Point-based approach to enhance the quality of geometric data for CAE applications

Abstract

Commercial CAD surface modelling software is based almost exclusively on Bézier, B-spline and NURBS representations. These methods offer simple interactive shape modification and computationally efficient interrogations, but have some serious practical limitations. The root cause of all these problems is that the parametric polynomial methods are not geometry-based, and the trouble is compounded by the master geometry philosophy which treats the CAD model as if it were absolutely correct. An alternative purely geometric approach to surface modelling has been established, where the surface shape is characterised by a grid of points lying on the surface, but it is recognised that this approach would require major changes in existing CAE systems. This application paper explains the rationale to develop algorithms, which would plug into existing CAE software systems, so that the user could benefit from the point-based construction without disturbing the established mode of operation. The new point-based approach has achieved significant success in ensuring that form tools produce panels within a specified tolerance.

Keywords:

• point-based surfaces
• forming tool design

Acknowledgements

The authors wish to acknowledge the financial support of the EPSRC under research grant GR/R35735/01, the contribution of researchers P.L. Chong, K.C. Ho, N. Liu and P.S. Lockyer, and the invaluable guidance provided by the industrial collaborators Abaqus, BAE Systems, Delcam, Landmark Components, Miracle Engineering, R.T. Palmer and Rolls-Royce.