护环液压胀形加载路径优化设计方法

以600 MW护环为例,研究了外补液液压胀形加载路径确定方法。把连续的胀形强化过程离散为多个子加载段,将各子加载段锥模作用力和环坯腔内液体压力的关系简化为线性关系,采用分段匹配的方法确定各加载段的合理子加载路径,再叠加为完整的合理加载路径,确定了加载路径的形式和关键参数。将环坯液压胀形质量作为目标,两段加载路径斜率、加载路径拐点液体压力和胀形终了液体压力为设计变量,采用遗传优化算法对护环液压胀形加载路径进行优化,并进行了缩比实验。研究结果表明,外补液护环液压胀形加载路径可近似为两段线性线形,拐点对应的环坯腔内液体压力在使环坯外层完全屈服的液体压力值附近,且通过优化获得加载路径的最优参数组合能够保证护环液压胀形制品的质量。     

液压胀形汽车桥壳的试验研究

利用研制的集增压器、冲液器、滑动胀形模具于一体的超高压液压胀形装置,在普通液压机上针对载重0.75t微型卡车后桥壳样件,进行了不同加载路径下的胀形试验,成功试制出桥壳样件。揭示了不同加载条件对管坯胀形的影响,找到了较好的加载路径;剖切胀形后试件,测量主要几何参数及管坯壁厚的变化规律;揭示出极限胀形系数与管坯轴向应变及材料延伸率之间的定量关系。试验研究为生产实践提供参考,为液压胀形桥壳的性能分析提供依据。     

铝合金方形管件液压胀形成形性的有限元模拟和实验研究

管材液压胀形件的变形复杂,难以确定其最佳成形路径。着眼于A6063铝合金方形管件的液压胀形,探索可以提高其成形性的最佳加载路径。使用ABAQUS EXPLICIT软件,对管材液压胀形过程进行有限元模拟,分析轴向和圆周方向的应变,假定管材在液压胀形中为平面应力状态,使用由S-R理论得出的FLD对不同应变路径下的管材液压胀形的成形性进行评价,并在此基础上确定最佳加载路径。为了验证理论结果的有效性,使用直径为Φ40 mm、厚度为2 mm的A6063铝合金管进行了实验研究,实验结果和理论预测基本一致。     

铝合金防碰撞吸能管液压成形加载路径研究

针对防碰撞吸能管成形需要,提出了对铝合金6061圆管液压胀形过程的轴向进给补偿-液压力加载路径控制过程.通过数值模拟方法,采用分析软件ABAQUS 6.10对铝合金6061管材液压胀形的加载路径进行了研究.以成形件不发生起皱、破裂两种失效方式以及最终成形壁厚分布为依据,分析了不同轴向进给和液压力加载路径对成形件质量的影...     

遗传算法结合有限元模拟对液压胀形加载路径的优化

加载路径对液压胀形件的最终质量有着至关重要的影响。在优化加载路径的过程中,设计变量的取值区间对模拟时间的减少及最优解的收敛有重要的意义。文章根据塑性理论分析,给出了管形件液压胀形过程中弹性变形阶段、塑性变形阶段及贴模阶段的轴向喂入量及内压力的工程计算表达式。选取应力比为优化变量,依据屈服准则,得出了胀形过程中合理的变量区间。利用有限元软件包、优化算法及工程计算表达式,得到了液压胀形最优的加载路径。实验结果和有限元模拟结果一致性较好,该方法为轴对称件的加载路径优化提供了新的思路。     

基于均匀增容的大变径比管件液压胀形加载路径研究

目前液压胀形加载路径设计多属于试错法,路径调试缺乏系统的指导思想,没有量化的反馈,因此,提出了基于均匀增容的液压胀形加载路径的设计方法。以管坯内部容积随轴向推进量线性均匀变化为目标,将整个液压胀形过程分为若个子步,通过调整每一子步的管坯内部压力,使每一子步的管坯内部容积沿均匀增容线变化,得到液压胀形管件。以某大型汽车桥壳管件预成形管坯为例,通过数值模拟得到了均匀增容的加载路径,给出了基于均匀增容线的合理成形区间,进行了生产试验,得到了外形轮廓清晰、壁厚减薄率满足设计要求的合格样件,试验结果表明:基于均匀增容的液压胀形加载路径适用于实际生产,样件成品率高、成形性好。     

汽车桥壳液压胀形的数值模拟及其实验研究

对汽车桥壳液压胀形进行了数值模拟并进行了实验验证.分析了第1次胀形时液体压力恒定不变、液体压力按轴向压缩量线性变化、极限失稳及胀裂的情况,揭示出起皱的主要原因是液体压力过低,起皱后不利于后续胀形,而胀裂的主要原因是液体压力过高;第2次胀形时试件退火是最终成形成功的重要影响因素.得到轴向压缩量与液体胀形压力间的合理加载路径.     

工艺参数对双层金属保温容器外壳同步液压胀形成形的影响规律研究

基于表面带有浮雕图案的双层金属保温容器外壳同步液压胀形成形技术特点和Dynaform软件,建立了相应的三维弹塑性有限元模型,采用正交试验法对篮球形双层金属保温容器外壳同步液压胀形成形过程进行了数值模拟;根据正交试验所得到的优化工艺参数,对足球及排球形双层金属保温容器外壳同步液压胀形成形过程进行了模拟研究,获得了同步液压胀形成形时,工艺参数对3种不同浮雕图案的成形质量、应力分布的影响规律,分析了影响外壳表面浮雕图案成形质量及产生成形缺陷的原因。结果表明,影响双层不锈钢真空保温容器外壳表面浮雕图案质量因素的主次顺序为:板料厚度、加载时间、加载压力;不同表面浮雕图案成形所需压力大小与图案复杂程度及纹理方向有关。     

汽车驱动桥壳液压胀形数值模拟及试验研究

利用ABAQUS软件建立桥壳液压胀形工艺的有限元模型,对汽车桥壳的预胀形和终胀形过程进行了数值模拟,并分析了不同的加载路径对桥壳成形的影响规律。模拟结果表明:预胀形阶段,胀形压力保持30 MPa不变,管坯发生轻度失稳形成三鼓形样件,合模后胀形压力增大至60 MPa,内凹部分贴模得到较好壁厚分布的预胀形管坯;终胀形初期,胀形压力保持20 MPa不变,轴向进给量达到30 mm后快速增大至120 MPa,可以成形出合格的样件。采用Q345B无缝钢管进行物理实验,获得了符合尺寸要求的桥壳样件,验证了数值模拟的可靠性。     

连接管件的先进塑性成形技术试验研究

介绍了3种先进的连接管件成形技术，即小弯曲半径管内压推弯成形技术、球形管接头的胀形成形技术和管件的内径滚压成形技术，对其基本成形过程进行了描述，并通过铝合金、不锈钢和钛合金管件的成形试验获得了主要工艺参数对成形的影响规律，结果表明采用这些方法成形所需的连接管件是非常有效的。     

有限长薄壁管胀形研究

本文采用塑性增量理论研究了有限长薄壁管胀形过程中的应力、应变关系，提出了薄壁管胀形的应力、应变数值计算理论，解决了薄壁管胀形工艺的工程计算问题。文中首次提出了内压可行域、轴压可行域的概念，阐述了正确制定胀形加载路径应遵循的原则。理论计算与测试结果吻合较好。为应用管材生产凸形零件奠定了理论基础。     

Forming limit diagrams of tubular materials by bulge tests

This study uses bulge tests to establish the forming limit diagram (FLD) of tubular material AA6011. A self-designed bulge forming apparatus of fixed bulge length and a hydraulic test machine with axial feeding are used to carry out the bulge tests. Loading paths corresponding to the strain paths with a constant strain ratio at the pole of the bulging tube are determined by FE simulations linked with a self-compiled subroutine and are used to control the internal pressure and axial feeding punch of the test machine. After bulge tests, the major and minor strains of the grids beside the bursting line on the tube surface are measured to construct the forming limit diagram of the tubes. Furthermore, Swift's diffused necking criterion and Hill's localized necking criterion associated with Hill's non-quadratic yield function are adopted to derive the critical principal strains at the onset of plastic instability. The critical major and minor strains are plotted to construct the forming limit curve (FLC). The effects of the exponent in the Hill's non-quadratic yield function and the normal anisotropy of the material on the yield locus and FLC are discussed. Tensile tests are used to determine the anisotropic values in different directions with respect to the tube axis and the K and n values of the flow stress of the tubular material. The analytical FLCs using the n values obtained by tensile tests and bulge tests are compared with the forming limits from the forming limit experiments.     

Analysis of tube bulge forming in an open die considering anisotropic effects of the tubular material

In this paper, a mathematical model considering the anisotropic effects of the tubular material was proposed to examine the plastic deformation behavior of a thin-walled tube during bulge forming processes in an open die. In the formulation of this mathematical model, the forming tube is considered as an ellipsoidal surface. Non-uniform thinning in the free-bulged region and sticking friction between the tube and die are also considered. In this analytical model, Hill's orthogonal anisotropic theory was adopted for deriving the effective stress and effective strain under a bi-axial stress state. The effects of the anisotropic values on the forming pressure and maximum bulge height were discussed. Experiments of bulge forming using annealed A6011 aluminum tubes were conducted. The analytical results of forming pressure were compared with the finite element simulations and the experimental data. The validity of this newly proposed model was verified.     

A simple experimental tooling with internal pressure source used for evaluation of material formability in tube hydroforming

Material properties have powerful impact on the tube hydroforming (THF) process and the quality of the deformed tube, so it is important to select proper materials and evaluate the material formability prior to conducting the process. A simplified and applied tooling, which has no use for any external hydraulic pressure source but internal one, was designed for charactering the material formability in THF. A pressurized-fluid supplier is automatically established to provide the internal pressure and axial load synchronously required for THF, and the ratio of the two loads is achieved by proper design of the supplier. As a stand-alone hydraulic bulging fixture, the tooling can be worked on a conventional press, even on a single action press. Free bulge forming (FBF), bulge forming with axial loading (BFAL), free and restrained bulge forming (free and fixed ends) can be fulfilled by the tooling, and furthermore, bulge forming with proportional loading to some extend can be realized. Comparative bulge forming experiments under various forming conditions were carried out with the tooling to validate this project and the results suggest that restrained conditions on the tube ends highly affect the FBF, while the ratio of the two loads dominates the BFAL.     

Evaluation of tubular materials by a hydraulic bulge test

This paper aims to evaluate the properties of tubular materials by hydraulic bulge tests combined with a newly proposed analytical model. Annealed AA6011 aluminum tubes and SUS409 stainless steel tubes are used for the bulge test. The tube thickness at the pole, bulge height and the internal forming pressure are measured simultaneously during the bulge test. From above experimental data, the effective stress–effective strain relations can be derived by this analytical model assuming the profile of the free bulge region as an elliptical surface. The flow stresses of the tubular materials by this approach are compared with those obtained by the tensile test and Fuchizawa's model. The finite element method is used to conduct the simulations of hydraulic bulge forming with the flow stresses obtained by the above-mentioned models. The analytical results of forming pressures versus bulge heights are compared with the experimental results to validate the approach proposed in this paper.     

汽车桥壳复合液压胀形成形系数研究及力参量匹配

本文推导出管坯复合胀形应力平衡方程及极限成形系数的数学表达式 ,求解了 0 75t轻型车后桥壳复合液压胀形极限成形系数 ,确定了成形力参量的匹配关系。理论研究为实际生产上确定复合胀形次数及其工艺参数提供了理论依据     

Evaluation of effect of flow stress characteristics of tubular material on forming limit in tube hydroforming process

The material properties for the analytical and numerical simulation in sheet metal processes, especially in tube hydroforming process, are generally obtained from the uniaxial tensile test of raw sheet material. However, the validation of the formability and reliability of the numerical simulation for the tube hydroforming process arises from the fact that the material characteristics of tubes are different from those of the raw sheet materials. In order to determine the most suitable material property of the tubular material for the evaluation of forming limit on the THF process, the uniaxial tensile test for the specimens of the raw sheet metal and the roll-formed tube and the free bulge test for the roll-formed tubular material are carried out in this paper. The forming limit curves are also derived using plastic instability based on three kinds of necking criteria, which are Hill’s local necking criterion for sheet and Swift’s diffuse necking criteria for sheet and tube, to describe and explain the forming limits for the roll-formed tubular material in the THF process. In order to acquire the informative data on the forming limit curves in the THF process, the loading condition of the free bulge test is controlled. The proper band from nearly necking initiation to nearly bursting initiation has been defined for the roll-formed tubular material in the THF process. It can be concluded that the flow stress of the tubular material should be determined from the actual free bulge test to find the practically valuable forming limit curve for the THF process.     

日本内高压成形技术进展(英文)

文章回顾了自2003年于日本举行的第一届内高压成形国际会议(TUBEH YDRO2003)后该技术在日本的发展概况。近年来,铝合金热态内高压成形技术得到了较快的发展,利用该技术生产的汽车副车架试制成功,并已应用在轿车上;移动模具的出现提高了内高压胀形极限,使T形三通管制管的成形高度显著提高。文中还讨论了在内高压成形工艺优化、拼焊管内高压成形、锥形管内高压成形、高强钢管内高压成形、液压冲孔、成形极限图及内高压成形设备方面的进展。     

Flow stress evaluation of zinc copper and carbon steel tubes by hydraulic bulge tests considering their anisotropy

The object of this paper is to evaluate the stress–strain characteristics of annealed C26800 zinc copper tubes and AISI 1215 carbon steel tubes considering their anisotropic effects by hydraulic bulge tests and tensile tests. In this analytical model, Hill's orthogonal anisotropic theory was adopted for deriving the effective stresses and effective strains under a biaxial stress state. The tube thickness at the pole, bulge height and the internal forming pressure were measured simultaneously during the bulge tests. The effective stress–effective strain relations could be determined by those measured values and this analytical model. The flow stress curves of C26800 copper and AISI 1215 carbon steel tubes obtained by this approach were compared with those obtained by the tensile test with consideration of material's anisotropy. The finite element method was also adopted to conduct the simulations of hydraulic bulge forming with the flow stress curves obtained by the bulge tests and tensile tests. The analytical forming pressures versus bulge heights were compared with the experimental results to validate the flow stress modeling proposed in this paper.     

汽车桥壳液压胀形环向小圆角成形的研究

本文推导出复杂形状管类件复合液压胀形时环向小圆角成形的平衡方程 ,得出了成形应力与环向圆角半径的解析关系 ;研究了环向小圆角成形机理 ,确定了液体胀形压力与轴向推力的匹配关系以及最佳的成形力参量。研究结果得到生产实践的证明。