Feature-based structural design of solid automotive components

Abstract

This paper describes a structural analysis and design system which is based on geometric primitives that represent certain form-features of the part and can be assembled into complete solid models that are defined in terms of a small set of design parameters. Design variables are accessible through a formal relational data base, thus making it possible to integrate more easily with a modular automated design system. The relational data base has been found to be naturally suited to use in conjunction with feature-based modeling. Each design primitive is stored in the data base with the primitive name as the relation name. The physical dimensions of each primitive are the attributes of the relation in a hierarchical form. To assemble the model, then, the data base is automatically interrogated for all instances of primitive relations. Loads and structural boundary conditions can be easily assigned to the model by identifying the appropriate primitive-model faces to be loaded or constrained. Analysis is performed through the use of fully automatic mesh generation which requires no user interaction. The meshing procedure recognizes lower-level features of the geometrical model (vertices, edges, and faces) so that not only are these necessary features retained, but they are also appropriately refined to represent the intent of the geometry accurately. For design optimization, a rule-based approach is used to associate the high-level, overall part dimensions with the dimensions of thhe primitives. A ny or all of the high-level dimension-set can be selected as design variables. For stress constraints, the feature-based model also provides a convinient way to handle the common problem with optimization of associating a specific element stress value with the constraint. In this case a stress constraint is assigned to each geometric feature (instead of to each element) and at the beginning of each interation the element associated with a feature are searched for the maximum stress to be constrained. Three actual automotive parts are used to demonstrate the capability.