某汽车燃料箱隔热板翻边成形工艺设计及研究

目的 为了成形高质量、少缺陷的汽车燃油箱隔热板.方法 采用整体翻边-局部反拉深的工艺方法,以隔热板曲面凸台圆角处的最大减薄率为试验指标,采取正交试验及极差分析确定最优成形工艺参数,并利用有限元数值软件对其成形过程进行模拟.结果 各因素对曲面凸台圆角减薄的影响主次顺序为:凸模下压速度、摩擦因数、凸模与顶出块夹紧力,最优成形工艺参数组合为:下压速度为10 mm/s、摩擦因数为0.12、夹紧力为40 kN.由等效应变结果分析得出,随着变形量的增加,左侧翻边曲面等效应变分布大于右侧,两侧翻边曲面交接处也积累了较大应变.实际成形件的最大减薄率为凸台位置的17.1％,满足生产要求.结论 在最优工艺参数下生产出合格隔热件,实际成形件的减薄情况与模拟结果基本一致,验证了模具设计和模拟的准确性,这对于成形结构复杂的异形构件具有一定的指导意义.     

基于数值模拟的冷拉钢丝表面精度Ra的优化

为研究拉拔参数对冷拉钢丝表面精度Ra的影响,采用有限元软件MARC建立了钢丝表面微观形态的分析模型,对钢丝拉拔过程进行了模拟仿真,利用正交试验设计法研究了主要拉拔参数(拉拔速度v、过渡圆弧半径R、模具定径带长度L、模具入模角α、摩擦系数μ)对钢丝成形表面精度Ra的影响,并对模拟结果进行了极差分析和方差分析.结果表明:冷拉钢丝在一定断面缩减率的条件下Ra最佳的拉拔参数组合为v=30 mm/s、R=1 mm、L=3 mm、α=11°、μ=0.4);各因素对Ra的影响程度次序为B(R)C(L)E(μ)A(v)D(α);随v和L的增大Ra先减少后增大,α、R及μ对Ra的影响并无明显规律.在此基础上对优化方案进行模拟仿真,发现钢丝表面粗糙度有了显著改善,这表明正交试验设计对冷拉钢丝表面精度优化的有效性.     

汽车侧围前连接板冲压成形质量优化研究

针对汽车侧围前连接板的成形质量缺陷问题,本文通过有限元软件分析工艺参数对成形质量的影响,并完成拉延模面的回弹补偿。首先,以最大减薄率和最大回弹量为评价目标,采用正交实验对压边力、模具间隙、冲压速度和摩擦系数4个工艺参数进行分析,获得影响成形质量最大的因素为压边力,冲压速度次之,确定最优工艺参数为:压边力300 kN、模具间隙1.20 mm、冲压速度90 mm/s、摩擦系数0.11;其次,采用节点位移法对拉延模面进行2次回弹补偿,将零件的回弹量控制在允许范围内;最后,将最优工艺参数和回弹补偿面应用于现场实验,测得试模件的最大减薄率为14.64%,最大正负回弹量为1.254 4 mm/-1.327 0 mm,试模件的最大减薄率和最大回弹量均在允许范围内,实验结果与仿真分析结果相近,验证了本实验方案的可行性。研究表明:通过优化工艺参数能够有效控制减薄、起皱和拉延不足等缺陷,并能够在一定程度上减少回弹量;通过对拉延模进行回弹补偿可以有效地控制回弹量。     

基于Deform和响应曲面法的钢丝拉拔工艺优化

目的对钢丝拉拔过程的成形质量和拉拔力同时进行优化。方法通过Deform-3D软件建立钢丝拉拔第一道次的有限元分析模型,并验证其可靠性。结合建立的有限元模型,采用正交试验设计,寻找钢丝拉拔过程的显著性影响因素,再以显著性因素为变量,以成形质量指标(文中定义为不均匀系数N)和拉拔力P为响应,建立响应曲面模型,对工艺参数进行优化。结果通过正交试验设计分析发现,模具半锥角和压缩率既是不均匀系数N的显著性影响因素,又是拉拔力P的显著性影响因素;通过分析建立的响应曲面模型发现,单独优化一个指标时,会劣化另一个指标,综合考虑两个指标,得到的较优的工艺参数为模具半锥角5°,压缩率17.65%,此时不均匀系数N为0.247,拉拔力P为2593.77N。结论经过验证,建立的有限元模型和响应曲面模型均具有可靠性,可用于钢丝拉拔工艺的研究和优化。     

电动汽车电池包铝合金顶盖拉延成形分析及工艺参数优化

目的 解决轻薄铝合金电池包顶盖拉延成形过程中的工艺质量问题。方法 采用Autoform软件对顶盖拉延成形过程进行仿真分析,在单一条件下分别研究压边力、冲压速度、凹凸模间隙以及摩擦因数对顶盖拉延成形规律的影响。以最大减薄率和最大增厚率为评价指标,通过对以上4个工艺参数进行正交实验优化,且采用正交综合评分法分析实验数据,得出影响评价指标的4个因素的主次关系(冲压速度>压边力>摩擦因数>凹凸模间隙)以及最优工艺参数。结果 最优工艺参数如下:冲压速度为1000 mm/s,压边力为800 kN,摩擦因数为0.12,凹凸模间隙为1.26 mm。采用最优工艺参数进行拉延成形实验验证,实验后测量实物顶盖,实际最大减薄率为14.3%,最大增厚率为8.6%。与仿真值比较,顶盖的实际最大减薄率误差为8.9%、最大增厚率误差为7.5%,实际值与仿真值之间的误差合理。结论 在实际生产中,该工艺参数优化的方法能够为后续轻薄铝合金顶盖的生产制造提供有价值的指导。     

基于克里金模型和NSGA-Ⅱ的汽车内板成形参数优化

目的 针对某汽车后背门内板冲压成形过程中易产生破裂和回弹等问题,提出了一种基于克里金模型和多目标遗传算法的优化策略。方法 研究摩擦因数、压边力和拉延筋阻力系数对产品最大减薄率和最大回弹量的影响,并确定了参数的拉丁超立方抽样区间。在抽样区间内抽取25组样本,利用数值模拟获取样本的最大减薄率和最大回弹量,并用克里金模型构建样本的响应模型。采用多目标遗传算法对响应模型进行优化,得到了帕累托前沿最优解集;从最优解集中选取了一组合适的工艺参数作为最优解,并进行了数值模拟和生产试制。结果 拉延筋阻力系数、压边力和摩擦因数对最大回弹量和最大减薄率的影响都具有较大的非线性,最大减薄率和最大回弹量存在一定的矛盾关系。综合考虑回弹量和减薄率得到的最优参数如下：摩擦因数为0.12、压边力为1 700 kN、拉延筋阻力系数为0.26。数值仿真结果表明,使用优化后的工艺参数能够避免板料开裂并且显著降低回弹量。生产试制结果表明,使用优化后的工艺参数能够得到表面质量良好、无破裂及起皱缺陷的零件。结论 应用该优化策略能够控制成形质量、减少试模次数、降低生产成本。     

6061铝合金飞机溢油口拉深成形研究

目的 掌握深腔薄壁溢油口拉深成形工艺,解决拉深成形过程中起皱和破裂问题,研究各参数对拉深成形的影响规律,最终成形出合格产品。方法 以6061铝合金飞机溢油口为主要研究对象,采用Dynaform有限元数值模拟软件建立有限元模型,分析成对拉深成形对材料流动的影响并与单一拉深成形进行对比,通过改变毛坯外形尺寸、凹凸模间隙和压边力等参数进行拉深成形模拟试验研究,最终通过拉深成形试验验证成形方法及各参数设置的合理性。结果 成对拉深成形能限制单一拉深成形圆弧开口位置材料收缩,改善开口处起皱和变形缺料的现象。随着凹凸模间隙的增大,最大减薄率逐渐降低而后升高,最佳成形凹凸模间隙为1.05t;随着压边力的增大,最大减薄率逐渐升高,最大增厚率逐渐降低,最佳成形压边力为50 kN;凹模圆角半径小于7 mm 时,板料最大减薄率逐渐减小,半径为4 mm时,最大减薄率下降最快,半径在7~8 mm范围内,板料最大减薄率趋于平稳,最佳成形凹模圆角半径为7 mm。结论 模拟得到了毛坯外形尺寸、凹凸模间隙和压边力等参数对拉深成形的影响规律,最终制造出了满足设计要求的产品,验证了各参数设置的合理性。     

某大曲率薄壁件成形参数优化

目的 根据某大曲率薄壁件形状需求,以最大减薄率为优化目标,采用数值模拟与响应面相结合的方法对其成形的工艺参数进行优化,以得到合格的零件产品。方法 首先,研究压边力、拉延筋阻力、摩擦因数、冲压速度等单因素参数对最大减薄率的影响规律。根据规律变化确定正交试验的参数范围,并对正交试验结果进行极差分析,确定本次板料冲压成形有限元分析的工艺参数对最大减薄率影响大小的排序为：摩擦因数>压边力>拉延筋阻力百分比>冲压速度;根据极差分析结果,选定对最大减薄率影响较小的冲压速度为3 000 mm/s、其他3个工艺参数为变量进行再次优化,以摩擦因数、压边力、拉延筋阻力为优化对象建立响应面。结果 通过响应面预测结果可知,摩擦因数为0.09、压边力为409.730 kN、拉延筋阻力为32.384%时,最大减薄率得到最小值7.926%。将该组工艺参数进行模拟,得到最大减薄率为9.40%,与响应面预测值仅相差1.474%,相对误差率为15.68%。结论 经过试验验证,试验和优化的数值分析结果吻合较好,最大减薄率仅相差0.60%,证明了该方法的可行性。     

超声振动冷拔传动轴有限元仿真分析

目的研究超声振动在冷拔传动轴过程中起到的减摩降载作用。方法以冷拔45钢50mm的传动轴为研究对象,利用ANSYS软件分别对常规和超声振动冷拔传动轴过程进行了有限元模拟仿真,对冷拔力和接触压应力进行了分析。结果超声振动冷拔的冷拔力和接触压应力都不同程度地减小。结论与常规冷拔过程相比,超声振动冷拔可以有效地减小冷拔力和摩擦力,有利于提高表面综合性能。     

固定短芯棒拔管残余应力分布规律研究

为了研究固定短芯棒拔管残余应力的产生机理和分布规律,采用弹塑性有限元法模拟拉拔过程,讨论模具形状参数、拉拔变形参数、摩擦条件对残余应力的影响.结果表明,当模具半锥角α较小时,随着α的增加,残余应力增大;在减径率εs一定的条件下,随着减壁量ΔS的增加,钢管内外表面的残余应力逐渐减小,在ΔS一定而εs增加时,内外表面上残余应力呈先增大后减小变化趋势;同时,轴向残余应力随着拉拔速度v和摩擦系数μ的增加而增大.     

Effect of Punch Geometry in the Deep Drawing Process of Aluminium

The effect of different punches head profile on deep drawing of 5005 H34 Aluminium circular blanks to manufacture a cup-shape product were studied. Experiments were conducted by a 150 ton hydraulic press with using different punches geometry and lubricants viscosity. The drawing force, blank holder pressure, and movement of the punch were measured during experiments to monitor effects of various manufacturing parameters during the drawing process. The surface finish and dimensions of all cups were determined after drawing processes. The geometry of the punch influences the friction force between the blank and punch, and consequently the stretching bottom surface of the cup. The Flat punch geometry produced cups with better surface finish, higher drawing force, and thinner cup wall thickness in comparison to other punches geometry. The Bore punch geometry enhances the stretching of the bottom part of the cup. The presence of lubricant in the process improves the stretching of bottom part of a cup for all punches profile.     

薄壁异形方半管零件充液成形工艺研究

目的 为解决薄壁异形方半管零件成形过程中易起皱、破裂、形状冻结性不佳的难题,引入充液成形工艺。为进一步掌握不同工艺参数对零件成形性能的影响,对薄壁异形方半管零件的充液成形过程进行研究。方法 以液室压力、压边力、拉深深度、摩擦因数等工艺参数为影响因子,进行正交试验,通过分析不同工艺参数下零件最大减薄率、贴模度、最大回弹量的变化规律,掌握充液成形工艺中不同工艺参数对零件起皱、破裂、形状冻结性的影响。结果 零件的破裂和起皱现象受液室压力影响显著,而零件的形状冻结性则受压边力影响较大。在数值模拟中,优化后的最优工艺参数如下:液室压力为15 MPa,压边力为120 kN,拉深深度为110 mm,摩擦因数为0.15。经模拟验证,与优化前相比,在该工艺参数下得到的结果更优,零件最大减薄率降低到11.5%、贴模度提高了0.212 mm、最大回弹量降低了1.955 mm。结论 通过模拟分析和现场试验验证可知,采用正交试验得到的最优工艺参数可以完成半管零件的成形,合理的工艺参数能有效抑制零件起皱、破裂、形状冻结性不佳的现象,从而提高半管零件的成形性能。     

一种椭圆模的建模及其拉拔力的解析研究

目的设计一种能提高产品成材率、降低能量消耗的拉拔模具,并对其进行工艺优化。方法在求解内部塑性变形功率过程中,利用线性的EA(平均面积)屈服准则,克服了非线性的Mises屈服准则积分困难的问题,得到了拉拔时内部塑性变形功率的解析表达式;通过对入口径向速度积分,得到了入口剪切功率的解析表达式;通过对速度场的曲线积分并利用积分中值定理,得到了摩擦功率的解析表达式;最终,基于上界法得到了拉拔力的解析表达式。结果通过有限元模拟,验证了拉拔力解析式的正确性,并与传统锥模进行了比较,最大应力降幅达到17.5%。结论利用椭圆曲线设计得到的椭圆模能够降低应力集中,提高拉拔制品的质量,减少拉拔时的能量消耗,可以为相关工程人员提供科学指导。     

Dry Sliding Friction Experiments at Elevated Velocities

Abstract: An enhancement of an existing tribometer device developed by Philippon et al. (2004, Wear 257 , 777–784) is presented in this work. This experimental device is made up of a dynamometer ring and a specific load sensor allowing to apply an apparent normal force on specimens and to measure frictional forces respectively. Problems such as static calibration of both distinct parts supported by conducted numerical simulations is given and described in detail. Further discussion, again supported by numerical analysis, validates the placing of the strain gauges and explains the problems of sensitivity of loading surface and cross‐sensitivity. The entire experimental setup is then discussed explaining the mounting of the strain gauges located on the tribometer device, showing the configuration of the Wheatstone quarter‐bridges, presenting the signal conditioning amplifier system and the digital oscilloscopes which all together create one uniform data acquisition system. The set up is adapted on a gas gun to carry the Steel 1080 on Steel VascoMax 300 experiments. The main set of experiments with sliding velocities varying from 10 to 60 m s^?1 are performed in the same tested setup. The recordings of normal and tangential forces leading to the friction coefficient determination are discussed. The values of dry friction coefficient μ according to the experimental parameters are in good agreement with those observed in the literature. Using this new configuration, the effects of the sliding velocity on the surface roughness changes and on the dry fiction coefficient are also investigated. Moreover, very interesting relations between wear and sliding velocity are observed.     

A study on the parametric optimization of drawing metal stamping process for aluminum alloy tailgate parts using response surface methodology

The tailgate-extension in a vehicle is a part that connects the upper and lower parts of the tailgate. Since this part does not require high strength, aluminum must be used in order to reduce the weight of the vehicle. However, when choosing aluminum, it is difficult to satisfy the shape quality with the existing manufacturing process. Therefore, this study was conducted for the purpose of optimizing the draw metal stamping process for the development of tailgate extensions for vehicles using aluminum. The response surface methodology was utilized to optimize the draw metal stamping process. The process design parameters were established as blank holding force, coefficient of friction and die speed. Finally, the reliability of the optimization process and finite element analysis was secured by conducting field experiments to review the derived optimal process conditions.     

Effects of deformation mode on surface roughening of austenitic stainless steels

Abstract

Free surface roughening of polycrystalline austenitic stainless steels during tensile and deep drawing deformation is investigated using scanning white light interferometry. A fractal analysis method is applied to analyse the surface profile data in two directions which are perpendicular to each other. It is shown that the surface profile is fractal within the length and is on the same order of magnitude as the grain size. The Hurst exponent H of the two deformation modes in different directions stabilises at H≈0·85. While the correlation lengths are different, the value in the longitudinal direction is about two times larger than the one in the transverse direction. The relationship between root mean square roughness and strain appears to be linear, and the roughening rate in tensile deformation is larger than the one in deep drawing deformation.     

高强钢控制臂件冲压工艺优化及稳健性分析

为获得高强钢控制臂件冲压工艺参数最优解,提高冲压工艺稳健性,基于6sigma稳健设计理论,采用数值模拟方法分析预成形模具间隙、局部翻边模间隙、预成形压边力、摩擦系数、板料轮廓尺寸等对拐角处材料减薄率的影响规律;将坯料位置、料片厚度、摩擦系数、塑性应变比、屈服强度、抗拉强度、板料尺寸等作为噪声变量输入,分析工艺的稳健性;根据敏感性分析结果,选用局部翻边模间隙、预成形模具间隙为变量,3σ水平设为目标,成形过程能力Cp值为1.0,进行优化计算;最后采用优化后的局部翻边模间隙、预成形模具间隙值,其他噪音变量不变,再次进行稳健性分析.研究发现,影响控制臂局部过度减薄甚至开裂的主要因素为预成形模具间隙及局部翻边模具间隙.根据模拟结果试模,零件的壁厚分布与模拟结果相比,最大误差小于6%.通过对关键参数的敏感性分析以及考虑噪声因素的稳健性分析,优化工艺参数后,成形质量水平提高,成形结果可靠.     

Axisymmetric fretting analysis in coated cylinder

Fretting is essentially a contact fatigue phenomenon, although bulk stresses and material properties contribute to final failure. The near surface state of stress developed under oscillatory contact between machine elements plays a major role in deciding the severity of fretting. It is possible to enhance tribological properties by coating the surface. There is rather scanty literature available on fretting analysis of coated components. Presence of such coatings has a large influence on the near surface state of stress. The effect of coatings on the severity of fretting is the focus of this paper. Results obtained for both hard and soft coatings are compared with the results obtained for the homogeneous case. The component geometry and loading are chosen to be cylindrical to enable 3D elastic axisymmetric fretting analysis. The results are compared with 2D models (strip and half-plane) to examine their utility and validity for understanding axisymmetric fretting. Contact pressure and frictional shear loading cases are solved separately and superposed appropriately depending on the coefficient of friction considered. Results for different values of coefficient of friction and elastic mismatch are illustrated through contour plots of stresses and strains. These results are expected to be helpful for identifying fretting failure zones and fracture mechanisms in coated components. Analytical results presented here could serve as useful benchmarks for calibrating numerical codes and experimental techniques.     

An experimental and numerical investigation on micro rolling for ultra-thin strip

The demand for miniaturized parts and miniaturized semi-finished products is increasing nowadays, because microforming processes can improve production rate and minimize material waste due to less forming passes. However, traditional macro metal forming processes and modelling cannot be simply scaled down to produce miniaturized micro parts. In this study, a 2-Hi micro rolling mill has been successfully built. Experimental and numerical investigations on the micro rolling process for ultra-thin SUS 304 stainless steel strip have been conducted. The experimental results show that the micro rolling deformation of ultra-thin strip is influenced by size effect which results from the specimen size difference and this size effect is embodied in the flow stress and the friction coefficient. Analytical and finite element (FE) models in describing size effect related phenomena, such as flow stress, friction, rolling force and deformation behaviour, are proposed. The material surface constraint and the material deformation mode are critical in determination of material flow stress curve. The analysis of surface roughness evolution with rolling conditions has also been performed. The identified analysis on deformation mechanics provides a basis for further exploration of the material behaviour in plastic deformation of micro scale and the development of micro scale products via micro rolling.     

Computation of the maximum torque of a cap liner using a power‐law friction and finite element analysis

In the ‘filled closed’ containers, the cap removal torque and the sealing of the contents are two crucial criteria in the closing quality, and the consumer perceives these two parameters as constituting a guarantee of packaging integrity. This work looks at the experimental study and the finite element analysis of the maximum torque of a metal cap with a liner over a glass bottle. For studying parameters influencing the cap removal torque (twist‐off torque), several experiments and simulations were conducted in order to evaluate the maximum torque of a loose crown cap. A test bench was built to measure the torque required to slide a cap liner on the top of a glass bottle, and the result of the experiment is compared with the predicted torque given by an axisymmetric finite element (FE) analysis. Since the behaviour of the cap liner is hyperelastic, compression and friction tests were conducted to evaluate the elastic properties and the non‐linear static friction behaviour of the elastomer seal. Contact regions, material non‐linear elasticity for the liner and large displacement options are included in the FE model in order to describe the evolution of the contact area and the distribution of contact pressure as a function of the applied force. The predicted maximum torque is then calculated by a numerical integration scheme over the contact surface, using an experimental coefficient of static friction as a function of the normal pressure. The predicted torque shows good agreement with that measured through experiments, thereby making it possible to understand the influence of the liner on the cap removal torque of a glass bottle. Copyright © 2010 John Wiley & Sons, Ltd.