混合压边液体内向流动动态充液拉深

为抑制液体内向流动动态充液拉深中凸缘增厚而造成的拉深阻力急剧增长,提出混合压边液体内向流动动态充液拉深新方法。对定间隙下设定恒定压边力的混合压边充液拉深压边形式实质进行分析,采用有限元研究混合压边方式下压边间隙、压边力以及径向压力的变化对成形过程的影响。研究结果表明:定间隙下设定恒定压边力的混合压边充液拉深压边形式的实质是设定压边间隙和设定压边力压边方式的混合;采用混合压边方式可以降低实际最大压边力,降低凸缘区的摩擦阻力,减少第二个谷底点的减薄率;压边力影响零件直壁部分壁厚分布,较大的压边力得到的零件直壁壁厚较薄;压边间隙的变化影响成形零件直壁壁厚分布,较小的压边间隙成形零件直壁较薄,第二个谷底点越接近零件底部。     

盒形件无模充液拉深液压加载路径的研究

凹模型腔内的液体预胀形压力和工作压力是决定充液拉深过程中能否拉深出合格零件的重要工艺参数.通过采用Dynaform软件,对无模充液拉深盒形件工艺进行数字仿真,就液体压力参数对板料成形性能影响进行分析与研究.结果表明,合理地控制凹模型腔内液体加载路径和压力参数可以有效地提高板料的成形性能和成形件质量.并由液体压力所带来的摩擦保持效应可使成形件壁厚分布均匀,一次拉深的盒形件最大相对高度可达到4.25.     

盒形件充液拉深成形工艺优化及试验研究

本文主要研究充液拉深成形技术在复杂异形长法兰类盒形件成形过程中的应用,首先对该类零件的材料进行了力学性能和成形性能测试分析,获取材料的成形极限,确定了充液拉深成形方案;建立了盒形件的有限元仿真模型,模拟了盒形件在充液拉深成形过程中材料的壁厚变化情况,通过成形缺陷分析对关键工艺参数低压充液时间TLP、整形时间TIP、最大压边力Fmax、液体流速Vel％,最大成形力Pmax及时效时间Tw等进行了重新设计,并通过数值模拟和试验验证相结合的方法优化了工艺参数;最终,完成了盒形件充液拉深成形流程再造,确定出最优的工艺参数,并成功实现盒形件的充液拉深成形,使其制造效率和产品质量大幅提升,为低塑性、难变形材料盒形件的批量制造奠定了工艺基础.     

先进充液柔性成形技术及其关键参数研究

基于所提出的具有均匀压边力并轴向加压的板材充液柔性成形技术,面向板材液压柔性成形技术的普遍规律,成形出拉深比较高的铝合金筒形件以及其他复杂形状的零件如方锥盒形件、方盒形件、轴对称锥形件等,对其中的关键技术如初始液压加载状态、液压加载最优路径、破裂控制等一些关键参数进行了研究和优化;考虑板平面方向性系数的影响,利用数值模拟的手段对其成形过程进行了分析,指导实验研究,得出了有益的结论。     

加载路径对汽车顶盖充液拉深成形影响数值模拟

板材充液拉深（hydromechanical deep drawing,HDD）是在拉深凹模中以一定压力液体作为传力介质代替刚性凹模传递载荷,使坯料在液体压力作用下贴靠凸模拟实现金属板材零件的成形。与传统拉深工艺相比,板料成形性显著提高,成形表面质量好,模具寿命长。随着成形设备和相关技术的发展,充液拉深工艺被广泛应用于汽车、飞机制造业。     

变曲率抛物线型零件充液拉深工艺优化

基于抛物线型零件充液拉深工艺,采用理论分析、有限元仿真及工艺试验优化了工艺参数,利用理论公式计算得到了关键参数的理论值,总结得到了该零件的理论成形工艺窗口,通过有限元进一步精确了工艺窗口的范围,得到了经仿真优化的液力加载曲线,结合工艺试验调整了局部参数,对试验中出现的成形缺陷进行了原因分析并给出了解决方案,经过验证得到了用于生产加工的实际液力加载轨迹,给出了抛物线型零件充液拉深一般的液力加载曲线特征,可作为同类型零件充液拉深成形工艺参考。     

火箭贮箱箱底充液拉深成形工艺的多目标优化

充液拉深成形技术能实现大型贮箱箱底的整体成形,然而成形件的质量受到许多工艺参数的影响。针对大型贮箱整体箱底构件充液拉深成形的起皱和破裂缺陷,以预胀压力、液室压力、压边力、压边圈圆角半径等工艺参数为研究对象,建立多目标优化模型。对贮箱箱底成形过程进行模拟,在此基础上,使用拉丁超立方采样法获得样本数据。采用克里金插值法(Kriging)和径向基函数(Radial basis function, RBF)建立工艺参数和质量指标之间的代理模型。利用NSGA-III算法和粒子群算法(Particle swarm optimization, PSO)确定了贮箱箱底达到目标(壁厚减薄率最小、破裂趋势最小、法兰边起皱最小、起皱趋势最小)时的最优工艺参数。最后通过实验验证了方法的有效性和结果的准确性。     

抛物面零件充液拉深工艺参数优化分析及成形装置改进

充液拉深是一种先进的板材成形方法.结合装饰零件的实际需求,通过数值模拟的方法对抛物面灯罩的充液拉深成形过程进行了研究,应用显式有限元分析软件DYNAFORM,分析了变压边力和液体介质压力对零件成形质量的影响,得到了变压边力和液体压力匹配的加载曲线.并对充液拉深成形系统进行了合理改造.分析结果表明,采用优化的变压边力和液...     

方盒形件分区压边方式拉深压边力的数值模拟

板料拉深成形是冲压生产中的一种少、无切削的先进加工方法,拉深成形的重要工艺参数之一是压边力,是保证零件成形质量的关键.根据方盒形件的拉深成形特点,将压边圈设计为直边区域、法兰转角区域及直边与转角交界区域的十六块分区压边方式,并对分区压边圈在不同压边力加载模式下进行了模拟分析.分析结果表明:对于方盒形件的拉深,将压边圈设计为适当的分区结构、各分区压边圈采取合理的变压边力加载模式可以充分改善板料的成形性能、达到抑制板料起皱和延缓破裂以及提高板料拉深成形质量.     

液体辅助压边周向充液拉深

为了克服液压辅助压边中橡胶膜易破损和发挥径向压力对提高板料成形极限的作用,提出液体辅助压边周向充液拉深新技术。将液池内液体通过增压活塞增压后,加载到毛坯凸缘上表面和凸缘边缘实现液体直接压边和高于液池压力的径向压力辅助拉深;采用导流孔将毛坯边缘的液体引至板料凸缘下表面部分区域,缩小液体实际压边区域,减少凸缘区摩擦阻力。初步试验验证该方案可行有效后,用有限元法对成形过程进行研究,并得到合理的工艺参数。通过试验建立极限拉深比和增压比的成形区域。研究表明:拉深得到的零件壁厚分布存在两个谷底值,分别对应冲模力的两个峰值;增压活塞增压比的增大影响成形零件的壁厚分布,较大的增压比下拉深得到的零件壁厚也较大;当液池压力18MPa时,采用2.4倍的增压活塞,得到拉深比达2.86的铝合金2A12O杯形件。     

Development of a hydroforming setup for deep drawing of square cups with variable blank holding force technique

Sheet hydroforming is a process that uses fluid pressure for deformation of a blank into a die cavity of desired shape. This process has high potential to manufacture complex auto body and other sheet metal parts. Successful production of parts using hydroforming mainly depends on design aspects of tooling as well as control of important process parameters such as closing force or blank holding force (BHF) and variation of fluid pressure with time. An experimental setup has been designed and developed for hydroforming of square cups from thin sheet materials. Square cups have been deep drawn using constant and variable BHF techniques. A methodology has been established to determine the variable BHF path for successful hydroforming of the cups with the assistance of programmable logic controller and data acquisition system. Finite element (FE) simulations have also been carried out to predict formability with both of these techniques. It has been found that it is possible to achieve better formability in terms of minimum corner radius and thinning in the case of variable BHF technique than in the case of constant BHF technique (constant force during forming and calibration). The results of FE analysis have been found to be in good agreement with experimental data.     

MULTIPOINT BLANK HOLDER FORCE CONTROL IN HYDROFORMING OF FUEL TANK

The study of multipoint blank holder force(BHF) control is carried out for hydroforming a complicated shape motorcycle fuel tank. By finite element method (FEM) simulation, the configuration of multipoint blank holder cylinders and the setting of local BHF are optimized, and the influences of the multipoint BHF on the hydromechanical deep drawing and conventional hydroforming processes are studied. The desired fluid pressure and whole BHF are predicted for hydromechanical deep drawing process. Finally, simulation results are testified by forming experiment, and they are in agreement very well.     

拉深工艺中新型变压边力装置的设计

在分析现有压边装置应用现状的基础上,提出了一种能够提供随法兰位置变化的新型变压边力装置。利用非线性电位器模拟理想变压边力曲线,更符合拉深过程中的压边力要求。利用电液伺服阀良好的快速响应性,可以调整拉深气垫作用在板料上的压边力大小。采用随动装置使电位器输出电压随法兰行程的变化而变化。实践表明,该装置可提高板料的可成形性、材料利用率,减少不良缺陷的发生。     

Experiment and numerical simulation on delamination during the laminated steel sheet forming processes

Laminated steel sheets, which have advantages in reducing vibration and noise, are widely used in home appliances, automotive components and building structures. With polymer layer laminated in steel sheets, the unique failure mode—delamination may occur in the forming process if the process parameters are defined improperly. In the presented work, firstly, the delamination is investigated by U channel forming in bending mode. Then, a step-bottom square cup drawing is also conducted to study the delamination in the deep drawing of the laminated sheet metal in more complex stress state. Nonlinear visco-elastic material model is applied to describe the mechanical behavior of polymer layer. Cohesive element and continuum shell elements are utilized to discretize the polymer layer and the outer steel sheets, respectively. The results of U channel forming indicate that increasing forming speed somewhat decreases the tendency of delamination, and increasing blank holding force (BHF) significantly diminishes the occurrence of delamination. Meanwhile, the results of the step-bottom square cup drawing reveal that the wrinkling of facial sheets often induces delamination. Increasing the BHF and the frictional coefficient prevents the occurrence of wrinkling and the delamination induced by wrinkling. However, when wrinkling is suppressed, further rising in BHF and frictional coefficient will increase the risk of direct delamination.     

A study of the control of the blank holding force using an MR damper in a drawing press

The predominant failure modes (wrinkling and tearing) must be avoided during the drawing process in sheet metal forming. These defects may be eliminated by using a controllable device for which the blank holding force (BHF) is adjustable. The purpose of this research is to verify the possibility of using a magneto-rheological (MR) damper for obtaining an almost constant BHF in drawing presses. The damper force is controlled by adjusting the current that is applied to the MR fluid, which is a functional material. To realize this aim, a prototypical press system is manufactured. A control test using a closed-loop PID controller is carried out for achieving the objective where by a constant BHF is retained at a constant prescribed force, while the press slide translates at a constant velocity. The results show that the BHF of the drawing press can be controlled effectively by using the proposed MR damper.     

Optimization of the structural and process parameters in the sheet metal forming process

The quality of the sheet metal forming product is determined by defects such as wrinkling, springback, etc. Optimization techniques can avoid such defects while the desired final shape is obtained. The design variables of the optimization process consist of the structural parameters and process parameters. The structural parameters are the initial blank shape, geometry, etc. and the process parameters are the blank holding force (BHF), the drawbead restraining force (DBRF), etc. In this paper, the two groups of parameters are separately optimized. The structural parameters are optimized by the equivalent static loads method for non linear static response structural optimization (ESLSO) and the process parameters are optimized by the response surface method (RSM). A couple of examples are solved by the iterative use of ESLSO and RSM, and the solutions are discussed.     

伺服驱动压边力控制系统建模与仿真

将伺服驱动技术应用于压边力控制,可以更有效地控制拉深成形过程,提高成形效果。采用伺服电机驱动的压边力控制系统由机械和数控系统两部分组成,系统参数匹配的合理性对压边力控制的动态性能影响较大,而系统的动态性能直接影响到压边力控制精度和效果。首先对双滑块六杆机构输入输出方程进行了线性化处理,建立了机械系统、数控伺服系统的数学模型,得到了压边力控制系统的数学模型和仿真模型,对控制系统进行了仿真分析,初步确定了控制系统的位置环PID参数。最后根据仿真分析结果进行了压边力控制实验系统的参数设定,实验表明,根据仿真值稍作调整就能达到实验系统的控制要求,大大缩短了系统调试时间。     

A closed-loop type algorithm for determination of variable blank holder force trajectory and its application to square cup deep drawing

In deep drawing, a low blank holder force (BHF) can cause wrinkling, while a high BHF can lead to tearing. Thus, it is important to determine the appropriate BHF to be utilized in the forming process. In this study, a variable blank holder force (VBHF) approach to deep drawing is employed, and a simple closed-loop type algorithm is developed to obtain the VBHF trajectory. The proposed algorithm is divided into two phases. The objective of the first phase is to check wrinkling and tearing. In this phase, a low BHF, which is the cause of wrinkling, is used as the initial BHF; it is then increased to prevent wrinkling. The algorithm is terminated when tearing occurs. In a numerical simulation, the distance between the die and the blank holder is used to measure wrinkling. On the other hand, the thickness of the blank is used to determine the tearing. Next, in the second phase, the deviations in thickness are examined. Wrinkles are also checked in the second phase. By iterating the above two phases, the VBHF trajectory can be obtained. One of the advantages of the VBHF is that it reduces the forming energy. The validity of the proposed algorithm is examined through both a numerical simulation and experiment.     

Closed-loop control of the blank holding force in sheet metal forming with a new embedded-type displacement sensor

Imposing an adaptable blank holding force (BHF) on the flange is an effective technique used to suppress the tendency towards sidewall tearing and to restrain the flange from wrinkling during sheet forming. To this goal, a novel photoelectric displacement sensor was adopted to detect the movement of sheet metal on the die shoulder, and a LVDT (linear variable displacement transducer) placed on the upper die was used to measure the wrinkle height during the process. The output of the PDS can be substituted into a simple formula to calculate the real-time minimum thickness of the sidewall. Together with the readout from the LVDT, the result of the calculation serves as feedback parameters for the BHF control. A tearing-wrinkling algorithm with two modes has been developed in the paper: the fixed-variance mode and the fixed-ratio mode. Beginning with very different initial values of BHF, the proposed BHF controls can attain formability at least as good as the optimal result of the test with constant BHF. The fixed-ratio mode enables the servo-system to react fast in high-speed operations. However, the uniformity of wall thickness is inferior to that of the fixed-variance control. In both cases, the optimal uniformity is obtained under the relatively low initial BHF, while a more uniform sidewall results in a smaller flange area and a product of lower final height is accordingly expected. This revised version was published online in October 2004 with a correction to the issue number.     

压边力在板料冲压成型中的控制研究

压边力的控制研究是板料冲压成型过程中的一个重要内容。首先分析了国内外对压边力的研究现状。然后提出了压边力曲线的预测和压边力的优化控制是压边力研究的两个主要方面，最后提出了采用模糊控制理论对压边力大小和板料的起皱进行跟踪控制，并给出了一个实例。