You can include thermal expansion in a model either by adding a Thermal Expansion (for Materials) subnode to the chosen material, or by using the Thermal Expansion.
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In most of the physics interfaces, you can enter tangent data directly by selecting Tangent coefficient of thermal expansion in the settings for Thermal Expansion. When using this option, a numerical integration of Equation 2-30 will be performed each time the thermal strain is used. This will have a negative impact on the performance, when compared to using a secant coefficient of thermal expansion.
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Precompute the expression in Equation 2-29 externally for the intended range of temperatures. This can for example be done in a spreadsheet program. Enter the computed result as a function, which is then used as any other secant temperature dependent thermal expansion coefficient.
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When using Tangent coefficient of thermal expansion, the integrate operator is used. It is called with the two integration limits being the reference temperature <phys>.Tref and the current temperature <phys>.T, where <phys> is the tag of the physics interface. If you define the expression for the coefficient of thermal expansion yourself, you must ensure that it depends on a ‘free’ variable, and not use the same temperature variable as you use to prescribe the current temperature <phys>.T.
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Using Functions in Materials in the COMSOL Multiphysics Reference Manual
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Replace the function name alpha_solid_1(T[1/K])[1/K], with the function name that you have assigned to the temperature-dependent measured thermal expansion coefficient and use the correct temperature units.
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Ensure that the value of Tm is changed from 293 K to the actual value of temperature that was used as the strain-free temperature to compute αm(T) in the function that you created.
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User-Defined Materials and Libraries in the COMSOL Multiphysics Reference Manual
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