Contact treatment algorithm for the trimmed NURBS surface

As a kind of surface description, the trimmed non-uniform rational B-spline (NURBS) surface is widely employed in CAD/CAM. The trimmed NURBS surface has many advantages in describing tool surfaces because of its simplicity in data preparation and the small amount of surface data compared to that of other surfaces. Despite its inherent advantages, the trimmed NURBS surface is rarely employed in the analysis of forming problems due to the complexity in the contact treatment. In this study, a contact treatment based on a sheet normal vector in the trimmed NURBS surface model is presented. For the sake of importing surface data, an initial graphics exchange specification (IGES) format input module has also been developed. The computed results for deep drawings of a clover shaped cup and an L-shaped cup are compared with experiments and the results of the commercial stamping analysis code PAM-STAMP.