Authors: Hsien-Chin Lan , Shyong Lee , Jian-Jia Huang , Yiin-Kuen Fuh , Jian-Yih Wang, Chih-Te Chiang
A sheet metal trough of aluminum alloy is manufactured by two-stage gas forming process at 500℃. The product with sloped side walls is of ~1.2 meter long and ~260mm opening width, comprising two near-conical shape sinks at two ends. The depth of one sink apex is ~350mm, 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 to V-shape groove was prepared prior to the gas forming work. Within a single die, gas pressure is used to form the V-shape blank into a perform die cavity prior to the pressure being reversed to form the sheet into the final component cavity. The preforming of the V blank creates length of line, while preserving metal thickness in certain regions 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, serious wrinkling situation was encountered, which had been predicted in the 2-D finite element analysis. An alternative preform geometry is proposed and the overall initial acting force offered by gas pressure is calculated. The subsequent deforming progression is simulated indicating of no wrinkle formation.
Keywords: superplactic forming (SPF); V-shape; saddle-contour; two-stage SPF