Soft Rock Plasticity

The soft rock plasticity model:

• describes the inelastic behavior of the material by an isotropic yield function that depends on the three stress invariants, a nonassociated flow assumption to define the plastic strain rate, and a strain hardening theory that changes the size of the yield surface according to the inelastic volumetric strain;
• requires that the elastic part of the deformation be defined by using the isotropic linear elastic material model or, in an implicit analysis, the power-law based porous elastic material model within the same material definition;
• captures the transition of the yield surface in the $\mathrm{\Pi }$ -plane from a rounded-triangular shape to a circular shape with an increase in pressure;
• allows for the hardening law to be defined by a piecewise linear form;
• can optionally include hardening in hydrostatic tension; and
• can be used with a regularization scheme for mitigating mesh dependence in situations where the material exhibits strain localization with increasing plastic deformation.

You can define the flow potential eccentricity, $ϵ$ . The eccentricity parameter is used to ensure uniqueness of the plastic flow near the hydrostatic compressive and tensile yield stresses.

Input Data	Description
Eccentricity	Specify, $ϵ\ge 0$ .

You also specify parameters to define the plastic yield and flow.

Input Data	Description
Friction Angle	Friction angle, $\beta$ , in the $p-t$ plane. The friction angle can range from $0^{°}\le \beta \le {89.9}^{°}$ .
Dilation Angle	Dilation angle, $\psi$ , in the $p-t$ plane. The dilation angle can range from $0^{°}\le \psi \le {89.9}^{°}$ .
n_y	Material parameter, $n_y\ge 1$ .
f0	Deviatoric plane correction parameter, $f_0\ge 0$ .
f1	Deviatoric plane correction parameter, $f_1\ge 0$ .
alpha	Deviatoric plane correction parameter, $\alpha \ge 0$ .
Init Vol Plastic Strain	Absolute value of the initial compressive volumetric plastic strain, ${\epsilon }_{vol}^{pl}{|}_0$ .
Use temperature-dependent data	Specifies material parameters that depend on temperature. A Temperature field appears in the data table. For more information, see Specifying Material Data as a Function of Temperature and Independent Field Variables.
Number of field variables	Specifies material parameters that depend on one or more independent field variables. A Field column appears in the data table. For more information, see Specifying Material Data as a Function of Temperature and Independent Field Variables.