板材成对液压成形工艺加载路径对成形性的影响(英文)

板材成对液压成形可以用于制造复杂几何截面的空腔构件,通过合理的工艺加载路径可以实现板材的流动控制。研究非焊接板材成对液压成形工艺以及两个主要工艺参数(合模力和液压力)的影响。通过理论计算研究不同合模力对应的极限液压力,得到极限液压力曲线,揭示不同工艺参数组合对变形行为的影响规律。通过有限元分析和实验研究验证了理论值,结果表明它们之间具有较好的一致性。实验采用2种线性加载路径和1种阶梯型加载路径研究加载路径对变形行为和零件成形性的影响,结果表明采用阶梯型加载路径可以得到很好的成形性。     

板材成形新技术及其发展趋势（I）

近些年来，面对全球化的竞争，越来越需要小批量，多样化，周期短的新的成形技术。薄板成形技术在成形工艺中占有很重要的地位，其多样化趋势已经变得越来越明显，出现了多种加工方法，它对将来的工业结构和产品的生产技术将是一场革命，文中介绍了变压边力技术，成对液压成形技术，粘介质成形技术，无模分层成形技术等几种柔性化程度高的板材成形技术及其发展趋势。     

板材多点成形技术研究综述

多点成形是一种先进的板材成形技术 ,吉林大学无模成形技术开发中心进行了大量的研究工作。本文介绍了该中心在板材多点成形设备、多点成形理论与实用技术等方面的研究成果     

基于LS-DYNA有限元平台火车车厢小弯梁板材成形研究

火车车厢小弯梁板材用于车厢顶部位置以提高承载能力,由于成形过程受到非线性相互耦合作用影响,其变形机理非常复杂.本文针对火车车厢小弯梁板材利用LS-DYNA有限元平台进行了动态数值模拟,得到了成形过程中应力场量、成形极限图和板材减薄率分布规律,进而分析了板材成形中出现破裂和拉裂等的机理.同时,探讨了工艺参数(摩擦系数、凹模圆角)对火车车厢小弯梁板材成形力的影响关系,其结果可为火车车厢小弯梁板材模具设计者提供一定的理论参考和依据.     

电磁成形技术在薄板成形中应用的研究进展

电磁成形技术是一种高能、高效成形技术,目前已在工业生产中获得广泛应用,是近年来一种新兴的板材塑性加工方法.本文从理论、试验和有限元仿真3个方面介绍了国内外电磁成形技术运用于薄板成形领域的最新成果,主要阐述了管件缩径成形和胀形成形、平板成形以及薄板校形方面的研究进展,讨论了在应用研究中存在的问题和进一步发展方向.     

板材多点成形过程数值模拟的研究

多点柔性成形是一种先进的板材成形技术。在多点成形过程中 ,板材的受力状态、变形特点、接触边界等与传统的冲压成形有很大的不同 ,商业软件不能有效地反应这些特点。本文给出了自主开发的板材多点成形过程数值模拟专用软件 (MPFORM)所采用的有关理论与公式 ,介绍了基于UL隐式格式的弹塑性大变形有限元方法、退化板壳有限元模型以及处理多点不连续接触边界的接触单元技术等 ,给出了球形面与马鞍面多点成形过程的MPFORM数值模拟结果     

轴对称件多道次数控点成形过程的理论分析

板材数控增量成形是国际上刚刚兴起的一项柔性加工技术，其实质是以累积的点成形来加工零件。该技术不需专用模具，可通过数控设备加工出成形极限较大、形状复杂的板材零件，应用面较广，适合于航天、汽车和民用产品中的小批量、形状复杂的板材零件加工，有着广阔的发展前景。本文以圆弧成形轨迹为例，对较为简单的二维轴对称成形进行分析，从板坯与成形件金属之间的映射关系入手，讨论了如何控制金属流动，才能使变形后应变均匀化程度得以提高，为成形轨迹的选定提供了理论依据。此外，还指出了增量成形能提高成形极限的原因，探讨了影响成形件表面质量的因素等。     

基于金属板材数控渐进技术的汽车座椅成形工艺

金属板材数控渐进成形工艺不需要专用的模具,是一种柔性的成形工艺.在工艺规划中,通过零件的数字模型来调节成形工具的运行轨迹,达到渐进成形零件形状的目的.由于汽车座椅形状复杂,金属板材渐进成形较困难.本文对其数控渐进成形工艺进行了分析,提出由建模、工艺分析、轨迹生成、HrpDSF处理、安装定位、加工润滑、后处理等组成的金属板材数控渐进成形工艺规划方法,成功地应用于汽车座椅的数控渐进成形中.并对汽车座椅数控渐进成形加工中,通常出现的破裂、回弹、起皱等严重影响成形质量的缺陷原因进行分析,采取不同的处理防范措施,取得满意的效果.为今后完善和发展金属板材数控渐进成形技术起到重要作用.     

等离子体弧柔性成形技术研究

等离子体弧柔性成形技术是利用热应力和热应变来实现板材成形的新型技术,在国内外逐渐成为研究的热点.因为等离子体弧与其它热源相比更经济、安全、灵活、实用,但是目前相关工作研究非常有限,如仅利用直线扫描路径研究板材成形情况,考察弯折区域金相组织的变化等问题,在探讨了薄板等离子体弧柔性成形技术的成形机理基础上,通过不同形状的板材,以实验分析的方法探索了直线扫描和曲线扫描的差异以及板材的几何形状对成形结果的影响.     

板材冲压成形的智能化控制技术

板材冲压成形智能化是一项涉及控制科学、计算机科学和板材塑性成形理论等领域的综合性新技术。该技术的研究已有十几年的历史, 但主要是集中在V 型弯曲的回弹控制方面。直至90 年代初, 才开始对筒形件拉深的智能化控制进行探索性研究。该技术的研究带动了数据库、神经网络及模糊控制等技术在板材成形领域中的应用, 并提出了一系列新的研究课题     

Experimental and numerical study on shaping of aluminum sheets with integrated piezoceramic fibers

Force-fit integration of piezoceramic fibers in micro-formed structures is a new approach for function integration in structural sheet metal parts. In a first step, a micro-structured surface is formed in a planar semi-finished sheet metal part by micro-impact extrusion. Piezoceramic fibers are then assembled into this micro-structured surface with a small assembly clearance. The fibers and the structured surface of the sheet metal are joined by a forming process. In the next step, the sheet metal with piezoceramic fibres within a locally micro-formed substructure is shaped by deep drawing into a 3D-geometry. In this paper, results of the micro-impact extrusion and the joining by forming experiments are presented. Furthermore, the design constraints for assembly and joining due to the dimensional and form deviations of the piezoceramic fibers are discussed. Results of a numerical study of micro-forming, joining by forming and the global loading during a deep drawing process step were in good agreement with the experimental investigations. The direct comparison between experiment and numerical simulation increases the process knowledge and shows further improvement potential.     

Mechanical flange forming in steel and copper foil

Flange forming is a process which is wide spread in macro range for blanks with thicknesses from less than 1?mm up to several millimeters. Flange formed geometries are used as preforms for threads but also as device to give guidance and contact face to bolts and axles in sheet metal. A great advantage of flange forming compared to other machining processes is low process cycle time combined with high material utilization. Thus, a reasonable repertoire of knowledge has been gained for flange forming in macro range. Due to ongoing miniaturization of today??s products, flange forming is an interesting process applicable in micro range as well whereas size effects do not generally allow transfer of process limits from macro to micro range. Therefore the maximum flaring ratio for flange forming in micro range for sheet metal foil of 10?C25???m for a stainless steel 1.4301 and Copper E-Cu58 is investigated and compared with results in macro range. It is shown that the maximum flaring ratio decreases with decreasing sheet metal thickness. The resulting flange heights of experiments are compared with theoretical estimations which show a good accordance.     

Three-dimensional sheet metal continuous forming process based on flexible roll bending: Principle and experiments

To effectively manufacture three-dimensional sheet metal parts with various curvatures produced in small batch quantities, continuous sheet metal forming, a new flexible forming technology is being developed. This process employs an upper flexible roll and two lower flexible rolls as a forming tool, and the shape of a flexible roll can be changed in vertical direction. With the rotation of flexible rolls, the sheet metal is bent in longitudinal and transverse directions simultaneously and is formed continuously. In the present study, the three-dimensional surface of formed part is described by sweep surface based on the characteristic of the forming process and the arc-length parametric equation for describing continuous forming part is developed. The three-roll bending deformation of sheet metal in longitudinal direction is analyzed and the longitudinal curvature equation of the formed part is derived. The shape of flexible roll axis controlled at a number of points is represented by the cubic spline curve and the transverse curvature of the formed part after springback is then calculated piecewise. Typically experiments for forming concave shape surface and saddle-type surface have been performed, the experiment results are measured and analyzed by a binocular stereo vision measurement system, it is demonstrated that the formed surfaces are in good agreement with the desired shapes and the presented equations are useful for the continuous forming process design.     

Study on the continuous roll forming process of swept surface sheet metal part

Continuous roll forming (CRF) is an effective process to manufacture swept surface parts of sheet metal. The forming tool in CRF is a pair of small-diameter bendable forming rolls, a swept surface is formed continuously after the rotating rolls sweep out the whole sheet metal blank. The two bent rolls and the non-uniformly distributed roll gap along the rolls’ length make the sheet metal bent in longitudinal and transverse directions simultaneously, the cross-section curve of the formed swept surface is controlled by the curved profile of the forming rolls and the spine curve is controlled by the differential elongations of sheet metal generated by roll gap. In this paper, a necessary condition for the formation of a swept surface is proposed and analyzed, the parametric equations of the formed surface in CRF are derived and the method to determine the roll gap for forming a given swept surface is presented. The numerical simulations and analyses on the CRF processes demonstrate the validity of the presented theoretical models. The experimental and measured results show that the formed surfaces are in good agreement with the desired surfaces, and swept surface parts with good forming precision can be obtained by CRF process.     

筒形件磁脉冲辅助冲压成形数值模拟

针对磁脉冲辅助冲压成形过程,提出了基于ANSYS平台的有限元分析程式,通过编制用户子程序,采用重启动分析法,建立了冲压预成形过程显式求解和瞬态磁脉冲成形"松散"耦合分析之间的动态连接,并用于5052-O铝合金圆筒形拉深件磁脉冲辅助冲压成形过程的有限元仿真研究。结果表明,所建立的有限元分析方案,能实现圆筒形件磁脉冲辅助冲压成形连续变形过程的模拟,板坯变形信息体现了准静态冲压变形和高速率磁脉冲成形之间的耦合。有限元模拟结果与实验吻合较好。     

Analytical and experimental investigations on deformation mechanism and fracture behavior in single point incremental forming

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. The characteristic of localized deformation is significantly different from conventional sheet metal forming process. To understand the fundamental material deformation mechanism during the ISF process is of great importance for ISF process design and optimization in achieving improved material formability, accuracy and more uniform thickness distribution. In this paper, an analytical model for single point incremental forming (SPIF) process has been developed to describe the localized deformation mechanism. With the consideration of both bending effect and strain hardening, the stress and strain states in the deformation zone are described. Analytical evaluation reveals that the deformation occurs not only in the contact zone, but also in the neighboring wall which has been already formed in the vicinity of the contact zone. In addition, the results also suggest that the fracture tends to appear at the transitional zone between the contact area and the formed wall. In order to validate the analytical results, SPIF simulation and experiments both have been conducted with good agreement obtained.     

板料成形过程模具圆角摩擦测试实验装置的研究

板料成形研究中的一个难点是如何采用实验方法定量测定板料成形过程中板料与模具之间的摩擦系数.通过对板料成形时的变形特点进行分析,提出一种新的板料成形过程模具圆角摩擦测试实验方法,并研制出相应的摩擦测试实验装置.该实验装置考虑了板料成形时周向收缩、厚向增厚的变形特点,能够在线测试出室温和加热状态下板料成形过程模具圆角处的摩擦系数.摩擦测试结果表明,所研制的摩擦测试装置具有灵敏度高、可重复性好、使用方便的特点,为深入研究板料成形过程中摩擦系数随工艺参数的变化规律提供了实验手段.     

A LOOP DRAWBEAD RESTRAINING FORCE MODEL IN SHEETMETAL DEEP DRAWING PROCESS

1. IntroductionIn the sheet metaJ fOrming process9 deep drawing is used frequently in the automotiveor packaging industry to manufacture products with comPlicated shapes and ctirvatures.In the deep drawing process, a sheet metal, the blank, is clamped between a die and a blankholder. The specific shape of the punch and the die is transferred to the blank during thedefor.atio.[1--4].In the deep drawing process, the material flow is restrained by both the friction con-dition and the blankholde…     

金属板材成形智能化控制技术研究及展望

对板材成形智能化控制技术进行了综述,介绍了智能化控制系统的4个基本要素,重点介绍了以板材V形弯曲智能化控制技术、板材拉深智能化控制技术为代表的板材成形过程中智能化控制原理,弯曲和拉深的实验证明该项技术实验效果良好,同时对该技术的进一步应用做出了展望,指出多学科研究成果的不断涌现加快了板材智能化成形工业应用进程。     

Mechanism investigation of friction-related effects in single point incremental forming using a developed oblique roller-ball tool

Single point incremental forming (SPIF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. In the SPIF process, a ball nose tool moves along a predefined tool path to form the sheet to desired shapes. Due to its unique ability in local deformation of sheet metal, the friction condition between the tool and sheet plays a significant role in material deformation. The effects of friction on surface finish, forming load, material deformation and formability are studied using a newly developed oblique roller ball (ORB) tool. Four grades of aluminum sheet including AA1100, AA2024, AA5052 and AA6111 are employed in the experiments. The material deformation under both the ORB tool and conventional rigid tool are studied by drilling a small hole in the sheet. The experimental results suggest that by reducing the friction resistance using the ORB tool, better surface quality, reduced forming load, smaller through-the-thickness-shear and higher formability can be achieved. To obtain a better understanding of the frictional effect, an analytical model is developed based on the analysis of the stress state in the SPIF deformation zone. Using the developed model, an explicit relationship between the stress state and forming parameters is established. The experimental observations are in good agreement with the developed model. The model can also be used to explain two contrary effects of friction and corresponding through-the-thickness-shear: increase of friction would potentially enhance the forming stability and suppress the necking; however, increase of friction would also increase the stress triaxiality and decrease the formability. The final role of the friction effect depends on the significance of each effect in SPIF process.