Two-stage superplastic forming of a V-shaped aluminum sheet into a trough with deep and irregular contour

A sheet metal trough of aluminum alloy is manufactured by a two-stage gas forming process at 500 C. The product with sloped side walls is of ∼1.2 m length and ∼260 mm opening width, comprising two near-conical-shaped sinks at two ends. The depth of one sink apex is ∼350 mm, which results in the depth/width ratio reaching 1.4. To form such a deep and irregular trough, a superplastic aluminum alloy 5083 initially bent into a V-shaped groove was prepared prior to the gas forming work. Within a single die, gas pressure is used to form the V-shaped blank into a preform die cavity prior to the pressure being reversed to form the sheet into the final component cavity. The preforming of the V blank creates a uniform length of line in order to improve the thickness profile of the final part. In this work, a preform has been designed to improve the forming of a complex component by providing a superior thickness profile as compared to a conventional single-stage forming cycle. However, a serious wrinkling situation was encountered, the cause of which has been analyzed using basic mechanics as well as numerical simulation.