搅拌摩擦焊超声振动系统的设计与分析

针对传统搅拌摩擦焊技术在焊接时出现的焊缝不均匀、焊缝质量差等缺陷,提出将超声振动系统与传统搅拌摩擦焊相结合,设计了超声辅助搅拌摩擦焊系统。在搅拌头传振杆上开出若干斜槽,使纵向振动在搅拌头传振杆中传播时出现扭转分量,实现振动模式之间的转换。利用Solid Works软件对超声振动系统进行实体建模,并用ANSYS Workbench软件对不同参数下超声振动系统的振动形态进行分析与对比。研究结果表明,通过改变搅拌头传振杆上狭缝的宽度和倾斜角,可以改善搅拌头的振动形态,进而改善焊接质量。     

基于ANSYS的超声搅拌摩擦焊系统设计与仿真

针对搅拌摩擦焊技术在厚板焊接时焊缝深层易出现组织疏松等焊接缺陷的问题,提出将超声振动能量导入到搅拌摩擦焊缝区,设计了超声搅拌摩擦焊接装置。利用ANSYS软件的多物理场耦合功能,将结构场与电场进行耦合,建立了整个超声搅拌摩擦焊系统的有限元计算模型并进行了模态分析和谐响应分析。计算结果表明,其共振频率为19.494kHz,与后来实际测量的共振频率19.56kHz接近。在施加1000V的正弦电压时,其振动输出端的最大振动位移发生在频率为20kHz左右,振幅约为72μm,满足设计要求。     

铝合金搅拌摩擦焊技术研究

论述了搅拌摩擦焊的焊接方法、工艺过程和基本原理；通过大量的工艺参数优化，解决了焊缝中的孔洞问题，使ＬＦ６板材搅拌摩擦焊的焊缝达到与母材等强，ＬＹ１２焊后未经热处理，连接强度接近母材的８０（。由金相分析可以看出，搅拌摩擦焊属于固相连接，焊缝晶粒细小，无气孔、夹杂、裂纹等焊接缺陷。初步应力测试发现，搅拌摩擦焊焊缝比熔焊焊缝的残余应力低。试验研究结果表明，搅拌摩擦焊焊接过程稳定可靠，焊接接头性能良好，具有广泛的应用前景。     

铝-镁异种合金搅拌摩擦搭接焊残余应力数值模拟

采用顺序热力耦合的方法建模,通过正交试验,利用ABAQUS软件分析了铝-镁异种合金搅拌摩擦搭接焊中焊接速度、搭接量、搅拌头转速对残余应力的影响,获得最优的工艺参数,通过试验验证模拟结果的准确性,并研究焊接速度、搭接量对残余应力的影响规律。结果表明：搅拌摩擦搭接焊的最优参数为焊接速度60 mm·min^-1、搭接量60 mm、搅拌头转速1 400 r·min^-1;在不同焊接工艺下,热循环曲线和残余应力的模拟结果与试验结果相吻合,相对误差分别小于7.5%和8.4%,验证了数值模拟结果的准确性;最大残余应力出现在焊缝末端的搭接面处,最优焊接工艺下的最大残余应力为137.7 MPa;与搅拌头转速相比,焊接速度与搭接量对残余应力的影响较大,随着焊接速度的增大,纵向残余压应力峰值升高,压应力作用范围变窄,而随着搭接量的增加,纵向残余压应力峰值降低,压应力作用范围变宽。     

铝-镁合金的超声振动强化搅拌摩擦焊试验研究*

研究铝镁异种合金的连接可拓宽轻量化结构的应用领域,具有重要的学术意义和工程实用价值。进行常规搅拌摩擦焊(Friction stir welding, FSW)和超声振动辅助搅拌摩擦焊(Ultrasonic vibration enhanced friction stir welding, UVeFSW)的对比试验,并对结果进行分析。试验结果表明超声的施加可以拓宽工艺参数窗口,改善焊缝表面的成形,减少缺陷,优化界面结构,细化均化晶粒,提高接头的力学性能。进行载荷测试后发现,超声的加入可以降低焊接所需载荷,这有利于降低设备体积。而温度场的测试则说明,超声波对于焊件有预热作用。     

关于铝合金薄板高速搅拌摩擦焊接搅拌头的新型设计

搅拌摩擦焊是新能源汽车电芯制造中代替传统激光焊接的关键方法。高速搅拌摩擦焊是提升电芯生产效率的关键工艺,科学的搅拌头尺寸参数设计方法可以有效减少高焊速条件下飞边沟槽缺陷,并提升电芯生产的合格率。基于对高焊速搅拌摩擦焊搅拌头的设计的理解,设计包括轴肩半径、轴肩摩擦系数、轴肩内凹角、轴针上半径、轴针下半径和轴针长度在内的高焊速搅拌头尺寸参数研究系统。针对铝合金薄板工业生产中质量需求,设计焊后焊缝质量评价指标。在考虑焊缝飞边大小、沟槽深浅以及左右材料交互比例的基础上,分析不同搅拌头参数影响下的焊接质量变化,获得搅拌头尺寸参数变化对焊接质量的影响规律,获得高焊速条件下的铝合金薄板搅拌摩擦焊搅拌头的最优设计。     

铝合金液冷冷板窄台阶搭接搅拌摩擦焊工艺研究

文中研究了铝合金液冷冷板窄台阶搭接搅拌摩擦焊工艺。冷板基底材料为6063 铝合金,盖板材料为3A21 铝合金。设计了窄搭接搅拌头,减小了轴肩宽度和焊接压力,增加了接头焊接时材料的流动性,针对不同焊深窄台阶冷板进行了窄搭接焊接工艺试验。研究表明,通过优化搅拌头形貌尺寸和工艺参数能够实现4-2（焊缝深度–台阶宽度,mm）、6-4 和9-6 的窄搭接搅拌摩擦焊焊接,焊接过程中进行定位预焊能有效避免产生焊缝S 型曲线,前进侧为6063 或3A21 时均能形成良好的焊缝。     

镁锂合金搅拌摩擦焊及电子束焊研究

对一种新型α+β双相镁锂合金的搅拌摩擦焊及电子束焊进行了实验研究,为该合金在精密制造领域的应用提供参考。利用金相显微镜、扫描电镜和显微硬度测试探明接头显微组织和力学性能的演变规律和特点。结果表明,在合理的工艺参数下,镁锂合金搅拌摩擦焊接头焊核区α+β双相都得到了明显的细化,演变为等轴晶,且α相体积分数相对减少。在焊接速度为15 mm/s,聚焦电流为500 ~ 540 mA,焊接电流为8~10 mA时,5 mm厚镁锂合金电子束焊焊缝完全焊透,焊缝区域由细小的等轴晶组织组成,α相分布更加弥散,呈网状分布在β晶界上。两种工艺下焊缝区显微硬度(HV)较母材均提升了13左右。综上,采用搅拌摩擦焊及电子束焊均可实现外观成型、组织以及性能优良的镁锂合金连接。     

机械振动对激光焊接接头组织的影响

振动焊接工艺能有效细化接头组织晶粒,降低残余应力,提高焊接质量。为了研究振动焊接工艺在激光焊接方面的应用,选用316不锈钢作为试验材料,利用机械振动辅助激光焊接的工艺方法,通过改变机械振动参数和焊接速度,利用光学显微镜和扫描电镜观察焊后接头组织,对比分析不同振动频率和焊接速度下接头的微观组织形貌。结果表明,机械振动可以细化焊后组织中形成的柱状晶,使柱状枝晶破碎且向不同方向生长,晶轴间与焊缝中心处的等轴晶增加。提高焊接速度后,振动的加入能够细化焊缝区出现的粗大柱状晶。同时,振动可以减少焊后在奥氏体基体晶界处形成的网状高温铁素体和点状碳化物,使其趋于弥散。试验还对焊接接头进行显微硬度测试,发现振动焊接下得到的焊缝区接头组织硬度较高,且较高共振频率下硬度增加明显。     

铝合金搅拌摩擦焊接头组织热稳定性

在焊后热处理过程中,搅拌摩擦焊接头焊核区细小的再结晶晶粒在高温下极不稳定,很容易发生晶粒异常长大降低接头性能。研究2024铝合金和7075-2024异质铝合金搅拌摩擦焊接头组织热稳定性,结果发现：增大搅拌头转速、降低焊速有利于提高接头组织热稳定性,接头焊核区晶粒尺寸差异越小,第二相粒子尺寸越小,密度越大,接头组织热稳定性越好;降低固溶温度或缩短固溶时间可以降低晶粒异常长大程度,但接头力学性能将发生下降。对于3 mm厚2024铝合金搅拌摩擦焊接头,在ω=2 500 r/min, v=20 mm/min的焊接参数下,495℃-30 min固溶处理后接头无明显晶粒异常长大现象。对于1.5 mm厚7075-2024异质铝合金搅拌摩擦焊接头,在ω=2 500 r/min, v=50 mm/min的焊接参数下,450℃-20 min固溶处理后接头晶粒异常长大基本得到控制,接头强度达到母材的90%。研究结果表明优化焊接工艺参数和焊后热处理工艺参数能获得较好的晶粒异常长大抑制效果,为铝合金搅拌摩擦焊接头组织性能调控提供参考。     

Development of a dynamic surface roughness monitoring system based on artificial neural networks (ANN) in milling operation

In the current research, a new method is applied to modify the conventional friction stir welding (FSW) process. Fixture, which fixes the workpieces, is shaken mechanically during FSW in a direction normal to weld line in order to increase the straining of weld region material. In other words, vibration of workpieces is accompanied by the rotating motion of tool. This new process can be described as friction stir vibration welding (FSVW). Al 5052 alloy specimens are welded by two welding methods, FSW and FSVW. Microstructure and mechanical properties of welded specimens are compared. Metallography analyses indicate that grain size decreases and hardness increases as FSVW method is applied. Tensile test results also show that strength and ductility values of friction stir vibration (FSV)-welded specimens are greater than those relating to friction stir (FS)-welded specimens. It is because of more work hardening of plasticized material, during FSVW, which leads to more generation and movement of dislocations. Correspondingly, grain size decreases and mechanical properties improve. Additionally, it is observed that the mechanical properties of the weld improve as vibration frequency increases.     

紫铜板搅拌摩擦焊接温度场有限元分析

FSW传热过程直接决定工件所经历的热循环,进而影响焊接接头的微观组织和力学性能。同时温度场的分析对于预测接头残余应力和变形,以及焊缝区硬度都具有重要意义。本文在工艺研究基础上,分析了FSW的产热过程;根据搅拌头形状与尺寸,建立了FSW三维传热有限元模型。使用Ansys有限元分析软件,结合有限几个测量点温度变化的实验数据,对6 mm厚度紫铜板FSW焊接过程的温度场进行了有限元分析和计算,获得了该焊接过程的温度场分布与变化规律。计算过程中考虑了工件下表面与支撑板接触热传导对温度场的影响,以及温度对紫铜材料热传导系数的影响,有限元计算结果与实验测量结果接近。     

Torque control of friction stir welding for manufacturing and automation

Friction stir welding (FSW) is a solid-state welding process that utilizes a rotating tool to plastically deform and forge together the parent materials of a workpiece. The process involves plunging the rotating tool that consists of a shoulder and a pin into the workpiece and then traversing it along the intended weld seam. The welding process requires a large axial force to be maintained on the tool. Axial force control has been used in robotic FSW processes to compensate for the compliant nature of robots. Without force control, welding flaws would continuously emerge as the robot repositioned its linkages to traverse the tool along the intended weld seam. Insufficient plunge depth would result and cause the welding flaws as the robot’s linkages yielded from the resulting force in the welding environment. The research present in this paper investigates the use of torque instead of force to control the FSW process. To perform this research, a torque controller was implemented on a retrofitted Milwaukee Model K milling machine. The closed loop proportional, integral plus derivative control architecture was tuned using the Ziegler–Nichols method. Welding experiments were conducted by butt welding 0.25 in. (6.35 mm)?×?1.5 in. (38.1 mm)?×?8 in. (203.2 mm) samples of aluminum 6061 with a 0.25 in. (6.35 mm) threaded tool. The results indicate that controlling torque produces an acceptable weld process that adapts to the changing surface conditions of the workpiece. For this experiment, the torque was able to be controlled with standard deviation of 0.231 N-m. In addition, the torque controller was able to adjust the tool’s plunge depth in reaction to 1 mm step and ramp disturbances in the workpiece’s surface. It is shown that torque control is equivalent to weld power control and causes a uniform amount of energy per unit length to be deposited along the weld seam. It is concluded that the feedback signal of torque provides a better indicator of tool depth into the workpiece than axial force. Torque is more sensitive to tool depth than axial force. Thus, it is concluded that torque control is better suited for keeping a friction stir welding tool properly engaged with the workpiece for application to robotics, automation, and manufacturing.     

Load bearing capacity of tool pin during friction stir welding

Although friction stir welding (FSW) is now widely used for the welding of aluminum and other soft alloys, premature tool failure limits its application to hard alloys such as steels and titanium alloys. The tool pin, the weakest component of the tool, experiences severe stresses at high temperatures due to both bending moment and torsion. It is shown that the optimum tool pin geometry can be determined from its load bearing capacity for a given set of welding variables and tool and work-piece materials. The traverse force and torque during friction stir welding are computed using a three-dimensional heat transfer and viscoplastic material flow model considering temperature and strain rate-dependent flow stress of the work-piece material. These computed values are used to determine the maximum shear stress experienced by the tool pin due to bending moment and torsion for various welding variables and tool pin dimensions. It is shown that a tool pin with smaller length and larger diameter will be able to sustain more stress than a longer pin with smaller diameter. The proposed methodology is used to explain the failure and deformation of the tool pin in independent experiments for the welding of both L80 steel and AA7075 alloy. The results demonstrate that the short tool life in a typical FSW of steels is contributed by low values of factor of safety in an environment of high temperature and severe stress.     

Analysis of transient temperature and residual thermal stresses in friction stir welding of aluminum alloy 6061-T6 via numerical simulation

Residual stress is lower in friction stir welding (FSW) compared with other melting weldment processes. This is due to being solid-state process in its nature. There are several advantages in utilizing stir welding process. Lower fluctuation and shrinkage in weldment metal-enhanced mechanical characteristics, less defects, and ability to weld certain metals otherwise impractical by other welding processes are to name just a few of these advantages. These have caused an ever increasing attention by the concerned to the process of FSW. In this investigation, three-dimensional numerical simulation of friction stir welding was concerned to study the impact of tool moving speed in relation with heat distribution as well as residual stress. Simulation was composed of two stages. Firstly, thermal behavior of the piece while undergoing the welding process was studied. Heat is generated due to the friction between tool and the piece being welded. In the second stage, attained thermal behavior of the piece from previous stage is considered as inlet heat of an elasto-plastic, thermo-mechanical model for the prediction of residual stress. Also, in the second stage, tool is eliminated and residual stress distribution is found after complete cooling of the piece and disassembly of the clamp. Material characteristic are introduced into the proposed model as temperature-dependent parameters. Obtained residual indicate that heat distribution along thickness varies and is asymmetrical enormously. Moreover, longitudinal residual stress in the weld which increases as speed of process and tool movement ascends. In the prediction of results of residual stress, only heat impact was studied. This was recognized as the main element causing minor difference in results obtained for simulation in comparison with that of actual experiment.     

Internal defect and process parameter analysis during friction stir welding of Al 6061 sheets

Welding parameters like welding speed, rotation speed, plunge depth, shoulder diameter etc., influence the weld zone properties, microstructure of friction stir welds, and forming behavior of welded sheets in a synergistic fashion. The main aims of the present work are to (1) analyze the effect of welding speed, rotation speed, plunge depth, and shoulder diameter on the formation of internal defects during friction stir welding (FSW), (2) study the effect on axial force and torque during welding, (c) optimize the welding parameters for producing internal defect-free welds, and (d) propose and validate a simple criterion to identify defect-free weld formation. The base material used for FSW throughout the work is Al 6061T6 having a thickness value of 2.1 mm. Only butt welding of sheets is aimed in the present work. It is observed from the present analysis that higher welding speed, higher rotation speed, and higher plunge depth are preferred for producing a weld without internal defects. All the shoulder diameters used for FSW in the present work produced defect-free welds. The axial force and torque are not constant and a large variation is seen with respect to FSW parameters that produced defective welds. In the case of defect-free weld formation, the axial force and torque are relatively constant. A simple criterion, (?τ/?p)_defective?>?(?τ/?p)_{defect free} and (?F/?p)_defective?>?(?F/?p)_{defect free}, is proposed with this observation for identifying the onset of defect-free weld formation. Here F is axial force, τ is torque, and p is welding speed or tool rotation speed or plunge depth. The same criterion is validated with respect to Al 5xxx base material. Even in this case, the axial force and torque remained constant while producing defect-free welds.     

Study of ultrasonic vibrations’ effect on friction stir welding

In this paper, effect of ultrasonic vibrations on friction stir welding (FSW) is studied. Ultrasonic vibrations were employed on the tool in pin direction (perpendicular to the welding direction). To do this study, a vibration tool was designed by Abaqus software in a way to have a longitudinal frequency about 20 kHz and was then manufactured and assembled with an ultrasonic transducer and was controlled using an ultrasonic generator to oscillate ultrasonically with a peak-to-peak amplitude of 10 μm. After preparation of experimental setup, some experiments were performed on AA6061-T6 as a work material, and the effect of ultrasonic vibrations on force, temperature, tensile strength, and hardness was investigated in FSW. Based on the achieved results, ultrasonic vibrations can decrease force and increase temperature in FSW.     

Stability of the friction stir welding process in presence of workpiece mating variations

This paper explores common process variations encountered in friction stir welding (FSW) and the limits to which acceptable joint strength is maintained while welding with a robotic FSW system. Part fit-up and mating variations are common in manufacturing, yet the limits to which a friction stir welding process can weld without major process adjustment are unclear. The effects on joint strength and mechanical properties of several of the most common mating variations (i.e., faying surface gap, misalignment, mismatch, etc.) are experimentally determined as individual effects as well as among common welding parameters. Experimental results on 5-mm-thick aluminum alloy 5083-H111 show that ultimate tensile strength, yield strength, and elongation begin to decrease from nominal weld conditions when either the tool offset distance from weld centerline or gap in abutted plates exceeds 25% of the average pin diameter (6?mm). In addition, vertical plate mismatch and lack of penetration can be tolerated up to 2.5% and 10%, respectively, before adverse effects on mechanical properties are observed. The work also indicates that of all the mating variations tested in this study, tool misalignment, followed by travel angle, has the most significant effect on the measured joint strength. Process stability testing has shown that the FSW process is able to endure part fit-up and mating variations within a defined tolerance, giving the practitioner an awareness of how well stock workpiece tolerances must be controlled before joint strength is adversely effected.