HYPERELASTIC_LAW#

Description#

This object class defines the model for hyperelasticity in hyperelastic, hyper_viscoelastic and hyperelastic viscoplastic models and potentials.

Syntax#

The syntax to specify a hyperelasticity object will consist of giving the keyword for a particular hyperelasticity model desired, followed by a list of appropriate coefficients which are dependent on the model chosen. The hyperelasticity type may be chosen among the following laws:

CODE

DESCRIPTION

st_venant_kirchhoff

St Venant-Kirchhoff hyperelastic material

modified_sv_kirchhoff

Modified St Venant-Kirchhoff hyperelastic model

ristinmaa

Wallin-Ristinmaa hyperelastic model

arruda_boyce

Arruda-Boyce hyperelastic model

mooney

Mooney hyperelastic model

ogden

Odgen hyperelastic model

van_der_waals

Van der Waals hyperelastic model

fung

Anisotropic hyperelastic model

The structure of the object is summarized below:

***behavior  [ hyper_elastic ] | [ finite_strain_plasticity ] \(~\,\) **hyperelasticity <HYPERELASTIC_LAW> \(~\,\) **model_coef \(~\,~\,~\,\) … [ **pull_back]

Stored Variables

The stored variables for this object include the Green-Lagrange total strain tensor, the Cauchy stress tensor, and the strain energy density \(W\). As an auxiliary output variable, the Piola-Kirchhoff stress tensor:

(403)#\[\ten S = \pder{W}{\ten E}\]

is stored but not saved during the calculation. The post-processor prefixes used for these variables are the following:

prefix

size

description

default

eto

T-2

Green-Lagrange strain

yes

sig

T-2

Cauchy stress

yes

welas

S

strain energy density

yes

If the option **pull_back is given, the Piola-Kirchhoff stress tensor is requested as output 1Only for the ****simulate calculation definition..

Compatible elements#

This object class is programmed to be used with all versions of the total Lagrangian elements (element types starting with total_lagrangian) and the updated Lagrangian elements (element types starting with updated_lagrangian). The behavior must therefore be used in conjunction with a declaration of these elements in the .inp file (see ***mesh under ****calcul).