*HEADING
  - OGDEN HYPER-VISCOELASTICITY, VISCO AND LINEAR PERT. STEPS, CPE4H
*NODE
1,
2,10.
3,10.,5.,
4,0.,5.,
*ELEMENT,TYPE=CPE4H,ELSET=ONE
1,1,2,3,4
*SOLID SECTION,ELSET=ONE,MATERIAL=SIMPLE
1., 
*MATERIAL,NAME=SIMPLE
*HYPERELASTIC,OGDEN,N=2,MODULI=INSTANTANEOUS
16.,2.,4.,-2.
*VISCOELASTIC,TIME=PRONY
0.5,0.,3.
*AMPLITUDE,NAME=STEP
0.,1.,10.,1.
*BOUNDARY
1,1,2
2,2,2
4,1,1
*STEP,PERT
** Step 1: Initial linear perturbation
*STATIC
*BOUNDARY
1,1,2
2,2,2
4,1,1
3,1,1,.1
2,1,1,.1
*EL PRINT
S,E
*EL FILE
S,E
*NODE FILE 
U,RF
*END STEP
*STEP,NLGEOM
** Step 2: Apply instantaneous uniaxial tensile stretch and allow to relax
*VISCO
2.,6.
*BOUNDARY,AMP=STEP
3,1,1,2.
2,1,1,2.
*EL PRINT,F=10
S,E
EE, 
CE, 
*EL FILE,F=10
S,E,EE,CE,CEP
*NODE FILE,F=10
U,RF
*END STEP
*STEP,PERT
** Step 3: Intermediate linear perturbation
*STATIC
*BOUNDARY
1,1,2
2,2,2
4,1,1
3,1,1,.1
2,1,1,.1
*EL PRINT
S,E
*EL FILE
S,E
*NODE FILE 
U,RF
*END STEP
*STEP,NLGEOM
** Step 4: Continue stress relaxation
*VISCO 
2.,4.
*END STEP
*STEP,PERT
*STATIC
** Step 5: Final linear perturbation
*BOUNDARY
1,1,2
2,2,2
4,1,1
3,1,1,.1
2,1,1,.1
*EL PRINT
S,E
EE, 
*EL FILE
S,E,EE
*NODE FILE 
U,RF
*END STEP