摩擦系数对航空铝合金三通管充液成形后壁厚分布的影响

在铝合金三通管的充液成形过程中,摩擦系数是影响其壁厚分布及支管高度的关键因素之一。通过建立三通管充液成形的有限元模型,在固定的充液压力、轴向进给参数下,采用有限元分析方法对三通管在充液成形中摩擦系数对壁厚的影响进行模拟分析,获得了摩擦系数对三通管成形壁厚的影响规律,得出摩擦系数为0.075时既能保证支管较小的减薄率,又能获得较好的壁厚分布的结论。同时,通过摩擦磨损试验机获得了不同润滑介质对应的摩擦系数,最终选取了一种摩擦系数接近0.075的润滑介质进行实际胀形验证,获得了满足壁厚及减薄要求的航空铝合金三通管件,可为三通管零件的充液成形提供一些理论指导。     

5B02铝合金管件直角推弯成形壁厚均匀性

基于ABAQUS有限元软件平台建立5B02铝合金管件90°推弯成形有限元模型,并进行成形过程的有限元模拟。将模拟结果与实验结果进行对比,结果表明,两者形貌、弯曲部位壁厚分布一致,验证有限元模拟的可信性。通过分析不同成形阶段弯曲内侧与外侧的金属流动与应变场,揭示出5B02铝合金管件90°推弯成形后壁厚分布不均匀的机理。利用模拟方法对比研究内压大小(填料的弹性模量)对壁厚分布的影响,找出了有益于壁厚均匀分布的工艺条件,为实际生产中5B02铝合金管件经90°推弯工艺后壁厚均匀性的控制提供理论依据。     

摩擦系数对薄壁T型管内高压成形的影响

为探究不同摩擦系数对成形T型三通管支管高度、壁厚差、最小壁厚及关键部位的壁厚变化的影响,利用DYNAFORM软件,对薄壁T型三通管内高压成形过程进行了模拟,研究了在0.01~0.2范围内6种不同摩擦系数情况下,支管高度和壁厚的变化,分析了最小壁厚和关键点随时间的变化情况,并选用4种不同润滑剂进行实验验证。结果表明:成形T型三通管的合适的摩擦系数区域为0.06~0.125,摩擦系数过大或过小都会影响T型三通管的成形效果。依据模拟结果,对薄壁铝合金管材进行成形实验,研究发现实际管材成形效果与DYNAFORM模拟结果较为吻合,验证了数值模拟结果的合理性。     

等径三通管整体液压成形壁厚分布规律

对铝合金薄壁三通管壁厚分布规律进行研究。将管坯放入模具型腔,通过轴向进给补料、内部增压,沿下模具型腔中间倒圆角处凸出一个较高的等径支管,形成等径三通管。通过数值模拟和实验对等径三通管整体液压成形的过程进行研究,分析了三通管整体液压成形4个不同阶段的管材壁厚分布规律和管材关键部位壁厚的变化规律。研究发现,成形管材底部的壁厚最大,过渡圆角周边处次之,支管顶端周边最薄。数值模拟和实验结果相吻合,为T型三通管零件生产奠定了基础。     

双壁间隙组合管整体弯曲成形特征分析

采用三维有限元模拟方法,分析双壁间隙组合管整体弯曲成形过程的应力和应变分布、壁厚分布及各组件间的接触,揭示弯曲过程的成形特征。结果显示:相比于单层管,双层管中内层管的等效应变相差不大,但外层管显著增大,说明更容易产生开裂,缺陷控制难度增大;内、外层管的中间填充物,在弯曲过程中与内、外层管之间有相对位移,产生摩擦力,且与外层管之间的摩擦力和弯曲方向相反,导致壁厚减薄量增加,壁厚分布不均匀。通过对实际试验件的壁厚进行测量,验证了有限元模拟结果与试验结果的规律一致,有限元模拟过程对物理试验具有有效的指导作用。     

内压对Y型三通管内高压成形影响研究

利用数值模拟对Y型三通管内高压成形过程进行了研究,研究了87MPa～145MPa范围内5条不同内压的加载路径的成形过程,分析了过渡区内凹、支管高度不足等缺陷产生的原因和内压为116MPa时零件成形过程中典型位置的壁厚变化,以及内压对零件壁厚分布的影响。数值模拟结果表明,106MPa～126MPa为成形Y型三通管合适的压力区间,但不同内压成形的零件最小壁厚不同。     

消音管内高压成形焊缝残余应力数值分析

为了探究消音管内高压成形过程中的开裂原因，利用MARC有限元分析软件，模拟了无缝管和焊接管在焊接及内高压成形过程中焊缝附近的温度、应力及壁厚分布情况. 结果表明,无缝管在胀形区会产生560 MPa的周向拉伸残余应力且该区域壁厚减薄率为4%，焊接管在过渡区产生了271 MPa的轴向拉伸残余应力. 轴向拉伸焊接残余应力是内高压成形过程中的不利因素，使焊接管在内高压成形后的轴向压缩残余应力变成轴向拉伸残余应力，导致焊接管容易胀裂. 对焊接热循环曲线和焊接残余应力进行了测量，模拟结果与试验结果吻合良好，验证了模拟结果的正确性．     

三通管内高压成形时壁厚影响因素的研究

分析了传统内高压成形三通管的成形过程,通过理论分析并结合试验和模拟进行比较,对比得出了加载路径、填充介质以及模具的圆角半径对内高压成形件的壁厚分布的影响,对工业生产有实际指导作用.     

三通管复合胀形与轴向压缩胀形工艺研究

采用显示动力分析软件ANSYS／LS—DYNA建立复合胀形三维有限元模型,深入研究了三通管液压胀形过程中应力应变分布规律,系统比较了轴向压缩胀形和复合胀形过程中应力应变变化规律、胀形支管高度、壁厚分布的差异。研究表明：复合胀形较轴向压缩胀形应力应变分布更均匀、壁厚分布更均匀、更易获得较大的支管高度。     

TA2钛环形管热推成形的三维有限元数值模拟

应用商业有限元软件ANSYS对TA2钛环形管热推弯曲成形过程进行了有限元数值模拟。并对成形过程中环形管内侧凹边、外侧凸边及侧面的应力、应变分布数据以及弯曲成形过程中壁厚的变化进行了分析。结果表明：管件峦变形过程中等效应力值总的变化随着弯曲角度的的增大而增大，而且弯曲管件的内侧凹边管壁的应力值比外侧凸边管壁要大，内壁受到压应力而外壁受到的拉应力；等效应力变数值内侧管壁的应变值比外侧管理壁要大，在弯曲过程中由于弯曲半径小，弯曲变形大，在弯制过程中，弯管内侧凹边受压缩使壁厚墙厚，而外侧凸边因受拉伸而壁厚减薄。数值模拟与实验所得结果一致。     

Optimization of loading conditions for tube hydroforming

Tube hydroforming is a developing technology with advanced features of lightness and unified part. This study investigates the best possible regulation for loading conditions between the internal pressure and the axial feeding by hydroforming of a T-shape metal tube. Using conjugate gradient method with finite element method, a program module is generated to check the hydroformed tube quality about its thickness uniformity and the geometry accuracy. Thereby, a batch mode and a sequential mode to optimize the loading conditions of the tube hydroforming process are created and investigated. Regarding the tube quality from the simulation results, the hydroforming process, which follows the loading curve generated by the sequential mode, is better than by the batch mode. The optimal loading procedure generated by this article can offer another possibility for engineer by determining the internal pressure and the axial feeding in tube hydroforming.     

弯曲预成形和液压成形对汽车装饰尾管壁厚分布的影响

针对某乘用车排气管路中的薄壁装饰尾管的整体制造难题,开展AISI 304不锈钢管材的弯曲预成形及液压成形工艺研究,从而进一步提高该产品的成形质量与成形效率。利用Dynaform软件,首先,研究弯曲预成形工艺对管材壁厚分布的影响规律,再基于此结果,完成在不同加载方式下的管材液压成形分析。结果表明:弯管Δd值较小时,管材第2次弯曲区域的减薄率有降低的趋势,并且随着Δd值的减小,这种趋势更加明显;基于所选定的Δd值,进行了液压成形有限元模拟,相比于线性加载方式,脉动加载使成品件易破裂区域的最大减薄率由17.6%降为12.1%,并且壁厚分布更为均匀;模拟与实验结果基本保持一致,最大偏差值为2.17%,成形出的零件无开裂倾向,且外观尺寸满足要求。     

Deformation Characterization of Friction-Stir-Welded Tubes by Hydraulic Bulge Testing

In this article, the large-diameter thin-walled aluminum alloy tubes were produced using a hybrid process combining friction-stir welding (FSW) and spinning. For this novel process, rolled aluminum alloy sheets with a thickness about 2–3 times the wall thickness of target tube, were FSW to form cylinders, and then the cylinders were subjected to spinning to get thin-walled aluminum alloy tubes. Both experimental and simulation study were conducted to investigate the deformation characterization of the FSW tube during hydraulic bulge testing, and the stress and strain states and thickness distribution of the FSW tube were investigated. It was found that the common defects of FSW tube can be significantly improved by specific welding devices. The ductility of the tube is considerably improved with nearly two times higher bulge ratio than as-spun tube after annealing treatment at 300°C. But the annealed tube still shows a high nonuniform wall thickness distribution due to the inhomogeneous deformation characteristics. With increasing deformation of the tube, the gap between the hoop and axial stress for the weld and base metal (BM) decreases. However, the hoop and axial stress of the weld are always greater than those of the BM at the same pressure.     

Microforming of superplastic 5083 aluminum alloy

The mechanical behavior of superplastic 5083 aluminum alloy during microforming process was investigated by finite element analysis.A micro V-groove die was modeled to analyze the effects of forming time,load and temperature on the microformability of the 5083 aluminum alloy.First,the microformability of the 5083 aluminum alloy was estimated using a microformability index.The simulation results show that the microformability increases with the forming load,time and temperature increasing.Superplasticity of the 5083 aluminum alloy during microforming using the V-groove die was also investigated in terms of the effective strain rate.The results show that the superplasticity of the 5083 aluminum alloy occurs in a specific part of the material for a specific period during the microforming process depending on the forming conditions and the microformability index.     

Wrinkling behavior of magnesium alloy tube in warm hydroforming

In tube hydroforming with axial feeding, under the effect of coupled internal pressure and axial stress, wrinkles often occur and affect the forming results. Wrinkling behavior of an AZ31B magnesium alloy tube was experimentally investigated with different loading paths at different temperatures. Features of wrinkles, including shape, radius and width, were acquired from the experiments, as well as the thickness distribution. Numerical simulations were carried out to reveal the stress state during warm hydroforming, and then the strain history of material at the top and bottom of the wrinkles were analyzed according to the stress tracks and yielding ellipse. Finally, effects of loading paths on expansion ratio limit of warm hydroforming were analyzed. It is verified that at a certain temperature, expansion ratio limit can be increased obviously by applying a proper loading path and realizing enough axial feeding.     

材料性能参数对液压成形件厚度分布的影响规律研究

厚度分布均匀性是管件液压成形质量的重要评价指标。文章提出了厚度分布均匀性评价指标函数,建立了空心阶梯轴零件的有限元模型,并通过实验验证了仿真结果的有效性。通过模拟研究了材料的应变强化系数K、加工硬化指数n和厚向异性指数R对液压成形管件厚度分布均匀性的影响规律。     

镁合金管材的热态内压成形起皱行为分析

利用数值模拟和塑性理论分析AZ31B镁合金管材的热态内压成形过程的变形机理,找出临界起皱应力、应力状态及皱纹形状的变化规律。结果表明:随着温度升高,管材轴向抗起皱能力下降,其机理是材料的屈服强度和弹性模量随温度升高而下降;皱峰和皱谷处应力轨迹均在环向应变伸长和轴向应变压缩的区域;随着补料量的增大,皱峰处应力向壁厚减薄的方向发展,皱谷处应力向壁厚增加的方向发展;内压与材料屈服强度之比(相对压力)决定初始屈服时皱峰和皱谷处壁厚的变化情况,即温度较高时,相对压力较大,初始屈服时皱峰和皱谷处应力状态越易处于管壁呈减薄趋势的区域;当温度较低时,相对压力较小,初始屈服的皱峰和皱谷处的应力状态越易处于管壁有增厚趋势的区域;随着温度升高,相同加载路径下皱纹的高度和波长增大,皱纹趋向于向中间移动,且波数减少。     

Analysis of thickness distribution of square-sectional hydroformed parts

Square-sectional parts are most commonly used on automobiles. The thickness uniformity is one of the key factors that affect the performance of hydroformed parts. In the present paper, the thickness distribution along the cross-section of a square-sectional hydroformed part is studied mathematically. The effects of the friction coefficient, the strain-hardening exponent and the anisotropic coefficient on the thickness distribution, and the variation regularity of the wall thickness are numerically explored. The analytical and simulation results show good agreement with those of the experiments. This study helps to further understand the mechanics of the tube hydroforming process and to provide more knowledge for die design and material selection.     

Numerical and Experimental Investigation of Temperature Effect on Thickness Distribution in Warm Hydroforming of Aluminum Tubes

Reduction of weight and increase of corrosion resistance are among the advantageous applications of aluminum alloys in automotive industry. Producing complicated components with several parts as a uniform part not only increases their strength but also decreases the production sequences and costs. However, achieving this purpose requires sufficient formability of the material. Tube hydroforming is an alternative process to produce complex products. In this process, the higher the material formability the more uniform will be the thickness distribution. In this research, tube hydroforming of aluminum alloy (AA1050) at various temperatures has been investigated numerically to study temperature effect on thickness distribution of final product. Also a warm hydroforming set-up has been designed and manufactured to evaluate numerical results. According to numerical and experimental results in the case of free bulging, unlike the constrained bulging, increase of the process temperature causes more uniform thickness distribution and therefore increases the material formability.