Development of semi-dieless metal bellows forming process

A novel semi-dieless metal bellows forming process with local induction heating and axial compression without using any conventional dies is proposed. Firstly, the thickening of a tube is induced by local heating and axial compressive force. Secondly, the buckling of the tube occurs, producing a convoluted shape. The seamless tubes used are stainless steel SUS304 with an outer diameter of 5 mm and a thickness of 0.5 mm and 0.3 mm. The effects of compression ratio on the profiles of the bellows such as convolution height, pitch and thickness are investigated experimentally. It is found that convolution height can be controlled by compression ratio. Additionally, the mechanism of this process for fabrication of the metal bellows can be clarified by loading curve during processing. Furthermore, the validity of a two-step compression technique for improving convolution height and pitch is verified. The fundamental of the proposed technique can be confirmed as a basic key processing to fabricating metal bellows with various dimensions and small quantities.     

钛合金波纹管超塑成形工艺研究

首次开发利用氩气的压力胀形和轴向加载的复合超塑性工艺成形技术制造钛合金波纹管的新工艺,可加工多波U型钛合金波纹管。超塑成形采用多层模结构,用模具来控制波形。超塑成形加载过程分为胀形、合模和定型3个阶段,以使成形件的壁厚分布均匀。确定了筒坯的下料尺寸;给出了各个成形阶段胀形气压和保压时间的计算公式;通过超塑胀形实验成形了Ti-6Al-4V钛合金双波波纹管。     

工艺参数对双层304不锈钢波纹管液压胀形的影响

为提高波纹管的成形质量以及合理选取胀形工艺参数,基于有限元分析软件ABAQUS模拟304不锈钢双层波纹管液压胀形过程,并利用实验验证了有限元模型的正确性。基于建立的模型,研究了内压力、模具行程、挤压速度和加载路径对波纹管成形的影响。结果表明,影响双层波纹管液压胀形壁厚减薄和波高的主要工艺参数为内压力和模具行程;随着内压力和模具行程的增大,最大壁厚减薄率和波高均线性增大,且内外层壁厚差值增大;过大的内压和挤压速度会导致波高不均匀性增大;降低起波阶段内压力及在成形初期施加轴向进给的加载路径有利于减小波纹管的减薄率。最后,通过双层波纹管的液压胀形实验验证了数值模拟的正确性。     

板料成形工艺的介观模型

提出了反映板料成形各种基本工艺本质特征的介观模型。这些介观模型,有别于单纯反映变形区内不同点应力应变状态的微观力学模型,也有别于直接反映各成形工艺变形特征的具体模型,它以平面单元变形前后形状变化的模式,在微观和宏观的结合点上,既抽象又具体地反映各基本变形工艺的本质特征。利用这些含有丰富信息量的介观模型,可以清楚地看出变形区内各点应变规律,能分析危险点的应力应变,帮助寻找改进工艺的方法。     

基于人工神经网络技术的板料拉深成形工艺优化的数值建模

文章利用人工神经网络技术,建立了板料拉深成形工艺参数和性能评价指标之间的映射关系,为各参数的研究和优化提供了重要参考;详细分析了其中的几项关键技术:拉延筋的描述、性能评价指标的建立和正交实验法确定训练样本。最后,对某翼子板进行拉深成形建模,通过对训练后的网络进行测试,网络误差小于5%,验证了所建网络模型的正确性和实用性,为工艺优化奠定了基础。     

工艺参数对板料成形性能的影响

传统上,人们对于工艺参数对板料成形性能的影响的认识只是定性的。利用板料成形的计算机数值模拟技术,可以定量地考察各种工艺参数对板料成形性能的影响。     

Models and modelling for process limits in metal forming

Modelling of metal forming processes is an essential task of production engineering. Due to the latest technological developments, a huge variety of models is already available and extending continuously. Thus, it is important to find a suitable model. This paper gives an overview on the common classification and characterization of modelling and models in metal forming, as well as introduces a model selection procedure. Based on this classification, various relevant process limits for metal forming are investigated regarding existing models. The conclusion of the paper shows open topics as well as upcoming challenges in modelling process limits in metal forming.     

板料数控增量成形加工参数研究

通过针对性试验,研究了板料数控成形工艺中走刀方式、刀间距、Z向进给量和刀头直径等主要参数对成形过程的影响,并分析了其影响机理。为进一步的板料增量成形工艺研究及应用奠定了较好的基础。     

Semisolid metal forming by novel sloping plate process

Semisolid metal forming by a novel sloping plate process was studied. A sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries with good microstructures and excellent property were prepared by cooling or preheating the sloping plate. During preparing semisolid alloy by the proposed process, the co-action of burst nucleation and dendrite fragmentation causes fine spherical microstructure formation, and casting temperature, cooling strength and sloping angle are the main factors influencing the alloy microstructure. Under the current experimental conditions, in order to prepare good quality semisolid billets, proper casting temperature ranges of 660-690 ℃ for AlMg3 alloy and 660-680 ℃ for AlSi6Mg2 alloy are suggcsted. A small car hub wheel of AlSi6Mg2 alloy was thixoformed, and its pattern and inner microstructure are fine. The reasonable technological conditions for preparing AISi6Mg2 slurry are also proposed： the sloping plate preheating temperature is 300 ℃, and the casting temperature is 680 ℃.     

Superplastic forming gas pressure of titanium alloy bellows

The complex superplastic forming (SPF) technology applying gas pressure and compressive axial load is an advanced forming method for titanium alloy bellows, whose forming process consists of the three main forming phases namely bulging, clamping and calibrating phase. The influence of forming gas pressure in various phases on the forming process was analyzed and the models of forming gas pressure for bellows were derived according to the thin shell theory and the plasticity deformation theory. Using the model values, taking a two-convolution DN250 Ti-6Al-4V titanium alloy bellows as an example, a series of superplastic forming tests were performed to evaluate the influence of the variation of forming gas pressure on the forming process. According to the experimental results these models were corrected to make the forming gas pressures prediction more accurate.     

管筒形零件机械扩径工艺过程的成形参数优化

管筒形零件机械扩径最终制品的横断面尺寸精度和形状精度,不同程度地受到各种工艺参数、模具参数、材料性能参数以及摩擦条件的影响。机械扩径工艺设计的重要内容之一,就是针对特定的毛坯规格,合理选择各种成形参数并使其成为一种最优组合,以获得最佳的制品尺寸和形状精度。文章基于MSC.Marc非线性有限元分析软件和遗传优化算法,应用Python语言设计了机械扩径成形参数优化的遗传算法程序,通过对MSC.Marc软件的二次开发,实现了遗传优化算法与MSC.Marc软件的连接,为管筒形零件机械扩径工艺过程的成形参数优化提供了一种新方法。针对大直径管线钢管机械扩径工艺,得到了以最终制品形状精度(横断面圆度误差)为优化目标的扩径率、模具直径和模具边缘圆角半径等成形参数的最优组合。采用最优的成形参数组合,可以显著提高最终制品的横断面形状精度。     

Heat treatment of blanks in forming bellows in two operations

Conclusion On the basis of the results of the investigation, the following regimes of softening heat treatment can be recommended for the forming of bellows of alloy 36NKhTYu in two operations: preliminary quenching from 920°C (10 min)+intermediate quenching from 940°C (10 min); this was confirmed by practice in the production of bellows.Belorussian Polytechnic Institute, Research Institute Teplopribor, Smolensk. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 6–7, January, 1991.     

金属成形工艺在航空紧固技术上的应用

结合航空紧固件的制造工艺,介绍了挤压、镦粗和滚压强化等成形技术在紧固件制造上的应用。同时,介绍了利用残余压应力提高寿命的干涉连接和孔强化技术以及二者结合的应用。指出了金属成形技术是保证紧固件及相关结构性能的重要关键技术,强调了加强其研究的重要性和必要性。     

基于人工神经网络的板料激光成形工艺优化

采用BP算法的人工神经网络系统，以激光能量、光斑大小、扫描速度、矩形板料的厚度和宽度作为输入层节点，预测板料激光成形的温度峰值和弯曲角度，并将该系统用于08F薄钢板激光弯曲成形的工艺参数优化之中，可以快速获得最大成形角度所对应的最优工艺参数组合。     

金属板材单点渐进成形过程的数值模拟

利用有限元软件LS_DYNA模拟金属板材单点渐进成形过程。并利用LS_DYNA的显式求解器分析当压头压下时,不同压头半径条件下,压头与板材接触区域的应力分布。根据对模拟数据的分析比较,讨论不同压头半径对板材成形时的影响。     

管筒形零件机械扩径工艺过程的多目标优化

管筒形零件的机械扩径成形过程是一个与管坯规格、管坯形状、材料性能、摩擦条件、变形程度、模具直径及其边缘圆角半径等诸多因素相关的塑性变形过程,其最终制品的尺寸和形状精度取决于这些参数的综合影响。在生产实际中,如何根据用户对制品尺寸与形状的精度要求来确定管坯规格、变形程度、模具尺寸等主要工艺参数,是机械扩径工艺设计的一个重要内容。它可以被抽象为一个在满足制品尺寸和形状精度要求条件下,寻求管坯规格等上述主要工艺参数最优组合的多目标优化问题。文章基于MSC.Marc非线性有限元分析软件和遗传优化算法,采用Python语言设计了基于加权组合法的遗传算法程序,实现了在多目标条件下对管筒形零件机械扩径成形工艺参数的优化。     

飞机复杂蒙皮拉形工艺参数优化设计

蒙皮拉形是一个复杂的材料成形过程,对其进行工艺参数的优化十分重要。文章阐述了蒙皮拉形中的主要成形缺陷,并将这些缺陷进行量化,作为拉形工艺优化的目标函数。分析拉形过程中的主要工艺参数,提出了筛选重要参数的方法,以确定对成形质量起决定性作用的工艺参数。应用响应面法建立了工艺参数与成形质量评价指标之间的函数关系,并采用评价函数法,将多目标优化问题转化为单目标优化问题,对拉形实例进行了工艺参数的优化。通过有限元仿真以及生产试验,验证了该工艺参数优化方法的有效性与准确性。     

A Theoretical study of the ironing process in sheet metal forming

Ironing is a very useful process when employed in combination with deep drawing to produce a uniform wall thickness and to increase the wall height. The analysis of the ironing process is conducted based on the general two-dimensional axisymmetrical shell theory incorporated with the Tresca maximum shear stress yield criterion for isotropic thin and thick sheets and the Hosford nonquadratic anisotropic yield criterion for anisotropic thin sheets. A complete plastic solution is obtained and the plastic stress field is found in closed form. A governing equation for a limit ironing ratio (LIR) is found and the total ironing force is also given in the closed form. The predicted maximum ironing reduction under some optimal conditions can reach up to 60%–70%, which is in good agreement with experimental observations. The results of the limit ironing ratio, stress field, and the total ironing force are given and compared with some results based on the finite element technique. The normal and tangential forces are compared with experimental results and it is shown that this prediction gives reasonable results. This study was done when the authors were with the Mechanical Engineering and Engineering Mechanics Department, Michigan Technological University, Houghton, MI 49931, USA.     

金属薄板直壁件数字化渐进成形过程的实验研究

金属薄板直壁件的成形是数字化渐进成形技术中的热点和难点之一。本文基于数字化渐进成形的基本原理提出了一种加工金属直壁件的方法,在实验中研究金属薄板直壁件的成形过程,了解直壁成形机理和控制成形过程的工艺措施。