Coefficient of Thermal Expansion

You can define the coefficient of thermal expansion using the secant or instantaneous method. The secant method includes field variable support for temperature, frequency, coordinate, or user defined field dependency. When you define the coefficient of thermal expansion using the secant method, and you use multiple field variable points, you must define the zero-thermal-strain reference temperature. When conducting a test to measure the thermal expansion, the zero-thermal-strain reference temperature is that temperature at which the test specimen has a zero thermal strain. As the specimen is heated from the zero thermal strain point, the thermal strain is measured at given temperature points. If fields other than Temperature are specified the temperature of the bodies must be the same as the zero-thermal-strain reference temperature value. If only Temperature field is defined then the zero-thermal-strain reference temperature value is specified by the MPAMOD command in the Mechanical APDL application, and written as the MPAMOD command in the ds.dat file. The MPAMOD command is written only if the temperature of the bodies using the material differs from the material's zero-thermal-strain reference temperature. The coefficient of thermal expansion values are computed according to the equation documented in Temperature-Dependent Coefficient of Thermal Expansion in the Theory Reference.

For more information on this topic, see Linear Material Properties in the Material Reference

Anisotropic Elasticity

You can define an anisotropic elasticity model by entering the stiffness terms in an elastic coefficient matrix [D]. The following graphic show the location of the terms for this symmetric matrix:

Each row corresponds to the terms of x, y, z, xy, yz, xz. The stiffness terms must be positive definite (requiring all determinants to be positive). The stiffness terms have units of Force/Area operating on the strain vector.