Thermal Expansion (for Materials)
Use the Thermal Expansion subnode to add an internal thermal strain caused by changes in temperature.
The Thermal Expansion subnode is only available with some COMSOL products (see http://www.comsol.com/products/specifications/).
Layer Selection
This section is only present in the in the Layered Shell interface, where it is described in the documentation for the Thermal Expansion (for Materials) node.
Model Inputs
The Volume reference temperature Tref is the temperature at which there are no thermal strains. As a default, the value is obtained from a Common model input. You can also select User defined to enter a value or expression for the temperature locally.
When using Common model input, you can see or modify the value of the volume reference temperature by clicking the Go To Source button (). This will move you to the Common Model Inputs node under Global Definitions in the Model Builder. The default value is room temperature, 293.15 K.
If you want to create a model input value which is local to your current selection, click the Create Model Input button . This will create a new Model Input node under Definitions in the current component, having the same selection as the current Thermal Expansion node.
From the Temperature T list, select an existing temperature variable from a heat transfer interface (for example, Temperature (ht)), if any temperature variables exist. Select User defined to enter a value or expression for the temperature.
See also Common Model Inputs and Model Input in the COMSOL Multiphysics Reference Guide.
Thermal Expansion Properties
Select an Input type to select how the thermal strain is specified. The default is Secant coefficient of thermal expansion, in which case the thermal strain is given by
where α is the secant coefficient of thermal expansion. α can be temperature dependent.
When Input type is Tangent coefficient of thermal expansion, the thermal strain is given by
where αt is the tangential coefficient of thermal expansion.
When Input type is Thermal strain, enter the thermal strain dL as function of temperature explicitly.
In all three cases, the default is to take values From material. When entering data as User defined, select Isotropic, Diagonal, or Symmetric to enter one or more components for a general coefficient of the thermal expansion tensor or the thermal strain tensor. When a nonisotropic input is used, the axis orientations are given by the coordinate system selection in the parent node.
A heat source term will be created by this node. It can be accessed from a Thermoelastic Damping node in a heat transfer interface in order to incorporate the reversed effect that heat is produced by changes in stress. The heat source term is only present when Structural Transient Behavior is set to Include inertial terms.
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Thermoelastic Damping
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Entropy and Thermoelasticity
Thermal Stresses in a Layered Plate: Application Library path Structural_Mechanics_Module/Thermal-Structure_Interaction/layered_plate
MEMS_Module/Actuators/layered_plate
Location in User Interface
Context Menus
 Solid Mechanics>Linear Elastic Material>Thermal Expansion
 Solid Mechanics>Nonlinear Elastic Material>Thermal Expansion
 Solid Mechanics>Hyperelastic Material>Thermal Expansion
 Solid Mechanics>Piezoelectric Material>Thermal Expansion
 Solid Mechanics>Cam-Clay Material>Thermal Expansion
Layered Shell>Linear Elastic Material>Thermal Expansion
 Membrane>Linear Elastic Material>Thermal Expansion
 Membrane>Nonlinear Elastic Material>Thermal Expansion
 Membrane>Hyperelastic Material>Thermal Expansion
 Multibody Dynamics>Linear Elastic Material>Thermal Expansion
Ribbon
Physics tab with Linear Elastic Material, Hyperelastic Material, Nonlinear Elastic Material, Piezoelectric Material, or Cam-Clay Material node selected in the model tree:
Attributes>Thermal Expansion