This is a simple one dimensional one element example to show how to use *MAT_SPRING_GENERAL_NONLINEAR keyword. Two different curves for describing force versus displacement during loading and unloading are given. Initial yield forces in tension and in compression are specified. Isotropic hardening without strain softening is chosen.
*BOUNDARY_PRESCRIBED_MOTION_NODE *BOUNDARY_SPC_NODE *CONTROL_TERMINATION *DATABASE_BINARY_D3PLOT *DATABASE_DEFORC *DATABASE_GLSTAT *DATABASE_HISTORY_NODE_SET *DATABASE_NODOUT *DEFINE_CURVE *ELEMENT_DISCRETE *ELEMENT_MASS *END *KEYWORD *MAT_SPRING_GENERAL_NONLINEAR *NODE *PART *SECTION_DISCRETE *SET_NODE_LIST *TITLE
*KEYWORD
*TITLE
GENERAL_NONLINEAR
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*CONTROL_TERMINATION
2.0E-01
*DATABASE_BINARY_D3PLOT
0.02
*DATABASE_DEFORC
1.0E-04
*DATABASE_GLSTAT
4.000E-04
*DATABASE_HISTORY_NODE_SET
1
*SET_NODE_LIST
1
2
*DATABASE_NODOUT
0.100E-03
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*NODE
1 0.000000000E+00 0.000000000E+00 0.000000000E+00
2 1.000000000E+03 0.000000000E+00 0.000000000E+00
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*SECTION_DISCRETE
1 0
0.0000000 0.0000000
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*MAT_SPRING_GENERAL_NONLINEAR
$ MID LCDL LCDU BETA TYI CYI
1 6 5 1.0 50.0 -50.0
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*PART
Spring-Damper Part Definition
1 1 1
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ELEMENT_DISCRETE
1 1 1 2
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*BOUNDARY_SPC_NODE
1 0 1 1 1 1 1 1
*BOUNDARY_PRESCRIBED_MOTION_NODE
2 1 2 99 -1.00E+00
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*DEFINE_CURVE
99
$
*DEFINE_CURVE
6
$
*DEFINE_CURVE
5
$
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ELEMENT_MASS
2 1 1.00000E-06
3 2 1.00000E-06
*END
