Material Property
The Material Property node () is a special case of a User Input that also supports linking with material properties from the Materials node in the Model Builder. A material property node is actually a collection of two user inputs: one list with the options From material or User defined and one property value field for user-defined values.
To add a Material Property first add a feature node or property node (for example, a Generic Feature, Domain Condition, or Device Model Feature), then:
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From the contextual toolbar (in this example, Generic Feature, Domain Condition, or Device Model Feature), click the Material Property () button.
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Right-click the feature node (in this example, Generic Feature, Domain Condition, or Device Model Feature) and select it from the Inputs submenu.
Also see Material Property (Auxiliary Definitions), which is a subnode to the Material Property Group node under Auxiliary Definitions.
The Settings window has the following sections:
Declaration
The material property can either be a basic material property or a property that belongs to a predefined material property group. Choose a Property type: Basic material property (the default), Built in predefined material property, Locally defined material property, or Imported material property from external resources.
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A Basic material property belongs to a predefined set of quantities that are commonly used in material libraries.
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Enter a valid Property name, Description, and Symbol (LaTeX encoded). See Variable Declaration.
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Choose a Physical quantity. The quantity identifies the corresponding property in the material libraries. A property in the material library has a certain dimension, but it is possible to use a smaller dimension for a material property in a feature. See Dependent Variable Declaration for more information about specifying a physical quantity.
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Choose the Dimension, which can only contain Scalar and Custom for a scalar material parameter.
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Enter and choose Default Values.
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For Built in predefined material property, choose a predefined Material property group from the list. Then choose a Material property and enter and choose Default Values.
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For Locally defined material property, choose a Material model from the list. Then choose a Material property and choose Default Values.
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For Imported material property from external resources, choose an Imported file from the list. Then choose a Link and a Material property. Then choose Default Values.
Select Locally defined from the top of the Physical quantity list to use one of the locally defined physical quantities, which you choose from the Link list. Click the Add button () to display a quick menu where you can select a source to add in to the list and use it as the current reference. A Confirm Operation dialog box will appear and ask for confirmation if there is already a reference exist in the Link list. Click the Go to Source button () to move to the Physical Quantity node for the selected local physical quantity.
Default Values
In the Default value for user defined field, which can be a table, enter the default value for the user-defined option.
Use the Default value list to set the default for the feature instance. Choose From material (the default), User defined, Common model input, First allowed value, or Custom default. First allowed value takes the first active value from the values specified by the Allowed Values child nodes. Use the Custom default option to enter a value. This value must always be active for the list in the feature instance.
Options
In the Model Builder most material properties get their values from the material assigned to the geometric entities overlapping with the selection of the feature instance. You can add a Material List to the feature, which allows you to choose among all materials added to a model. Select the Couple to material list check box to specify that this property gets linked to the material selected in the list. Then choose the list to couple against in the Material list, either by entering a name in the Name field or by choosing a particular material list reference.
For a Basic material property, the Pick material property from property groups in selected materials check box is available. Select this check box to make the material property take its values from the property groups of the material that is selected in the material list.
For a Basic material property with the Physical quantity set to Diffusion coefficient, the values that you can choose from are the property groups of the material selected in the material list that define the output property for the diffusion coefficient.
In addition to the options From material and User defined, you can add extra items to the list in the feature instance with Allowed Values child nodes. An alternative option is also entering them directly to the Extra list items table.
A feature input supports several levels of matching that you choose from the Feature input match type list. You can find a brief explanation of the matching options below:
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Always match. If there is any matching announced variable, always use the first one found.
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Synchronized. Match to a matching announced variable, if the provider to that variable fulfills the following conditions (see below for an example):
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It has a feature input of the quantity chosen in the Synchronized physical quantity list.
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That feature input chooses an announced variable from the provider owning the synchronized feature input.
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Always match within physics interface. If there is any matching announced variable by the current physics interface, use the first one found.
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Model input match. Also matches within the physics interface, but you can disable the matching through an interface setting.
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Never match. Never do any automatic matching. The default option is User defined, but you can always manually choose among the found announced variables.
For all the options except the Synchronized option, it is possible to set a regular expression in the Match tag filter combined text field and list. The predefined options here are None (the default), and all physical quantity field names. None is equivalent to an empty tag and should be used unless it is necessary to limit matching in some sense. Use the regular expression if the input should accept several match tags; use, for example, the expression ^$|explicit to either match the default empty tag or an announced variable using the tag explicit. There are several resources on the Internet that explain the exact syntax of regular expressions.
Click the Select Physical Quantity as Tag button () to pick a physical quantity from the list in the Physical Quantity dialog box that appears. Click the Custom Tag button () to use a custom tag that you type in for the announce tag. Click the Reset to None button () to reset the filter to None.
Use the Synchronized option in situations when the matching depends on another feature input in the provider (typically a physics feature) of an announced variable. For example, assume feature “A” has a feature input with the Never match option that picks up variables with the quantity electric potential. Feature “B” announces an electric potential without a tag and has a synchronized feature input that should pick up a current variable only from the feature that picks ups an electric potential from feature “B.” To make feature “A” a possible match, it has to announce a current variable with an Electric potential match tag. The synchronized feature input uses the Synchronized option but also needs the Electric potential option in the Synchronized physical quantity list. When the user selects the electric potential from a physics feature of type “B” in the input list of a physics feature of type “A”, the input (often hidden) in physics feature of type “B” automatically picks up (or auto-match) the electric current from physics feature “A”.
Restrictions
See User Input for information about this setting.
GUI Options
If you want the material property to disappear when it is inactive, select the Hide user input in GUI when inactive check box. Select the Show no description check box to hide the text label containing the description above the GUI component of the property. Similarly, you can hide the symbol from the GUI by selecting the Show no symbol check box. Select the Show no user defined input check box to hide all user defined input. As a final option, it is possible to add a divider above the GUI component and any description text label. The divider is a horizontal line with an optional descriptive text. Select the Add divider above the material property check box to add the divider. When selected, you can enter the divider text in the Text field.
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Designing the GUI Layout
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Materials in the COMSOL Multiphysics Reference Manual