A New Method of Predicting the Formability of Materials

The paper presents a new method, based on standard laboratory cup tests, for predicting the formability of materials; in the example provided, the forming potentials of four new materials are shown.

The properties of stretchability and drawability, which are the principal factors defining a material's forming limits, may be assessed using the Olsen spherical cup test and the Swift flat-bottomed cup test. In the shape analysis procedure described, the minimum amount of deformation needed to fix a desired shape is determined. Then necessary adjustments to tooling for optimum sheet metal usage are made based on calculations from a new type of chart showing stretch forming ratio and draw forming ratio, providing a comparison of the formabilities of a number of materials. It is shown that, in the absence of reliable cup testing data, values can be obtained using laboratory tensile testing results; this is possible because computer-determined correlations of certain tensile parameters to standard cup test results have been made.