displace M from original configuration by 1.0 units
*STATIC
*BOUNDARY
XMOVE,1,,1.0
*NODE FILE,FREQ=1,NSET=XMOVE
U, V, A
*ELFILE,FREQ=0,ELSET=EOUT
*EL PRINT, ELSET=LEFT1
NFORC,
*NSET,NSET=LEFT
1,21,41
*ENDSTEP
*STEP, NLGEOM,INC=200
Step 2: Let it move.
*DYNAMIC,NOHAF
0.01,1.
*PRINT, FREQ=10
*BOUNDARY,OP=NEW
SLIDE,2,2
*SECTION PRINT, NAME=LEFT, SURFACE=LEFT,freq=100
*SECTION FILE,  NAME=LEFT, SURFACE=LEFT,freq=100
*ENDSTEP
*STEP, NLGEOM
Step 3: Remove Elements
*STATIC
*PRINT, FREQ=1
*BOUNDARY,FIXED
NALL,1,2
*MODEL CHANGE,REMOVE,TYPE=ELEMENT
REMOVE,
*ENDSTEP
*STEP, NLGEOM,INC=200
Step 4: Let it move again for two cycles.
** Period should be half the original period.
*DYNAMIC,NOHAF
0.01,1.
*PRINT, FREQ=10
*BOUNDARY,OP=NEW
SLIDE,2,2
*BOUNDARY, OP=NEW, FIXED
HOLDEM, 1, 2
*ENDSTEP
*STEP, NLGEOM
Step 5: Add elements again
*STATIC
*PRINT, FREQ=1
*BOUNDARY,FIXED
NALL,1,2
*MODEL CHANGE,ADD,TYPE=ELEMENT
REMOVE,
*ENDSTEP
*STEP, NLGEOM,INC=200
Step 6: Let it move. Period should be original period again.
*DYNAMIC,NOHAF, INITIAL=NO
0.01,1.
*PRINT, FREQ=10
*BOUNDARY,OP=NEW
SLIDE,2,2
*ENDSTEP