THE SHAPE DISTORTION IN DRAWING PROCESS WITH TC1Mδ0.8 TITANIUM ALLOY SHEETS

采用有限元数值模拟与成形工艺实验相结合的方法,对0.84 mm厚的TC1M钛合金板材杯形件室温拉深成形及回弹过程进行了研究.结果显示,拉深制件不仅出现凸耳和杯口厚度不均等熟知的现象,还揭示出因钛合金各向异性所引发的杯口内壁非圆化,这类形状畸变对制件的几何精度将产生不利影响.600 ℃温热拉深能有效地抑制卸载回弹,杯口内壁非圆化得以消除,但却无法改变钛板的各向异性性质,凸耳和杯口厚度不均等畸变现象依然存在.     

一种提高筒形件拉深效率新途径的模具设计

通过拉深成形的研究和试验,发现拉裂总是在某些危险部位最先产生,从而导致整个拉深成形失败,而且这些危险部位的产生与拉深过程中金属的流动趋势有很大的关系.提出了一种通过在拉深过程中某一时刻给工件的侧壁变薄部位主动施加一定的外力,改变侧壁的金属流动趋势,防止变薄区材料尤其是危险断面的进一步变薄,使壁厚变厚处更多地参与变形,拉深件壁厚分布趋向均匀,从而推迟了开裂的产生,拉深件的成形效率也将大大提高.设计制造出了将该途径应用于筒形件拉深的模具,指出了模具设计要点.实践证明,该模具对提高筒形件的拉深效率和质量是切实有效的.     

杯形件温引伸数值模拟

用MARC/AutoForge软件对杯形件温引伸工艺进行了数值模拟 ,分析了凹模锥角及凸、凹模与工件之间摩擦系数对引伸工艺的影响 ,为杯形件温引伸工艺的制定提供了依据。     

A developed process for deep drawing of metal foil square cups

Deep drawing of non-axisymmetric cross-section cups from thin sheets or metal foils has become increasingly important, especially for miniaturization of mechanical components. However, with a thin sheet thickness, conventional deep drawing processes are not able to offer reasonable drawing ratios due to early formations of localized wrinkling and fractures at cup corners. In this paper, a friction aided deep drawing process has been developed to increase the deep drawability of thin sheets and metal foils. Productions of square cups have been chosen to verify the current proposed process since the shape provides recognizable non-homogeneous deformation, which can then be compared to conventional processes. In the proposed process, a circular blank holder of a square hole is divided into eight identical segments of 45°. During the deep drawing process, four of the eight segments will move radially inward while the other four segments will move radially outwards cyclically under a pre-determined blank holding pressure. A finite element model of the technique was used to simulate virtual experiments to evaluate and optimize the controlling parameters that influence the cup height and forming process. Taguchi and Pareto ANOVA statistical methods were subsequently used to determine the optimum conditions for best cup height. The results have shown that the new technique is capable of producing deep square cups from soft aluminum sheet (Al-O) of 0.5 mm thickness with a high drawing ratio of 3.3. In addition, it was also observed that the radial displacement was the most significant parameter in influencing the cup height.     

Friction aided deep drawing of sheet metals using polyurethane ring and auxiliary metal punch. Part 1: experimental observations on the deep drawing of aluminium thin sheets and foils

Friction aided deep drawing based on the Maslennikov process is investigated as a method to facilitate the deep drawing of sheet metals with poor drawability. Aluminium foils and thin sheets of 0.1–0.4 mm in thickness are used as a model for the material with poor drawability. An auxiliary metal punch is used together with a polyurethane ring to increase the drawing efficiency and to improve the dimensional accuracy of the drawn cup. The effect of drawing conditions such as thickness, hole diameter and the hardness of the polyurethane ring on the cup height are mainly investigated. Also, the optimum number of drawing operations required to achieve a given drawing ratio is examined by repeating compression and unloading the polyurethane ring. The experimental results show that even for foil and thin sheets, deep cups with drawing ratios of 2.25 and with good shape and dimensional accuracy can be obtained by repeating the drawing operation about ten times. The achievable drawing ratio is appreciably larger when compared with that obtained by the conventional deep drawing process.     

轴对称零件拉深成形中失稳破裂及其承载能力的分析

分析了圆锥形零件拉深过程中 ,毛坯靠模时破裂失稳处的变形特点和受力情况。在拉伸失稳理论的基础上 ,推导出了圆锥形零件拉深成形时的极限承载能力 ,即破裂极限载荷的计算公式 ,并用实验对理论计算公式进行了分析验证。     

Friction aided deep drawing of sheet metals using polyurethane ring and auxiliary metal punch. Part 2: analysis of the drawing mechanism and process parameters

Friction aided deep drawing using a polyurethane ring as a pressure medium has been analyzed by the slab and the energy methods to understand the main features of the process and to find the optimum conditions to achieve successful drawing. The effect of an auxiliary metal punch on the stress distribution of the deformed blank and the increase in height of the drawn cup is also discussed. From these studies, the reason why the unusual circumferential crack occurs at the flange of the deformed blank has been clarified, based on the radial stress distribution of the deformed blank. A process parameter, which denotes the drawing characteristics of the friction aided deep drawing, has been proposed. In addition, the drawing region diagram has been presented to facilitate the drawing pressure control with the progress of the drawing process. It is shown that the successful drawing region is narrow at the early stage of drawing, although it becomes wide as the drawing proceeds. Therefore, in the early stage of drawing, special care should be paid to the drawing pressure control to avoid the flange crack.     

钣金成形中润滑剂润滑效果试验研究

钣金成形中润滑状况是影响成形的一个重要因素,成形过程中局部润滑状况的改善可以提高成形性。通过杯形件拉深试验,在需要润滑的局部涂抹润滑剂,采用3种不同的成形性评价方法研究润滑剂的润滑效果。对试验中使用的4种润滑剂进行了润滑效果研究,结果表明,4种润滑剂的润滑效果(由好到差的顺序)为,聚四氟乙烯薄膜,肥皂,猪油,鸡油。     

板料成形模拟中惯性效应的探讨

为了研究冲压成形过程动力显式有限元分析中惯性效应对板材变形的影响 ,针对圆筒件拉深建立了一个力学模型 ,采用能量法对该模型进行了分析 ,探讨了决定惯性效应对板材变形影响程度的主要因素 ,提出了合理选择模具运动速度的方法。通过数值计算对力学模型分析结果进行了验证     

薄壁杯形件单道次拉深旋压成形质量试验研究

通过试验研究了拉深旋压工艺参数对工件壁厚、工件外径及成形性能的影响。试验结果表明,旋轮进给比f、旋轮与芯模间隙δ等对工件壁厚、名义拉深比K和拉深旋压成形性有很大的影响。在毛坯厚度较小的情况下,较大的进给比和名义拉深比都容易导致工件产生起皱和开裂,给出了使拉深旋压能顺利进行的工艺参数范围。     

圆筒件极限拉深系数mk研究

考虑材料加工硬化的影响,本文通过对圆筒件及带凸缘的圆筒件首次拉深过程中变形区材料的应力和应变的理论分析 ,推导出圆筒件及带凸缘圆筒件首次拉深时极限拉深系数的近似计算公式.由推导公式计算的结果与实验值相比误差较小.在实际拉深此类零件时,可由推导的公式直接计算出圆筒件及带凸缘圆筒件首次拉深时极限拉深系数.     

Tool temperature control to increase the deep drawability of aluminum 1050 sheet

A feasibility study on the tool temperature control to increase the deep drawability of Al-1050 sheet is performed. The conventional deep drawing process is limited to a certain limit drawing ratio (LDR) beyond which failure will ensue. The purpose of this study is to examine the possibilities of relaxing the above limitation through the tool temperature control, aiming towards a process with an increased LDR. The idea which may lead to this goal is strengthening the punch-nose radius part by cold punch which has frequently been potential failure area in cup drawing process, while heating the remainder of the blank to reduce the stress on the cup sidewalls. Over the ranges of conditions investigated, the deep drawability of Al-1050 is found to be strongly sensitive to the temperature of the die and punch. The experimental implementation shows that the tool temperature control is very effective way to promote deep drawability of Al-1050.     

A Method for evaluating limiting drawing ratios

Sufficient data have now been generated to assess the influence of material, process, and tooling variables on the limiting drawing ratio, when deep drawing cylindrical cups from circular blanks. The influence of these parameters is less well understood in the deep drawing of nonaxisymmetric cups, and the data that exist have generally been collected from drawing tests. A theoretical approach is presented for predicting the limiting drawing ratio when deep drawing prismatic cups. For a given blank geometry, the drawing load is calculated to plastically deform the flange, overcome friction between the flange and the blank holder, and to bend the material over the die radius. Deformation in the cup wall is ignored. The onset of yielding in the flange is determined using a finite-element code. The calculated drawing load is compared to a theoretical maximum, and when the two values coincide, this yields the limiting blank size under the assumed processing conditions, i.e., blank holder force, die radius, blank shape, and coefficient of friction. The theoretical predictions were compared with experimental results when deep drawing square cups from optimum blank shapes, and the correspondence was found to be acceptable.     

不锈钢材的橢圆杯拉伸成形分析

采用Prandtl-Reuss塑流法则和Hill的屈服判据,结合有限变形理论及updated Lagrangian formulation的概念,将四边形四节点退化壳元素偶合到刚性矩阵中,组成三维有限元素的分析模式来处理板材成形问题。以材料拉伸试验所得的样片断裂面厚度为数值分析的破断准则,探讨椭圆杯拉伸成形过程中冲击荷载与冲程的关系、工件厚度分布、变形过程及成形极限等。由数值分析与实验结果得知,冲击荷载随着冲程的增加而增大,当载荷达到最大值后,样片随着冲程的增加而继续变形,直到拉伸完成为止。工件最小厚度集中在工件与压头长轴接触处,因长轴的曲率半径比短轴的小,故料片在长轴处承受了最大拉伸应力。经由椭圆压头周长与初始样片周长所定义的极限拉伸比得知,此椭圆杯成形的极限拉伸比为2.136。     

锥形件拉深变形过程研究

本文对锥形件拉深变形过程进行了分析，并通过坐标网格法探讨了变形过程中的应力应变分布及应力分界圆的变化情况，指出了在锥形件拉深变形过程中整个坯料都是变形区，揭示了随着拉深过程的进行，零件破裂和起皱的趋向性都是增加的。     

应变硬化指数对圆筒形件拉深性能的影响

应用有限元软件PAM-STAMP 2G研究了圆筒形件拉深成形过程中不同厚向各向异性系数条件下硬化指数n值对板料拉深性能的影响。研究结果表明,随着厚向各向异性系数的增大,板料的极限拉深比增大。在小厚向各向异性系数的情况下,硬化指数对板料的拉深性能影响大;在大厚向各向异性系数的情况下,硬化指数对板料拉深性能的影响不大。在小的厚向各向异性系数r值下,可以通过增加板料的硬化指数n值来增大板料极限拉深比。     

Deep drawing of square cups with magnesium alloy AZ31 sheets

The square cup drawing of magnesium alloy AZ31 (aluminum 3%, zinc 1%) sheets was studied by both the experimental approach and the finite element analysis. The mechanical properties of AZ31 sheets at various forming temperatures were first obtained from the tensile tests and the forming limit tests. The test results indicate that AZ31 sheets exhibit poor formability at room temperature, but the formability could be improved significantly at elevated temperatures up to 200 °C. The test results were then employed in the finite element simulations to investigate the effects of process parameters, such as punch and die corner radii, and forming temperature, on the formability of square cup drawing with AZ31 sheets. In order to validate the finite element analysis, the deep drawing of square cups of AZ31 sheets at elevated temperatures was also performed. The experimental data show a good agreement with the simulation results, and the optimal forming temperature, punch radius and die corner radius were then determined for the square cup drawing of AZ31 sheets.     

不锈钢咖啡煲杯嘴的侧向无压边拉伸成形工艺及模具设计

针对某型号不锈钢咖啡煲杯嘴的局部成形，介绍了侧向无压边拉伸成形工艺及模具设计。     

基于神经网络的拉深力智能化预测系统

结合塑和学理论、正交试验法及神经网络技术建立了精确计算形件拉深力的智能化预测系统。根据Ｈｉｌｌ的各向异性理论导出了新的计算杯形件拉深过程中拉深力变化的理论公式,并坟出了最大拉深力,应用正交试验法分析了各工艺参数对最大拉深力的影响。针 对在应用ＢＰ网络时遇到的两个关键问题进行了讨论并提出了解决方案。应用人工神经网络技术把理论公式与试验数据结合在一起建立了智能化预测系统。     

薄壁铜管固定芯头拉拔和游动芯头拉拔的对比分析

为提高薄壁铜管拉拔后的成形质量,探讨不同拉拔工艺对薄壁铜管成形性能的影响,利用有限元软件MARC分别对两种拉拔成形工艺建立有限元模型,对比分析薄壁铜管固定芯头拉拔和游动芯头拉拔对拉拔力、铜管拉拔后等效应力、应变和残余应力的影响。结果表明:在相同工艺参数下,与固定芯头拉拔相比,游动芯头拉拔所需拉拔力明显更小,等效应力也相对更小,等效应变相等,残余应力在轴向和周向更小,且分布更均匀,在径向都趋近于0。在不考虑其他因素下,游动芯头拉拔更有助于提高薄壁铜管的产品质量。