XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''"> Overview of Geometry
Computer models of geometry serve many purposes. CAD geometry models can serve as blueprints for manufacturing, a source for technical illustrations, and a source for parts procurement. By comparison, the geometry modeling capabilities in Patran are directed towards creating a complete FEA model. This FEA model will eventually include a finite element representation of the geometry, and assignments of loads, boundary conditions, material properties, and element properties. The completed FEA model is what your analysis program eventually sees as input data.
Creating a geometric model facilitates the use of one of Patran’s most powerful features, automated finite element mesh generation. In addition, you will benefit by working at a geometric level as much as possible. Once you have created a geometric model, you can assign loads, boundary conditions, element properties, and material properties directly to regions of the geometry instead of to the finite element mesh. This allows you to create different finite element meshes or analysis parameters while retaining the basic underlying definition of your model.
With the Geometry application, you can define the physical structure of your model- the first task in simulating the product design. Next, you assign the finite elements mesh, loads and boundary conditions, and materials and element properties to the model. In many cases, these assignments are made directly to the geometric model.
Options for Starting the Geometry Model
Patran provides a great variety of options for creating, modifying, and qualifying a geometry model. You may start your model in one of three ways:
• Select the Geometry application on the Patran Main form, then choose from over 130 Create, Transform, and Edit actions on the Geometry form to create new structures.
• Import models created in a CAD system into Patran using the File/Import menu option, then edit them. (For more information on importing CAD models, see Chapter 3.)
• Copy an existing Patran model database, and use the existing model as the basis for your
new model.
Model Building Tasks
Patran maintains complete accuracy of the original geometry, whether it comes from a separate CAD part file, or from within Patran. Regardless of how you start your model, the Geometry application form provides numerous options for editing, managing, updating, and verifying the entities in your model. There is also flexibility in the sequencing of the geometry and meshing tasks. Typically you complete the entire geometry model first before moving on to the finite element mesh application; however, you may also complete geometry, then mesh your model one portion at a time.