Temperature Dependent Material Data
Many material properties, such as Young’s modulus, coefficient of thermal expansion, and yield stress, can have a significant dependence on temperature. In many cases, materials supplied in the material libraries and databases have such dependencies incorporated.
Materials in the COMSOL Multiphysics Reference Manual
If a material property under the Materials branch has a temperature dependence, you have to input the temperature to be used in the Model Inputs section in the Settings window for the node in the physics interface that references the property. It is possible that not all aspects of a material are defined in the same node in the Model Builder tree. For example, if a problem is run with thermal expansion and plasticity, then:
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Young’s modulus, Poisson’s ratio, and density are given in the Linear Elastic Material node.
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Yield stress and hardening function are given in the Plasticity node.
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Coefficient of thermal expansion is given in the Thermal Expansion (for materials) subnode.
The Plasticity node is available as a subnode to the Linear Elastic Material node when you have either the Nonlinear Structural Materials Module or the Geomechanics Module.
For each of these nodes there is a Model Inputs section on the Settings window. Some of these sections may be empty, specifically if none of the properties given in that node has a temperature dependence. In general you have to supply the temperature in all the Model Inputs sections. This can be done either by explicitly giving a temperature or by selecting a temperature variable from another physics interface.
If there is a Temperature Coupling node under the Multiphysics branch, then you cannot change the temperature input under Model Inputs. The temperature is automatically taken from the connected Heat Transfer in Solids interface.
Density
All Structural Mechanics interfaces are formulated on the material frame. This means that the equations of motion are formulated for a certain volume in its initial configuration.
The preservation of mass requires that the mass density is constant. In a structural mechanics problem this means you must not use a temperature dependent density. All effects of volume change with temperature are incorporated through the thermal expansion effects.