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Barotropic elasticity:

This elastic constitutive model accounts for the barotropy (dependence on the mean effective stress) and pyknotropy (dependence on the void ratio) of a material.

Input syntax

*Mechanical = Barotropic_Elasticity
E^{ref} (F/A), nu (-), n (-), p^{ref} (F/A)

Material parameters

The material parameters for Barotropic_Elasticity are:

Index Symbol Unit Description
1 \(E^{ref}\) F/A Reference Young’s modulus.
2 \(\nu\) - Poisson’s ratio.
3 \(n\) - Barotropic exponent in \(f_p=(p/p^{ref})^n\).
4 \(p^{ref}\) F/A Reference pressure (internally enforced as \(p^{ref}\ge 1\)).

State variables

  • Void_Ratio: Void ratio
  • fp: Barotropy function (output only)
  • fe: Pyknotropy function (output only)

The void ratio can be initialized in two different ways:

  • Using the *Initial conditions, type = state variables command in the input file, e.g.
*Initial conditions, type = state variables
element_set_name, void_ratio, <value>

  • Using the interface for user-defined initial state variables. In this approach, the vector holding the state variables is filled directly in a fortran subroutine as described in Section User defined state variables. The position of the state variables in the associated vector are as follows:

  • statev(1) = \(e\)

Upcoming release

With the upcoming release, omitting the initialisation of the void ratio will deactivate the pyknotropy dependency.