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/MAT/LAW92/mat_ID/unit_ID

mat_title

Parameter input

D

Function input

Itype

fct_ID

#RADIOSS STARTER

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/UNIT/1

unit for mat

                 Mg                  mm                   s

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#-  2. MATERIALS:

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/MAT/LAW92/1/1

Generic RUBBER

#              RHO_I

            1.000E-9

#                 mu                   D                 LAM

          2.8000E+01           1.4000E-1               1000.

#    IType    fct_ID                  NU

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#ENDDATA

/END

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

With

and

with

The Cauchy stress is computed as:

2.

If fct_ID is not defined, which means choice parameter input, then keep the function input line (the fourth line) blank. If the fct_ID is defined, which means choice function input, then the input parameters , D and are ignored and are automatically identified by fitting of the provided stress vs strain curve.

For that the nonlinear least squares algorithm is used to fit the Arruda-Boyce parameters. Assume that the model is fully incompressible in fitting the Arruda-Boyce constants to the test data, except in the volumetric test.

The material constants are obtained using a least-squares-fit procedure, which minimizes the relative error in stress between the theoretical nominal stress and given experimental data, the relative error E is minimized.

where, is a stress value from the test data and is the theoretical nominal stress given by for each engineer strain i.

The nominal stress is computed for each mode assuming the full incompressibility:

Uniaxial Mode:

So

Equibiaxial Mode:

So

Planar (Shear Mode):

So