板料成形性理论评价与深入研究

破裂和起皱是板料冲压成形中最主要的两种缺陷。本文对各种判断破裂的拉伸失稳理论和判断起皱的塑性屈曲理论进行了综述 ,指出现有的各种理论存在的缺点和不足。提出了基于极限分析的一般变分原理的思想和方法 ,将板材塑性屈曲时所满足的全部方程归结为一个泛函的求极值问题 ,用直接法可以方便求得金属板料塑性屈曲问题的近似解析解。最后 ,指出了发展一种能综合判断板料破裂和起皱问题的全面或广义成形性理论的必要性 ,并给出了一些研究方向和研究内容。

An overall review and comprehensive investigation into formability theory of sheet metal forming

Wrinkling and splitting are two kinds of common defects in sheet metal forming processes. An overall review is summarized on various tensile instability theories for prediction of splitting and the plastic buckling theories for prediction of wrinkling, and the shortcomings of these various theories are pointed out meanwhile.Based on the general variational principle method for the bound analysis, the sheet metal during plastic wrinkling is supposed to satisfy all equations, including differential equations of equilibrium, strain compatibility equations, yield criteria and flow rules. This problem comes as to solution of the maximum value of a variational function so that an approximately analytical solution to the plastic wrinkling in sheet metal processes can be conveniently obtained by the direct method. It is indicated that it is necessary to develop a universal formability theory as a general rule for prediction of splitting and wrinkling in metal sheet forming. Some research topics are given concerning this universal formability theory.