Abstract
Approximate theoretical solutions have been derived for the equations relating to thermoforming of superplastic materials by free bulging of circular and rectangular sheet, by bulging of circular sheet into conical and cylindrical dies, and by bulging of rectangular sheet into V-groove dies and between parallel walls. By defining the appropriate forming pressures such that deformation proceeds well within the superplastic-strain-rate range, these solutions can be used to predict thickness distributions in and forming times for the thermoformed parts. A number of experiments have been conducted, involving the bulging of superplastic eutectic Sn-38Pb sheet into dies of various shapes at room temperature, within the strain-rate range 0·01-0·2 min−1. These experimental results, together with other results for Zn-22Al eutectic alloy sheet formed at 250°C, taken from the literature, have been compared satisfactorily with the proposed theoretical solutions.
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