【作者】 华俊杰；

【导师】 周杰；

【作者基本信息】 重庆大学 ， 材料加工工程， 2010， 硕士

【摘要】 板料成形是一种十分重要的金属塑性加工方法,被广泛应用于汽车、航空、航天等领域。汽车工业在国民经济中占有重要地位,它是衡量一个国家工业水平的重要标志。近年来世界汽车工业面临三大问题:能源、公害和安全,这些要求使得在车身上采用高强度钢板代替普通钢板成为必然趋势。高强度钢板可以减轻汽车重量并增加安全性,但由于其自身材料特性,存在的最大问题是成形性能差和回弹较大。当今国内外大多数学者主要采用变压边力技术、热成形和液压成形技术来控制高强度钢板成形质量。本文提出一种新的成形工艺方法——可控拉深筋技术,以提高高强度钢板成形性能。目前国内尚没有相关的研究,国外仅美国密西根科技大学对可控拉深筋技术有初步研究。本文首先分析半圆形直球头固定拉深筋与间断式拉深筋对盒形件拉深成形的影响规律,从而提出通过可控拉深筋技术来提高高强度钢板成形性能。利用数值模拟软件Dynaform建立可控拉深筋JAC590Y高强度钢板盒形件的拉深成形有限元模型,设计了6种不同截面和端部形状的可控拉深筋及3种不同拉深筋运动路径方式。采用正交设计确定试验方案,以高强度钢板成形极限图作为评价标准并结合最优化理论,分析不同可控拉深筋及其运动路径对盒形件成形性能的影响。得到以下结论:获得了不同可控拉深筋路径下的极限拉深深度,确定了路径2即上升——停止——下降为最优运动路径及其最优组合,其中6种不同可控拉深筋最优路径下各试验组得到的最大极限拉深筋深度与固定5mm拉深筋相比分别提高了25%、10.34%、31.51%、12.85%、20.80%、10.01%,并通过极差分析得到最优路径下主要影响因子为H1和H2。在最优路径下,6种可控拉深筋作用下的凸模拉深力和可控拉深筋阻力从拉深成形开始增加速率大到随后增加速率小,最后开始下降。研究表明不同可控拉深筋路径对盒形件侧壁和凹模圆角部位的应变路径影响不大,而对凸模圆角处的影响较为显著。最后通过GA-BP神经网络与拉丁超立方抽样法相结合构建了可控拉深筋主要影响因子H1和H2与极限拉深深度之间的响应面。为了验证有限元结果的正确性,从而设计实验装置来进行检验和分析。基于可控拉深筋运动原理设计了可控拉深筋高强度钢板盒形件拉深实验装置,该实验装置分为模具结构、杠杆机构、液压及电气控制系统四部分。最终将可控拉深筋成形规律运用到高强度钢板汽车覆盖件的拉深成形模拟中,以汽车引擎盖边板为研究对象,同样选择JAC590Y高强度钢板。通过模拟结果分析得到零件最小厚度值的变化幅度最为明显。然后选取两不同试验组下整个零件厚度分布进行了分析,验证了可控拉深筋对零件最小壁厚值变化影响显著。通过对零件最小厚度平均值进行极差分析得到因子H2的影响最为显著,同时得到可控拉深筋拉深成形的最佳运动路径水平组合。建立GA-BP神经网络来研究因子H2对零件成形的影响规律,建立其影响规律曲线及相应的回归方程。更多还原

【Abstract】 Sheet metal forming is a very important plastic working technology which has been widely used in such industrial domains as motorcar, aviation and spaceflight, etc.. Automotive industry plays an important role in China, and it’s an important marker to measure the industrial level of a country. In recent years, there are three major issues of energy, pollution and safety in the all world’s automotive industry. So it’s an inevitable trend to use High-Strength Steel(HSS) instead of common plate. HSS can reduce vehicle weight and increase security, but because of its own material properties, there is the biggest problem of poor formability and more springback. At present, most domestic and foreign scholars mainly control the forming quality of HSS by means of variable holder force technology、thermal and hydraulic forming technology. So this paper puts forward a new forming technological method——the controllable drawbead(CD) technology in order to improve the formability of HSS. Now there is not yet relevant research in China, and only Michigan Technological University has been preliminary studying the CD technology.Firstly, the CD technology was put forward by the laws of box drawing forming with semicircle straight fix and discontinuous drawbead in order to improve the formability of HSS. The finite element model of CD-JAC590Y HSS box deep drawing was established by numerical simulation Dynaform. Six different cross section and end shape CDs and three different CD movement paths were designed. The test scheme was determined by orthogonal test design. By means of the evaluation criteria of HSS forming limit diagram and optimization theory, different CDs and their moving paths influenced by box forming formability were discussed. The following conclusions are obtained:The limit drawing depths、the optimal moving path(ascent——halt——descent) and the optimal combinations in different CD moving paths are obtained. Besides, the maximum limit drawing depths of six different CDs in different test groups respectively increase 25%、10.34%、31.51%、12.85%、20.80%、10.01% compared to those of 5mm fix drawbead. Main influence factor H1 and H2 of the optimization moving path by range analysis are found. Meanwhile, the increasing rate of punch drawing force and CD resistance with deep drawing is from lager to small, finally begins to decline. The results show that the different CD moving paths have little effect on the strain paths of box sidewall and die corner, which have significant effect on punch corner. Eventually, the response surfaces composed of the CD main influence factor H1、H2 and limit drawing depth are established by the combination of GA-BP neural network and Latin Hypercube.Secondly, in order to verify the correctness of simulation result, it is necessary to design the experimental device to check and analyze the simulation result. The CD-HSS box drawing experimental device included four parts of die structure、lever mechanism、hydraulic and electric control system were designed based on the CD movement principle.Finally, the CD forming laws were applied to the deep drawing simulation of HSS automobile panel based on CD technology. The automobile engine tunnel-side panel was selected as an example. At the same time, the model of CD-JAC590Y HSS deep drawing was established. The results show that part smallest thickness significantly influenced by CD is determined. Then two different test groups are selected to research the whole part thickness distribution law. It is verified of part smallest thickness significantly influenced by CD. The main influence factor H2 and CD optimization moving path combination by range analysis of part average smallest thickness are found. Meanwhile, the model of GA-BP neural network is established to research part forming influence law of the factor H2. In the end the influence law curve and regression equation are obtained.更多还原