TA18钛合金管材多行程皮尔格冷轧过程三维有限元模拟：I 理论解析、模型建立与验证

皮尔格冷轧技术制备的TA18钛合金管材具有高比强度、冷加工性能好、织构分布合理等优异的综合性能,在飞机和航天器液压管路系统、石油勘探钻杆中得到了广泛的应用。根据多行程皮尔格冷轧过程力学分析,获得了成形过程的精确运动模式和管材应力状态。然后,基于有限元软件ABAQUS/Explicit,建立了TA18钛合金管材多行程皮尔格冷轧三维有限元模型,并解决了建模关键技术,包括:虚拟曲柄连杆机构实现方法、多行程周期式运动控制方法、复杂模具几何实体定义、滚动与滑动摩擦定义。利用能量守恒原理和实验验证了模型的可靠性,以及利用成形过程等效应力和等效塑性应变分布评估了模型。     

Method of evaluating workability in cold pilgering

A new method of evaluating the workability of a tube in cold pilgering has been studied on the basis of material deformability and the effects of process conditions. A circumferential compression test of a tube is confirmed to be an effective evaluation method for deformability. The critical reduction in height upon crack initiation in the compression test is also found to be a good measure of material deformability. Systematic cold pilgering tests and the numerical analysis of cold pilgering are conducted. As a result, the ratio of radial strain to circumferential strain during pilgering is a good indicator of process conditions, and a common mechanism of inner fissure formation during pilgering in stainless steel, titanium alloy, and zirconium alloy is proposed. Finally, a suitable expression for workability is obtained by considering material deformability and the effects of pilgering conditions. These findings will assist the selection of appropriate pilgering conditions to prevent the formation of fissures on the inner surface of a tube.     

具有复合组织的不锈钢管周期轧制过程的数值模拟

应用ANSYS软件对具有复合组织的电磁离心铸造1Cr18Ni9Ti不锈钢管的周期轧制过程进行了三维有限元数值模拟.模拟结果表明,管坯轴向塑性越好,在轧制过程中产生的剪切应力σrz和剪切应变εrz越小,管坯变形能力越强.降低工具与管坯摩擦系数,可以减小σrz和εrz.减小管坯外层柱状晶区与内层等轴晶区之间σrz的不连续性,提高管坯的变形能力和成形管材的质量.在电磁离心凝固时适当地加大励磁电流以增加铸管中等轴晶区比例,不但可以提高铸管的力学性能,还可以减小管坯在轧制过程中所产生的σrz和εrz,进而使其轧制变形能力增强,其成形管材质量也得到改善.通过轧制实验验证,模拟结果与实验结果吻合良好.     

A fully 3D finite element simulation of cold pilgering

Cold pilgering is a quite complex tube forming operation, highly non steady state, where the metal undergoes a long series of small incremental deformations resulting in both diameter and thickness reduction. A simplified model, based on the slab method, has been built and used in the last few years [1]. In the present paper, we apply our 3D finite element software Forge3 to analyse one forward stroke (the elementary part of the process) of a cold pilgering operation. The main purpose of the present study is to check the hypotheses and the results of the simplified model, which is used routinely. Strain curves compare well, which is important: the simplified model is based upon an estimation of incremental strain components. Comparison of force-displacement curves show some discrepancies partly due to too coarse a discretisation. Torque, which could never be obtained in our previous studies, either experimentally of by the simplified model, is computed here. Stress maps at various locations are presented. For some of theses data, the effect of varying the difference of friction between the tube/mandrel and tube/die interfaces is described.     

An analysis of the eccentric nosing process of metal tubes

In this paper, the finite-element method is used to investigate the cold eccentric nosing process of metal tubes with an eccentric conical die from circular tube billets. A series of simulations on the eccentric tube nosing using the program DEFORM-3D was carried out. The influences of the process parameters such as tube length, tube thickness, die fillet radius, die angle, friction factor, strength coefficient and strain-hardening exponent of the billet material on the critical nosing ratio of the tube are examined.     

Plasma distribution in the slender bore excited by coaxial rf electrode

A metal coaxial radio-frequency (rf) electrode has been utilized to produce plasma and deposit the coating onto the inner wall of the tubes. The inner electrode acts both as a plasma source and as a sputtering target to achieve plasma-based IBAD. The non-uniformity of thickness of deposited films and plasma density in the bore has been investigated for tubes with different lengths and inner diameters. The experimental results demonstrate that plasma density is higher at two ends of the tube and lower in the middle section of the tube. The uniformity of plasma density may increase with the inner diameter of tubes increasing, but will decrease with the length of tubes increasing. Copper films have been deposited using this technique and the variation of film thickness agrees with the distribution of plasma density along the bore axis. It is also observed that the uniformity of plasma density is higher than that of film thickness due to diffusion behavior of plasmas.     

A new method for production of variable thickness aluminium tubes: Numerical and experimental studies

Tube drawing is one of the mostly used techniques for producing tubes in various sizes. In this method, tube passes through the die and mandrel to produce constant wall thickness tube. In some applications like transportation industry, design necessities cause requirement for these kinds of tubes. Furthermore some manufacturing processes like tube hydroforming dictate have a tube with variable thickness. In this study, with a modification made to the classical tube drawing process, the sinking and fixed-mandrel tube drawing methods were mixed together to produce tubes with variable thickness in the axial direction. An optimization method, namely the leapfrog optimizer for constrained minimization, was coupled with a finite element model to study design specifications i.e. effect of initial tube geometry on this new process. The obtained results from finite element method (tube drawing force, the minimum and maximum final thickness of tube) were compared with the experiments performed in the designed and manufactured machine and acceptable agreement was observed. Based on these results, the maximum and minimum thicknesses in the final produced tube are mostly dependent on the thickness and outer diameter of initial tube respectively.     

Investigation of the formability limit of aluminium tubes drawn with variable wall thickness

Structural aluminium tubes have very important industrial applications, particularly in automobile industry. Tube drawing process is widely used to reduce the outer and inner diameters of tubes. An important issue in the tube drawing process to obtain variable wall thickness is how to determinate and predict its formability limits. Previously published works generally deal with the formability limit of conventional tube drawing based on experimental analysis, analytical method and finite element method. However, in the case of variable wall thickness tubes, there is a lack of knowledge and data in order to predict their limit of formability. In the present study, both theoretical and experimental methods are proposed for estimating the formability limit of the variable wall thickness aluminium tubes used for the transportation purposes. A modification of a conical mandrel was proposed and a special control system for mandrel displacement during the process was used to carry out the drawing tests. During the drawing process, the tube pulling axis was controlled at constant speed while the mandrel was moved to achieve the continuously variable wall thickness. The formability limit in term of minimum wall thickness and maximum area reduction was obtained before tube rupture. These values are useful data for the determination of the extent of deformation during a drawing process that a material can experience without failure. The maximum drawing stress ratio was also determined experimentally. Further, an extension of an upper bound solution developed in previous publications is proposed to predict the drawing stress field. The maximum drawing stress ratio was used as a criterion for fracture analysis. It was shown that the analytical model with its new extension combined to the fracture criterion predicts quite well the thickness and area reduction limit. The experimental studies were completed by examining the microstructure and strain field at the limit state.     

油管疲劳累积损伤的磁记忆检测

研究了油管的破坏形式及磁记忆检测方法，使用应力集中磁指示仪对油管螺纹和周向裂纹进行了检测和数据分析。结果表明，磁记忆是检测油管缺陷和应力集中程度的有效方法。得出了油井中应重点检测靠近井口的1～10和80～90根油管，给出了油管上的重点检测部位。     

Coating the inner walls of metal tubes with carbon films by physical vapor deposition at low temperature

Tubes are often required to exhibit better performance in corrosion and wear behavior than the material the tube is made of can offer. The situation can be improved when the tube is coated with a protective film. This can be achieved by sputter coating with an ion beam. A sputter target is located inside the tube. Energetic ions are accelerated into the tube and impinge onto the target. Thus, material is sputtered from the target onto the inner walls of the tube. Two apparatus for coating tubes of different lengths and diameters are described. Aluminum and stainless steel tubes were coated with amorphous carbon films. Results on adhesion, corrosion performance in aqueous media and thickness uniformity are shown.     

离心球铁铸管退火炉结构改进

离心铸造球墨铸铁管的主要生产方法是“冷模法”,用“冷模法”生产的球铁铸管必需经过热处理才能够达到使用要求,传统离心球铁铸管退火炉存在生产效率低,处理效果差等缺点。在试验基础上对离心球铁铸管退火炉炉体进行了改进．改进后在保证铸管退火质量的同时有效提高了生产效率。     

基于油膜力的油膜厚度补偿模型的研究与应用

为了满足轧制中带钢厚度精度的控制要求,必须对由轧制速度变化引起的带钢厚度波动进行油膜补偿.提出了一种基于油膜力的油膜厚度补偿方法,并进行推证,得到适合现场应用的数学模型.以此数学模型为基础,开发了一套完整的数据采集、数据处理和现场应用方法,并将该模型成功应用于热连轧生产中.实际应用表明,对热连轧机组采用该油膜厚度补偿算...     

Tube/tube joining technology by using rotary swaging forming method

With the development of the manufacturing technology, a challenge has been proposed on the joining of difficult welding materials and the poor connection interface of materials. In this paper, rotary swaging technology is utilized as a joining by plastic deformation forming method to join tube/tube parts with different diameters. Experimental set-up of rotary swaging forming was designed and fabricated, in which the forging energy can be adjusted by changing the rotation speed of AC server motor. The rotary swaging model and tension testing model are established by using FE simulation software Forge 2D. The effects of forming parameters on the tension strength of the joined tubes and the joining mechanism are investigated. The results show that a concave arc joint can be formed at the overlapping parts of the tubes. To obtain the high joining strength, the distance from the end of the inner tube to the center of the hammer die need to exceed a certain value. The maximum strain and stress occur at the concave arc joining region in which the thickness variation of the two joined tubes is small. To exam the joining strength, the tension test was performed. The two tubes tend to slide out during tension process and the maximum stress occurs at the relative sliding region. The ratio on tensile load of the joined tubes to the maximum tensile load of the single tube can reach to 68% for the inner tube and 47% for the outer tube. Therefore, the joining strength of the tube/tube parts, formed by using rotary swaging method, is enough high.     

Modeling of the inlet zone in the mixed lubrication situation of cold strip rolling

In this paper a method to simulate the oil thickness and length of elastic deformation in the inlet zone of cold rolling has been developed. The mixed film lubrication model was adopted to describe the behavior of the lubricant and asperity deformation. The elastic Von Karman equation was used to describe the elastic deformation of strip in the inlet zone. The length and lubricant film thickness of the inlet zone can be obtained by a numerical method. Results of simulations show that the reduction, rolling speed, back tension have a significant influence on the lubricant film thickness and the inlet zone length.     

斜盘式柱塞泵滑靴最佳油膜厚度的计算与仿真

滑靴的最佳油膜厚度是影响柱塞泵容积效率、寿命的重要因素之一.为了使柱塞泵具有高容积效率和长寿命,需要对最佳油膜厚度设计方法进行深入研究.首先通过公式推导得到最佳油膜厚度的理论计算公式,并应用Simulink仿真软件搭建仿真模型求得滑靴最佳油膜厚度.在此基础上,深入分析影响最佳油膜厚度取值大小的因素,同时将分析结果应用到...     

Eddy current measurement of the wall thickness and conductivity of circular non-magnetic conductive tubes

A method to determine the wall thickness and conductivity of non-magnetic tubes using eddy-current measurements is presented. The equivalent circuit impedance formulae for an infinitely long solenoid with a conductive tube inside are derived. This simplified theoretical model is applied to calculate the tube wall thickness using the measured resistance and inductance of a real long coil with a long tube inside. In order to take into account the coil's finite length, an apparent fill factor is introduced. The last parameter is determined experimentally and used as the fill factor in the theoretical model. We report experimental tests for brass and copper tubes of nominal diameters in the range 12–20 mm and nominal thickness from 0.9 to 2.5 mm. An uncertainty of the wall thickness measurements typically within 2% is obtained.     

基于显著性的薄壁铝合金管小弯曲半径数控弯曲工艺参数优化(英文)

薄壁铝合金管小弯曲半径数控弯曲是个多因素耦合、多模具约束下的复杂过程。提出以有限元模拟为基础,基于显著性的工艺参数优化方法,即采用析因因子设计分析工艺参数对成形质量,即最大壁厚减薄率和最大截面畸变变化率影响的显著性,获得影响显著的参数,即管与防皱模间间隙的最优值,并确定其他影响不显著的参数值,包括管与模具间的间隙和摩擦、芯棒伸出量和助推速度。结果应用于规格为d50mm×1mm×75mm和d70mm×1.5mm×105mm(管外径D0×管壁厚t0×弯曲半径R)的铝合金管弯曲,获得了合格的管件。     

大型回转工作台导轨油膜厚度控制方法研究

静压回转工作台导轨油膜厚度随载荷、切削力、油温、黏度等时变工况因素的变化而改变,导致其厚度偏离目标值,影响工作台回转精度。研究油膜厚度的调节方法,对保证零件加工精度具有很重要的工程实际意义。针对变频调速供油的静压回转工作台,分析油膜厚度形成原理及特性,采用工况系数法和3次插值法分别建立了2种油膜厚度控制模型,建模时综合考虑工作台结构尺寸、外载荷及油液黏度等参数的影响。采用米依DT3300电涡流传感器测量系统与Siemens 840DSL数控系统,搭建了油膜厚度检测与调节综合实验平台,通过?2 500 mm静压工作台变载荷实验,验证了两种控制模型对不同载荷下油膜厚度调节的合理性和可靠性,为静压工作台油膜厚度的研究提供了参考。     

不同工况下弹流润滑与齿轮动力学耦合研究

为探究线接触下齿轮传动系统与弹性流体动力润滑的耦合特性,研究采用广义有限元法建立两级齿轮传动系统,通过有限元法求啮合刚度,考虑齿轮润滑状态下的油膜刚度效应,综合叠加齿轮油膜刚度与啮合刚度,使用Newmark积分法对动力学方程进行求解,分析了耦合润滑后不同工况下齿轮啮合位置处的动力学特性和润滑特性。结果表明：齿轮综合刚度会随转速的增加而减小,随负载增加而增大;转速相比于负载对于油膜厚度影响较大,且考虑了轴的柔性后,传动系统在共振转速区内振幅变化显著,会对油膜厚度和系统振动产生一定影响,耦合油膜后在高速共振区内齿面动载荷变化明显。     

基于SVM的轧机油膜厚度补偿模型的建立

研究单机架热轧中厚板轧机的油膜厚度补偿问题,利用SVM方法建立了轧机油膜厚度补偿模型,并对回归预测结果进行分析,同时与成熟的基于Reynolds方程的轧机相对油膜厚度补偿方法进行比较,结果表明:采用基于SVM的轧机油膜厚度补偿模型可以对轧机油膜厚度进行良好的补偿,补偿精度较好.