压边力曲线对极限拉深高度的影响

运用ANSYS模拟软件对不同压边力曲线在筒形件拉深过程中的影响进行分析。分析发现,能够达到筒形件极限拉深高度,并且不发生起皱和破裂的压边力有一个数值范围,范围中的压边力曲线可以作任何类型的变化。但不同类型的压边力曲线愈接近压边力数值范围内的下限值,压边力曲线的变化幅度愈小,拉深件的危险断面处,厚度愈大或厚度减薄率愈小,厚度和厚度减薄率在数值上也愈趋于一致,对提高拉深过程的稳定性和拉深件质量最为有利。     

筒形件极限拉深系数的优化

基于筒形件拉深过程中危险断面的最大拉应力公式,建立了合理的数学模型,利用复合形法对筒形件极限拉深系数进行了优化,可提高拉深件的成形极限,减少拉深次数,对冲压生产与模具设计具有重要参考价值。     

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。     

半球形零件拉深成形

<正> 1 半球形零件拉深变形的基本特征 半球形件的拉深系数,对于任何直径均为定值,即m=0.71。虽然这个拉深系数要比筒形件的极限拉深系数大得多,但拉延过程中大部分毛坯材料处于悬空状态,因此,对半球形件拉深成形,要比圆筒形件困难得多,拉延过程要着重注意球头部胀形拉破和球壁部产生内皱这两种趋势。因为半球形件拉深变形与圆筒形件不同,筒形件拉深成形毛坯件的变形区域,仅仅局限于压边圈下面     

1Cr18Ni9Ti不锈钢筒形件拉深工艺

介绍了不锈钢筒形件拉深时,合理改变拉深凸、凹模间隙,采用新的润滑剂和润滑方法,在取消或改变热处理工序的情况下,拉深出表面质量理想的不锈钢筒形件。     

筒形件拉深压边力区间的理论确定

本文建立了筒形件拉深的力学模型,运用能量法推导出筒形件拉深过程中抑制起皱的最小压边力与拉深高度的关系,通过压边力诱发的拉深力和材料的承受极限,推导出抑制拉裂的最大压边力与拉深高度的关系。通过案例,给出了筒形件拉深的合适压边力区间。     

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.     

筒形件无压边圈拉深工艺参数优化设计

通过对筒形件极限拉深系数的影响因素进行分析，确定合适的凸凹模圆角半径是提高拉深件质量的重要途径，将塑性理论和优化算法相结合，以筒形件达到最小的极限拉深系数为优化目标，对筒形件无压边圈拉深工艺参数优化设计进行了研究。并且通过具体算例证明了所采用的优化模型及算法是有效的。     

厚壁筒形件拉深筒壁变薄环的产生与消除

以汽车发动机制动室缸体拉深成形为例，分析了厚壁筒形件拉深时筒壁产生变薄环的原因，介绍了采用变薄拉深工艺将其消除的方法。该方法对内壁质量要求较高的筒形件成形具有普遍的实用意义。     

椭球底直筒形件拉深成形极限分析

通过对椭球底直筒形件的拉深过程进行应力应变分析,推出该类零件的变形机理,得出该类零件成形的拉深系数和相对高度的关系,并通过试验进一步验证其正确性。     

筒形件深拉伸褶皱预防方法的研究

分析轴向弯矩致使筒形件深拉伸褶皱产生的机理,得到材料褶皱发生的临界状态的平衡式。根据板料产生皱褶的临界相对厚度,讨论在不压料条件下板料的屈服强度σs、弹性模量E、泊松比μ、硬化指数n和拉深系数m等因素对筒形件法兰褶皱产生的影响。讨论在压料条件下,模具参数、拉深工况、板料初始几何参数、材料性能参数等因素对抑制法兰褶皱的临界压边力的影响,制定出防止法兰褶皱产生的工艺措施。     

人工神经网络在拉深系数选取中的应用

应用人工神经网络技术建立了多次拉深工艺中相对厚度值与极限拉深系数之间的BP网络模型 ,并用C语言编制了应用软件 ,将程序运行的结果与资料数据进行了比较和分析 ,表明人工神经网络应用于拉深系数方面是可行的     

连杆出件机构运动优化设计

概述了冷轧薄板的冲压性能的评价指标，介绍了冷轧薄板的化学成分、织构和晶粒尺寸、表面质量、厚度尺寸公差、冷轧工艺条件、拉伸试验值对冷轧薄板冲压性能的影响，并应用ANSYS／LS-DYNA软件对板材弯曲成形过程进行了模拟。了解这些影响因素对冲压生产具有一定的指导作用。     

Forming limits of nickel coating on right region

The forming limits of nickel coating on the right region were studied, so as to direct the preparation of the material and help the production of workpieces. The electrodeposited nickel coating was prepared on steel substrate to form advanced structures, and its plastic instability was investigated by the Swift Plastic Instability Theory. By using the compound law for laminated sheet metals, explicit equations for the calculation of the instable eigen values were deduced. The forming limit diagrams of the nickel coating on the right region were plotted. It is exhibited that the forming limit of the coating sheet is between the forming limits of the individual nickel coating and steel substrate. The forming limit of the nickel coating is not so good as that of the steel substrate, and the forming limit strain of the coating sheet tends to diminish with the increase of thickness of the coating. The greater the normal anisotropic coefficient of the materials is, the better the forming limit is.     

Numerical simulation of two-stage deep drawing of complex-shaped parts

1　INTRODUCTIONInrecentyears ,withtherapiddevelopmentofcomputersoftwareandhardware ,andtheintersectionandcombinationofcomputertechnology ,graphics ,mechanicsandprocessengineering ,thecomputeraid edengineering(CAE)technologybasedonnumericalsimulationhasbeenwidelyappliedinthesheetmetalformingfield[1,2 ] .Nevertheless ,untilnow ,thenu mericalsimulationisconfinedtosimulatesomebasicmodesofdeformationsuchasbending ,deepdraw ing ,bulgingandflanging .Forthedeformationofcomplexwork pieces ,forexa…     

Critical sheet thickness for weld nugget growth during resistance spot welding of three‐steel sheets

Abstract

One of the most important issues in resistance spot welding of three‐sheet stack joints is the insufficient growth of the weld nugget, which may cause problems in places needing larger weld nuggets (i.e. sheet/sheet interface). In this paper, the effect of sheet thickness on the pattern of weld nugget development during resistance spot welding of three‐steel sheets of equal thickness is studied. Results showed that there is a critical sheet thickness of 1·5?mm at which the fusion zone size at the sheet/sheet interface is nearly equal to the fusion zone size at the geometrical centre of the joint. Increasing the sheet thickness beyond the critical size causes a shift in the location of weld nugget formation from the geometrical centre to the sheet/sheet interfaces. Below the critical sheet thickness, the weld nugget growth in the geometrical centre of the joint is higher than that in the sheet/sheet interface.     

先进高强钢电阻点焊接头的断裂模式分析与预测

研究了先进高强钢(advanced high strength steel, AHSS)两层板电阻点焊接头的断裂模式,不同的断裂模式会影响点焊接头断裂时的机理、力学性能及断裂位置,基于不同组合下的临界熔核尺寸、最大载荷、断口宏观形貌、初始断裂位置、宏观金相组织以及微观硬度曲线等试验结果,阐明了板材厚度和板材强度两类因素对于断裂模式的影响规律. 结果表明,板材强度因素会直接影响断裂模式、初始断裂位置以及最大载荷;板材厚度因素影响断裂模式但不改变初始断裂位置及最大载荷. 临界熔核尺寸的影响因素有板材厚度、板材强度、熔核中缺陷以及拔出断裂位置距熔合线的距离. 在此基础上,文中提出了临界熔核尺寸(D_CR)的预测模型及预测方法,该方法与试验值符合较好,为实际工业应用中的临界熔核尺寸判定提供了理论依据.     

1060铝板单道次渐进成形圆孔翻边临界翻边参数的数值模拟研究

利用DYNAFORM软件构建有限元模型,对1060铝板单道次渐进成形圆孔翻边进行了研究,分析了预制孔径大小对壁厚分布规律的影响。结果表明:预制孔径过小会导致翻边出现中部减薄区;增大预制孔径,壁厚呈线性变化区和均匀分布区,中部减薄现象消除;预制孔径较大时,翻边壁厚线性分布。探究了在5种板料厚度下,不同翻边孔径对应的临界预制孔径,以及临界预制孔径对应的翻边高度,并将翻边孔径和临界预制孔径以及临界预制孔径和翻边高度之间的关系拟合成参数化方程。发现增加板料厚度,临界预制孔径减小,翻边件的成形极限增大。     

PREDICTION OF PATH-DEPENDENT FAILURE IN ALUMINUM SHEET METALS UNDER FORMING OPERATIONS

1.IntroductionGurson[1]developedayieldcriterionforvoidedmaterialsofwhichthematricesaremodeledbythevonMisesyieldcriterion.Liaoetal.[2]developedamacroscopicyieldcriterionthatcanaccountforthematrixplasticanisotropycharacterizedbyHill'squadraticanisotropicyieldcriterion.Theaimofthisworkistodevelopafailurepredictionmethodologythatcanbeusedtopredictfailureinanisotropic,rate--sensitivesheetmetalsunderformingprocesses.TheMarciniak--Kuczynskiapproach[3]isadoptedherebyassumingaslightlyhighervoidvolume…     

Effect of strain gradient and curvature on forming limit diagrams for anisotropic sheets

Recent work on sheet metal formability had shown that the position of forming limit diagrams (FLDs) in punch stretching is higher than that in in-plane stretching because of a strain gradient effect resulting from bending a flat sheet into a curved sheet by punch stretching. To our knowledge, none of the developed theoretical models in the study of localized necking can be used to predict this phenomenon accurately so far. In this study, a new model, using Barlat and Lian’s new nonquadratic anisotropic yield criterion, is proposed by introducing a strain gradient term in the constitutive equation to consider the effect of the first order strain gradient (curvature), in the thickness direction resulting from bending, on the localized necking in anisotropic sheets. The developed model is used to study the effects of curvature on FLDs and to predict FLDs in punch stretching and inplane stretching for various materials. It is found that the theoretical predicted results are in good agreement with experimental data.