摘要
The cylindrical part of sheet metal based on hot-granule medium-pressure forming (HGMF) technology was investigated.The stress functions of the free deformation zone and the fracture instability theory were combined to establish the analytical expression of the critical pressure of punch. The results show that the active friction between the granule medium and the sheet metal, as well as the non-uniform internal pressure presented by the solid granule medium, can obviously improve the forming performance of the sheet metal. The critical pressure of punch increases with the increment of the friction coefficient between the granule medium and sheet metal, as well as the plastic strain ratio, whereas it decreases with the increase of the material-hardening exponent. Furthermore, the impact on the critical pressure from high to low order is the plastic strain ratio, the friction coefficient,and material-hardening exponent. The deep-drawing experiment with HGMF technology on AZ31B magnesium alloy sheet verified the instability theory.Key words: hot-granule
采用热态固体颗粒介质成形工艺对金属板材筒形件成形展开研究,得到板材变形过程中的应力分布函数,并结合板材破裂失稳理论给出自由变形区冲头临界破裂成形压力的解析表达式。研究结果表明,颗粒介质所具有的主动摩擦效应和内压非均匀分布特征能显著提高板材的成形性能;冲头临界破裂成形压力随颗粒介质与板材间摩擦因数和材料塑性应变比的增加而上升,随材料硬化指数的增加而下降。各因素对冲头临界破裂成形压力影响由大到小的顺序为塑性应变比、摩擦因数和硬化指数。最后,采用AZ31B镁合金板材HGMF工艺试验对失稳理论进行验证。
基金
Projects(51305385,51305386)supported by the National Natural Science Foundation of China
Project(QN20131080)supported by the Science Research Youth Foundation of Hebei Province Universities,China
