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.     

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。     

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。     

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.     

基于径向基神经网络杯形件拉深成形变压边力预测技术研究

分析了RBF神经网络的预测策略和方法,并建立了板料拉深成形的变压边力预测神经网络模型.采用正交设计法进行样本参数的制定,利用板材成形CAE软件Dynaform获得训练数据,利用被训练好的神经网络对薄板成形过程中变压边力的预测技术进行了研究.数值模拟结果表明,此方法对拉深成形变压边力的预测是可行的.     

基于回弹控制的高强度薄板拉深成形参数优化设计

为提高高强度薄板拉深成形中板料的成形精度和表面质量,使板料能够与其他零件装配,分析了拉深成形工艺中板料回弹的形成机理,建立了薄板拉深成形板料回弹数学模型。通过板料的平均弯矩度量板料回弹量,构建了板料回弹控制准则,提出了基于回弹控制的高强度薄板拉深变压边力优化设计方法。通过基于回弹控制的高强度薄板拉深变压边力优化设计流程,获得满足起皱控制准则、破裂控制准则和回弹控制准则的高强度薄板拉深优化后的变压边力轨迹。以某贮箱箱底的拉深成形为例,验证了所提方法的正确性和有效性。     

板材充液拉深动态加载系统开发与应用

液室压力和压边力加载路径是充液拉深工艺中决定零件成形质量的关键工艺参数。针对传统被动加压方式加载路径单一,液室压力较低,不能满足复杂结构零件和高强度材料的成形要求,提出采用闭环控制技术实时调节液室压力和压边力的动态加载方式。设计可控压边和高压增压系统,并应用基于上、下位机的检测控制系统实时调节凸模速度、压边力和液室压力满足设定的工艺参数。在动态加载系统上进行异型结构不锈钢零件的充液拉深试验,动态加载路径下试验件一次整体成形,且表面质量好,贴模精度高。结果表明,充液拉深动态加载系统能够实现复杂加载轨迹和局部高压,适用于复杂结构和高强度材料零件的成形制造。     

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。     

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。     

WRINKLE LIMIT BLANK HOLDER FORCE MODELS IN SQUARE-BOX DEEP DRAWING WITH VARIABLE SEGMENT BLANK-HOLDERS

Constituting the reasonable control models of the wrinkle limit blank holder forces is the sticking point of the processes of the deep drawing with variable blank-holder forces, especially in the square-box forming. To begin with, a mode of segmenting flange of the square-box into eight zones is put forward according to the fact that the uniformity of flange deforming can be improved by controlling segment blank-holders. Considering the integral influence of shear stress, a new concept, strain relaxation factor is defined. Hereby, the law of distribution of stress and stain in the deforming flange of square-box is achieved. Then based on these mechanical analysis models and the energy principle, the wrinkling flexivity functions of the straight flange and the circle flange are given, and the corresponding formulae of wrinkling limit blank-holder force in these two situations are also educed. In these processes, ply-anisotropy, strain hardening, thickness and friction are considered. In the end, a calculating example is designed to validate the rationality of the formulae of wrinkling limit blank-holder force, at the same time, the influences of the ply-anisotropy exponent and the strain hardening exponent on the wrinkle limit blank holder forces are also analyzed.     

基于新型双层组合压边圈的变压边力控制

介绍了一种新型的双层组合压边圈。在无需对常规薄板拉深液压机进行改造的情况下，只需要改变压边圈的结构，即能实现连续、灵活方便地控制实际压边力的分布状态和大小，从而提高大型复杂零件的薄板拉深成形质量。     

圆锥形件拉深过程中变压边力的研究

起皱和断裂是板料成形过程的主要失效模式，合理控制成形过程中的压边力，可以消除这些缺陷，提高成形性能。本文以圆锥形件的成形为例，采用Dynaform软件对变压边力控制的成形工艺进行了数值模拟计算，得到了最佳压边力变化曲线。本文还对模拟结果进行了实验验证。结果表明，变压边力拉深工艺能够极大提高板料的极限拉深高度。     

矩形盒拉深时变压边力的数值模拟

建立了矩形盒拉深成形的三维仿真分析模型，并将其与实验结果进行了对比验证。在概述压边力在生产过程中的用途和意义的基础上，讨论了变压边力对薄板拉深成形过程的影响，利用DYNAFORM模拟软件研究了随拉深时间和压边圈位置变化的压边力对拉深成形质量的影响，得到了相应的数值模拟结果，为实际生产过程中合理调节压边力的大小提供了理论依据。研究表明，采用变压边力控制技术可以显著改善矩形盒的成形性能。     

Modeling and numerical simulation of multi-gripper flexible stretch forming process

Multi-gripper flexible stretch forming (MGFSF) is a recent technological innovation of sheet metal forming process. Straight jaws in traditional stretch forming machines are substituted for a pair of opposed clamping mechanisms movable relative to each other during the forming process. In this paper, spherical part is selected as the study object, and numerical simulations of the MGFSF process under two representative loading paths of horizontal-vertical (HV) loading path and horizontal-tilting-vertical (HTV) loading path have been carried out using a commercially available FEM software (ABAQUS). Four levels of horizontal forces in HV loading path are selected to investigate their influences on strain and forming error distributions of the simulated parts. In addition, four levels of tilting forces in HTV loading path are also taken into consideration. The simulation results reveal that HV loading path would result in a larger strain but a smaller forming error in the forming zone. In contrast, HTV loading path would result in a smaller strain but a larger forming error in the forming zone. Finally, experimental validations are conducted on self-developed apparatus, and the experimental results show a good correlation with the simulation results.     

水平定向钻虚拟样机建模与仿真

为了全面分析水平定向钻的性能，针对不同领域，分别建立了机械、液压、强度和控制等子系统模型，通过参数关联形成了一个完整一致的水平定向钻整机虚拟样机模型。通过对模型的机械系统动力学性能、液压系统管路压力与流量以覆关键部件的应力和应变仿真分析，为实际产品设计与优化提供了理论依据。     

Metal flow controlled by back pressure in the forming process of rib-web parts

In the forming process of rib-web parts, which are widely used in automobiles and aircrafts, severe streamline disorder often occurs because of unreasonable metal flow. In this study, a back-pressure-controlled forming method that can control the direction of metal flow was introduced. The effects of key parameters on metal flow were investigated, including the back-pressure value, loading mode, and back-pressure distance. The results showed that streamline defects can be avoided and the final forming load can be reduced by reasonably controlling the back-pressure parameters. The constant back-pressure mode was more conducive to achieving good forming quality compared with the linear-increased back-pressure mode. From the stress analysis of metal flow, it was demonstrated that the stress state in the rib root is changed by the back pressure, which makes the metal flow more easily along either the tangential or the radial direction. The advantages of the back-pressure-controlled forming method were confirmed by applying it to a compressor scroll rotor.     

圆筒形件拉深失稳及各因素影响分析

对板料成形中圆筒形件拉深的破裂失稳及产生破裂失稳的临界压边力进行研究.由于凸、凹模圆角及其间隙的存在,圆筒形件拉深的筒壁区实际为凸、凹模圆角之间的公切线部分.根据Mises-Hill屈服函数及Tresca准则求出凸缘变形区、凹模圆角区和筒壁区的应力分布,得到危险断面处的应力表达式,从而求出不产生破裂失稳的临界压边力的解析表达式,并进一步分析获得拉深比、硬化指数、厚向异性系数、摩擦因数以及径向推力等因素对临界压边力的影响规律.采用液压压边与周缘加径向推力的拉深模具对08Al板料进行拉深试验,试验结果与理论计算结果具有很好的一致性.     

Research on the forming process of three-dimensional metal parts fabricated by laser direct metal forming

To improve the forming quality of parts fabricated by laser direct metal forming (LDMF), the forming process of three-dimensional parts under open-loop LDMF system was studied in this paper. The influencing rule of scanning space on the forming quality was studied, and the optimal scanning space was derived. The software of control system about scanning style is also optimized, and thus, the forming quality of parts is improved. During fabricating three-dimensional parts, uneven heat distribution caused by multi-overlapping is one of the main factors affecting the sidewall forming quality. To solve the uneven heat distribution, the strategy of changing scanning speed was put forward. The influence of the standoff distance on the height of single-trace cladding layer was studied, and it was suggested that uneven surface of parts was caused by instability of process parameters, which could be compensated automatically in the condition of suitable standoff distance in the process of LDMF. Thus a so-called self-regulation effect is reached. Typical multi-overlapped parts with good forming quality are fabricated using the above-mentioned methods.