铝/钢连续驱动摩擦焊焊接扭矩和能量输入特征

基于摩擦扭矩是连续驱动摩擦焊焊接界面摩擦阻力做功的综合体现,采用主电动机定子电压电流法(Voltage and current of main motor,VCMM),获得了1050纯铝和E235低碳钢连续驱动摩擦焊过程焊接界面的摩擦扭矩,分析转速、顶锻压力对接头摩擦扭矩和不同焊接阶段能量输入的影响。结果表明:初始摩擦阶段是接头热量的积累阶段,以粘着摩擦产热为主;转速较低时,接头摩擦扭矩曲线只存在一个峰值或前后峰值特征不明显,此时接头发生失稳摩擦,转速升高,扭矩降低,初始摩擦阶段、准稳态阶段和焊接全过程能量输入都增加,但由于顶锻过程摩擦加热功率的降低使得顶锻阶段能量输入缓慢减小;后峰值扭矩和顶锻阶段能量输入与顶锻压力的变化呈正相关。     

摩擦叠焊单元成形过程分析

借助高速摄像机拍摄典型的圆柱形塞棒+圆柱形孔的摩擦叠焊单元成形摩擦液柱成形(Friction hydro pillar processing,FHPP)完整过程,观察塞棒与孔的红热状态和外观变化,还将本试验的FHPP焊接过程按塞棒消耗量由短到长进行分段焊接,制作各分段单元纵切面试样。将采集的焊接过程参数变化曲线与高速摄像图片以及各分段焊接单元的焊接试样剖面图进行对比分析,针对各参数以及焊接过程单元形貌随时间的变化,将焊接过程划分为焊前、焊接、保持三个阶段。焊接过程各参数有相应波动,尤其扭矩波动较大。研究发现焊接过程产生不连续的摩擦剪切面,摩擦剪切面不断"产生-压溃-挤出",完成摩擦叠焊单元的成形。摩擦挤出物可分为塞棒飞边与母材飞边两部分。     

导电摩擦焊电流行为的研究

本文研究了一种新颖的焊接方法－－导电摩擦焊，即在摩擦焊过程中向工件通入一定数值的电流，形成复合热源加热。由于电流的引入，增大了摩擦焊规范参数调节范围，对摩擦焊过程中焊接温度场起很好的调节作用，从而可有效地减少焊接时间，降低主轴功率与扭矩峰值，减少焊接变形量以及改善接头性能等。     

基于改进遗传算法的拉锻式塞补焊工艺参数寻优

由于焊接工艺参数对拉锻式塞补焊的焊接质量有显著影响,所以对实数遗传算法进行了改进,并使用改进遗传算法对塞补焊工艺参数进行Matlab编程寻优。通过对2219-T6铝合金进行寻优结果的塞补焊试验,通过试验验证了改进遗传算法可以提高焊接质量。     

工艺参数对铝合金摩擦叠焊成形的影响

以7075铝合金作为试验对象,对摩擦叠焊过程进行数值模拟,研究不同工艺参数对铝合金摩擦叠焊单元成形的影响。为了便于分析计算,将其简化为二维轴对称模型,应用ABAQUS有限元分析软件,建立摩擦叠焊过成二维轴对称热力耦合模型,并且采用FRIC子程序和网格重划分技术进行分析。通过设定不同的工艺参数组合,分析焊接过程温度场、应力场和轴向进给量,获得不同工艺参数对摩擦叠焊单元成形产生的影响。结果表明:轴向压力和旋转速度能够影响焊接时间;较大的轴向压力和旋转速度增加应力的峰值;轴向压力和旋转速度会对轴向位移产生影响,但轴向压力对位移的影响要大于转速。     

7075-T6铝合金摩擦塞焊焊接区域温度场的数值模拟

以7075-T6铝合金为待焊材料,基于库伦摩擦定律建立摩擦塞焊的产热模型,利用ABAQUS软件模拟7075-T6铝合金的摩擦塞焊过程,建立焊接区域温度场的有限元模型,采用热流密度为定值和基于试验数据的热流密度的两种热源加载方式模拟摩擦塞焊焊接区域的温度场,并进行了试验验证。结果表明:两种热源加载方式下焊接区域温度场的变化趋势是一致的,但是相同时刻下,采用热流密度为定值的热源加载方式得到的铝板温度较高;采用两种热源加载方式得到焊接铝板测温点的温度变化趋势均和试验结果的相吻合,但采用基于试验数据的热流密度得到的模拟结果更准确,因此通过有限元产热模型来模拟7075-T6铝合金摩擦塞焊接区域的温度场是可行的。     

铝合金车体非刚性支撑搅拌摩擦焊修复设备研制

现有搅拌摩擦焊修复设备多为固定龙门式结构,且需要背部刚性支撑,移动适应性较差。针对铝合金货车车体破损修复问题,提出一种采用搅拌摩擦焊对其进行在线修补作业的方案,设计了一种移动式非刚性支撑搅拌摩擦焊修复设备。为了解决非刚性支撑焊接修复过程中支撑力不足、大变形等问题,设计了旋转伸缩臂、花瓣式砧板等结构,为焊接提供足够的顶锻力,并利用有限元分析对花瓣式砧板结构进行优化设计,改善支撑效果;设计了铣焊半径自动调整结构,用于不同大小尺寸破损的修复焊接。该移动式非刚性支撑搅拌摩擦焊修复设备能够在不拆解车体板材的情况下,修复6 mm厚铝合金车体,现场实际应用表明：采用该非刚性支撑搅拌摩擦焊修复效果良好,焊接表面光滑无飞边,内部无沟槽隧道缺陷,焊缝抗拉性能达到母材的71.6%左右。     

摩擦焊机主交流电机输出功率的计算机检测

摩擦焊机主电机输出功率是摩擦焊接过程能量消耗和供能状况之间联系的纽带，是研究摩擦焊能量转换的重要环节．本研究借助高性能的微机系统，实现了对摩擦焊机主电机输出功率的检测，并给出了摩擦焊机主电机输出功率曲线的数学模型，为进行摩擦焊精确的能量控制和功率极应控制方法创造了良好条件．     

轴向拉力对铝合金拉拔式摩擦塞焊接头组织及力学性能的影响

拉拔式摩擦塞补焊是一种固相连接技术,具有接头强度高,焊后残余应力和变形小等优点,在航天领域具有潜在的应用前景。研究轴向拉力对2A70铝合金拉拔式摩擦塞焊焊接成形及接头性能的影响,并分析焊接缺陷、微观组织及断口形貌特征。结果表明,轴向拉力在20~30 kN范围内能够得到良好的焊缝成形;轴向拉力为20 kN时,结合界面存在未焊合缺陷;轴向拉力提高至22 kN及以上,未焊合缺陷完全消除;轴向拉力提高至28~30 kN时,塞棒与母材形成完好的冶金结合,焊接接头的抗拉强度可达到376 MPa,接头系数为83.6%。当轴向拉力较低时（22~25 kN）,结合界面上易出现弱结合缺陷,微观特征为沿结合界面断续分布的微孔,可导致接头抗拉强度和断后伸长率下降;焊接接头中,塞棒侧热影响区硬度值最低,分析表明该区域的晶粒形态和尺寸未发生明显变化,但θ'相部分溶解,θ相发生粗化,导致局部强度下降;断口形貌显示,在优化参数下断口呈现韧性特征。研究结果可为铝合金拉拔式摩擦塞补焊工艺及机理分析提供借鉴和参考价值。     

摩擦焊接过程的热力耦合有限元分析

采用热力耦合有限元分析方法,综合考虑摩擦焊接过程中不同的产热机制、随温度变化的材料性能、飞边形成及摩擦系数随速度、温度、压力的变化规律,直接由焊件材料的性能参数及设定的焊接规范参数(轴向压力与转速随时间的变化曲线)对焊接全过程的焊接参数(摩擦转矩、轴向缩短量及平均温度)、物理参量场(温度场、应力场、变形场)及焊合区金属晶粒尺寸的变化规律进行了数值模拟,得到了焊接过程中摩擦表面上切应力、加热功率、温度及轴向压应力的分布及变化规律,实现了对焊合区金属晶粒尺寸的数值模拟。     

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.     

A gun drill mechanics model analysis based on 15-5PH solid solution stainless steel

Referencing special energy model, a new gun drill mechanics model was established and the influence of the cutting parameters on axial force and torque was based on 15-5PH solid solution stainless steel through theoretical analysis and cutting tests. On the basis of the existing model, the model coefficients were modified under various cutting conditions and the integral area of the cutting edge was enlarged. The eccentricity at the bottom of the drill groove was taken into account in the integral area of the cutting edge. In the meanwhile, the torque calculation was simplified reasonably according to the theoretical analysis. The feasibility of the model was verified by experiments and the influence of cutting parameters on the axial force and torque was analyzed. The experiment data had shown that the relative error between the calculated values and the experimental values were within the acceptable range. The axial force and torque increased with the increase in cutting speed and feed rate.     

齿式离合器结合过程动态特性的仿真

为了分析齿式离合器齿轮在轴向结合过程中的动态冲击载荷,进而为工程设计提供参考,以存在转速差和轴向相对运动的内啮合齿轮副作为研究模型,采用系统动力学分析软件ADAMS分析了轮齿结合过程的动态特性,给出了完整结合过程的动态转矩、轴向力和转速等关键参数.分析了轮齿结合过程的机理,并基于数值仿真定量分析了主要结构参数和运行参数对内啮合轮齿轴向结合过程及其冲击载荷的影响.结果显示存在转速差和轴向相对运动的齿轮副在结合过程中产生较大的轴向力和转矩冲击值,并且轮齿转速差、结合速度和轴向推力等参数对冲击载荷具有较大影响,该结果可为相关离合器的设计提供依据.     

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.     

Frictional behaviour of mild steel in friction welding

Experiments were carried out on the friction welding of mild steel tubular specimens having an outside diameter of 19 mm and inside diameter of 12.7 mm. The average rubbing speed was varied from 0.42 m/s to 3.36 m/s and the axial force from 2.4 kN to 19 kN. The resulting variations in the resisting torque, axial force and axial shortening during the welding cycle were measured and recorded.The results obtained indicate that the frictional behaviour of mild steel under these particular conditions is greatly influenced by the rubbing speed and to a lesser extent by the value of force normal to the rubbing surfaces. A theory is proposed for the frictional behaviour of mild steel under these conditions which seems to give a reasonable explanation for most of the observed results.     

Multiresponse optimization of laser welding of stainless steels in a constrained fillet joint configuration using RSM

This paper presents experimental design approach to process parameter optimization for CW Nd/YAG laser welding of ferritic/austenitic stainless steels in a constrained fillet configuration. To determine the optimal welding parameters, response surface methodology was used to develop a set of mathematical models relating the welding parameters to each of the weld characteristics. The quality criteria considered to determine the optimal settings were the maximization of weld resistance length and shearing force, and the minimization of weld radial penetration. Laser power, welding speed, and incident angle are the factors that affect the weld bead characteristics significantly. A rapid decrease in weld shape factor and increase in shearing force with the line energy input in the range of 15–17 kJ/m depicts the establishment of a keyhole regime. A focused beam with laser power and welding speed respectively in the range of 860–875 W and 3.4–4.0 m/min and an incident angle of around 12° were identified as the optimal set of laser welding parameters to obtain stronger and better welds.     

Optimization of friction stir welding process of AA7075 aluminum alloy to achieve desirable mechanical properties using ANFIS models and simulated annealing algorithm

Current work deals with experimental investigation, modeling, and optimization of friction stir welding process (FSW) to reach desirable mechanical properties of aluminum 7075 plates. Main factors of process were tool pin profile, tool rotary speed, welding speed, and welding axial force. Also, main responses were tensile strength, yield strength, and hardness of welded zone. Four factors and five levels of central composite design have been utilized to minimize the number of experimental observations. Then, adaptive neuro-fuzzy inference systems (ANFIS) have been used to generate mapping relationship between process factors and main response using experimental observations. Afterward, the developed models were applied as objective function to select optimal parameters, in which the process reaches to its desirable mechanical properties by using the simulated annealing algorithm. Results indicated that the tool with square pin profile, rotary speed of 1,400 RPM, welding speed of 1.75 mm/s, and axial force of 7.5 KN resulted in desirable mechanical properties in both cases of single response and multi-response optimization. Also, these solutions have been verified by confirmation tests and FSW process physical behavior. These verifications indicated that both ANFIS model and simulated annealing algorithm are appropriate tools for modeling and optimization of process.     

Process parameter analysis of inertia friction welding nickel-based superalloy

A two-dimensional axisymmetric model for the inertia friction welding (IFW) of a nickel-based superalloy was developed. The influences from the axial pressure, initial rotational speed, and moment of inertia of the flywheel on the interface temperature and axial shortening were systemically examined. The analysis shows that the mechanical energy mainly depends on the initial rotational speed, and a relatively high axial pressure will increase conversion efficiency from mechanical energy to effective welding heat. The axial shortening is found to be approximately proportional to the square of initial rotational speed while logarithmical to the axial pressure. Based on this work, the weldability criteria for IFW nickel-based superalloy was established. Additionally, the approach for welding parameter optimization was performed considering the evolution of temperature profiles from various parameters. The results show that the axial pressure has a more obvious effect on the width of high-temperature zone than the rotational speed during the quick shortening stage.     

Effect of process parameters on tensile strength of friction stir welding A356/C355 aluminium alloys joint

In the present investigation, A356/C355 aluminium alloys are welded by friction stir welding by controlling various welding parameters. A356 and C355 aluminium alloys materials have a set of mechanical and physical properties that are ideally suited for application in aerospace and automobile industries and not widely used because of its poor weldebility. To overcome this barrier, weldebility analysis of A356 and C355 aluminium alloys with high speed steel (Wc-Co) tool has been investgated. An attempt has been made to investigate the influence of the rotational speed of the tools, the axial force and welding speed on tensile strength of A356/C355 aluminium alloys joint. The experiments were conducted on a milling machine. The main focus of investigation is to determine good tensile strength. Response surface methodology (box Behnken design) is chosen to design the optimum welding parameters leading to maximum tensile strength. The result shows that axial force increases, tensile strength decreases. Whereas tool rotational speed and welding speed increase, tensile strength increases. Optimum values of axial force (3 /KN), tool rotational speed (900 RPM) and welding speed (75 mm/min.) during welding of A356/C355 aluminium alloys joint to maximize the tensile strength (Predicted 223.2 MPa) have been find out.