Three models are available to define the material transformation. Select the Transformation model — Temperature threshold (default), Arrhenius kinetics, or User defined. The first two models use integral forms over time to express the fraction of transformation θit as a function of temperature, while you can set it manually with the third option.

For Temperature threshold, select the type of analysis — Overheating analysis (default) or Overcooling analysis, depending on the expected temperature variations. See the Parameters section for the additional settings specific to each type of analysis.

For Arrhenius kinetics, define the parameters used in the Arrhenius equation to calculate the degree of transformation (see Arrhenius Kinetics for more details):

A user defined value can be set for the initial irreversible transformation indicator in the Initial Values section.

Enter values or expressions for the Enthalpy change L and the Fraction of transformation θit to define the heat source associated with the transformation as:

Specific thermodynamics properties before and after complete transformation may be defined by selecting the Specify different material properties for the transformed state check box.

Choose a Transformed material, which can point to any material in the model. The default uses the Domain material. The properties before transformation are the ones specified in the Heat Conduction, Solid and Thermodynamics, Solid sections of the parent Solid node. The effective material properties are dynamically updated with the transformation evolution.

A user defined value can be set for the initial irreversible transformation indicator in the Initial Values section.

This section is available when the Specify different material properties for the transformed state check box is selected.

Select a Thermal conductivity kd — From material (default) or User defined, to be used for transformed solid. For User defined choose Isotropic, Diagonal, Symmetric, or Full based on the characteristics of the thermal conductivity and enter another value or expression in the field or matrix.

When the material and spatial frames differ (due to the presence in the model of a Moving Mesh node, or a Solid Mechanics interface for example), you can select on which frame the Thermal conductivity kd is specified.

By default the Deformation model for thermal conductivity is set to Standard. With this option, the thermal conductivity is supposed to be given on the material frame. If the material frame does not coincide with the spatial frame, a conversion is applied to get the variables ht.k_dxx, ht.k_dyy, and so on. This option is often suitable for moderate elastic strains.

By selecting the Large strain option, the thermal conductivity is supposed to be given on the spatial frame. In case of isotropic materials, the thermal conductivity variables ht.k_dxx, ht.k_dyy, and so on, are directly equal to the values you have set. In case of anisotropic materials, the rotation of the material is also taken into account following

where R is the rotation matrix between the material and the spatial frames.

This section is available when the Specify different material properties for the transformed state check box is selected.

Select a Density ρd and Heat capacity at constant pressure Cp, d — From material (default) or User defined, to be used for transformed solid. The heat capacity describes the amount of heat energy required to produce a unit temperature change in a unit mass.

This section is available when the Transformation model is set to Temperature threshold or Arrhenius kinetics. Set a value or expression for the Initial irreversible transformation indicator, αinit, to be used as an initial condition for any of the time integral analyses.

Physics tab with Solid selected in the model tree: