FAST ACCURATE PREDICTION OF BLANK SHAPE IN SHEET METAL FORMING

By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM.

Plasma-Jet Forming of Sheet Metal Shapes

Plasma-jet forming is a newly proposed flexible sheet metal forming process. A non-transferred arc plasma torch is used as a controllable heat source to produce internal stress in sheet metals, causing plastic deformation without the necessity of hard tooling. This method has potential for rapid prototyping of sheet metal parts by reducing development costs and lead times. A robotic system has been used to perform simple linear bends in several different alloys. In order to develop a controllable process and to improve the forming accuracy, the effects of various process parameters on the obtained shape changes and on the resulting structure and properties have been studied. The overall goal is to understand the roles of the forming parameters and their inter-relationship in optimizing the forming procedure-a high forming speed without damage to the material structure or properties.

Modeling of the Shape Forming of Composite Roll

A shape modeling of spray formed composite roll, which is utilized to predict the shape and dimension of roll during spray forming process, is developed in this paper. The influences of the principal spray forming parameters, such as the spatial distribution of melt mass flux, spray distance, rotating and translating speeds of substrate bar etc. , on the geometry and dimension of spray formed product were investigated.

Method for near-net forming of a sand mold with digital flexible extrusion technology

In order to further improve the precision forming efficiency of a sand mold digital patternless casting and reduce the amount of sand mold cutting, a method for near-net forming of the sand mold with digital flexible extrusion technology was put forward. The theory, optimization algorithm and technology for sand mold nearnet forming were studied. Experimental results show that the sand mold forming efficiency can be increased by 34%, and the molding sand can be reduced by 44%. The method for near-net forming of a sand mold with digital flexible extrusion technology can effectively promote the application of digital patternless casting technology in the mass production of castings and thus greatly improves the efficiency and automation of sand mold manufacturing.

Heat shock behavior of permanent die during non-solid near-net forming process

Heat shocks caused by alloy melt and coat spraying are the main reason of die plastic deformation and early fracture. Based on theoretical analysis of heat shock phenomenon, two characteristic parameters of die damage caused by heat shock were proposed, which are heat shock plastic deformation index (HSPI) and heat shock crack index (HSCI). The effect of heat shock on die plastic deformation and fracture behaviors was described quantitatively by these two parameters. HSPI represents approaching of heat shock stress to die yield stress. Plastic deformation will happen on a die if this index reaches 1. HSCI represents approaching of heat shock stress to die tensile strength. Die fracture will happen if this index reaches 1. According to theoretical analysis of heat transfer, theoretical models of HSPI and HSCI were established. It is found that, the smaller the interfacial thermal resistance (ITR) is, the higher the pouring temperature and die temperature are before heat shock, and the greater the HSPI and HSCI are, which can be fitted as exponential curves, linear and cubic curves.

Modeling and experimental verification of tubular product formation during spray forming

A mathematical model is formulated to predict the shape evolution and the final geometry of a tubular product prepared by spray forming. The effects of several important processing parameters on the shape evolution of the tube are investigated. The model is validated against experiments of spray formed large diameter tubes. The experimental and the modeling results show that there are three distinct regions in the preform, i.e., the left transition region, the middle uniform diameter region and the right transition region. The results show that the atomization parameters as and bs, traversing speed v of the substrate, the outer diameter D0 of the substrate, and the initial deposition distance d0 play important roles in the contour and the wall thickness of the spray formed tube. But the angular velocity ω of the substrate has little effect on the buildup of the deposit. After a certain time from the beginning of the process, the deposit will come into a steady growth state. In addition, an equation is provided to estimate the wall thickness of the deposit under the steady growth state based on the mass conservation.

Shape formation of closed-cell aluminum foam in solid–liquid–gas coexisting state

The mold pressing process was applied to investigate the formability of closed-cell aluminum foam in solid–liquid–gas coexisting state.Results show that the shape formation of closed-cell aluminum foam in the solid–liquid–gas coexisting state was realized through cell wall deformation and cell movement caused by primary α-Al grains that slid,rotated,deformed,and ripened within cell walls.During formation,characteristic parameters of closed-cell aluminum foam were almost unchanged.Under proper forming conditions,shaped products of closed-cell aluminum foam could be fabricated through mold pressing.

Recognition in Shape and Form’s Characteristics of Japanese&Vietnamese Traditional Daily Products

This paper presents the major analyses carried out on shape and form’s characteristic database from Japanese and Vietnamese traditional daily products(TDPs).The aim of the research is to recognize the vital specifications representing for a national style by comparing two different countries together.By using Quantification Theory Type III and Cluster analysis,firstly,the analyses were undergone separately for Japanese and then Vietnamese product data in succession so that a view of general direction for each country was caught.The result showing a difference in scale of“Complexity”and“Specification”axis between Japan and Vietnam leads to performance of the analysis done on combine database of the two countries to get a clearer view of correlation between them.However,the biggest difference between the two countries lies in“Form”(Geometric—Organic)axis.Continuously,for studying more deeply into outline of product shape,the main ratios that affect the appearance or gorgeousness of product’s outline were taken into account and analyzed.By comparing this result to the previous ones,finally a wider and more detail perspective of Japan and Vietnam shape’s specification in a mutual relationship was discovered.

基于“阳化气,阴成形”理论辨治痿证

津气两伤是痿证的病变基础,亦是“阳化气,阴成形”失衡的结果。阳化气不足,阴成形失衡,而致脏腑功能失调,水饮痰瘀内生,四肢九窍失养,发为痿证。本文基于“阳化气,阴成形”理论,探讨高颖教授采用助阳化气法治疗阳化气不足的重症肌无力,益肾调形法治疗阴成形失衡的多发性硬化,阴阳双补法治疗阴阳俱损的运动神经元病。治疗痿证,需审证求因,明辨阴阳,调整偏颇,在疾病早期给予中医药治疗,以延缓疾病演变进程、改善预后。

镁合金尾翼类构件径向同步加载工艺研究

目的针对常规挤压工艺成形尾翼类构件飞行时翼片径向产生挠曲变形的问题,提出了一种可调控金属流动的径向同步加载成形方法。方法结合ANSYS、Deform-3D有限元模拟和物理实验,分析径向同步加载的金属流动行为、等效应变和金属流线分布,通过拉伸实验测试成形翼片挤压方向(Extrusion Direction,ED)和横截面方向(Transverse Direction,TD)的力学性能,并通过观察显微组织揭示径向强化机理。结果径向同步加载通过对坯料施加周向压应力促进了金属径向流动,形成了沿径向分布良好的金属流线,有利于提升径向力学性能;采用该工艺试制构件表面质量良好,无宏观缺陷,且形成沿径向分布的宏观流线;翼片径向力学性能显著提升,屈服强度提升了57.8 MPa,抗拉强度提升了80.1 MPa,延伸率提升了1.4%,其强塑性的提升与纤维组织和块状LPSO相的纤维强化密切相关。结论实现了尾翼类构件的径向同步加载整体成形,通过调控金属流动形成径向分布良好的金属流线,提升了成形翼片径向强度,为高性能镁合金尾翼类构件的整体成形提供了理论基础和技术支撑。

难变形金属小模数齿形件电流辅助分形旋压成形工艺优化

目的针对30CrMnSiA合金结构钢小模数齿形件电流辅助分形旋压成形工艺,探究工艺参数对小模数齿形件成形质量的影响规律,分析工艺参数间的相关性,获得优化后的工艺参数组合。方法选取小模数齿形件齿廓偏差、齿距偏差、轮齿饱和度为成形质量响应指标,以电流密度、占空比以及旋轮进给速度为影响因素,设计响应面试验方案;根据有限元模拟结果建立成形质量回归预测模型,分析电流密度、占空比以及旋轮进给速度对小模数齿形件成形质量的影响规律,计算获得最优的参数组合并进行试验验证。结果电流密度、脉冲占空比、旋轮进给速度对小模数齿形件成形质量有显著影响,成形质量随着电流密度与占空比的升高而升高,随旋轮进给速度的升高而先升高后降低;且电流密度与旋轮进给速度、脉冲占空比与旋轮进给速度在对轮齿饱和度的影响上有一定的交互性;通过建立的回归模型预测得到的优化工艺参数如下:电流密度为17.5 A/mm2、脉冲占空比为40%、旋轮进给速度为0.6 mm/min。结论回归模型预测值与试验值的相对误差小于8%,说明所构建的成形质量回归预测模型是准确的,利用优化后的参数可制备出成形质量良好的小模数齿形件。

基于机器学习嵌接有限元的蠕变时效成形全过程形性演变预测

针对蠕变时效成形中存在的蠕变变形和时效强化动态交互耦合作用导致成形精度难以准确预测和控制问题,提出了一种基于机器学习的方法来预测蠕变时效过程中的形性演变。利用单向拉伸蠕变时效实验数据训练神经网络(NN)模型,用以描述蠕变时效本构关系。对比统一本构模型、反向传播NN(BPNN)模型、粒子群优化BPNN(PSO-BPNN)模型、遗传算法优化BPNN(GA-BPNN)模型对形性演变的预测效果,发现GA-BPNN和PSO-BPNN模型分别对蠕变应变和屈服强度具有较高的拟合精度。通过子程序将NN模型与有限元程序嵌接,实现了蠕变时效成形全过程的模拟,预测了铝合金板材蠕变变形和屈服强度的演变。针对回弹,相较于统一本构模型26.5%的误差,GA-BPNN模型的预测精度有较大提高,误差仅为5.1%。证明了采用机器学习的方法探寻蠕变时效本构关系并通过BPNN模型嵌接有限元模拟实现形性演变精确预测具有可行性。

基于模流平衡的U型材挤出口模结构优化

应用Polyflow软件分别建立了U型件模型、带内外气体辅助层厚度不同的U型件模型和U型件开口有倾角的模型。针对传统挤出、不同内外层辅助气体厚度、不同开口倾角下3种情况进行了数值模拟计算,并用Origin软件对部分结果进行了分析。研究发现,使用气体辅助技术比型腔结构优化更有利于模流平衡;当内外气体辅助层厚度不同时,内层气体层厚度偏大、外层气体层偏薄时,更有利于抑制U型件开口收缩的变形;而对口模开口臂倾斜角度的修正更有利于减小或调整U型件开口收缩的变形。

修形斜齿轮成形磨削中齿廓精度补偿方法

建立了斜齿轮齿廓修形的坐标方程与成形磨削砂轮修整的几何算法,优化出齿廓修形后的砂轮截面廓形;通过数值模拟分析,得到了机床位置误差与齿廓偏差之间的耦合关系;编制了成形磨削齿廓精度调整软件,计算出斜齿轮修形与之对应的成形砂轮廓形和齿廓精度调整参数。通过修形斜齿轮的成形磨削试验,验证了砂轮廓形修整的正确性和齿廓精度调整的有效性。

Shape V 7.1软件在结晶化学单形绘制及单形推导中的应用

Shape是一款可灵活处理晶体结构的软件。结合教学实践,介绍了Shape V7.1在结晶化学中单形推导方面的使用过程及技巧。文中列举了对称型L22P和对称型3L44L36L29PC晶类推导单形实例,以演示此过程。通过Shape软件的使用使传统教学过程更有吸引力、更有效,使学生在实习过程中,能够更好地理解对称要素、对称要素的组合规律、各单形的推导等,有效提高学习效率。

马鞍形蒙皮拉形工艺参数仿真优化与试验验证

对某马鞍形蒙皮零件在拉形过程中的起皱和破裂现象进行了研究,以得到消除缺陷的方法。采用作图法,对该蒙皮零件进行了工艺性分析,确定了工艺参数的范围,用正交试验方法设计了数值模拟方案,利用AI-FORM软件拉形模块进行了模拟仿真,并对仿真结果进行了评估,确定了一种最优的方案,并再次进行了有限元仿真验证,最后在拉形机上进行了拉形试验。发现试验结果与有限元仿真结果吻合很好,消除了起皱和破裂等缺陷,提高了零件的成形质量。结果表明,对此蒙皮零件,拉形轨迹前部分采用较大伸长率,拉伸到4.9%,后部分采用较小伸长率,最终拉伸到7%,有利于避免起皱和破裂。另外,相较于FormCAM,AI-FORM在起皱模拟方面具有明显优势。

纵向V型肋卷边C形不锈钢梁抗弯承载力试验研究

为研究在冷弯薄壁C形不锈钢梁腹板增设纵向加劲肋后对其极限抗弯承载力的影响,本文考虑腹板高度、高宽比以及加劲肋尺寸的不同,进行4组试件的对照试验研究。结果表明:对卷边C形不锈钢梁腹板进行加肋能良好地抑制腹板鼓曲,有效提高其极限抗弯承载力;加大加劲肋的尺寸会略微提高其极限抗弯承载力,但刚度略有降低;增加卷边C形不锈钢梁的腹板高度可有效提升其极限抗弯承载力和抵抗变形的能力。

基于“阳化气,阴成形”理论探析陈永灿辨治慢性萎缩性胃炎伴肠上皮化生经验

慢性萎缩性胃炎伴肠上皮化生是慢性胃炎发展到胃癌的必经阶段。陈永灿认为,“阳化气,阴成形”理论可诠释慢性萎缩性胃炎伴肠上皮化生的发展及诊疗过程。“阳化气”不足导致“阴成形”太过,使脾胃生理机能改变,从而发展为慢性萎缩性胃炎伴肠上皮化生的病理过程。通过“阳化气,阴成形”理论对本病的病机进行探析,临床治疗首先辨别阴阳状态,提出扶阳气、祛阴浊的治疗原则,以标本兼治。