*HEADING
AIRSPRING -- AXISYMMETRIC MODEL
*NODE
1,    0.       , 2.E-2
4,    20.E-2   , 2.E-2
6,    20.E-2   , 0.
26,   40.E-2   , 0.
32,   37.771E-2, 6.293E-2
38,   36.211E-2, 10.698E-2
39,   36.211E-2, 11.35E-2
40,   36.211E-2, 12.E-2
500,  0.       , 9.E-2
*NODE, NSET = RIGID
1000, 0.       , 12.E-2
*NSET, NSET = CAVITY
500,
*NSET, NSET=ALL, GENERATE
1,37,1
40,2000,1
*NSET, NSET=FLEX, GENERATE
1,37,1
51,999,1
*NSET, NSET=FLEX, GENERATE
1001,2000,1
*NGEN, LINE = C
6,  26, 2, , 30.E-2   , 0.       , 0., 0., 0., 1.
26, 32, 1, , 30.E-2   , 0.       , 0.
32, 38, 1, , 43.211E-2, 10.698E-2, 0.
**
** RUBBER SPRING
**
*ELEMENT, TYPE = MGAX1, ELSET = SPRING
2,   4, 6
26, 26, 27
*ELGEN, ELSET = SPRING
2,  11, 2, 2
26, 14, 1, 1
*MEMBRANE SECTION, ELSET = SPRING, MATERIAL=RUBBER
5.0E-3,
*REBAR LAYER
RBAR1, 3.5E-3, 3.5E-3, 0, STEEL,  8.66,1
RBAR2, 3.5E-3, 3.5E-3, 0, STEEL, -8.66,1
*MATERIAL, NAME = RUBBER
*HYPERELASTIC, POLYNOMIAL, N = 1
3.2E6, 0.8E6
*DENSITY
1000.,
*MATERIAL, NAME = STEEL
*ELASTIC
2.5086E9,0.3
**
** RIGID BODY/SURFACE
**
*NODE,NSET=RIGNODE
11001, 36.211E-2, 10.698E-2
11021, 41.711E-2,  5.198E-2
12000, 41.711E-2, 10.698E-2
*NGEN,NSET=RIGNODE,LINE=C
11001, 11021, 1, 12000
*ELEMENT,TYPE=RAX2,ELSET=RIGELEM
11001, 1000,40
11002, 40, 11002
11003, 11002, 11003
*ELGEN,ELSET=RIGELEM
11003, 19, 1, 1
*RIGID BODY, REF NODE=1000, ELSET=RIGELEM
**
** FLUID CAVITY
**
*ELEMENT, TYPE = MGAX1, ELSET = FLUID
201,  1,  4
299, 40, 1000
*MEMBRANE SECTION, ELSET=FLUID, MATERIAL=A1
1E-3, 
*MATERIAL,NAME=A1
*ELASTIC
1E5, 0.1
*SURFACE, TYPE=ELEMENT, NAME=CAVSURF
 SPRING, SPOS
 FLUID, SPOS
*PHYSICAL CONSTANTS, ABSOLUTE ZERO=-273.16, UNIVERSAL GAS CONSTANT=8.314
*FLUID CAVITY, NAME=SPRINGCAV, BEHAVIOR=GAS, REF NODE=500, SURFACE=CAVSURF, AMBIENT PRESSURE=101.36E+3

*FLUID BEHAVIOR, NAME=GAS
*MOLECULAR WEIGHT
0.044
*NSET, NSET=FLEX, GENERATE
7,25,1
28,37,1
51,999,1
*NSET, NSET=FLEX, GENERATE
1001,2000,1
*NSET,NSET=FLEX
2,3,5
**
*BOUNDARY
1,1,2
4,1,2
4,6,6
6,1,1
RIGID,1,2
RIGID,6,6
FLEX,5,5
*INITIAL CONDITIONS, TYPE=STRESS, REBAR, UNBALANCED STRESS=STEP
SPRING,,70.
*NSET,NSET=RIG
40,1000
*SURFACE,TYPE=ELEMENT,NAME=ASURF
ECON,SPOS
*SURFACE,TYPE=ELEMENT,NAME=BSURF
RIGELEM,SNEG
**
** CONTACT DEFINITION
**
*ELSET,ELSET=ECON,GENERATE
26,38,1
*CONTACT PAIR,INTERACTION=SMOOTH
ASURF,BSURF
*SURFACE INTERACTION,NAME=SMOOTH
************** HISTORY DEFINITION **********************
**
** STEP 0 - EQUILIBRATE MEMBRANE INITIAL STRESSES
**
*STEP, NLGEOM,Convert Sdi=YES
*STATIC
*BOUNDARY
FLEX,1,6
*OUTPUT,FIELD
*NODE OUTPUT
U,
*ELEMENT OUTPUT
LE,
*ENDSTEP
**
** STEP 1 - INFLATION STEP (5 ATMOSPHERES)
**
*STEP, NLGEOM,Convert Sdi=YES
*STATIC
0.1,1.0
*MONITOR, NODE=26, DOF=1
*CONTROLS, PARAMETERS=TIME
 6
*PRINT, CONTACT = YES
*BOUNDARY, OP=NEW
CAVITY,8,8, 5.066E5
1,1,3
4,1,2
4,5
6,1,1
RIGID,1,6
FLEX,5,5
*OUTPUT,FIELD
*NODE OUTPUT
U,RF
CF,
*ELEMENT OUTPUT
S,
*CONTACT OUTPUT,VARIABLE=PRESELECT,SECONDARY=ASURF
*EL PRINT, FREQUENCY=99
*NODE PRINT, NSET=CAVITY, FREQUENCY=99
PCAV, CVOL
*NODE PRINT, NSET=RIGID, FREQUENCY=99
U, RF
*NODE FILE, NSET=CAVITY
PCAV, CVOL
*OUTPUT,HISTORY
*NODE OUTPUT,NSET=CAVITY
PCAV,CVOL
*NODE OUTPUT, NSET=RIGID
U, RF
CF,
*END STEP
**
** STEP 2 - SEAL CAVITY, RELEASE GRIP ON
**          RIGID SURFACE,
**          AND LOAD RIGID SURFACE
**
*STEP, NLGEOM,Convert Sdi=YES
*STATIC
1.0, 1.0
*MONITOR, NODE=1000, DOF=2
*BOUNDARY, OP=NEW
1,1,3
4,1,2
4,5
6,1,1
RIGID,1
RIGID,6
FLEX,5,5
*CLOAD
RIGID,2,-150.E3
*END STEP
**
** STEP 3 - PERTURBATION STEP
**          2 LOAD CASES
*STEP, PERTURBATION,Convert Sdi=YES
*STATIC
*BOUNDARY, OP=NEW
1,1,2
4,1,2
4,6,6
6,1,1
RIGID,1
RIGID,6
FLEX,5,5
** LOAD CASE 1
** UNIT AXIAL DISPLACEMENT WITH CAVITY PRESSURE FREE
*LOAD CASE, NAME="PRESSURE FREE"
*BOUNDARY, OP=NEW
RIGID, 2, 2, 1.E-3
*END LOAD CASE
** LOAD CASE 2
** UNIT LOAD WITH CAVITY PRESS FIXED
*LOAD CASE, NAME="PRESSURE FIXED"
*BOUNDARY, OP=NEW
CAVITY, 8, 8, 0
RIGID,  2, 2, 1.E-3
*END LOAD CASE
***OUTPUT,FIELD
***NODE OUTPUT
**U,
***ELEMENT OUTPUT
**S,
*END STEP
**
** STEP 4 - NONLINEAR LOAD DEFLECTION CURVE
**
*STEP, NLGEOM,Convert Sdi=YES
*STATIC
0.1,1.0
*CLOAD
RIGID,2,-240.E3
*END STEP