双重拉深筋力能特性的实验研究

以双重拉深筋中最常见的双圆筋为对象，设计了专门的实验装置。通过大量实验，对拉深筋的阻力、压筋力和夹持力与其高度及各圆角半径间的关系进行了系统的研究。研究表明，拉深筋的阻力、压筋力和夹持力主要受其高度的影响，而拉深筋圆角半径的影响相对较弱；内侧拉深筋高度对拉深筋阻力的影响大于对压筋力与夹持力的影响，外侧拉深筋则相反，对压筋力与夹持力的影响较大。同时对双拉深筋与单拉深筋的力能特点进行了对比，指出双拉深筋的阻力可达到单筋的2倍以上，而压筋力和夹持力则明显大于单筋的2倍。提出了双拉深筋的设计调整原则。给出了双拉深筋的高度和圆角半径的合理取值范围。     

基于板料后续性能的拉深筋结构参数试验研究

布置结构合理的拉深筋,可以有效地提高零件的成形质量.为制定合理的拉深筋结构设计原则,以拉深筋阻力和通过拉深筋后板料的后续成形性能为试验指标,就半圆形拉深筋结构参数对各试验指标的影响进行正交试验研究,讨论拉深筋结构对板料后续性能的影响,分析拉深筋阻力与板料后续性能的关系.研究结果表明,不同的拉深筋结构参数组合,对板料可能产生相近的阻力效果,但是后续性能却不一定相同;在拉深筋结构参数中,筋圆角半径R对拉深筋阻力及板料后续性能的影响最显著,凹槽圆角半径r1、r2的影响最弱,而且程度相当.在此基础上,根据试验数据及分析结果给出综合考虑拉深筋阻力和板料后续成形性能的拉深筋结构参数的设计原则,此原则依据拉深件的成形深度来设计拉深筋参数,对大型覆盖件拉深模具的设计具有积极的指导作用.     

TRIP600高强度钢板成形U型件回弹控制研究

针对高强度钢板冲压成形过程中普遍存在的精度问题,以U型件为研究对象,在分析TRIP600高强度钢板材料性能的基础上,分别研究了U型件成形时压边力和拉深筋的工作圆角半径对回弹的影响。结果表明,TRIP600高强度钢板在成形U型件时,回弹随着压边力的增加而发生有限减小;拉深筋工作圆角半径越大,回弹值越大。     

镀锌钢板圆筒拉深件表面损伤行为的研究

采用不同凹模圆角半径下的圆筒拉深实验,对热镀锌钢板DC53D+Z和合金化热镀锌钢板DC53D+ZF拉深成形工件表面损伤行为进行研究。实验结果表明,在不同凹模圆角半径下,DC53D+Z表面损伤有熨平纹和表面划痕两种形式,而DC53D+ZF的表面损伤则有镀层龟裂和表面划痕两种形式;随着凹模圆角半径的减小,DC53D+Z熨平纹现象增加,DC53D+ZF垂直拉深方向的裂纹增加。利用ANSYS/LS-DYNA有限元分析软件,建立基于界面结合的镀锌板圆筒拉深有限元模型,对镀锌钢板拉深过程进行模拟。模拟结果表明,随着凹模圆角半径的减小,镀层沿拉深方向的第一主应变增加。数值模拟结果与实验结果对比表明,镀层沿拉深方向的第一主应变是影响表面损伤程度的主要原因。     

凹模圆角半径对拉深件的影响与极值

拉深凹模、凸模圆角半径对制件质量和拉深工作影响很大,其中尤以凹模圆角半径r_d为甚。现有各种冲压资料手册中,拉深凹模圆角半径r_d值往往只根据拉深中材料所承受的变形拉力结合产品情况而制订并推荐的,对于质量要求较高的制体来说,就显得有点勉强。至于凹模圆角半径如何左右制件的成形情况、形状和直径、高度、厚度等尺寸精度,如何影响制件的质量等问题的系统分析和探讨更少,本文就其试论之,供参考。     

解决拉深件开裂质量问题的途径

拉深开裂是拉深产生的主要质量问题之一,适当地增大凸、凹模圆角半径,增大模具间隙,降低拉深力,增加拉深次数可以避免拉裂的产生.本文在分析了毛坯与模具接触面之间的摩擦对拉深开裂的影响之后,具体介绍了一种用高分子薄膜覆盖于模具表面防止拉深开裂、提高拉深件表面质量和劳动生产率的生产实例.     

波形套的试验研究

基于前期提出的波形套缩径-胀形复合成形方法，设计了5套模具，试制出不同规格的波形套。测出波形套的工作特性曲线，揭示出几何参数对其特性曲线的影响规律：在最大外径不变时，随着波纹圆角半径r0的增大，特性曲线中弹性区的斜率增大，进入塑性变形所需要的压力亦增大；在波纹圆角半径r0不变时，随着波形套最大外径的增大。特性曲线中弹性变形区的斜率减小，进入塑性变性所需要的压力亦减小。为进一步给出波形套的设计方法奠定了基础。     

剪切间隙对不锈钢板材分切断面质量的影响

通过斜刃横剪分切加工实验,研究了剪切间隙对304不锈钢板材分切断面形貌特征、加工硬化及剪切力的影响.结果 表明,剪切间隙直接影响了分切断面特征和加工硬化程度,随着剪切间隙的增大,分切断面平整性变差,塌角增大,剪切带高度先增大后减小,在相对剪切间隙为4％时能得到较好的分切断面质量;分切断面边缘最大硬度先增大后减小,硬化层深度不断增大.分切断面形貌与加工硬化密切相关,沿板材剪切方向的硬度值先增大后减小,在剪切带与断裂带交界处附近加工硬化最大.剪切力的变化趋势反映了剪切间隙的影响,在间隙过小或过大时,板材易产生裂纹而提早发生断裂,刃口附近板材变形程度减小,使剪切带高度、加工硬化程度及Z方向剪切力减小.     

筒形件颗粒软凹模拉深成形试验研究

分析了颗粒软凹模成形的工艺特点,设计了筒形件颗粒软凹模拉深成形试验模具,对筒形件颗粒软凹模拉深成形进行了试验研究,成形出了质量良好的圆筒零件.颗粒软凹模拉深成形零件各部分的厚度均减小,而且随着拉深高度的增加,减薄量增大.与刚性模具拉深工艺相比,该工艺可有效提高板材的拉深成形极限.颗粒软凹模拉深成形和刚性模具拉深筒形件各部位表面微观形貌的对比分析表明:颗粒软凹模成形可抑制凸模圆角区域微裂纹的产生.     

铝-钢复层板材的力学性能与拉深成形性能

对一种国产铝-钢复层板材的力学性能及拉深成形性能进行了试验研究。研究了退火温度对该材料力学性能的影响及两种板材复合后表现出来的各向异性。根据圆筒形拉深试验的结果,讲座了凸模圆角半径R p对板材极限拉深比R max的影响并由此发现铝-钢复层板材R max值与铝或钢所处的内外面位置有关。分析了造成这种现象的原因。     

两种强化模型在拉伸筋阻力计算中的比较

将等向强化模型与运动中化模型分别引入逐级更新Ｌａｇｒａｎｇｅ有限元列式,采用八节点平面 应变单元,对拉伸筋阻力进行了数值计算,并将两种模型的计算结果进行了比较与讨论,运动强化模型更好地反映了板料在拉伸筋处的弯曲反弯过程,可以更准确地预测拉伸筋阻力。     

拉伸筋阻力的一种简便解析模型

采用平面应变假设,通过对板料在拉伸筋处变形过程的分析,并考虑了材料的各向异性、应变速率敏感与包辛格效应,推导出一种计算拉伸筋阻力的简便计算解析模型。将计算结果与有关试验结果进行了对比,证明了该计算方法的有效性。     

圆盘剪分切工艺有限元仿真研究

基于金属板材圆盘剪分切工艺,应用DEFORM-2D仿真软件建立了金属板材的圆盘剪分切模型,采用Oyane韧性断裂准则仿真研究了304不锈钢板材圆盘剪分切加工过程,探讨了圆盘刀轴向间隙、刃角半径、压板力、板厚等工艺参数对分切断面形貌特征的影响规律。轴向间隙是影响分切断面形貌特征的主要因素,随着轴向间隙的增大,塌角高度增大,剪切带高度减小。刃角半径对断面的塌角高度、剪切带高度影响不大,对毛刺高度影响最大,随着刃角半径增大,毛刺高度增大。压板力对断面的塌角高度、剪切带高度影响很小,对毛刺影响较大,随着压板力增大,毛刺高度有下降趋势。板厚对分切断面塌角和毛刺影响不大,对剪切带高度影响很大,随着板厚的增大,剪切带高度增大。     

基于有限元逆算法的拉深筋工艺设计和优化

汽车覆盖件拉深成形中，一般通过设置适当的拉深筋控制成形过程中的板料塑性流动规律来提高覆盖件成形质量。针对覆盖件工艺设计需求，提出一种基于有限元逆算法的拉深筋工艺优化算法。该算法以灵敏度优化方法为基础，考虑了板料的成形度、破裂和起皱等成形缺陷。在板料成形模拟FASTAMP系统中，开发了拉深筋优化模块，并以实际覆盖件为例，验证了该算法能快速准确地模拟等效拉深筋力的布置情况以及优化板料的成形性。     

The Friction and Wear of Metals and Binary Alloys in Contact with an Abrasive Grit of Single-Crystal Silicon Carbide

Sliding friction experiments were conducted with various metals and iron-base binary alloys (alloying elements Ti, Cr, Mn, Ni, Rh, and W) in contact with single-crystal silicon carbide riders. Results indicate that the coefficient of friction and groove height (corresponding to the wear volume) decrease linearly as the shear strength of the bulk metal increases. The coefficient of friction and groove height generally decrease with an increase in solute content of binary alloys. A separate correlation exists between the solute to iron atomic radius ratio and the decreasing rates of change of coefficient of friction and groove height with increasing solute content. These rates of change ate minimum at a solute to iron radius ratio of unity. They increase as the atomic radius ratio increases or decreases linearly from unity. The correlations indicate that atomic size is an important parameter in controlling friction and wear of alloys.     

Analysis of drawbead process by static-explicit finite element method

The problem analyzed here is a sheet metal forming process which requires a drawbead. The drawbead provides the sheet metal enough tension to be deformed plastically along the punch face and consequently, ensures a proper shape of final products by fixing the sheet to the die. Therefore, the optimum design of drawbead is indispensable in obtaining the desired formability. A static-explicit Finite element analysis is carried out to provide a perspective tool for designing the drawbead. The finite element formulation is constructed from static equilibrium equation and takes into account the boundary condition that involves a proper contact condition. The deformation behavior of sheet material is formulated by the elastic-plastic constitutive equation. The finite element formulation has been solved based on an existing method that is called the static-explicit method. The main features of the static-explicit method are first that there is no convergence problem. Second, the problem of contact and friction is easily solved by application of very small time interval. During the analysis of drawbead processes, the strain distribution and the drawing force on drawbead can be analyzed. And the effects of bead shape and number of beads on sheet forming processes were investigated. The results of the static explicit analysis of drawbead processes show no convergence problem and comparatively accurate results even though severe high geometric and contact-friction nonlinearity. Moreover, the computational results of a static-explicit finite element analysis can supply very valuable information for designing the drawbead process in which the defects of final sheet product can be removed.     

Studying Formability Limits By Combining Conventional and Incremental Sheet Forming Process

In this work it is assessed the potential of combining conventional and incremental sheet forming processes in a same sheet of metal.This so-called hybrid forming approach is performed through the manufacture of a pre-forming by conventional forming,followed by incremental sheet forming.The main objective is analyzing strain evolution.The pre-forming induced in the conventional forming stage will determine the strain paths,directly influencing the strains produced by the incremental process.To conduct the study,in the conventional processes,strains were imposed in three different ways with distinct true strains.At the incremental stage,the pyramid strategy was adopted with differ-ent wall slopes.From the experiments,the true strains and the final geometries were analyzed.Numerical simulation was also employed for the sake of comparison and correlation with the measured data.It could be observed that single-stretch pre-strain was directly proportional to the maximum incremental strains achieved,whereas samples subjected to biaxial pre-strain influenced the formability according to the degree of pre-strain applied.Pre-strain driven by the prior deep-drawing operation did not result,in this particular geometry,in increased formability.     

基于Dynaform对拉延筋在板材拉深中的应用研究

板材冲压工艺应用十分广泛,如何提高板材在拉深工艺中的成形质量,是从事冲压的技术人员和研究人员一直关注的热点问题。在板材拉深成形控制中设置拉延筋是既经济灵活又广泛运用的方法。在参考国内外资料的基础上,应用CAE中的专用分析软件Dynaform分别模拟了有拉延筋和无拉延筋存在的板材拉深成形过程,并对各自的数值模拟的结果进行对比分析,得出了拉延筋可以更有效地提高拉延件的成形质量的结论。