基于电场法的二道次渐进成形预成形型面设计和研究

发布时间：2018-01-03 05:22

本文关键词：基于电场法的二道次渐进成形预成形型面设计和研究　出处：《重庆大学》2016年硕士论文　论文类型：学位论文

【摘要】：板材渐进成形技术在小批量、多品种以及概念产品试制领域具有独特的优势,有效减小模具设计、制造成本,易于实现成形加工的自动化操作。在航天航空、汽车制造、船舶、医疗器械等行业有着很大的应用前景,当前完善和掌握该技术是渐进成形技术研究和成熟过程中亟待解决的关键问题。在金属板料数控单点渐进成形中,经常遇到复杂零件局部存在直壁特征面的情况,导致零件无法一次成形,增加道次数能够在一定程度上解决该难题,并优化成形质量,但增加成形道次无疑会拖延制件生产周期,提高各方面成本,因此在满足制件性能要求的前提上,应尽量减少成形道次。同时,每道次成形策略是制约加工效果的关键,预成形型面和成形轨迹影响制件厚度分布、几何精度。为采取成形质量和生产周期二者间的折衷方案,所以本文选择二道次为成形方案,借鉴电场法在锻造预成形设计领域的研究成果,在渐进成形型面设计中引入电场法思路,为零件直壁预成形型面的设计提供理论依据,这对渐进成形技术的产业化推广有重要意义。对此本文主要进行以下内容研究:(1)依据静电场与板材变形过程中材料速度场的场方程以及能量最小原理的相似性,说明电场法模拟板材最小阻力塑性变形路径的可行性。并以胀形过程为例,通过ANSYS静电场模拟分析了等势线在板材实际加工中的参考意义。引入基于电场法的预成形型面设计一般流程到二道次渐进成形,利用UG、ANSYS、Mimics有限元软件实现等势线的模拟、提取及建模拟合,以等势线作为直壁件第一道次加工轮廓。(2)借助响应面模型得到直壁件最佳成形效果的参数组合。本文以板材孔洞体积分数作为渐进成形板材的损伤破裂预测评价准则,构建工艺参数预成形型面?、进给速度ν、层间距△z与目标函数fc之间的响应面模型近似函数关系。通过拉丁超立方试验设计,利用ABAQUS模拟随机抽取的20组参数组合,分析观察各工艺参数对孔洞体积分数fc的影响作用,得到?=0.304V、ν=1916mm/min、△z=0.3mm的参数组合,并发现预成形型面对最终成形效果影响程度最大,进给速度在1750-2100mm/min范围内有利于成形加工的进行,层间距在0.3-1.5mm内越小孔洞体积分数越小。(3)采用所得参数组合在渐进成形机床上实际加工板料,将加工所得直壁件进行切割后,将截面厚度的测量值与模拟结果进行对比,发现板厚最大减薄率的模拟值略大,但模拟与实际加工测量所得的截面厚度曲线基本吻合,表明了模拟的有效性以及优化参数组合的可行性。
[Abstract]:Sheet metal progressive forming technology has unique advantages in the field of small batch, multi-variety and conceptual product trial production, effectively reducing the die design, manufacturing costs, easy to realize the automatic operation of forming processing in aerospace. Automobile manufacturing, ships, medical devices and other industries have a great application prospects. At present, perfecting and mastering this technology is the key problem to be solved in the research and maturation of incremental forming technology. It is often encountered that there is a feature surface in the part of complex parts which can not be formed at one time. Increasing the number of passes can solve the problem to a certain extent and optimize the forming quality. However, increasing the forming pass will undoubtedly delay the production cycle and increase the cost of all aspects. Therefore, in order to meet the performance requirements of the parts, we should try to reduce the number of forming passes. At the same time. The forming strategy of each pass is the key to restrict the machining effect. The preform surface and the forming track affect the thickness distribution and geometric precision of the parts. The tradeoff between the forming quality and the production cycle is adopted. Therefore, this paper chooses the second pass as the forming scheme, draws lessons from the research results of electric field method in the field of forging pre-forming design, and introduces the electric field method in the design of the progressive forming surface. It provides the theoretical basis for the design of the straight wall preform surface. This is of great significance to the industrialization of incremental forming technology. According to the field equation of material velocity field and the similarity of energy minimization principle between electrostatic field and plate deformation process. The feasibility of simulating the minimum resistance plastic deformation path of sheet metal by electric field method is illustrated, and the bulging process is taken as an example. The reference significance of isopotential line in sheet metal processing is analyzed by ANSYS electrostatic field simulation. The general process of pre-forming surface design based on electric field method is introduced to two-pass progressive forming, and UG is used. The simulation, extraction and modeling of the isopotential line are realized by ANSYS Mimics finite element software. Take the isopotential line as the first secondary machining contour of the straight wall part. According to the response surface model, the parameter combination of the optimum forming effect of the straight wall parts is obtained. In this paper, the volume fraction of the holes in the sheet metal is used as the criterion for the prediction and evaluation of the damage and fracture of the progressive forming sheet. How to construct the preformed surface of process parameters? , the response surface model approximate function relation between feed velocity, interval z and objective function FC. Through Latin hypercube test design, 20 groups of parameter combinations are simulated by ABAQUS. The effect of each process parameter on the volume fraction FC of the cavity is analyzed and observed. The parameter combinations of 0.304V, v 1916mm / min and 0.3mm are found to have the greatest influence on the final forming effect. The feed speed of 1750-2100mm / min is propitious to the forming process. The smaller the hole volume fraction is in the range of 0.3-1.5 mm, the smaller the volume fraction of the hole is, and the smaller the volume fraction is, the smaller the hole volume fraction is, and the smaller the volume fraction is, the smaller the hole volume fraction is, and the smaller the volume fraction of the hole is. By comparing the measured results with the simulation results, it is found that the simulated value of the maximum thinning rate of the plate thickness is slightly larger, but the section thickness curve obtained by the simulation and the actual processing measurement is basically consistent. The effectiveness of the simulation and the feasibility of optimizing the combination of parameters are demonstrated.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG306

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