Deformation Behavior and Ductility in Free Forging with Convex Die.

凸模自由锻造的变形行为和延展性。

• 批准号: 04650624
• 负责人: MORITOKI Hitoshi
• 金额: $ 1.28万
• 依托单位: Akita University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650624/
• 关键词: Forging; Limit of Ductility; Plastic Instability; Forming Limit; Localized Necking

Improvment for spring characteristic and strength of sheet metals has been brouhgt by giving them plastic deformation through free forging with convex shape dies. Here, the deformation behavior and ductility in sheet metal forging with cylindrical dies are investigated. Slab method under plane strain is used in order to evaluate deformation behavior. Forging region of a sheet increases with forging process at the early stage of forging, but after the middle stage its increase changes to decrease. At the center of the forging sheet the sterss along longitudinal direction is tensile, in many cases, thouhgh depending upon tool radius and friction coefficient, and it becomes maximum near middle stage, after which it decreases and shifts to compressive. When the maximum tensile stress is too high, ductile fracture may be possible to arise.We proposed general criteria for ductility based on plastic instability, and tried to predict the formability of various metal formings. They correspond t … More o modified diffuse necking by Swift and to modified localized necking by Storen & Rice. The materials used are strengthened aluminium, phospher bronze and stainless steel. The cracking of the aluminium and steel occurs at the interior of materials under plane strain, but that of the bronze does at sheet edge under plane stress. Ductiltiy limit obtained by experiment is compared with analytical estimation on the aluminium, because the bronze shows different view of fracture, and the fracture of the steel and a part of the bronze occurs after very large deformation where very high hydrostatic pressure arises, which rejects all of application of any criteria proposed on phenomenological basis and plastic instability.The ductility on the aluminum shows, on the whole, good agreement between experiment and analysis, though experimental values are a little higher than analytical ones. The cracking appearing after very large deformation should be inverstigated considering all possible items producing effects on the change of stress state, for example, the flatting of dies under high pressure. Less

采用凸模自由锻造，使板材产生塑性变形，从而提高了板材的弹性和强度。本文研究了金属板料圆柱模锻造的变形行为和塑性。采用平面应变下的平板法来评价其变形性能。在锻造初期，随着锻造工艺的进行，板料的锻造区域逐渐增大，但在锻造中期以后，其增大的区域逐渐减小。在锻板中心处，沿着纵向的应力为拉伸应力，但在许多情况下，应力随刀具半径和摩擦系数的变化而变化，在锻板中部附近应力达到最大值，之后应力减小并转变为压缩应力。当最大拉应力过高时，可能发生延性断裂，提出了基于塑性失稳的延性判据，并尝试预测各种金属成形件的成形性。对应于t ...更多信息 o Swift的修正扩散颈缩和斯托伦& Rice的修正局部颈缩。所用材料为强化铝、磷青铜和不锈钢。在平面应变下，铝和钢的开裂发生在材料内部，而青铜在平面应力下的开裂发生在板边。对铝合金的塑性极限进行了实验研究和理论分析，结果表明，青铜的断裂形态与理论分析不同，钢和部分青铜的断裂是在大变形后发生的，在此过程中产生了很高的静水压力，这与唯象理论和塑性失稳理论相矛盾，铝合金的塑性总体上表现为：实验值略高于分析值，但实验值与分析值吻合较好。对于大变形后出现的裂纹，应考虑到所有可能影响应力状态变化的因素，如模具在高压下的压扁。少