圆筒件再拉深性能的预测

通过分析圆筒件再拉深变形过程,运用主应力法、摩擦理论和板料弯曲理论,推导出极限拉深比的预测公式。对工业纯钛TA1圆筒件进行拉深成形试验,分析了平均厚向异性-R、摩擦系数μ、凹模半锥角α、凹模圆角rd、圆筒件壁厚比tmax/tmin等参数对再拉深性能的影响。结果表明:拉深试验预测值与实验结果相符合,极限拉深比随着平均厚向异性-R的增加呈线性增加,但随着摩擦系数μ、圆筒件壁厚比tmax/tmin的增加呈线性减小。     

圆筒拉深件形状与厚度变化数值模拟分析

借助Dynaform软件,模拟分析了在不同拉深凹模圆角半径情况下,模具间隙及压边力等工艺参数对直壁圆筒拉深件外形尺寸及侧壁厚度的影响规律,并得到了该拉深件最优的凹模圆角半径参数,其值比经验公式计算结果小。通过进行两个不同凹模圆角半径的对比拉深试验,验证了数值模拟结果相对于经验公式的准确性和科学性,从而为该类零件拉深工艺方案的优化提供参考。     

304不锈钢壳级进模变薄拉深工艺及数值模拟

根据经验公式和理论数据对某304不锈钢壳进行直径减小、壁厚变薄的变薄拉深级进模设计,并运用Deform-3D对连续变薄拉深成形过程进行数值模拟,揭示了成形过程等效应力和行程载荷曲线的分布规律。模拟与试验结果表明:成形过程中,坯料的最大应力集中在与凹模圆角和凹模工作带相接触的区域;随着凸模圆角减小,凸模圆角与直壁连接处应力增大,出现危险区域;为防止最后一道拉深过程中凸模容易磨损及产品被拉伤,应合理设计拉深系数、变薄量及凹模圆角;直径减小壁厚变薄拉深件的直壁壁厚均匀。     

拉深模凹模圆角半径的选择

此文关于拉深模相对凹模圆角半径对圆筒件壁厚变化的研究结果，有助于制件的强度计算和合理选择拉深模的凹模圆角半径。所给的毛坯直径修正系数经验公式，可供模具设计参考，使浅拉深件无需切边，高度尺寸即可达到图纸的精度。     

304奥氏体不锈钢拉深过程有限元模拟

不锈钢制品由于其美观的外表和良好的使用性能,在国民经济各行各业被广泛使用,但不锈钢在拉深过程中硬化严重,易出现起皱、破裂现象,使成品率降低。本文应用ABAQUS有限元软件模拟了304奥氏体不锈钢圆筒件在不同摩擦条件下的拉深成形过程,分析了摩擦系数对304不锈钢圆筒件拉深成形过程的影响。结果表明,304奥氏体不锈钢圆筒件拉深过程中,较适宜的摩擦系数为0.08～0.15。当摩擦系数过小时,将在坯料与凹模圆角处发生破裂;而摩擦系数过大,则严重影响坯料的拉深极限。     

筒形件粉末软凹模拉深数值模拟及实验

采用MSC.Marc软件对圆筒件粉体软凹模拉深成形进行数值模拟,分析成形过程中应力状态和变形情况,设计圆筒件粉体软凹模拉深成形实验模具,对圆筒件粉体软凹模拉深成形进行实验研究。有限元模拟与实验结果表明,与刚性凹模拉深成形相比,粉体软凹模成形工艺可以改善零件成形受力状态和壁厚分布,能有效抑制圆筒件凸模圆角破裂危险区域微裂纹的产生,提高板材的成形极限。     

筒形件粉末软凹模拉深数值模拟及实验

采用MSC.Marc软件对圆筒件粉体软凹模拉深成形进行数值模拟,分析成形过程中应力状态和变形情况,设计圆筒件粉体软凹模拉深成形实验模具,对圆筒件粉体软凹模拉深成形进行实验研究。有限元模拟与实验结果表明,与刚性凹模拉深成形相比,粉体软凹模成形工艺可以改善零件成形受力状态和壁厚分布,能有效抑制圆筒件凸模圆角破裂危险区域微裂纹的产生,提高板材的成形极限。     

模具温度对铝合金板拉深性能的影响

借助商用有限元仿真软件ABAQUS,采用热力耦合有限元法对汽车用铝合金板5083-O的圆筒件温拉深过程进行数值模拟.在此基础上,利用试验设计方法,分析初始温度布置对拉深能力的影响,并给出拉深件破裂失效形式.研究结果表明,凸模底部和凹模法兰的温度决定着铝合金板拉深能力,在凹模法兰处于较高温度250℃而凸模底部处于室温的拉深模式中,临界凸模行程最大;而拉深件的破裂失效即可能出现在凸模圆角区附近,也可能出现在凹模圆角区附近.可见,差温拉深中温度布置对发挥板料成形能力十分重要.     

模具参数对304不锈钢圆筒拉深件残余应力的影响

过大的残余应力容易导致圆筒拉深件应力腐蚀开裂失效。通过7组切环实验及有限元模拟研究了模具参数(凹模圆角半径和凸凹模间隙)对304不锈钢圆筒拉深件残余应力的影响,测得了各圆环的张开距离,采用ABAQUS有限元软件计算出圆筒件中的残余应力。结果表明:环向残余应力先随着凸凹模间隙的增大而增大,但当凸凹模间隙大于1.06t时,环向残余应力基本不受凸凹模间隙的影响;凹模圆角半径对筒形拉深件环向残余应力几乎没有影响;中部径向残余应力随着凸凹模间隙和凹模圆角半径的增大而增大。因此,选择较小的拉深间隙对减小304不锈钢圆筒拉深件中的残余应力是有效的。     

5A02-O铝合金锥底筒形件充液拉深有限元模拟

锥底筒形件由锥底和较高的直壁筒组成,其充液拉深过程中液压加载路径既不同于筒形件,也有异于锥形件。利用DYNAFORM有限元软件对锥底筒形件充液拉深过程进行模拟,研究了不同液室压力加载路径对充液拉深锥底筒形件壁厚分布、破裂与起皱等的影响规律,分析了锥底筒形件液压加载路径控制策略。研究结果表明:采用2拐点的液压加载路径适合锥底筒形件充液拉深成形,第1个拐点位置为凸模底部圆角圆心,与凹模圆角圆心在同一条水平线上,第2个拐点位置为凸模锥底上部圆角圆心,与凹模圆角圆心在同一条水平线上;充液拉深得到的锥底筒形件壁厚分布存在2个波谷点,第1个波谷点在锥底筒形件锥形底部圆角和锥壁的结合处(A点),第2个波谷点在锥底上部圆角和直壁结合处(B点);对于不同的拉深比和锥角,应该采用合理的液压加载路径。     

Finite element modeling and experimental results of brass elliptic cups using a new deep drawing process through conical dies

This paper introduces a new technique for deep drawing of elliptic cups through a conical die without blank holder or draw beads. In this technique an elliptic-cup is produced by pushing a circular blank using a flat-headed elliptic punch through a conical die with an elliptic aperture in a single stroke. A 3D parametric finite element (FE) model was built using the commercial FE-package ANSYS/APDL. Effects of die and punch geometry including, half-cone angle, die fillet radius, die aperture length and punch fillet radius on limiting drawing ratio (LDR), drawing load and thickness strain of the cup have been investigated numerically for optimal process design. A die with half cone angle of 18° has shown the best drawability for the new technique. An experimental set-up has been designed, manufactured, and used for experimental production of elliptical shaped sheet-metal cups. A total of seven punches having aspect ratios ranging from 2 to 2.25 and a die with an aspect ratio of 2 have been manufactured and used. Tensile tests were carried out to obtain the stress–strain behavior for the formed sheet metal. Experiments were conducted on blanks of brass (CuZn33) with initial thicknesses of 1.5, 1.9, 2.4 and 3 mm at different clearance ratios (c/t). Effects of blank thickness and clearance ratio on limiting drawing ratio, drawing load and thickness strain were numerically and experimentally investigated. Finite element model results showed good agreement with experimental results. An elliptic cup with a limiting drawing ratio (LDR) of 2.28 has been successfully achieved using the proposed technique and set-up.     

椭球形制件复合成形规律的研究

采用理论分析、数值模拟与实验验证相结合的方法,对椭球形制件的复合成形规律进行了研究。建立了应力分界圆半径的数学表达式,理论分析表明,应力分界圆半径的大小与板料的初始尺寸、厚度、摩擦系数、压边力大小和凹模圆角半径等因素有关。当压边力、坯料尺寸以及摩擦系数加大,而相对圆角半径减小时,应力分界圆半径变大,复合成形中胀形成分加大;反之,应力分界圆半径减小,拉深成分增加,揭示了复合成形的阶段性特征。数值模拟结果表明,应力分界圆半径是动态变化的,椭球形制件复合成形具有明显的阶段性特征,没有直线段的椭球形制件的成形可分为纯胀形、以胀形为主的胀形-拉深复合成形和以拉深为主的拉深-胀形复合成形3个阶段;在成形的第Ⅰ、Ⅱ阶段初期,坯料尺寸和压边力的大小对应力分界圆半径影响不大;在第Ⅱ阶段后期和第Ⅲ阶段,随毛坯尺寸和压边力的增大,应力分界圆增大。在变形过程中存在两个可能发生失稳起皱时刻,即第Ⅱ阶段初期和第Ⅲ阶段初期。试验验证了理论分析和数值模拟所得的结果。     

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.     

摩擦对收口的影响研究

建立了弹体毛坯收口工艺的刚粘塑性有限元模型,分析了在不同摩擦因子条件下弹体毛坯应力应变分布规律及可能产生的缺陷,为了获得所需的收口毛坯形状尺寸,其模具与坯料之间的剪切摩擦因子应控制在m=0.15以下。     

Development of a new process for producing deep square cups through conical dies

In this article, a new process for increasing the drawability of square cups has been developed. A circular blank is pushed by a flat-headed square punch through a conical die with a square aperture. The deformed blank conforms to the square shape of the die throat and finally a square cup is obtained. The developed technique has a simple tooling set in which the drawing process can be efficiently preformed in a single-acting stroke without using draw beads or blankholder. A commercial finite element simulation package, DYNAFORM, is used to investigate the developed setup in order to determine the optimum die cone angle. An experimental setup is built accordingly with a half cone angle of 18°. Brass alloy (67/33 Cu–Zn) and commercially pure aluminum (Al99.5w) sheets are used in the experimentations. The effects of the original blank thickness (t_o=1, 1.5, 2, 2.5, and 3 mm) and the orientation of the blank rolling direction (0°, 22.5°, 45°, and 67.5°) to the punch side on the limiting drawing ratio (LDR) and punch load are experimentally investigated. The present process successfully produces square cups with drawing ratios of 2.92 for brass and 2.74 for aluminum. The new process has shown superiority over the conventional methods through achieving high drawing ratio especially for thick sheets (2–3 mm). Comparison between experimental results and the available published work showed that the required punch force in the new process is significantly reduced while the LDR is increased.     

基于正交试验和能量转换的精密级进模多步拉深成形研究

应用正交试验方法,采用Dynaform对精密级进模多步拉深成形进行有限元数值模拟。结合能量转换原理,研究各步拉深中凹、凸模圆角半径、拉深高度以及压边力等工艺参数对成形件厚度和回弹的影响,并找出各因素影响的主次顺序。以射频(RF)连接器的壳件为例,通过上述方法优化各步成形参数,用以指导模具设计。     

Finite element simulation on the deep drawing of titanium thin-walled surface part

The deep drawing of titanium thin-walled surface part was simulated based on a self-developed three-dimensional finite element model. After an investigation on forming rules, a virtual orthogonal experimental design was adopted to determine the significance of processing parameters, such as die radius, blank holder force, and friction coefficient, on the forming process. The distributions of thickness and equivalent plastic strain of the drawn part were evaluated. The results show that die radius has a relative major influence on the deep drawing process, followed by friction coefficient and blank holder force.     

工艺参数对TA0半球件冷拉深成形的影响规律

以TA0薄壁半球形零件冷拉深成形为研究对象,采用数值模拟与试验研究相结合的手段,在研究该拉伸成形过程中零件的应变及壁厚分布规律及组织演变规律的基础上,对破裂、起皱缺陷位置进行了预测。同时,采用正交试验分析方法,研究了单位压边力、摩擦系数、凹模圆角半径和凸凹模间隙等工艺参数,对该拉深成形过程的影响规律。结果表明,单位压边力、摩擦系数、凹模圆角半径对拉深过程均有显著影响,其中贡献率分别为凹模圆角半径41.04%,摩擦系数30.27%,压边力24.68%。     

Influence of variables in deep drawing of AA 6061 sheet

Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance as forming process,also serves as a basic test for the sheet metal formability.The effect of equipment and tooling parameters results in complex deformation mechanism.Existence of thickness variation in the formed part may cause stress concentration and may lead to acceleration of damage.Using TAGUCHI's signal-to-noise ratio,it is determined that the die shoulder radius has major influence followed by blank holder force and punch nose radius on the thickness distribution of the deep drawn cup of AA 6061 sheet.The optimum levels of the above three factors,for the most even wall thickness distribution,are found to be punch nose radius of 3 mm,die shoulder radius of 8 mm and blank holder force of 4 kN.     

汽车轮毂端盖拉伸成形模计算机辅助工程

建立了汽车轮毂端盖拉伸成形三维弹塑性有限元模型,并利用MARC软件对其拉伸变形过程进行了数值模拟。分析了金属材料在拉伸成形时的流动及拉伸成形后的残留应力和应变分布情况,研究了凸模圆角半径对板料成形性能的影响及防止产生起皱与破裂的措施。研究结果表明,当凸模圆角半径值小于2~3倍料厚时,材料易产生拉裂现象。模拟结果与实际生产吻合较好,说明所建立的有限元模型是合理的。