Preferences establish parameters that affect an entire modeling and analysis process. Whenever you start a new database, the New Model Preferences dialog box is displayed in which you can set certain initial parameters for the model (for more information, see Modifying Preferences, 70). As you continue your work, you can specify additional preferences in the areas of graphic displays, geometric construction, and finite element modeling and analysis. Some options you choose in the Preferences menu are applied immediately, others, however will not take effect until after you exited the current work session and restarted Patran.

Several preferences have their equivalents in specific application commands where you can override the preferenced parameter. The override, however, will apply to that one instance only, for subsequent operations the parameter will return to its default value as defined in the Preferences menu. For example, the Preferences menu establishes a default construction plane. In the course of building a model, however, you may select a different construction plane for placing a circle. Once the circle has been created, the construction plane will revert to its Preferences menu default. If all later geometry is to be located relative to the newly selected construction plane, consider changing the default in the Preferences menu.

Analysis codes are the finite element programs you use to perform the analysis. Possible analysis codes include MD Nastran (default), MSC.Marc, and various others may also be accessible. The analysis code you pick here depends on what is available at your site.

Finite element analysis codes have their own specific way of defining components of a FEM model and of formatting analysis input and output data. Therefore, the code you select will also determine the following:

The analysis code you selected also determines which kind of finite element analysis can be accessed. Structural, thermal, and fluid dynamics analyses are the most frequently used types available for most analysis code applications.

You can change the analysis code preference at any time during the modeling process. Keep in mind that changing the analysis code changes; code-specific forms in the Analysis application, available analysis types, element types, and element and material property definitions. If you decide to change the analysis code, Patran will transfer as much code-specific data as possible to the new code according to the Preference Mapping option you select.

Patran offers three mapping options each providing a unique level of conversion and user control.

The mapping option you select will depend on the issues pertinent to your model and to the analysis codes. For example: 1) do the fem entities (nodes, elements, mpc’s) map over correctly; 2) are there equivalent loads and boundary conditions, contact, material and element properties; 3) are there equivalent analysis procedures, and will they convert correctly when you change the analysis preference?

Tolerance specifies the maximum distance within which two like entities (e.g., nodes), are said to be coincident. Tolerance, being a global parameter, remains valid for both geometric and FEM construction. The same tolerance value will apply to geometric entities imported in a CAD database.

Model tolerance may be specified as an absolute number (normally 0.005) or it may be based on the maximum model size. In the latter case, the recommended tolerance is 0.05% of the expected maximum model size. However, you may specify a different tolerance depending on how accurately the imported geometry was constructed.

Occasionally Patran issues a warning in conjunction with a command or entity selection. Warning messages are output to the history window and to the session file and, by default, are also shown on the screen. You may choose to sound just a warning bell rather than the screen display, or omit warning notifications altogether.

If your system is set up to access a hardware graphics device for graphics displays (The settings.pcl file, 47) you can choose to render shaded images through that device. Hardware generation of images typically takes less time but, in general, software rendering is more accurate and even offers more display options (e.g., texturing effects).

In earlier versions of Patran (e.g., PATRAN 2), curves, surfaces, and solids were created as parametric cubic, bicubic, and tricubic geometry. An option in the Preferences Geometry dialog box enables you to create parametric cubic geometry that can be exported to a neutral file.

The vehicle that Patran uses to create solid geometry is a modeler named Parasolid. Parasolid assumes model units in meters. Although Patran is “unitless” (dimensions can be interpreted in any unit system), because of Parasolid, a scale factor is used when creating solid geometry ( see Parasolid Model Units, 163). The default scale factor is set in the Preferences menu.