管材内高压胀形的实验研究与数值模拟

介绍了管材无模轴压胀形的实验,研究表明,适度的褶皱有助于提高成形极限。有限元数值模拟显示,随着内压—轴压匹配模式的改变,内压增长率对褶皱的演化表现出不同的影响效果。针对管坯—模具间摩擦对T型管复合胀形成形性的影响,分别从实验和有限元数值模拟两方面进行了研究。     

管材内压液力成形的稳定性分析

管材内压液力成形过程中 ,管坯在内压与轴向压力的共同作用下发生变形。成形过程中常见的缺陷是起皱和破裂 ,这两种缺陷的产生都和管的失稳有关。本文运用薄膜理论分析了管坯在轴向力单独作用下的压缩失稳 ,得出临界轴向压力的计算公式 ;从失稳应变强度入手 ,分析了圆柱管在内压和轴向压力共同作用下的分散性失稳 ,根据失稳应变强度的计算公式 ,分析了应力状态系数 a、厚向异性指数 rh、应变强化指数 n等因素对管的失稳应变强度的影响规律     

方截面轻体件的内高压成形研究

管坯内压液力成形工艺由于能够节省材料、降低成本、提高零件机械性,因此近年来在汽车、航空航天等领域中得到了广泛应用。本文针对目前该工艺存在的轴向量与内压之间的匹配关系问题,通过有限元模拟手段分析了由圆柱管坯成形空心方截面零件过程中加载路径对工艺的影响,为该工艺面向生产提供了一定的参考依据。     

微小管轴向超声辅助液压成形装置的设计与开发

针对现有的超声振动液压成形装置中振动主要施加在模具上、振动能量传递路径长、结构复杂等特点,开发了一种将振动直接作用于管材的微小管轴向超声辅助液压成形装置,可在普通压力机上进行超声和常规的轴压胀形。该装置选用标准模架作为轴向进给机构,结构简单、成本低,通过设计耦合了变幅杆功能和密封结构的一体化工具头,将超声振动顺利叠加在轴压胀形过程中,并以TP2无缝内螺纹铜管为试验材料进行了相关试验。结果表明:该装置拆装方便、操作简单,振动的加载降低了对成形过程中轴压载荷和液压力的要求,加强了材料的轴向流动。     

管轴压精密成形过程中管坯脱模点的预测

管轴压精密成形过程中 ,存在着管坯脱离模具而由约束变形到自由变形的转变 ,因而明确管坯脱模点的位置 ,将对整个成形过程的研究具有重要意义。本文采用有限元数值模拟 ,对成形过程中管坯的脱模特性及其影响因素进行了研究 ,结果表明 :管轴压成形过程中管坯的脱模状况 ,受到变形几何参数和材料参数的共同作用 ,其中几何参数是影响管坯脱模点位置的决定因素 ,材料参数则对脱模时的成形力影响很大     

管材液力成形技术的研究进展

针对航空航天、核能工程与新能源汽车等国家重大科技工程领域中具有大膨胀率及大截面变化比等复杂结构特征的管类零件,开展将液压成形与机械力加载相结合的管材液力成形技术的研究。根据零件几何结构特征和施加载荷方向的不同,将该技术进一步分为轴向加载、径向加载以及多向复合加载液力成形工艺。从工模具开发、有限元仿真、加载路径优化及在典型复杂管类零件上的应用等多个方面,对管材液力成形技术的研究进展进行阐述和介绍。结果表明,该技术通过结合外部的机械力作用,在降低成形时管材内所需液体压力及设备吨位的同时,还能够实现变形量高达近70%的复杂管类零件的整体成形,从而提高了产品的成形性能和表面质量,进一步拓展了液压成形技术在管材精密成形中的应用,为高性能金属复杂管类零件的开发提供了有效的技术支撑。     

薄壁箱形金属管材冲压成形试验研究

以薄壁箱形金属管材为对象,研究了冲压成形过程中冲压速度、约束条件等因素对成形质量的影响。研究表明:冲压过程中增加薄壁箱形管材侧壁约束可以提高薄壁箱形管坯整体受压变形的稳定性,利用侧壁挡板和内腔充沙等措施,可明显减弱管坯产生侧壁屈曲;合适的冲压速度可有效消除管坯顶面屈曲;合理控制冲压速度和约束条件等工艺参数可有效提高薄壁箱形金属管材冲压成形质量。     

新型管材冲击液压成形装置的设计

针对常规的管材液压成形技术需要昂贵的专用设备及模具、生产效率低等不足,开发了一种简单实用、可在冲床或压力机上使用的管材冲击液压成形装置,可用于薄壁金属管材的自然胀形、轴压胀形和异形截面中空件的冲击液压成形。该装置无需外部高压供给系统和专用液压成形设备,通过撞击轴压头挤压容腔中液体的方式来为管材提供液压力和轴压力。通过设计轴压头的行程和调节溢流阀的溢流压力值等来实现最大液压力和轴向进给量的合理匹配,并以304不锈钢毛细管和H65黄铜毛细管为试验管材做了相关试验。研究结果表明:该装置结构简单、操作方便;可实现最大液压力与轴向进给量的协调控制;合理的载荷匹配能显著地提高管材冲击液压成形的成形性能;H65黄铜毛细管破裂时所需的液压力小于304不锈钢毛细管破裂时所需的液压力。     

润滑条件对管件液压成形结果的影响

介绍了液压成形技术在国内外的现状以及常用分析方法,对管坯与模具之间的摩擦机理进行了分析.通过数值方法和实验研究,探讨了润滑条件对汽车仪表板梁成形过程中的补料量、管坯壁厚等参数的影响,为实际生产中补料量的确定、润滑方案的选择、模具的设计等提供理论参考.     

金属管接头复合成形弯曲缺陷的研究

分析了管接头的缩口—轴压—胀形复合成形过程中弯曲现象产生的原因,运用刚塑性有限元法分析了模具圆角半径和摩擦因子对该现象的影响,最后给出了减小弯曲现象的措施。     

Finite element analysis of sheet Hydromechanical forming of circular cup

Sheet hydroforming is a process of converting flat sheet into desired component geometry by using water pressure in a controlled manner. This paper dealt with sheet Hydromechanical forming (SHMF) of circular cup. In this process, blank is first placed on the lower die (a fluid chamber combined with draw ring) and then after sealing the blank between blank holder and draw ring, punch progresses to deform the blank. Pressure of the fluid chamber is also increased simultaneously with the punch progression. The present work endeavours to understand the effect of strain hardening exponent, anisotropy ratio and interfacial friction between blank and tools surfaces for different modes of deformation––stretching to drawing mode on sheet Hydromechanical forming of circular cups.A finite element (FE) model was developed for simulating the SHMF process using dynamic explicit, commercial code, LsDyna. The model after experimental validation used for studying the effect of above parameters on the process. The analysis reveals that higher cup depth with minimum thinning for forming dominated by stretching mode can be achieved with material of higher anisotropy ratio, strain hardening exponent by using a rough punch and effective lubrication at blank-die–blank holder interfaces. On the other hand in case of drawing as mode of deformation, thinning is influenced mainly by interfacial friction condition between blank and tool surfaces as compared to material properties.     

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。     

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.     

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.     

Finite element modelling and control of new metal forming processes

The classical formulations for material forming either in the solid or in the liquid state are briefly recalled, in terms of material constitutive behavior, friction law, integral forms and finite element discretization. A few important numerical issues are discussed, including meshing, remeshing and adaptivity, parallel computing and coupling between work-piece and tools. Five examples of applications of finite element models to new processes are presented: friction stir welding, hot stamping of quenchable steels, tube hydroforming, thixoforming and self piercing riveting. It is concluded that many new forming processes can be designed and optimized much more effectively using the numerical simulation technology.     

铝合金拼焊板充液成形技术研究

铝合金拼焊板充液成形技术是拼焊板成形技术和充液成形技术的综合运用,兼具了这2种先进成形技术的双重优点,在汽车、航空航天等领域具有广泛的应用前景。介绍了铝合金拼焊板焊接方法、激光焊接的特点与难点,探讨了拼焊板充液成形技术的原理、特点及国内外研究现状,指出了开展此项研究的必要性和重要意义。     

支叉管零件充液成形工艺

针对某军机支叉管类零件的结构型面复杂、曲率变化大的特点,其传统的成形方式主要采用落压成形,在成形过程中易产生起皱、破裂和表面质量差等问题.因此,提出采用被动式充液成形来加工支叉管零件,并利用有限元软件ANSYS/LS-DYNA建立有限元分析模型,对其充液成形过程进行有限元仿真模拟,研究不同压边力对充液成形的影响,从模拟...     

深盒形件液压拉深成形工艺研究

用DYNAFORM有限元仿真软件对深盒形件液压拉深成形过程进行了模拟,分析了压边力和液体压力对盒形件成形质量的影响。研究结果表明,合适的压边力和液体压力能控制盒形件拉深缺陷的发生,采用液压拉深盒形件可获得更好的壁厚分布。     

基于灰色系统理论的汽车横梁充液成形用坯料优化

类似汽车横梁这些复杂管类结构件的充液成形,是一个不均匀的变形过程,坯料的相对形状及尺寸,是影响金属流动的关键因素,从而对充液成形零件的最小壁厚、最大壁厚等评价对象有重要影响。以坯料的弯曲角度、弯曲半径、轴线高度差为因子,建立正交试验设计方案,进行有限元模拟,获得不同坯料尺寸下的最小壁厚、最大壁厚参考序列。利用灰色系统理论,计算各个参考序列与比较序列之间的关联系数,将多目标转化为以关联度为目标的单目标。进一步计算各坯料结构尺寸的平均关联度,获得优化的坯料尺寸组合参数,以此进行有限元模拟和生产实验。验证结果表明,该优化方法能够获得满足质量要求的充液成形的汽车横梁。     

板成形数值模拟影响因素的正交试验分析

根据正交试验原理，应用板料成形软件对不同压边力、模具与板料间摩擦系数、凸凹模间隙和板料初始尺寸进行数值模拟，将数值模拟的厚度同实际成形件的厚度进行比较，得出上述因素对前翼子板成形结果的影响，并预测了前翼子板较优的理论成形条件。