*HEADING
 test Bergstrom-Boyce hysteresis in biaxial tension
 test short and long term hyperelasticity solutions.
*NODE,NSET=ALL
1,
2,1.
3,1.,1.,
4,0.,1.,
*ELEMENT,TYPE=CPE4,ELSET=ONE
1,1,2,3,4
*NSET,NSET=SIDE1
1,2
*NSET,NSET=SIDE2
2,3
*NSET,NSET=SIDE3
3,4
*NSET,NSET=SIDE4
4,1
*SOLID SECTION,ELSET=ONE,MATERIAL=ARRUDA
*MATERIAL,NAME=ARRUDA
*HYPERELASTIC,ARRUDA-BOYCE,MODULI=LONG TERM
1.71,2.8284,1.e-2
*hysteresis
1.0,1.22474,4.,-1.0
*************************
**MULTIPLE LOAD CASES TEST
*************************
*DIAGNOSTICS,NONHYBRID=WARNING
*STEP,PERTURBATION
*STATIC
*LOAD CASE,NAME="TENSION ON SIDE 2"
*BOUNDARY,OP=NEW
SIDE4,1
SIDE1,2
SIDE2,1,1,5.
*END LOAD CASE
*LOAD CASE,NAME="TENSION ON SIDE 3"
*BOUNDARY,OP=NEW
SIDE4,1
SIDE1,2
SIDE3,2,2,5.
*END LOAD CASE
*END STEP


*STEP,NLGEOM,INC=100,unsymm=yes
BIAXIAL TENSION
*STATIC
1.e-5,1.e-5
*BOUNDARY,OP=NEW
SIDE4,1
SIDE1,2
SIDE2,1,1,5.
SIDE3,2,2,5.
*EL PRINT,f=100
S, 
LE, 
MISES, 
*NODE PRINT,f=100
U,RF
*OUTPUT,FIELD,FREQ=100
*ELEMENT OUTPUT
S,LE
*NODE OUTPUT
U,RF
*END STEP
**
*STEP,NLGEOM,INC=1000,unsymm=yes
 RELAXATION
*STATIC
100.,1.e13
*END STEP