共查询到20条相似文献,搜索用时 62 毫秒
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为揭示磁脉冲成形的增塑机制,采用理论分析与微观组织观察相结合的方法对5052铝合金板材磁脉冲动态拉伸过程中动态成形行为和塑性失稳机制进行了系统研究.结果表明,惯性力在动态成形中起主要作用,惯性力对试样的结构失稳具有抑制作用,从而使试样的塑性提高并产生分散失稳;5052铝合金动态成形和准静态成形的成形性质相似,不会产生特殊的组织结构,塑性变形机制均为位错滑移机制;准静态成形过程以均匀单系位错滑移为主,断裂伴随着位错的缠结和攀移;而动态成形过程中,位错滑移趋于多系开动,在大面积区域出现明显的交滑移现象,且滑移带较准静态成形时窄且密,位错组态更均匀;动态成形的多系滑移和位错均化作用可在比准静态成形高的多的塑性应变水平下形成,从而使材料表现出较高的塑性和强度. 相似文献
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针对铝合金筒形件传统拉深成形中由于成形性差容易出现拉裂问题,采用拉深预成形和磁脉冲辅助成形相结合的方法对5052-O铝合金板材进行筒形件成形性试验研究,探索磁脉冲辅助冲压成形工艺提高材料成形性的可能性。并研究应用磁脉冲成形减小预成形筒形件圆角半径的工艺可行性。结果表明:与普通冲压相比,磁脉冲辅助冲压成形能够提高材料的成形性,且提高放电电压和增加放电次数能增强圆角的再变形能力,圆角变形更加均匀。普通拉深筒形件减薄最严重部位出现在筒壁和圆角相接处,而磁脉冲辅助冲压成形筒形件有两个减薄严重部位:侧壁与圆角相接处和筒底与圆角相接处。 相似文献
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Zhenghua Meng Shangyu Huang Jianhua HuWei Huang Zhilin Xia 《Journal of Materials Processing Technology》2011,211(5):863-867
As the lightest structural metal, magnesium (Mg) is attracting increasing interest from both the industrial and academic fields. Magnesium alloy parts are mainly processed by die casting due to their poor sheet formability at room temperature. Warm forming is a popular method of forming; Mg alloy sheets produced in this manner show excellent formability around 200-400 °C. Electromagnetic forming (EMF) can improve the formability of metal sheets without the need for lubricants. In this paper, a new approach, called warm and electromagnetic hybrid forming (WEMF), is presented. The effects of voltage, capacity, and temperature on the bulging height of Mg alloy sheets are investigated. Results show that the bulging height of Mg sheets increases with moderate discharging energies. Enhancing the discharging voltage is also a more efficient method for increasing bulging height compared to simply increasing the capacity. When the discharging energy is kept constant, the bulging height first decreases (<150 °C) and then increases (>150 °C) from room temperature to 230 °C. The formability of Mg alloy sheets improves with increasing temperature, while the forming efficiency of WEMF decreases under similar conditions. 相似文献
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电磁成形是一种高速率成形方法,它能够有效提高金属板材的成形极限。但是电磁成形过程复杂,涉及到磁场?结构场之间的耦合分析。数值模拟提供一种手段去解决耦合问题。然而,大多数的数值模拟都限于2D。建立3D有限元模型去分析电磁平板胀形。成形过程中考虑了板料与底模的接触和板料变形对磁场的影响。板料中心节点和半径20mm处节点的位移随着时间的变化与实验结果一致。分析了塑性应变能和塑性应变。 相似文献
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João P.M. Pragana Carlos M.A. Silva Ivo M.F. Bragança Luis M. Alves Paulo A.F. Martins 《CIRP Annals》2018,67(1):301-304
This paper proposes a new joining by forming process to produce lap joints in metal sheets. The process combines partial cutting and bending with mechanical interlocking by sheet-bulk compression of tabs in the direction perpendicular to thickness. The lap joints are flat with all the plastically deforming material contained within the thickness of the two sheets partially placed over one another. The design of the lap joints is performed by a simple analytical model and the overall concept is validated by means of numerical modelling and experimentation. Destructive shear tests demonstrate the effectiveness and performance of the new proposed lap joints. 相似文献
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Manish Kamal J. Shang V. Cheng S. Hatkevich G.S. Daehn 《Journal of Materials Processing Technology》2007,190(1-3):41-50
A very agile method, that relies solely on simple single-sided tooling, to form open-box-like enclosures with surface detail such as highly embossed surface features is demonstrated and analyzed. For example, this method may be used to fabricate personal electronics cases. The technique uses electromagnetic forces in a two-step process. In the first step a newly developed uniform pressure electromagnetic actuator is used to make a micro-embossed pre-form that can contain very fine surface detail in the part by micro-embossing features in the forming die. This blank is then trimmed. In the second major step electromagnetic flanging is used to give greater depth and steeper walls to the case. Both electromagnetic operations use one-sided tooling and very light equipment. In principle the tooling needed for this type of process can be put to use within days or hours of finalizing the component design and precise tooling tolerances or precise alignment are not required. This work shows the essential feasibility of this approach to manufacturing either small or large lots of components. 相似文献
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The strain path and forming limit analysis of the lubricated sheet metal forming process 总被引:1,自引:1,他引:1
Few previous attempts have been made to analyze numerically the strain path and the forming limit in complex lubricated sheet metal forming. Since usual approaches of solving the lubrication model are limited to axisymmetric and plane strain cases only, this paper developed a unified procedure for combining the finite element code of sheet metal forming, the current lubrication/friction model and forming limit theory, to predict the strain path and fracture strains for either a steady or an unsteady three-dimensional process including both axisymmetric and plane strain cases. The availability of the method must be proved by a published problem, and an axisymmetric stretch forming process was therefore adopted as a benchmark. Numerical results showed that the present analysis provides good agreement with the experimental data of the strain path and the fracture strain for various tribological parameters such as lubricant viscosity and composite roughness of tooling and workpiece, and the advantage of the developed model is that it can be applied to solve the complicated 3D geometric problems. 相似文献