Forming strategies and Process Modelling for CNC Incremental Sheet Forming

Incremental Sheet Forming (ISF) is a process capable of producing complex sheet components by the CNC movement of a simple tool in combination with simplified dies. Earlier work revealed two major process limits, namely the limitation on the maximum achievable wall angle, and the occurrence of geometric deviations. The work detailed in this paper focuses on forming strategies to overcome these process limits, including the processing of tailor rolled blanks. Additionally, finite element modelling of the process is presented and discussed with respect to the prediction of the forming limits of ISF.     

板料多点与渐进复合成形技术研究

基于多点成形技术和渐进成形技术在板料成形领域应用的特点,提出多点成形与渐进成形相结合的复合成形方法,并提出两种可行的复合方式,分别说明其成形原理及成形过程,以及两种复合成形方式的适用范围.     

滑动摩擦接触对母线弯曲成形质量的影响

目的 研究滑动摩擦接触对1060纯铝母线弯曲成形质量的影响,得到表面质量更好的工件,降低废品率。方法 采用自行设计的V形三点式自由弯曲成形的摩擦力测试装置,通过更换不同表面粗糙度的凹模圆角、不同润滑介质以改变接触状况,进行一系列摩擦试验。通过钨灯丝扫描显微镜获得板料弯曲件表面微观形貌图,通过MATLAB软件对所采集的数据进行曲线处理。结果 得到不同粗糙度的凹模圆角以及不同润滑介质条件下的弯曲力-行程曲线。经测定,凹模圆角表面光滑时,无润滑状态下,最大摩擦力约为440 N;采用聚乙烯薄膜作为润滑介质,最大摩擦力约为100 N;采用聚四氟乙烯薄膜作为润滑介质时,最大摩擦力约为20 N。凹模圆角表面粗糙时,无润滑状态下,最大摩擦力约为235 N;采用聚四氟乙烯薄膜作为润滑介质时,最大摩擦力约为28 N。结论 添加润滑介质可以有效降低板料与凹模圆角之间摩擦力大小,进而提高弯曲件表面成形质量。滑动摩擦条件下,无论光滑还是粗糙的凹模圆角,采取润滑措施均能有效提高弯曲成形工件的表面质量,且聚四氟乙烯薄膜作为润滑介质时,得到的板料表面质量最好。     

基于工艺参数的渐进成形回弹量预测与控制

以圆锥凸台为研究对象,有限元软件ABAQUS为模拟平台,成形件的回弹量为研究指标,采用正交试验法分析了工具头半径、层间距、工具头速度及其之间的交互作用对回弹量的影响;基于模拟结果进行了非线性回归分析,建立了针对工艺参数的回弹量非线性预测模型。最后对该预测模型进行了实验验证,结果表明,该模拟结果与实验结果吻合,证明可通过调整工艺参数来控制渐进成形零件的回弹量,该方法对于提高板材渐近成形技术的成形质量具有重要意义。     

花键冷滚压成形过程中的接触比

花键冷滚压成形工艺是一种少无切削的先进成形工艺,应用前景广泛.目前对花键冷滚压成形过程中接触状态研究较少.本文分析研究了渐开线外花键在自由分度式冷滚压成形过程中的接触比.从不考虑滑动现象和考虑滑动现象两种情况下对滚压过程最大接触比进行了系统理论研究.给出了标准渐开线花键冷滚压成形过程中接触比的规格范围.对研究花键冷滚压成形过程中的接触面积和有限元模型的简化具有重要的意义.     

触指成形工艺分析及其模具设计

分析了触指的成形工艺,提出了触指成型模具的设计方案。设计时对工序的布置进行了精细的考虑以保证零件的尺寸精度。和传统模具相比,该模具操作简便,生产效率高,能满足大批量的生产要求。     

多道次单点渐进成形工艺参数优化研究

使用数值模拟方法和实验手段对下压量、工具头直径、摩擦系数、进给量等因素对多道次单点渐进成形零件厚度均匀性的影响进行研究。结果表明,影响成形零件厚度均匀性因素的大小依次为:工具头直径、进给量、摩擦系数和下压量。工具头直径对成形零件厚度均匀性影响最为明显,工具头直径越大,成形零件厚度均匀性越好;合适的摩擦系数和进给量能够加工出厚度较为均匀的零件;下压量对成形零件厚度均匀性影响不大。     

单点渐进成形装置研制

单点渐进成形是一种基于分层逐步成形的原理,每一层采用局部塑性变形,最终达到产品目标形状的先进工艺.在加工小型板材三维零件时只需要简单工装即可实现成形,但对于中、大型覆盖件则需要精度高的装置以保证工件的成形质量.利用数控铣床提供的X、Y、Z方向移动定位等功能,开发制造了适于数控铣床的单点渐进成形加工的专用装置.通过大量实...     

工业纯铝板料渐进成形极限图研究

板料渐进成形极限图和传统成形极限图有显著不同,到目前为止尚未有统一的测试方法.提出了一种测试板料渐进成形极限图的方法,成形工具分别沿往复圆弧和交替往复圆弧轨迹运动,对0.9mm工业纯铝板进行渐进成形.板料破裂后,获得了主应变和次应变,建立了该种板料渐进成形极限图.通过板料渐进成形分别成形了一些零件,测量了零件的主应变和次应变并绘制了它的渐进成形极限图.结果表明,所获得的工业纯铝渐进成形极限图能较为准确地预测渐进成形中板料的破裂,测试方法适用于渐进成形极限图的建立.     

Single Point Incremental Forming and the Forming Criteria for AA3003

Single Point Incremental Forming (SPIF) is a modern method of forming sheet metal, where parts can be formed without the use of dedicated dies. The ability of SPIF to form a part is based on various forming parameters. Previous work was not accomplished with the help of design of experiments, thus reducing the number of parameters varied at any time. This paper presents two designs of experiments, which formalise the forming parameters critical in SPIF and the degree to which they affect formability.     

A Process/Machine coupling approach: Application to Robotized Incremental Sheet Forming

In this paper, a Process/Machine coupling approach applied to Robotized Incremental Sheet Forming (RISF) is presented. This approach consists in coupling a Finite Element Analysis (FEA) of the process with an elastic modelling of the robot structure to improve the geometrical accuracy of the formed part. The FEA, assuming a rigid machine, is used to evaluate the forces at the interface between the tool and the sheet during the forming stage. These forces are used as input data for the elastic model, to predict and correct the tool path deviations. In order to make the tool path correction more effective, the weight of three numerical and material parameters of the FEA on the predicted forces is investigated. Finally, the proposed method is validated by the comparison of the numerical and experimental tool paths and geometries obtained with or without correction of the tool path.     

薄板的各向异性对等离子电弧弯曲成形过程的影响

为了研究各向异性的金属薄板对等离子电弧加热弯曲成形的影响规律,采用等离子电弧以直线分别沿1Cr18Ni9Ti薄板轧制方向(RD)和垂直于轧制的方向(TD)进行加热弯曲成形试验.结果表明随着电弧扫描速度的降低,电弧功率增大以及扫描次数的增加,薄板塑性变形的各向异性影响减弱;反之则增强.该研究对薄板等离子电弧加热弯曲成形的实际应用有重要意义.     

激光直接制造工艺对Ni合金成形的影响

选用Ni60合金粉末材料进行了简单零件的激光直接成形试验,借助金相分析、扫描电子显微分析,研究了不同加工工艺对其成形的影响。结果表明:零件成形的宏观质量与单道熔覆层厚度关系密切,在激光功率1100W、激光扫描速度2～3mm/s、送粉量70～100mg/s条件下可获得外观光滑的零件;在送粉量一定的情况下,成形过程熔覆层的高度波动与零件形状有关,可以通过调节扫描速度来改善其高低不平的程度;克服制造缺陷的方法是注意基体的预热和成形零件的缓冷处理,激光功率和扫描速度需要在加工过程中适当调节。     

工艺参数对电渣熔铸熔滴形成过程的影响研究

在电渣熔铸过程中,熔化后的金属液以独立熔滴的方式过渡到渣液下方的铸锭区.熔滴的体积和形成时间都直接影响到电极的熔化率和材料的净化程度等重要指标.建立温度场、流场和电场耦合数学模型,并采用分步法对熔滴的形成过程进行数值模拟研究,获得了在重力、渣液浮力和渣金界面张力等因素作用下的熔滴形成过程,并探讨了不同的工艺条件下熔滴的体积和形成时间的变化规律.     

基于数值模拟的板材渐进成形过程研究

以圆锥台为例,运用ABAQUS/Explicit建立弹塑性有限元模型,研究了半顶角(α)、工具头直径(D)和下压量(△Z)对零件壁厚和成形质量的影响.结果表明,半顶角对制件厚度变化起主导作用,其值越小,厚度减薄越严重;大工具头直径和小下压量有利于获得厚度分布均匀的制件.     

金属钽板的渐进成形实验研究

钽是理想的生物适应性材料,在外科修复体中有广泛的应用前景,利用渐进成形技术进行钽板修复体制作很有意义.以轧制的1mm钽板为对象,建立了钽板渐进成形实验模型,研究钽板的渐进成形性能,初步探讨了工具头材质及形状尺寸、进给量、表面润滑等因素对钽板渐进成形性能的影响,测算出1mm钽板的成形极限角度.     

Analysis of Material Formability in Incremental Forming

Incremental forming is an innovative sheet metal forming technology in which a blank is plastically deformed through the progressive action of a small-size punch, whose movement is governed by a CNC machine. In this way the tool locally deforms the material through an almost pure stretching deformation mechanics.The paper is focused on material formability in incremental forming. Several tests were developed, aimed to the achievement of different straining conditions in the material and consequently to the determination of Forming Limit Diagrams for progressive forming operations. The features and the application of such FLD are discussed in the paper.     

工艺参数对AA5754铝镁合金板料成形的影响

AA5754铝镁合金板料是汽车工业中使用最为广泛的材料之一,它的成形性能与钢板有着本质的不同.采用有限元数值模拟技术,通过对带法兰圆筒形件进行数值模拟,着重分析了摩擦系数、压边力、相对凹模圆角半径以及相对凸模圆角半径四个主要工艺参数对从5754铝镁合金板料成形性能的影响.并与ST16钢板的成形性能进行对比,得出在相同工艺参数条件下,AA5754板料成形性能不如ST16钢板的结论.     

Influence of the Workpiece Stiffness on the Electromagnetic Sheet Metal Forming Process into Dies

Electromagnetic sheet metal forming is a high speed forming process using pulsed magnetic fields to form metals with high electrical conductivity such as aluminum. Thereby, workpiece velocities of more than 300 m/s are achievable, which can cause difficulties when forming into a die. The kinetic energy, which is related to the workpiece velocity, must be dissipated in a short time slot when the workpiece hits the die; otherwise undesired effects, for example rebound can occur. One possibility to handle this shortcoming is to locally increase the stiffness of the workpiece. A modal analysis is carried out in order to determine the stiffness of specific regions of the workpiece so that an estimation concerning the feasibility of the desired geometry is possible in advance without doing cost and time consuming experiments. Thereby, the desired geometry of the workpiece will be fractionized in significant sectors. This approach has to define the internal force variables acting on the cutting edge, which are required to constrain the numerical model. Finally, a method will be developed with the objective of calculating the stiffness of each sector. The numerical results will be verified by experiments. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

Influence of Metallurgical Conditions on the Lining Wear in the Kaldo Process

The influence of different metallurgical conditions on the lining wear in the Kaldo process when refining high phosphorus iron has been systematically investigated revealing the following main featuresThe lining is protected by a lime-saturated layer of slag during the main part of the first blowing period.The lining wear starts in connection with the melting of this protective layer which occurs at the end of the first period. After that, the wear rate increases rapidly.The rapid increase of the lining wear is caused by direct combustion in a strongly oxidizing atmosphere of liquid iron which has been dragged up on the lining surface.By decreasing the oxygen activity in the furnace atmosphere at the end of the oxygen-blowing period the wear can be decreased considerably. In practice this has been solved by directing the oxygen jet with high impulse steeply into the bath during this period of the blowing. In this way the lining life in Domnarvet’s 30 ton Kaldo furnace has been increased by about 75% without reducing the steel yield. Blowing time and consumption of oxygen have at the same time decreased by about 10%.