This paper on "Interpretative CAD Layer Structures and Their Influence on Efficiency in FE Pre-Processing" was presented at the NAFEMS World Congress on The Evolution of Product Simulation From Established Methods to Virtual Testing & Prototyping - 24-28 April 2001, The Grand Hotel, Lake Como, Italy.

Abstract

When preparing models of components of various levels of complexity in the FE process, ZF Friedrichshafen AG currently works in the heterogeneous CAE environment. This presentation aims to highlight the problems faced today taking the example of the transition from Pro/E to I-deas. A FEM-mesh is generated from 3D data. Standard interfaces such as STEP, IGES and VDAFS interconnect these different systems. The data quality, complexity and consistency of CAD geometry and topology are continuously monitored to ensure that the process chain is as efficient and stable as possible. Frequent software release cycles with an ever greater number of features, sometimes entailing changes to the existing data structure, make the process of testing interfaces a time-consuming and costly operation. Various features, such as fillets, depend on high transfer quality to yield satisfactory results. Furthermore, irrespective of the level of user/operator expertise with the software, the quality of data always has to be of a sufficiently high standard.
The objective has to be to find a way to idealize a model quickly, reliably and effectively, and for that model to deliver a high standard of quality while at the same time lending itself readily to modification and changes.
The results of our many years of experience with an interpretative CAD layer structure can be summarized in the following terms: low cost of geometric reworking, maximum flexibility and user control during the model abstraction process, the lack of specific know-how required to repair corrupt and degenerated geometry, and the assurance that work can be conducted independently of data history. This system avoids the need for costly and error-prone loops used for simplifying models and geometry suppliers do not face disputes over specific modeling specifications. An interpretative CAD layer structure is characterized by number of features: natural handling, simple and FE-specific structuring at the layer level is helpful, access to supplied basic data is possible at any time and there is a substantial reduction in the resources required -- i.e. in the number of elements.
This paper will present the procedure, experience and results derived from practical application of this system.