Shape Memory Alloy
This node models heat transfer in shape memory alloys, and takes into account the martensite and austenite composition. This feature is designed to be coupled with the Shape Memory Alloy feature of the Structural Mechanics interface which calculates the alloy composition from the mechanical and thermal loads. Changes in martensite and austenite composition modify the alloys thermal properties (thermal conductivity and heat capacity), and release (from austenite to martensite state) or absorb (from martensite to austenite state) energy.
It uses this version of the heat equation to model heat transfer in alloys:
(6-14)
with the following material properties, fields, and sources:
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ρ (SI unit: kg/m3) is the alloy’s density.
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Cp (SI unit: J/(kg·K)) is the alloy’s heat capacity at constant pressure.
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k (SI unit: W/(m·K)) is the alloy’s thermal conductivity (a scalar or a tensor if the thermal conductivity is anisotropic).
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u (SI unit: m/s) is the velocity field defined by the Translational Motion subnode when parts of the model are moving in the material frame.
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Q (SI unit: W/m3) is the heat source (or sink). Add one or more heat sources as separate physics features. See Heat Source node and Thermoelastic Damping subnode for example.
For a steady-state problem the temperature does not change with time and the first term disappears.
Model Input
This section contains fields and values that are inputs for expressions defining material properties. If such user-defined property groups are added, the model inputs appear here.
Volume Reference Temperature
This section is available when a temperature-dependent density defined in a material is used. On the material frame, the density is evaluated in relation to a reference temperature in order to ensure conservation of the mass in the presence of temperature variations. By default the Common model input is used. This corresponds to the variable minput.Tempref, which is set to 293.15 K by default. To edit it, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Volume reference temperature in the Expression for remaining selection section.
The other options are User defined and all temperature variables from the physics interfaces included in the model.
This model input does not override the Reference temperature Tref set in the Physical Model section of the physics interface, which is used to evaluate the reference enthalpy, and a reference density for incompressible nonisothermal flows.
Temperature
This section is available when material properties are temperature-dependent. By default, the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 K by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.
Shape Memory Alloy
The Martensite volume fraction, ξ, and the Density of the alloy (defined for both austenite and martensite states) should be set in this section.
In addition, the following options are available for the computation of the Effective conductivity by accounting for both austenite and martensite properties:
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Volume average (default), which calculates the effective conductivity of the alloy as the weighted arithmetic mean of austenite and martensite conductivities:
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Reciprocal average, which calculates the effective conductivity of the alloy as the weighted harmonic mean of austenite and martensite conductivities:
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Power law, which calculates the effective conductivity of the alloy as the weighted geometric mean of austenite and martensite conductivities:
When the material and spatial frames differ (due to the presence in the model of a Moving Mesh node, or a Solid Mechanics physics interface for example), you can select on which frame the thermal conductivities of the austenite and martensite phases are specified.
By default the Deformation model for thermal conductivity is set to Standard. With this option, the thermal conductivities are 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 effective conductivity variables. This option is often suitable for moderate elastic strains.
By selecting the Large strain option, the thermal conductivities are supposed to be given on the spatial frame. In case of isotropic materials, the effective thermal conductivity variables are directly equal to the weighted average of 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.
Austenite
Select any component material from the list to define the austenite material properties. The default uses the Domain material.
The default Thermal conductivity kA is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Full based on the characteristics of the thermal conductivity, and enter another value or expression. For Isotropic enter a scalar which will be used to define a diagonal tensor. For the other options, enter values or expressions into the editable fields of the tensor.
The default Heat capacity at constant pressure Cp,A is taken From material. For User defined enter a value or expression.
Martensite
Select any component material from the list to define the martensite material properties. The default uses the Domain material.
The default Thermal conductivity kM is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Full based on the characteristics of the thermal conductivity, and enter another value or expression. For Isotropic enter a scalar which will be used to define a diagonal tensor. For the other options, enter values or expressions into the editable fields of the tensor.
The default Heat capacity at constant pressure Cp,M is taken From material. For User defined enter a value or expression.
Location in User Interface
Context Menus
Heat Transfer in Solids and Fluids>Specific Media>Shape Memory Alloy
Heat Transfer in Solids>Specific Media>Shape Memory Alloy
Heat Transfer in Fluids>Specific Media>Shape Memory Alloy
Heat Transfer in Porous Media>Specific Media>Shape Memory Alloy
Heat Transfer in Building Materials>Specific Media>Shape Memory Alloy
Bioheat Transfer>Specific Media>Shape Memory Alloy
Ribbon
Physics tab with Heat Transfer in Solids and Fluids, Heat Transfer in Solids, Heat Transfer in Fluids, Heat Transfer in Porous Media, Heat Transfer in Building Materials or Bioheat Transfer selected:
Domains>Specific Media>Shape Memory Alloy