智能与控制在塑性加工制备与成形中的应用

对材料制备与塑性加工方面的智能控制特点进行了介绍与分析。首先对钢铁、铜及铜合金管材连铸连轧过程控制加工特点进行了阐述 ,其次介绍了镁合金的“轧制 等通道角挤压 拉制”连续加工制备技术和镁合金薄板半固态双辊铸轧工艺。对于薄板增量加工成形技术 ,介绍了飞机整体壁板增量压弯技术、薄板单点无模增量成形技术和多点无模增量成形技术。讨论了薄板可动凹模液压成形技术、异型截面管件液压成形技术和细长杆件空间弯扭成形技术原理。最后对于微小件加工技术进行了简要介绍     

Influence of variables in deep drawing of AA 6061 sheet

Deep drawing is one of the most important processes for forming sheet metal parts.It is widely used for mass production of cup shapes in automobile,aerospace and packaging industries.Cup drawing,besides its importance as forming process,also serves as a basic test for the sheet metal formability.The effect of equipment and tooling parameters results in complex deformation mechanism.Existence of thickness variation in the formed part may cause stress concentration and may lead to acceleration of damage.Using TAGUCHI's signal-to-noise ratio,it is determined that the die shoulder radius has major influence followed by blank holder force and punch nose radius on the thickness distribution of the deep drawn cup of AA 6061 sheet.The optimum levels of the above three factors,for the most even wall thickness distribution,are found to be punch nose radius of 3 mm,die shoulder radius of 8 mm and blank holder force of 4 kN.     

Pressure estimation in the hydroforming process of sheet metal pairs with the method of upper bound analysis

Hydroforming is one of the new technologies in the manufacturing processes, in which hollow pieces are formed under pressure of a fluid. The basic parameter in this process is the pressure control of the fluid. This article deals with the process of hydroforming of a pair of metal sheets. After obtaining the kinematically admissible velocity field, the pressure equation is obtained by the upper bound analysis. This equation can be applied for each part if the instantaneous geometry of the deformed sheet in the die cavity zone during the process can be analytically expressed. The effects of the parameters of work-hardening, friction and blank size have been taken into considerations. To validate the results of this work a hemispherical part formed in the hydroforming of single-sheet process has been considered. The results obtained by this analysis have been compared with the experimental results.     

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。     

汽车大型铝合金覆盖件的充液成形技术

铝合金覆盖件的应用是汽车轻量化的关键,但其制造难度较大。通过研究铝合金发动机罩外板的充液成形工艺过程,了解先进柔性技术在汽车领域应用的可行性。分析了工艺参数中液室压力与凸模行程匹配及压边力对板料减薄率的影响,从成形极限上判断零件无起皱、破裂现象的范围。获得最优的整形液室压力为12～20 MPa,压边力过小,板料不能充分塑性变形,压边力过大,板料易失稳破裂,最优的恒定压边力范围为1600～2000 k N。研究表明,采用板材充液成形柔性制造工艺,可降低噪音,无冲击线,且由于液室压力的作用,滑移线减小,可提高大型铝合金弱刚度板材的质量。     

飞机铝合金双曲度蒙皮充液成形的数值模拟与试验

针对某型飞机上蒙皮零件,基于有限元分析软件Dynaform,对主动式充液成形和被动式充液成形两种方案进行了数值模拟对比分析。根据数值模拟结果,认为该零件较适合采用主动式充液成形,其次,通过修改工艺补充面和优化成形工艺参数,有效地控制零件的最大减薄量。同时,保证一定的减薄量,使板料达到塑性变形状态,从而有效减小回弹。再通过回弹分析,根据回弹量计算结果,运用Think Design软件对模具型面进行回弹补偿,将回弹量控制在合格范围内。最终通过实际试模,验证了数值模拟的准确性及适用性,加工出表面质量良好、精度满足要求的合格产品。     

Numerical simulation of aluminum alloy ladder parts with viscous pressure forming

1　INTRODUCTIONTheeffectofstressstatesonaxisymmetricsheetformabilityhasbeenstudiedundertheconditionofsolidmetalpunchforming [14 ] ,andtheeffectofblankholderpressure (BHP) ,frictioncoefficientandpunchconfigurationonthestressstateshasbeenob tained .Becauseofthedisadvantagesofsolid punchforming ,newformingtechnologyisneededtoim provethestressstatesofthesheetinformingprocessandtomeettherequirementofforminglow plastici ty ,complexshapeparts .Viscouspressureforming(VPF)isarecentlydevelopedfle…     

Numerical/experimental investigations for enhancing the sheet hydroforming process

In this work the authors present some results of their research activity aimed to enhance the sheet hydroforming process. The main focus is the adoption of a movable inferior plate through which the control of the blank forming is realised. Tests on hemitoroidal parts using an innovative equipment with a movable die were carried on at the Institute of Metal Research (Chinese Academy of Sciences) in cooperation with the Aalborg University, putting in evidence main defects and fracture causes. Finite element simulations of the modified hydroforming process using a movable inferior plate were performed at the Centre of Excellence for Mechanical Computation (Polytechnic of Bari), with the aim of evaluating critical strain values and their location, strain paths, load curves and stress maps were analysed. Specimens with proper geometrical shape were designed to avoid possible ruptures and to reduce material thinning in the critical regions.     

板料增量成形的研究进展

板料增量成形是采用简单模具对板料进行逐次塑性加工的一种工艺,不需要专用的模具就可以成形较为复杂的零件,同时还具有成形力小、柔性高的特点,特别适合多品种小批量零件的生产方式,因此得到国内外学者的重视。本文重点从板料的增量压弯成形、增量拉深胀形、增量微成形3个方面对板料增量成形的发展进行综述,还对板料增量成形工艺的发展前景进行了展望,指出进行理论创新、开发新的模拟软件、探索新的成形方案、开发增量成形新设备是发展趋势。     

板材零件成对液压成形的分析与试验研究

板材成对液压成形技术是一种新的板材成形技术,具有成形性好、制造工期短、费用低等优点,特别适用于批量小、形状复杂板材零件的生产。本文对板材成对液胀成形技术进行了理论分析和试验研究,介绍了该技术的技术原理和特点,提出了提高其成形极限的措施。结果表明：理论分析结果和实验结果是一致的。     

Optimal Programming of Multi-point Cushion Systems for Sheet Metal Forming

Numerical optimization technique coupled with finite element analysis of the stamping/sheet hydroforming process was developed to predict four possible modes for application of blank holder force (BHF) in multiple-point cushion systems, namely a) BHF constant in space/location and time/stroke, b) BHF variable in time/stroke and constant in space/location, c) BHF variable in space/location and constant in time/stroke and d) BHF variable in space/location and time/stroke. The BHF was predicted by (a) minimizing the risk of failure by tearing (thinning) in the formed part and (b) avoiding wrinkling. The developed technique was applied to predict the BHF to form a) an automotive part (liftgate-inner) from AA6111-T4 aluminum alloy, b) an asymmetric part from aluminum alloy AA5083-H32 by sheet hydroforming process with die (SHF-D) and c) a round cup by sheet hydroforming with punch (SHF-P). Experimental results showed that the FEM based optimization methodology can reduce trial and error effort and is able to predict the blank holder force necessary to form the parts without fracture and wrinkling in the investigated stamping and sheet hydroforming operations.     

汽车中空异形板件液压成形的实验与仿真分析

为研究基于液压成形的汽车钣金件成形规律,以汽车中空异形板件为研究对象,自行设计并搭建板材液压成形实验测试系统,以此开展板件液压成形的实验研究,借助DYNAFORM有限元软件对板材液压成形进行有限元仿真分析,通过与实验测试结果的对比,验证了建立的有限元模型与数值模拟的正确性。以此为基础,探究压边力、压边力加载路径、液室压力、压边间隙和板材与凹模之间的摩擦系数等关键工艺参数对板材液压成形厚度的影响规律,提出汽车中空异形板件液压成形工艺,为板材液压成形技术在汽车钣金件成形中的应用提供参考。     

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.     

Metal flow in the precision forging of aluminum alloys

To research impeller parts flow behaviors in the die forging process, the finite element method is used to study the deformation flow behavior of different shapes in the blank forming process. The results show that the blade parts of the forgings were hard to fill, but with the section of the blade shifting down, the metal has a marked trend to flow toward this area of the die cavity. Compared with a cylindrical shape, the die cavity of the blade part can be filled more easily and the uniformity of metal flow will increase. Using a ladder shape to manufacture forgings of impellers can meet requirements for design and properties.     

复杂冲压件液压成形装备的设计与制造

介绍了一种板料液压成形成套装备,包括模具结构、液压控制系统和计算机控制系统。该装备具有结构简单、经济实用、可实现变压边力控制等特点,可获得高质量的复杂板料成形件。     

成对铜片级进模设计

叙述了车用连接导通制件中成对铜片的冲裁弯曲成形工艺,介绍了制件的排样及模具结构设计特点,并对模具主要工作零件进行设计,阐述了切断活动凹模镶件的设计。模具经生产实践证明:模具结构紧凑合理,成形的制件形状和尺寸达到图纸技术要求,可为同类制件的模具设计提供参考。     

成对铜片级进模设计

叙述了车用连接导通制件中成对铜片的冲裁弯曲成形工艺,介绍了制件的排样及模具结构设计特点,并对模具主要工作零件进行设计,阐述了切断活动凹模镶件的设计。模具经生产实践证明:模具结构紧凑合理,成形的制件形状和尺寸达到图纸技术要求,可为同类制件的模具设计提供参考。     

薄板件多点成形与模具成形时起皱现象的对比分析

起皱是传统冲压成形和多点成形时共有的现象,尤其在无压边成形方式下很容易发生。文章采用有限元数值模拟手段,针对两种多点成形工艺和整体模具成形过程中产生的起皱现象进行了探讨,分析了无压边成形过程中不同的成形工艺对球形件起皱的影响。文章用显式动力学算法进行了数值模拟,结果表明,采用多点模具成形工艺成形1mm厚度的板料时,曲率半径为200mm的成形件起皱明显;但在相同条件下,用多点压机成形工艺的成形件结果良好,甚至成形厚度为0.5mm,曲率半径为150mm的球形件也没有起皱;而在这两种条件下,整体模具成形都有微小的起皱发生。也就是说,多点压机成形方式比多点模具成形方式以及整体模具成形方式效果更好,缺陷少,能够得到更大的变形量。     

基于Dynaform的汽车前托架成形分析及参数优化

分析讨论了汽车前托架零件的成形工艺及有限元分析前处理中工具体与板料的网格划分;探究了摩擦系数、压边力对板料成形的影响。结果表明,较小的摩擦系数增加了零件的起皱趋势,但对破裂缺陷有较大改善;基于模面破裂危险区的形变分析,对模面修改后进一步进行压边力优化,从而进行了符合实际工艺的多阶段前托架成形优化分析。采用优化后的工艺参数和模面形状进行实际试冲,得到了合格的零件,板料变薄率和增厚率分别在20%与5%的允许范围内。实际试冲与数值模拟的板料厚度应变误差在4%范围内,且板料轮廓收料情况相符。     

Combined tube and double sheet hydroforming for the manufacturing of complex parts

Modern lightweight construction, especially in the automotive industry, requires more and more complex components, which can be manufactured in one process step using the hydroforming technology. The combination of the tube and double sheet hydroforming is a new forming process, where a tube and two blanks are formed simultaneously in a die cavity, combining the advantages of both hydroforming variants. This paper deals with the fundamental considerations and investigations related to connection between tube and double sheet. The finite element analysis and laboratory trials were used in order to design the shape of the die cavity and to avoid wrinkles, material tearing and the collapse of the tube section during forming. The paper will also illustrate an analytical model for the prediction of the edge shape in the constrained bulging of a rectangular cup together with several technical solutions, which enabled a complete forming of the investigated part. Finally, the definition of a hydroforming material factor based on the analytical model of the hydraulic bulging process enables the right choice of sheets with different material strength and thickness for the hydroforming of hybrid components.