铝合金筒形件磁脉冲辅助冲压成形试验研究

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。     

筒形件的切边与整形工艺

筒形件，这里是指经过无压边拉深成形且无凸缘的筒形拉深件，如图1所示。与图2所示的有压边的筒形拉深件或有凸缘无压边筒形拉深件相比，无凸缘筒形件的切边工艺较难实现。在此，对无压边、无凸缘筒形件的切边工艺及模具设计进行探讨。     

宽凸缘筒形件拉深工艺及模具设计

宽凸缘筒形件在冲压成形中金属流动复杂,板料变形困难,容易出现起皱和拉裂.以宽凸缘拉深件为研究对象.设计了一副带压边圈的反拉深模具结构,并对该模具在成形过程中工件产生的质量问题进行了分析,最终获得了合格工件.     

基于数值模拟的带凸缘筒形件冲压工艺及模具设计

介绍了升降器零件成形工艺,该零件主要特点是带凸缘筒形件,涉及落料、拉深、冲孔、翻边等冲压工序.传统升降器外壳冲压工艺存在冲压工序多、复合程度低、制造成本高等缺点,为了克服这些缺点,本文分析了汽车车门玻璃升降器外壳件冲压工艺,研究比较了5种工艺方案,最终确定的方案为落料拉深复合、冲小孔与翻边预冲孔复合以及翻边切边复合.根据选定方案进行模具设计,运用有限元分析软件对成形过程进行分析,以确保冲压的顺利进行.提出升降器外壳件新冲压工艺设计,采用新工艺,取得了良好效果.     

直壁筒形件凸模支撑渐进成形工艺的数值模拟

以ANSYS/LS-DYNA软件为分析平台,构建了凸模支撑渐进成形过程的有限元模型,成功模拟了用平行直线型路径方案渐进成形直壁筒形件的过程,并通过实验验证了该数值模拟方法的可行性。对数值模拟结果进行后处理得到直壁筒形件的应力应变分布、节点运动以及壁厚的变化规律。结果表明,平行直线型路径方案能够成形出壁厚较为均匀的直壁筒形件,在筒形件口部区域等效应力和等效应变达到最大。     

应用均匀设计方法提高筒形件的成形质量

均匀设计是试验设计方法的一种。采用有限元技术和均匀设计方法对筒形件在拉深成形过程中的摩擦系数、压边力、凹模口圆角半径等工艺参数进行优化设计。优化后的仿真结果在提高成形裕度和抑制厚度的变化方面取得很好的效果。该方法还可以明显减少模拟计算次数，提高优化效率，改善板料冲压成形的仿真计算精度。     

带凸缘锥形零件拉延成形工艺研究

针对带凸缘锥形零件的成形特点,根据金属薄板冲压成形原理及生产实验进行工艺计算与分析,找出该类型零件拉延成形时废品率高的原因。选用成本相对较低的08Al带凸缘锥形零件,选用液压成形设备,将压边力调整在195～260kN之间,通过在模具压边圈上加工环形槽、增加塑料布润滑等措施,将两次成形改进为一次成形,取得较好的成形效果。通过近3年的批量生产验证,对于宽凸缘中等深度锥形件,通过采取相应的措施,只要保证拉延系数或相对高度的其中一个指标符合要求,即可以有效提高该零件的产品合格率。     

基于Dynaform的镀镍薄板冲压成形及回弹研究

针对筒形件成形过程中可能存在的起皱、拉裂以及变形不同步等缺陷,借助Dynaform软件对镀镍薄板的冲压成形和回弹进行了有限元仿真分析。根据零件的成形极限图、厚度变化结果调整了冲压工艺参数,获得了较好的成形效果。并对镀镍筒形件进行了回弹分析,发现其回弹较小,不会影响成形状态。在仿真分析的基础上进行了实际冲压试验,其结果与有限元模拟结果基本吻合,均在法兰部分发生轻微起皱,没有出现拉裂现象,符合零件成形要求。研究表明,仿真分析可以为镀镍薄板的冲压成形及工艺参数优化提供依据,降低了生产成本、缩短了模具制造周期,提高了生产效率。     

基于理想形变理论的有限元逆算法在板料成形中的应用

基于理想形变理论,研究了金属板料成形的有限元逆算法,并开发了计算程序.采用线性三角形膜单元和厚向异性的刚塑性材料模型,计算了一个带凸缘的方盒形件,并与Dvnaform的一步逆向法和增量法的计算结果进行了比较.实例分析结果表明,在工程允许精度范围内,本文方法能够有效分析零件的成形性能.由于该方法计算速度快,所以可用于零件...     

无凸缘筒形件的工艺计算方法

无凸缘筒形件是生产中应用较为普遍的一种拉深制件。本文主要对无凸缘筒形件拉深的工艺计算提出了较为详细的计算方法和步骤 ,经生产、教学实践应用 ,具有较好的适用性。     

Investigation of Influencing Parameters for Tribological Conditions in Dry Forming Processes

Environmental awareness and a growing demand for efficient resource utilization encourage the realization of lubricant-free forming processes. A first step in accomplishing dry sheet metal forming is to gain knowledge about the changing tribological conditions and to identify the relevant influencing parameters. The commonly used flat strip drawing test was selected to investigate the tribological conditions in the flange area of deep drawing processes. The influencing factors of contact pressure and varying drawing velocities were analyzed under dry and lubricated conditions. Additionally,the tool and workpiece surfaces were characterized. Besides lubrication, the contact pressure mainly determines the tribological conditions. In lubricated tests higher normal pressure reduces friction, whereas without lubrication higher pressure results in slightly increasing friction. A changing drawing velocity affects the friction when lubricant is applied. In dry experiments, no influence of velocity was found. Results of surface characterization reveal adhesion as main wear mechanism under dry conditions. Based on the investigated influence of the process parameters, an increase in process understanding for dry forming operations is derived.     

Control of wall thickness distribution by oblique shear spinning methods

A flexible method of forming circumferentially variant wall thickness distributions on the same shape is attempted using two oblique sheet spinning processes. The fundamental strategy entails the inclination of the flange plane of the workpiece during forming. In one type of synchronous dieless spinning, edge-hemmed aluminum blanks are formed for truncated cone shells, by synchronizing the motion of the spherical head roller in the axial and radial directions with the angle of the general purpose mandrel fixed on a bidirectionally rotating spindle. On the other hand, in the other type of force-controlled shear spinning, flat aluminum discs are formed by feeding perpendicularly to the flange plane of the workpiece and maintaining the thrust force along the plane via the roller tool, exerted onto the rotating truncated-cone-shaped die. The estimated wall-thickness distribution based on a simple shear deformation model nearly conformed to the measured thickness distributions of the products formed at several inclination angles of up to 15 degrees in the forming and both spinning methods. The low-cost value-added forming method seems to be practicable not only for metal spinning but also for other incremental sheet forming processes.     

板材分段多点成形中局部剧烈塑性变形的研究

局部剧烈塑性变形是分段多点成形中特有的一种缺陷,对其进行深入的研究有利于分段多点成形技术的进一步实用化.本文以圆柱形工件为例,对分段多点成形过程进行数值模拟,详细分析了局部剧烈塑性变形的产生机理,并采用非均匀有理B样条曲面(NURBS)方法,进行过渡区的协调设计来抑制局部剧烈塑性变形的产生,实验证明这种方法能够显著提高工件的成形质量.     

基于载荷下降法的双相钢DP590拉深减薄率研究

采用载荷下降法研究了双相钢DP590在不同压边力下拉深成形的减薄率。采用BCS-50AR通用板材成形性试验机进行有无润滑条件的对比拉深试验,获得成形力-凸模位移关系曲线。试验结果发现,拉深件凸缘部位和凹模圆角处的润滑有利于拉深成形,而无润滑条件下的拉深容易破裂。拉深件凸缘部位增厚,凹模圆角处和筒壁部位均有不同程度的减薄。危险断面处的减薄率最大,破裂情况下的最小减薄率为28.6%,无破裂情况下的最大减薄率为19.3%,达到实际生产要求。     

板坯电磁成形载荷计算方法及分布特性

用平面螺旋和多叠式线圈加工平板毛坯是电磁成形的一种基本方式,其理论研究包括电路分析和动态变形分析两个方面,其中电路分析的目的是确定作用在工件上的脉冲电磁力,并用于变形分析。通过分析板坯电磁成形中工作线圈在强脉冲电流激励下的动态响应过程,建立了线圈磁场、工件表面感应涡流及磁场的计算公式,给出了成形载荷的计算方法。通过数值分析讨论了载荷的分布特性,数值求解结果与相关实验研究结论一致。将成形载荷数值求解结果用于变形分析时,成功地预测了铝板毛坯的自由胀形过程。     

An investigation of cold extruding hollow flanged parts from sheet metals

Hole flanging with cold extrusion can avoid necking or fracture as encountered in conventional sheet metal-forming operations. Substantial flange height and lip thickness can be achieved with flange extrusion because the forming load is compressive. Using a hydraulic press, flange extrusions of 5 and 10 mm inner diameters were produced in pieces of cup-shaped galvanized steel, as well as aluminum 5052 workpieces with a thickness of 0.8 mm, both of which had a pre-hole on the cup bottom. As the punch load was exerted on the cup rim, a clamping force was applied to suppress dilation on the cup bottom.The experiments showed that with sufficient clamping force, significant flange height could be extruded. The utmost extruded flange of 5 mm i.d. was 6 times larger than that drawn from the conventional method, whereas that of 10 mm i.d. was 3.8 times larger than that drawn from the conventional method. However, no flange was extruded and buckling occurred on the cup bottom when the clamping force was insufficient. The experiments confirmed the results predicted by the FE simulation. For a selected flange inner diameter, the ratio of the extruded flange height to the increase in cup bottom thickness was directly related to the normalized clamping pressure, i.e. the ratio of clamping pressure to workpiece yield strength. Therefore, both the application of a larger clamping force or the use of low-strength workpiece materials facilitated the extrusion of flange while suppressing the dilation of the cup bottom. Flange extrusions with a larger diameter correspond to a smaller extrusion ratio or reduction of area. Experiments showed that a significant flange height could be extruded with a 10 mm inner diameter for both galvanized-steel and aluminum 5052, while results for extrusions with a 5 mm inner diameter were unfavorable when using galvanized-steel. High-strength materials and a high extrusion ratio required greater clamping force for the flange extrusion process, and consequently caused excessive forming load on the forming dies as well as on the hydraulic press, thus rendering the process less effective.     

马鞍形板材件多点“三明治”成形实验研究

多点“三明治”成形是一种针对小批量多曲率板材工件制造而提出的新成形方法。用该方法成形时,上模采用聚氨酯模具,下模为型面可调节的多点模具。为了使多点模具型面连续化和消除工件表面的压痕,在成形过程中使用了金属护板和弹性垫板。由于工件板材两侧都和聚氨酯相接触,因此成形后工件的表面质量好。为了研究采用多点“三明治”成形复杂三维曲面工件的成形过程以及成形可能会出现的表面缺陷,文章选用马鞍面作为目标形面进行了实验研究,提出了用于提高工件的贴模程度,通过改变上模形状的分步成形方法,并得到了Q235B板材厚度和可成形马鞍形工件深度之间的关系曲线。     

Influence of the Workpiece Stiffness on the Electromagnetic Sheet Metal Forming Process into Dies

Electromagnetic sheet metal forming is a high speed forming process using pulsed magnetic fields to form metals with high electrical conductivity such as aluminum. Thereby, workpiece velocities of more than 300 m/s are achievable, which can cause difficulties when forming into a die. The kinetic energy, which is related to the workpiece velocity, must be dissipated in a short time slot when the workpiece hits the die; otherwise undesired effects, for example rebound can occur. One possibility to handle this shortcoming is to locally increase the stiffness of the workpiece. A modal analysis is carried out in order to determine the stiffness of specific regions of the workpiece so that an estimation concerning the feasibility of the desired geometry is possible in advance without doing cost and time consuming experiments. Thereby, the desired geometry of the workpiece will be fractionized in significant sectors. This approach has to define the internal force variables acting on the cutting edge, which are required to constrain the numerical model. Finally, a method will be developed with the objective of calculating the stiffness of each sector. The numerical results will be verified by experiments. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

基于田口试验的轮毂法兰盘热锻工艺优化

采用Deform-3D有限元数值模拟软件对轮毂法兰盘热锻成形进行数值模拟,并对初定成形工艺方案进行分析,确定了预锻+终锻成形方案。针对工件表面应力较大、模具磨损较为严重的问题,通过田口试验优化法对成形参数进行优化组合。模拟结果表明,当轮毂法兰变形温度为1200℃、模具温度为230℃、变形速率为1.0 mm·s~(-1)、摩擦系数为0.05时,工件应力、模具载荷和模具磨损能有效降低,且工件成形质量较优。各参数对零件质量和模具磨损的影响程度依次为:摩擦系数变形速率变形温度模具温度。     

某外壳零件成形工艺分析

针对底部带孔的有凸缘圆筒件成形工艺过程,确定了拉深工序的成形工艺参数,结合数值模拟方法模拟验证了拉深的成形过程。对冲孔成形工艺进行了模具设计,从而优化了工艺方案,对同类工件的成形工艺提供一定的借鉴,最终保证了圆筒件拉深成形工序的顺利进行。