Using CAD Models and Their Semantics to Prepare F.E. Simulations

The preparation of simulation models from Computer Aided Design (CAD) models is still a difficult task since shape changes are often required to adapt a component or a mechanical system to the hypotheses and specifications of the simulation model. Detail removal or idealization operations are among the current treatments performed during the preparation of simulation models. Most of the time, model exchanges are required between the engineering office and the simulation engineers, often producing losses of information and lacking of robustness. Thus, inefficient processes and remodelling phases form the usual practice. In this paper we show that geometric models can be extracted from CAD software as well as some of their semantics. This semantics can then be transferred, used and eventually preserved during the shape adaptation process required for a given Finite Element Analysis (FEA). The software environment enabling this transfer simultaneously requires the description of the initial B-Rep NURBS model as well as that of the adapted one. The process set up is based on STandard for the Exchange of Product model data (STEP) to provide a robust link between CAD and shape adaptation environments. In order to describe the appropriate variety of shapes required for the Finite Element (FE) preparation, a specific data structure is proposed to express the corresponding topology of the models. Hence, it is shown that the operators associated to the FE preparation process can take advantage of this data structure and the semantics of the initial CAD model that can be attached to the adapted model. Examples illustrating the various process steps and corresponding operations are provided and demonstrate the robustness of the approach.