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Modeling Thermal Expansion
In this example, a temperature field is applied to the bracket and pin assembly and the thermal stresses are calculated.
COMSOL Multiphysics contains physics interfaces for structural analysis as well as thermal analysis. You can define the analyses separately and then simulate the thermal–structure interaction by coupling them using the appropriate variables and terms in the structural analysis equations, or you can add a predefined multiphysics interface at the beginning of the setup. In principle, you have three different options:
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Start the analysis by adding a Thermal Stress, Solid multiphysics interface. This will add a Solid Mechanics interface, a Heat Transfer in Solids interface, and a Thermal Expansion multiphysics coupling.
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Add a Solid Mechanics interface, a Heat Transfer in Solids interface, and a Thermal Expansion multiphysics coupling manually.
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Add a Solid Mechanics interface and a Heat Transfer in Solids interface. Under the Linear Elastic Material, add a Thermal Expansion subnode, and make sure that it picks up the computed temperature.
These different types of approaches are relevant for many other multiphysics simulations too.
If you know from the beginning of your simulation project that you are going to perform a coupled analysis, adding the multiphysics interface is the recommended approach. Not only is it more convenient, but doing so will also in general change some settings in the involved physics interfaces to better suit the combined analysis. An example of this is that when you add the Thermal Stress, Solid multiphysics interface, the Solid Mechanics interface will assume that a time-dependent analysis is quasistatic from the structural point of view, so that inertial terms are ignored. This, in turn, will affect the time-stepping algorithm chosen in a time-dependent solver.