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It is a well known industry fact, that the geometry of material in contact with tooling, is a major factor which affects its formability. A collary to this is that many problems can be identified and solved using geometry based mechanics approaches. Because of the simplicity in modelling, and hence speed of processing, the geometric based tooling contact techniques are gaining more and more acceptance as tools for product, process and tooling design of automotive stampings. The paper describes the implementation of a stretch/draw formulation of tooling contact, in two dimensions. The formulation is based on a belt friction assumption, with special elements developed to deal with thickness distribution around the contact area. The program tracks the change in the location of the neutral point at every forming step. The program is designed to handle multi-tooling as well as multi-stage forming operations.

Surface defects occur during forming, material unloading and during further material processing. During forming operations the compressive forming stresses are the cause of defects. During material unloading and further material processing, springback and residual stresses are the major cause of such defects. The conditions for the occurrence of surface defects at these three stages are examined and discussed. A computer aided methodology is presented for estimation of the residual stresses, application of the approach is given for some practical examples.