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…     

薄板件粘性介质压力成形过程的压边力控制

对铝合金以及高温合金薄板件成形过程中产生的缺陷进行了分析,并根据零件特征采用了不同的压边力控制工艺成功研制出了完全符合设计要求的零件。     

阶梯形件粘性介质压力成形的试验研究

介绿了用粘性介质压力成形（VPF）方法制造阶梯形件的工艺过程,通过调整压边力与介质注入压力的配合,分两步来控制板料的成形,成功地制出阶梯形零件。该方法在第一工步采用较小的压边力拉深预成形,使板料尽量流入型腔,第二工步则加大压边力和介质注入压力使板料最终贴模成形。结果表明采用这种新工艺成形的零件厚度分布均匀,减薄量小,表面质量好,尺寸精度高。     

铝合金圆锥形零件粘性介质温成形研究

采用热力耦合有限元数值模拟方法对铝合金圆锥形零件粘性介质温成形过程进行了模拟分析,研究了成形过程粘性介质和板材的温度分布、不同温度条件下成形零件壁厚分布、成形载荷等.结果表明,圆锥形零件的底部圆角区域为成形危险区域.非等温粘性介质温成形过程中,在粘性介质内部形成的非均匀温度场影响了板材的温度分布.当粘性介质温度略低于板材温度时,坯料中心区域温度较低,有利于延迟底部圆角成形时的破裂,提高了零件壁厚的均匀性.分别进行了室温和加热时铝合金圆锥形零件粘性介质压力成形试验,试验结果与数值模拟具有相同的规律.     

粘性介质压力成形技术(VPF)研究——王仲仁教授指导的学术新方向

粘性介质压力成形技术(VPF),是20世纪90年代出现的板材软模成形新技术。介绍了粘性介质压力成形技术的基本原理,分析了粘性介质压力成形技术的特点,采用有限元方法数值模拟分析了粘性介质性质对板材变形的影响规律;给出了高强度镍基高温合金小半径曲面波纹形超薄壁厚构件、低塑性铝合金阶梯形构件、轴对称曲面件粘性介质局部内压扩径、外压缩径等粘性介质压力成形实例和分析。     

一种柔性变压边力的智能冲压过程研究

板料成形时易产生破裂、起皱以及尺寸和形状精度不良的倾向。在伺服压机的基础上,研究一种柔性可变压边力的独立加载闭环控制系统。选择圆筒形工件为模拟对象,利用有限元软件分析圆筒形工件在不同定值下及变压边力下冲压仿真结果。比较得到成形圆筒形工件的最优压边力曲线以及冲压载荷随时间变化的曲线,加载到装置的控制系统,使压边单元与板材始终处于贴合状态。该闭环系统通过压机变载、变行程等不同的运动模式协同柔性压边装置对冲压成形过程进行控制,柔性控制压边力和冲模载荷,来适合零件不同变形阶段的特点。实验证明:该系统可以最大限度提高金属板材成形性能,不仅防止了板材变薄在尾部产生褶皱以及工件拉裂的情况,而且可以提高板材拉深极限。     

粘性介质压力成形研究进展(上)

随着技术的发展，采用高强度难变形材料超薄板制成的板金零件越来越多，而且成形件的三维型面日趋复杂，对这些零件的尺寸精度及表面质量，尤其是厚度均匀性的要求越来越高，这就对成形技术提出更高的要求。而通常的软模成形技术以及常规冲压由于各自的特点构成了相应的适用范围，仍存在许多不足。而粘性介质压力成形(Viscous Pressure Forming，VPF)工艺由于采用粘性物质作为成形过程传力介质，具有独特的优点因而具有广阔的应用前景。     

Inner and outer pressure forming of nickel based super-alloy thin-walled part with variable diameter sections

A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature, and the principle of the method was provided. Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio （35%）. The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet. The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections. The thinning of wall-thickness is less than 4%. This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.     

基于模糊控制的Y形管内高压成形加载路径优化

以薄壁Y形管为例,进行Y形管有限元建模。运用Dynaform有限元仿真软件进行内高压成形数值仿真,探讨Y形管成形规律、主要缺陷形式及缺陷产生位置;分析几何形貌参数、摩擦因数和加载路径等工艺参数对成形质量的影响。选取起皱间隙和贴模长度作为逻辑控制输入,评价成形状态;为优化Y形管内高压成形加载路径,将成形过程分为4个阶段进行模糊控制系统设计。结果表明：加载路径优化后,充模效果获得较大提升。将内高压成形工艺和模糊控制系统应用于某汽车排气系统Y形歧管,进行结构改进与成形工艺优化,获得了满足质量的合格零件。     

球形件整体成形充液胀形技术

针对球形件整体成形中的充液胀形工艺,分析中间序零件的特点,制定成形工艺方法,通过数值模拟和实际试验,研究补料量、胀形压力对零件成形的影响,并通过数值模拟分析与试验结果进行对比分析,证明了数值模拟可以给试验提供正确方向,说明数值模拟的准确性。球形件成形补料量对零件成形精度影响较大,如果补料量过大,则成形过程中会出现环形堆料、起皱等问题;如果补料量不足,则导致零件减薄增大,甚至出现破裂。此外,在合理的补料量条件下,需要根据不同合模阶段建立合理的胀形压力,如果胀形压力建立不合理,同样会出现减薄过大、起皱、堆料等问题。     

Multi-layer sheet hydroforming: Experimental and numerical investigation into the very thin layer in the middle

Sheet hydroforming has gained increasing interest in the automotive and aerospace industries because of its many advantages such as higher forming limitation, good quality of the formed parts and complicated parts can be formed, etc. The main advantage is that the uniform pressure can be transferred to everywhere at the same time. Based on the hydromechanical deep drawing (HDD) with uniform pressure onto the blank, the multi-sheet hydroforming with the very thin middle layer is investigated. Some features of the formed internal, external and middle layers including high drawing ratio, wall thickness distributions, free wrinkling and fracture, etc., are discussed in details. The process parameters’ effect on the forming process and the ways to improve the sheets formability are discussed both for in experiment and simulation. The results from a simulation were in reasonable agreement with those from an experiment.     

反胀压力对铝合金球底筒形件充液拉深过程的影响

充液拉深工艺是一种先进的板材柔性成形方法。结合航天部件的实际需求,通过数值模拟的方法,对5A06铝合金球底筒形零件的初始反胀充液拉深成形过程进行了研究。应用基于LS-DYNA3D内核的动力显示分析软件eta/Dynaform5.5,分析了液室初始反胀压力与液室压力对零件壁厚分布以及起皱、拉裂等缺陷的影响规律,讨论了反胀压力与液室压力的匹配关系,得到了合理的加载区间。结果表明,采用优化的初始反胀压力和液室压力耦合加载条件,可以有效的抑制零件球底部的过度减薄,控制悬空区的内皱,提高零件成形质量。     

粘介质成形工艺特点与应用分析

简要介绍了近来出现的利用粘性介质传压进行冲压成形的一种新工艺。通过粘介质成形实验与以水为介质的液压成形模拟的对比分析,得出了ＶＰＦ过程中的一些工艺特点,并分析了ＶＰＦ工艺在飞行器制造中的应用前景。     

变压边力对矩形件成形性能的影响

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压边力 ,可以消除这些缺陷 ,提高成形性能。本文通过对随位置变化的变压边力作用下的矩形盒拉深过程进行数值模拟 ,研究各部位压边力变化对整体成形性能影响、及其影响范围 ,为分块压边圈的压边力的调整提供一定的依据。     

Study on hydromechanical deep drawing with uniform pressure onto the blank

Sheet hydroforming has many virtues and has gained increasing interest in industries recently. In this paper, hydromechanical deep drawing (HDD) with uniform pressure onto the blank is proposed and investigated in detail both primarily in experiments and simulation. Final cups with drawing ratios of 2.46 and 3.11 were, respectively, obtained using Al–Mg–Si alloy (Al6016-T4) and soft aluminum (Al1050-H0) that have the strong anisotropic properties. The influence of process parameters on the sheet deformation was studied and the typical failure types including fracture and wrinkling were discussed. Finally, FEM was used to analyze the forming process, and the results from the FEM simulations were in good agreement with those from the experiments.     

多点位控制压边数值模拟研究

板料冲压成形的主要缺陷是起皱和撕裂 ,当模具的几何形状确定后 ,压边力是关键的成形控制参数 ,它不仅是凸模行程或时间的函数 ,还应随压边位置的不同而变化。确定拉深过程中板料各部位所需压边力的变化规律 ,可实现压边力的优化控制 ,对复杂拉深件如汽车覆盖件的成形尤为有利。该文以非轴对称抛物面车灯反光罩为例 ,采用DYNAFORM软件对其成形过程进行了数值模拟 ,比较了均布控制压边力和多点位控制压边力对成形的影响     

高温合金波纹件粘性介质压力成形过程危险点的数值模拟

粘性介质压力成形（Viscous pressure forming,VPF)适合于高强度难变形材料钣金零件的制造。本文应用有限元商业软件DEFORM^TM进行模拟，对比分析采用粘性介质压力和刚性凸模成形高温合金波纹形薄壁件过程中材料危险点的变化。发现前者板料成形的危险点会发生转移，释缓了应力集中，降低了缺陷了发生的可能性。因此，有利于提高板料的菜性。     

盒形件粘性介质拉深过程流动性的有限元分析

为研究工艺参数对铝合金盒形件粘性介质拉深过程材料流动性能的影响,采用ANAYS/LS-DYNA软件对其成形过程进行有限元模拟,分析了成形过程中坯料形状、摩擦系数和压边力大小对材料流动和壁厚减薄的影响。研究结果表明,使用圆形坯料可促进盒形件圆角处材料的流动,降低盒形件的最大减薄率;改善润滑条件、调节压边力大小,则可有效控制坯料的流动,提高成形性。     

Effects of temperature and blank holding force on biaxial forming behavior of aluminum sheet alloys

Biaxial forming behavior is investigated for three aluminum sheet alloys (Al 5182 containing 1% Mn (5182+Mn), Al 5754, and 6111-T4) using a heated die and punch in the warm forming temperature range of 200–350 °C. It is found that, while all three alloys exhibit significant improvement in their formability compared with that at room temperature, the non-heat-treatable alloys 5182 + Mn and 5754 give higher part depths than that of heat-treatable 6111-T4. The formability generally increases with decreasing BHP (BHP), but increasing the forming temperature and/or BHP minimizes the wrinkling tendency and improves the forming performance. The stretchability of the sheet alloys increase with increasing temperature and increasing BHP. For the alloys and forming conditions involved in the current study, the formability, measured in terms of part depth, comes mainly from the drawing of metal into the die cavity, although stretching effects do influence the overall forming behavior. The optimum formability is achieved by setting the die temperature 50 °C higher than the punch temperature to enhance the drawing component. Setting the die temperature higher than the punch temperature also improves the strain distribution in a part in such a manner that postpones necking and fracture by altering the location of greatest thinning.     

补料压力对内高压成形空心曲轴影响的实验研究

通过采用实验,研究了空心双拐曲轴内高压成形中压力参数的作用,完成了不同补料压力下的工艺实验,并对起皱,开裂等缺陷的产生原因进行了分析,确定了内高压成形空心双拐曲轴的成形区间,指出了摩擦润滑在内高压成形中重要性.