Property Groups
The Settings window for Property Group is where output properties and the model inputs are added, local properties are defined, and expressions for material properties are entered in a specific property group such as Basic. The property groups are subnodes to a material node. The Settings window for Property Group is displayed when you click the property group node (for example, Basic) under the material node (typically with the material’s name— Aluminum, for example) in the Model Builder.
Figure 9-7: An example of a Basic Settings window for Property Group.
Output Properties and Model Inputs
The predefined material properties in the property group appear in the Output properties table. Under Quantities you can add additional material properties to the Output properties list or add model inputs to the Model inputs list.
Output Properties under Quantities is only available from the Basic material properties and with user-defined property groups.
The model inputs are physical quantities, such as temperature, that are used as inputs in the expressions that define the output properties (for example, to describe a temperature-dependent physical quantity). For example, adding Temperature as a model input with the variable name T makes it possible to use an expression for the heat capacity at constant pressure Cp, such as 300[J/(kg*K)]*T[1/K], which works regardless of the name of the actual dependent variable for temperature in the model that uses the temperature-dependent material. Without the model input, the expression above only works with a temperature variable called T.
If required, edit the expressions in the Output properties list’s Expression column. Edit directly in the table or by clicking the Edit button (), which opens a dialog box for easier specification of orthotropic and anisotropic material properties (tensors). Select Isotropic, Diagonal, Symmetric, or Anisotropic when entering the data in the material property’s dialog box. In the Expression column, use a syntax with curly braces such as {k11, k21, k31, k12, k22, k32, k13, k23, k33} to enter anisotropic material properties for a 3-by-3 tensor kij in the order k11, k21, k31, k12, k22, k32, k13, k23, and k33. 1, 2, and 3 represent the first, second, and third direction in the active coordinate system. In many cases (for example, when entering the elasticity matrix for structural mechanics), the matrix must for physical reasons be symmetric. The upper diagonal part of the matrix you enter will then be mirrored when forming the actual constitutive matrix, and the lower diagonal part is ignored.
Use the Move up (), Move down (), and Delete () buttons to organize the tables as needed.
Local Properties
Here you can enter a user-defined Property and its corresponding Expression and organize the table as needed. These local properties are useful for parameterizing functions that describe material properties if they contain inputs other than those that are model inputs (such as temperature and pressure). For example, a local property can be a reference value at a certain temperature. Use the Move up (), Move down (), and Delete () buttons to organize the tables as needed.
About Automatic Adding of Property Groups to a Material
Material property groups are automatically added to the material node in the Model Builder. You can also add additional predefined property groups or create a User-Defined Property Group (on the Materials toolbar, click User-defined Property Group () or right-click the Material node). The available properties are collected in property groups according to the physical context.
Each property group has a Settings window for Property Group. When a Model Builder node is clicked (for example, Basic), the Settings window for Property Group displays specific information about that property group. The physical properties for all property groups are summarized in a Material Contents table on the Settings window for Material.