The variable tangent material model is available for 2D elements. This material model is used for the analysis of geological materials. The model describes an isotropic material, in which the bulk and shear moduli are functions of the stress and strain invariants. The functional relationship used replaces an explicit yield condition. The variable tangent material properties are listed below. In addition to these properties, it may be necessary to define some.
Constant G is used to define loading and unloading constants of shear moduli.
Constant Gamma 1 is used to define the loading and unloading shear moduli.
Constant Gamma 2 is used to define the loading and unloading shear moduli.
The unloading bulk modulus of elasticity can be found from the equation: E/3*(1-2n) where E is the modulus of elasticity of the material and n is the Poisson's ratio of the material. This term is used when the model is in a loaded state.
Constant K0 is used to define the loading bulk modulus.
Constant K1 is used to define the loading bulk modulus.
Constant K2 is used to define the loading bulk modulus.