先进板材液压成形技术及其进展

文章立足于板液压成形这种先进成形技术,面向创新,介绍了其原理及特点,并分类探讨了板液压成形技术最新进展,指出了今后的发展趋势。     

水胀成形液压系统分析

利用传统拉深成形方法加工真空杯等圆筒状件时存在很多弊端,而采用液压胀形技术则可克服传统工艺的缺陷.介绍液压胀形系统工作原理及特点和此技术在实际生产中的应用.     

一种采用拉深与液压胀形的复合成形工艺与模具设计

以某家用电器的钣金零件为例,进行成形工艺分析,拟定工艺方案,结合具体生产条件优化工艺,确定零件可行性成形方案。结合不锈钢钣金成形的特点,采用拉深成形作为预成形,液压胀形作为关键成形的方案。生产实践表明,该复合成形工艺及模具结构合理,能保证零件质量,生产效率达到预期要求。     

板材拉深成形性能智能化预测系统

对板料成形性能智能化技术的特点及其开发和应用的意义进行简要的介绍，并详细阐述了板料成形性能智能化系统的整体结构和功能，详细论述了该系统开发的关键技术部分：用户信息输入部分、推理和评定部分的设计思路和具体内容。     

管材液压成形技术的发展——从前8届国际塑性加工会议看管材液压成形技术的发展

文章回顾了前8届国际塑性加工会议论文集中关于管材液压成形方面的文献,发现,早期的管材液压胀形技术内压较低,后来发展到可同时实现超高压和轴向补料;可成形零件的轴线由直线变为二维或三维空间曲线,种类大幅增加;适用于内高压成形的材料也由铝、铜、低碳钢等增加了不锈钢、铝合金、镁合金;同时热态内压成形技术也蓬勃发展起来。     

烧结不锈钢丝网多孔板材的冲压成形研究

以烧结不锈钢丝网多孔板为材料,在室温条件下通过胀形试验和筒形拉深试验研究材料的冲压成形性能。胀形试验结果显示,材料的胀形极限随着厚度及直径的增大而增大;厚度为1. 4和1. 75 mm的多孔板在直径Φ110 mm的冲模下胀形高度达到30 mm未出现破裂,说明材料具有良好的塑性。筒形拉深试验显示,拉深力随板材的厚度、直径的增大而增大,随孔隙率的增大而减小;厚度为1. 2 mm时,拉深极限比为1. 8。根据塑性力学基本理论,推导了烧结不锈钢丝网多孔板的拉深力预测公式,将理论预测与实际试验数据对比,验证了公式的适用性。研究结果表明,烧结不锈钢丝网多孔材料具有较好的塑性,可进行冷冲压成形,有助于拓展多孔隙功能材料的应用领域。     

板材液压成形实验研究

分析了液压胀形变形特点及成形机理,对板材液压成形进行了实验研究,分析了坯料厚度变化规律,确定了提高材料胀形成形极限的具体措施。     

椭球壳体无模液压成形实验探索

无椭球壳体的整体无膜胀形成形工艺进行了实验研究。实验壳体采用单曲率椭球内接多面壳体。对实验壳体的尺寸变化、变形过程中的表面应变分布、变形前后的壁厚变化规律进行了测试分析,探讨了壳体的趋球变形过程,壳体的长短轴变化趋势及塑性变形规律,实验证明,在封闭椭球壳体内塑性趋球规律仍然起作用,椭球无模液压整体成形工艺值得进一步探讨研究。     

Technology of sheet hydroforming with a movable female die

An improved sheet hydroforming process is proposed and investigated experimentally and numerically. A movable female die keeps in contact with the deformed area of the sheet blank so that further deformation of the deformed area is restricted. Under the sealing, the sheet blank under the flange can be drawn in. So the hydroformed part has less thinning than the hydrobulge formed part only, and the limit drawing ratio of the sheet can be remarkably improved. This process is especially suitable for forming of small batch production of sheet metal parts with complicated shapes. The female die can be replaced with other female die of various shapes, and can also be made of very cheap materials such as plaster and hard wood instead of metal when the part number is very small. Thus complex-shaped sheet parts can be formed with less expensive tool systems.In this paper, the hydroforming processes of part A (without a movable die) and part B (with a movable die) were investigated by experiment and by elastoplastic FEM. The effects of various process parameters on the deformation of the sheet blanks were investigated. The forming conditions affecting wrinkling and rupture have been analyzed. The effects of friction and contacting force acting on the experimental results are also discussed.     

Process control at the sealing line during sheet metal hydroforming

Sheet metal hydroforming is a deep drawing process that uses a pressure medium for load transmission. The process is mainly influenced by the control of the blank holder force and the fluid pressure. This report describes investigations of a newly developed process-control system. Process variables can be controlled by the sealing state of the tool. The detection is performed by a CCD-camera system that allows the continuous recording of occurring leakages. Different control strategies can be used to control the multiple process parameters. This paper describes the performance and the limits of the aforementioned technology.     

Process layout avoiding reverse drawing wrinkles in hydroforming of sheet metal

Sheet metal forming processes like the fluid form process or hydromechanical deep drawing have the potential for the manufacture of parts having high precision, large drawing ratio, and low costs especially for small and medium lot sizes. In deep drawing using a separating membrane between the liquid and the sheet the process layout for drawing of complex parts must avoid not only the typical failures of bottom fracture, first and second order wrinkles, but also an additional type of wrinkles which are maybe created at the beginning of the process. The development of these wrinkles is described using an analytical model, which was validated by experimental results. The model was used to develop the process layout for deep drawing of a complex sheet metal part.     

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。     

Friction aided deep drawing of sheet metals using polyurethane ring and auxiliary metal punch. Part 2: analysis of the drawing mechanism and process parameters

Friction aided deep drawing using a polyurethane ring as a pressure medium has been analyzed by the slab and the energy methods to understand the main features of the process and to find the optimum conditions to achieve successful drawing. The effect of an auxiliary metal punch on the stress distribution of the deformed blank and the increase in height of the drawn cup is also discussed. From these studies, the reason why the unusual circumferential crack occurs at the flange of the deformed blank has been clarified, based on the radial stress distribution of the deformed blank. A process parameter, which denotes the drawing characteristics of the friction aided deep drawing, has been proposed. In addition, the drawing region diagram has been presented to facilitate the drawing pressure control with the progress of the drawing process. It is shown that the successful drawing region is narrow at the early stage of drawing, although it becomes wide as the drawing proceeds. Therefore, in the early stage of drawing, special care should be paid to the drawing pressure control to avoid the flange crack.     

板料多道次拉深成形规律和性能的研究

在物理模拟的基础上，研究了板料拉深成形过程中，材料的性能参数和工艺参数对板料成形性能的影响，着重分析了对多道次拉深成形的影响。结果表明，无论是材料性能参数还是材料的工艺参数都对再拉深的影响比对单道次拉深的影响林大得多，但两种参数对多道次拉深的影响过程前后是一致的。同时可以看出，多道次拉深之间是相互影响的，不能割裂开来考虑。     

Two-step method of forming complex shapes from sheet metal

A two-step method of forming a part and a method of designing a preform shape are being discussed. The part may be formed from lightweight material to an extent that would normally exceed the forming limits of the material if the part were attempted to be formed in one-step conventional stamping die. Critical areas including deep pockets and sharp radius areas of the final part are formed from a preform or intermediate shape part. The first forming step can be conducted by variety of sheet metal forming methods; the preformed blank is further formed in a fluid pressure forming process to a final part shape wherein broad radius areas and pockets of accumulated metal of the preform are formed into deep pockets and sharp corners of the final shape. Electrohydraulic forming technology is employed for the second forming step.     

Friction aided deep drawing of sheet metals using polyurethane ring and auxiliary metal punch. Part 1: experimental observations on the deep drawing of aluminium thin sheets and foils

Friction aided deep drawing based on the Maslennikov process is investigated as a method to facilitate the deep drawing of sheet metals with poor drawability. Aluminium foils and thin sheets of 0.1–0.4 mm in thickness are used as a model for the material with poor drawability. An auxiliary metal punch is used together with a polyurethane ring to increase the drawing efficiency and to improve the dimensional accuracy of the drawn cup. The effect of drawing conditions such as thickness, hole diameter and the hardness of the polyurethane ring on the cup height are mainly investigated. Also, the optimum number of drawing operations required to achieve a given drawing ratio is examined by repeating compression and unloading the polyurethane ring. The experimental results show that even for foil and thin sheets, deep cups with drawing ratios of 2.25 and with good shape and dimensional accuracy can be obtained by repeating the drawing operation about ten times. The achievable drawing ratio is appreciably larger when compared with that obtained by the conventional deep drawing process.     

Springback in stringer sheet stretch forming

Stringer sheets are sheet metal structures stiffened by bifurcations in the cross-section. In order to create spatially curved light-weight structures they may serve as preforms for sheet metal hydroforming. The stiffness of sheets altered by stringers is expected to affect the hydroforming results. In particular influences of the geometric inhomogeneity on the extent and orientation of springback are of interest. They are investigated by means of mathematical analysis and forming experiments. A modal analysis of formed stringer sheets is conducted in order to understand the different impacts of stringers on the elastic behaviour of parts and springback after forming.     

Investigation of active-elastic blank holder systems for high-pressure forming of metal sheets

Hydroforming constitutes a subgroup of sheet metal forming processes utilizing a pressurized forming medium. Besides the hydroforming of hollow sections, the high-pressure forming (HPF) of metal sheets is demonstrably one innovative method for the production of complex sheet metal components and offers high potentials to improve the properties and qualities of sheet metal parts. This report describes investigations of a newly developed active-elastic blank holder technology, which is used for HPF of metal sheets. Unlike the use of semi-rigid blank holder systems, the active-elastic blank holder system shows improvements with respect to the material flow in the flange area and reduced sheet thinning in critical corner regions of the work-piece. In addition to numerical analysis concerning the development and design of the active-elastic blank holder, current experimental examinations will be presented. The focus is on a comparative evaluation of the simulation and production of rectangular metal parts, by using conventional semi-rigid tools and active-elastic tools.