*HEADING
  - POLY. HYPERELASTICITY, UNIAXIAL TENSION W/ LINEAR PERT. STEPS
*NODE,NSET=ALL
1,
2,1.
3,1.,1.,
4,0.,1.,
5,0.,0.,1.
6,1.,0.,1.
7,1.,1.,1.
8,0.,1.,1.
*NSET,NSET=FACE1
1,2,3,4
*NSET,NSET=FACE2
5,6,7,8
*NSET,NSET=FACE3
1,2,5,6
*NSET,NSET=FACE4
2,3,6,7
*NSET,NSET=FACE5
3,4,7,8
*NSET,NSET=FACE6
4,1,8,5
*ELEMENT,TYPE=C3D8RH,ELSET=ONE
1,1,2,3,4,5,6,7,8
*SOLID SECTION,ELSET=ONE,MATERIAL=YEOH
*MATERIAL,NAME=YEOH
*HYPERELASTIC, YEOH
100., -1., 0.01
*STEP,PERTURBATION
Initial static linear perturbation, uniaxial tension
*STATIC
*LOAD CASE,name = "uniaxial tension 1"
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,.1
*END LOAD CASE
*LOAD CASE,name = "uniaxial tension 2"
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,.2
*END LOAD CASE
*LOAD CASE,name = "uniaxial tension 3"
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,.3
*END LOAD CASE
*OUTPUT,FIELD,VARIABLE=PRESELECT
*END STEP
*STEP,NLGEOM,INC=20
Step 2: Uniaxial tension, stretch=3.5
*STATIC,DIRECT
1.,10.
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,2.5
*EL PRINT,F=100
*NODE PRINT,F=100
*END STEP
*STEP,PERTURBATION
Step 3: Static linear perturbation, uniaxial tension
*STATIC
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,.1
*EL FILE
S,E
*NODE FILE 
U,RF
*END STEP
*STEP,NLGEOM,INC=20
Step 4: Uniaxial tension, stretch=6.
*STATIC,DIRECT
1.,10.
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,5.
*END STEP
*STEP,PERTURBATION
Step 5: Static linear perturbation, uniaxial tension
*STATIC
*BOUNDARY
FACE1,3
FACE3,2
FACE6,1
FACE4,1,1,.1
*EL FILE
S,E
*NODE FILE 
U,RF
*END STEP