内高压成形起皱行为的研究

对内高压成形起皱过程进行了理论分析、数值模拟和实验研究．分析了加载路径、成形区长径比等因素对皱纹数量和工件成形效果的影响．结果表明：不是所有的皱纹都是失效形式,在某些情况下,管料起皱后仍然可以成形,关键是获得有益皱而不是死皱,通过起皱在成形区聚料是一种有效的预成形方法,该方法拓宽了内高压成形区间．

RESEARCH ON WRINKLING BEHAVIOR IN TUBE HYDROFORMING

The common defects in tube hydroforming are buckling, wrinkling, bursting and folding. Wrinkling occuring as the axial force reaches a critical value is considered as one of defects in the past. Theoretical analyses, numerical simulation and experiment were conducted to control and use wrinkles in tube hydroforming. Effects of loading path and the ratio of length to diameter on the number of wrinkles and forming result were discussed. It has been shown that not all wrinkles are defects and tube can successfully be formed after wrinkling in some cases. The key issue is to obtain useful wrinkles instead of dead wrinkles. However, the thickness distribution is not even in the axial direction. Accumulation of material in the expanding area by formation of wrinkles is an effective method for preform. By use of this method, the zone of process window can be enlarged for hydroforming.