铝合金搅拌摩擦焊热源模型建模专家系统

在铝合金搅拌摩擦焊三维体积热源模型建模过程中,轴肩、搅拌针侧面以及搅拌针底面摩擦产热的热流密度加载范围存在不确定性,需校核确定,增加了建模难度与工作量.针对该问题,建立三维搅拌摩擦焊热源模型,并确定其不确定热源模型参数,研究了这些参数变化对模拟焊缝温度的影响规律.在此基础上,基于参数变化影响规律建立了搅拌摩擦焊热源模型...     

薄板7075铝合金搅拌摩擦焊三维有限元数值模拟

薄板7075高强度铝合金在经过搅拌摩擦焊接后,存在不同程度的焊后残余变形,对精度要求较高的航空结构件的制造和装配带来了困难.本文通过建立4mm薄板7075铝合金搅拌摩擦焊热源模型,利用ANSYS对搅拌摩擦焊接过程中的温度场和应力应变场进行热机耦合数值分析,解释了薄板铝合金搅拌摩擦焊的温度场和表面残余应力的分布.采用古典摩擦理论建立合适的热源模型,将搅拌头的机械载荷和压板的压力考虑到模型当中.分析结果表明,此数值模拟对研究薄板高强度铝合金的搅拌摩擦焊具有一定的借鉴意义.     

热量自适应搅拌摩擦焊热源模型

当前采用的温度场热源数值模型在准确表征焊接过程材料性能和产热机制与温度变化关系上存在困难.依据摩擦学原理,以材料屈服强度ReL为产热基本参数建立新型热源模型,产热量随温度、材料性能改变,实现搅拌摩擦焊产热自适应过程,更准确地描述了搅拌摩擦焊过程物理现象的本质.温度场试验与模拟结果的比较表明,该热量自适应热源模型具有较高的计算精度.     

复合热源搅拌摩擦焊技术概述

复合热源搅拌摩擦焊是在传统搅拌摩擦焊工艺的基础上,以常用焊接热源作为辅助热源的搅拌摩擦焊技术,旨在克服传统搅拌摩擦焊工艺的缺点和不足.文中概述了由等离子弧、火焰、激光、钨极氩弧、电流辅助、感应加热、超声波等辅助的复合热源搅拌摩擦焊的原理、国内外研究及应用,并对该领域的发展趋势进行了展望.     

铝合金型材搅拌摩擦焊的质量控制

铝合金型材在轨道交通装配制造业中应用日益广泛,但采用传统的焊接方法经常会产生各种焊接缺陷。随着现代焊接技术的迅速发展,采用搅拌摩擦技术焊接铝合金型材,使得焊接质量不断提高。搅拌摩擦焊焊接铝合金型材,主要问题是引弧端及熄弧端往往容易产生隧道缺陷。本文主要通过阐述搅拌摩擦焊焊接原理及焊接工艺参数,分析缺陷产生的原因,提出有效的改进方法,从而降低并彻底解决缺陷的产生问题,降低搅拌摩擦焊焊接产品的废品率,提高搅拌摩擦焊焊接质量。     

高强铝合金薄板搅拌摩擦焊残余应力及变形的热力耦合模拟

针对航空领域中常用的7B04高强铝合金,基于剪切摩擦生热理论,建立了适用于薄板搅拌摩擦焊(FSW)过程的自适应热源模型,利用有限元软件MSC.Marc建立了FSW过程的热力耦合有限元模型,并通过子程序二次开发,将建立的热源模型载入到有限元模型中,对7B04铝合金薄板的FSW过程进行瞬态热力耦合模拟。预测并分析了FSW过程中铝合金板材内部的温度分布与演化、焊接接头附近区域的残余应力分布及板材的最终变形情况,通过开展FSW工艺试验从温度场和残余应力两方面对模型的可靠性和模拟结果的准确性进行了验证。此外,利用经过验证的有限元模型对搅拌头机械载荷在残余应力和变形中的影响作用进行了深入分析。     

搅拌摩擦焊接头设计

一般认为,搅拌摩擦焊是铝合金长、直焊缝(平板对接和搭接)的理想焊接方法。实际上,由于搅拌摩擦焊过程不存在被焊接材料的熔化,焊缝成形和质量不会受到焊缝或工件位置改变的影响,依靠设备来保证,搅拌摩擦焊具有相当的柔性,可以实现1-D、2-D、3-D结构的焊接。工业生产中,搅拌摩擦焊不仅可以焊接筒形零件的环缝和纵缝,而且考虑搅拌摩擦焊不受重力影响,所以可以实现全位置空间焊接,如水平焊、垂直焊、仰焊以及任意位置和角度的轨道焊。(未完待续)图1示出了多种典型的搅拌摩擦焊接头形式,目前在实际工业制造中搅拌摩擦焊全部实现了图1所示的多种接头的焊接,如多层对接、多层搭接、T形接头、V形接头、角接等。经过不断的开发研究,针对高速船舶、列车等大量使用的工业型材和结构零件,如图2所示,技术人员设计了多种方式的铝合金挤压型材的搅拌摩擦焊接头,针对搅拌摩擦焊过程中,没有焊丝填充,没有焊缝余高,对于结构强度要求较高的型材,可以在型材焊缝处预留焊接余高的方法解决。搅拌摩擦焊接头设计$北京赛福斯特技术有限公司     

搅拌摩擦焊热源数值模型

针对搅拌摩擦焊特点,基于粘着摩擦原理,在综合分析前进边和返回边不同位置摩擦功率的基础上,建立了搅拌摩擦焊热源数值模型.温度场试验与模拟结果表明,该模型能综合反映前进边与返回边热循环曲线的差异及其原因,具有较高的计算精度.     

搅拌摩擦焊技术在高速列车制造中的应用

搅拌摩擦焊在轨道车辆车体生产中具有广泛的应用前景。在"复兴号"高速列车车体中就采用了这项技术,例如车钩座板采用单轴肩搅拌摩擦焊工艺,平顶、设备舱底板等采用双轴肩搅拌摩擦焊工艺。以这两种部件的生产制造工艺为载体,阐述了搅拌摩擦焊技术在高速列车制造中的应用情况。继续深入研究该技术,对提高国内高速列车的综合制造水平,占领搅拌摩擦焊技术领域的制高点具有重要意义。     

曲面件搭接接头搅拌摩擦焊温度场的数值模拟及参数优化

采用点点之间连接的方法实现了曲面结构件的搅拌摩擦焊焊接热源模型的加载,研究了飞机中蒙皮与桁条结构的搅拌摩擦焊搭接接头温度场的动态变化过程.结果表明,随着焊接速度的减小、旋转速度的增加以及搅拌头压力的提高,搅拌摩擦焊过程中的温度峰值升高,焊缝区域的高温区域扩大.从提高材料流动性以及避免出现熔焊的角度,提出了搅拌摩擦焊焊接工艺参数的优化方案.     

Numerical and Experimental Investigations on the Loads Carried by the Tool During Friction Stir Welding

A computational fluid dynamics (CFD) model is presented for simulating the material flow and heat transfer in the friction stir welding (FSW) of 6061-T6 aluminum alloy (AA6061). The goal is to utilize the 3-D, numerical model to analyze the viscous and inertia loads applied to the FSW tool by varying the welding parameters. To extend the FSW process modeling, in this study, the temperature-dependant material properties as well as the stick/slip condition are considered where the material at the proximity of the FSW tool slips on the lower pressure regions. A right-handed one-way thread on a tilted FSW tool pin with a smooth, concaved shoulder is, additionally, considered to increase the accuracy of the numerical model. In addition, the viscous and frictional heating are assumed as the only sources of heat input. In the course of model verification, good agreements are found between the numerical results and the experimental investigations.     

汽车制造驶上搅拌摩擦焊之路

新世纪汽车制造轻量化的发展趋势使铝合金、镁合金等轻质合金材料所占的比重越来越大，从而促进了新型搅拌摩擦焊技术在汽车制造中的应用。在简要介绍搅拌摩擦焊技术的基础上，重点一对搅拌摩擦焊技术在汽车稠造业中的应用进行了探讨和综述，并对国内外的搅拌摩擦焊工艺装备进行了简单介绍。     

Review of recent trends in friction stir welding process of aluminum alloys and aluminum metal matrix composites

Welding is a vital component of several industries such as automotive, aerospace, robotics, and construction. Without welding, these industries utilize aluminum alloys for the manufacturing of many components or systems. However, fusion welding of aluminum alloys is challenging due to several factors, including the presence of non-heat-treatable alloys, porosity, solidification, and liquation of cracks. Many manufacturers adopt conventional in-air friction stir welding (FSW) to weld metallic alloys and dissimilar materials. Many researchers reported the drawbacks of this traditional in-air FSW technique in welding metallic and polymeric materials in general and aluminum alloys and aluminum matrix composites in specific. A number of FSW techniques were developed recently, such as underwater friction stir welding (UFSW), vibrational friction-stir welding (VFSW), and others, for welding of aluminum alloy joints to overcome the issues of welding using conventional FSW. Therefore, the main objective of this review is to summarize the recent trends in FSW process of aluminum alloys and aluminum metal matrix composites (Al MMCs). Also, it discusses the effect of welding parameters of the traditional and state-of-the-art developed FSW techniques on the welding quality and strength of aluminum alloys and Al MMCs. Comparison among the techniques and advantages and limitations of each are considered. The review suggests that VFSW is a viable option for welding aluminum joints due to its energy efficiency, economic cost, and versatile modifications that can be employed based on the application. This review also illustrated that significantly less attention has been paid to FSW of Al-MMCs and considerable attention is demanded to produce qualified joint.     

2219铝合金FSW/VPPA交叉焊缝气孔缺陷

2219铝合金在搅拌摩擦焊（FSW）后,进行变极性等离子弧焊（VPPA）十字交叉焊接,其交叉接头存在气孔缺陷.针对6 mm 2219铝合金进行FSW/VPPA交叉焊接试验,探究了交叉焊缝的气孔类型,分别对比不同FSW热输入量、不同的VPPA焊接速度对交叉焊缝气孔缺陷程度的影响.结果表明,FSW热输入量越大,交叉焊缝气孔缺陷程度呈下降趋势,这与FSW过程产生瞬时空腔有关;而VPPA焊速越大,交叉焊缝气孔缺陷程度呈上升趋势.因此,为了抑制FSW/VPPA交叉焊缝气孔的产生,可以对FSW过程进行惰性气体保护、适当地提高FSW热输入量以及降低VPPA焊接速度.     

Friction model for friction stir welding process simulation: Calibrations from welding experiments

The accurate 3D finite element simulation of the Friction Stir Welding (FSW) process requires a proper knowledge of both material and interface behaviors, but friction, the key phenomenon of this process, is quite difficult to model and identify. According to the extreme encountered conditions and the highly coupled nature of the material flow, simple tribological tests are not representative enough, so the welding process itself has been utilized in most analyses of the literature, although its complexity has led to use simplified numerical models and approaches. The recent development of more accurate 3D simulation software, which allows modeling the entire complexity of the FSW process, makes it possible to follow a much more rigorous inverse analysis (or calibration) approach. FSW trials are conducted on an Al 6061 aluminum plate with an unthreaded concave tool. Forces and tool temperatures are accurately recorded at steady welding state, for different welding speeds. The numerical simulations are based on an Arbitrary Lagrangian Eulerian (ALE) formulation that has been implemented in the Forge3^® F.E. software. The main feature of the numerical approach is to accurately compute the contact and frictional surface between the plate and the tool. A first study using Norton's friction model show the great sensitivity of welding forces and tool temperatures to friction coefficients, the need to take into account the changes brought to the contact surface by slight friction variations (thanks to the ALE formulation), the possibility to get very accurate calibrations on forces, and the impossibility to properly render the tool temperature profile. On the other hand, the use of Coulomb's friction model allows obtaining realistic temperature profiles and so calibrating a friction coefficient that offers an excellent agreement with experiments, on forces as much as on tool temperatures, for various welding speeds.     

铝合金搅拌摩擦焊过程热力演变的三维数值模拟

对搅拌摩擦焊过程中搅拌头速度变化进行分析,建立了考虑搅拌摩擦焊过程中焊缝产热的热源模型.对2024铝合金搅拌摩擦焊温度场和应力场进行了三维有限元模拟,表明焊缝两侧温度和应力分布的不对称现象不明显,主要由于焊接速度远小于搅拌头转速所致,但随着焊接速度加快,这种不对称现象逐渐加强.焊接过程中焊缝中心温度低于搅拌头边缘温度,焊接前方和两侧均为压应力,后方为拉应力;焊接结束后与搅拌头接触区的横向和纵向残余应力为较大拉应力,远离焊缝残余应力较小;沿厚度方向上,横向和纵向残余应力均逐渐降低.有限元计算结果与短波长X射线应力测试结果进行对比,结果表明,二者趋势基本吻合.     

Numerical Simulation for the Optimization of Polygonal Pin Profiles in Friction Stir Welding of Aluminum

The tool with polygonal pin profile has been widely employed in friction stir welding(FSW) of aluminum, but there is hardly an effective optimization methodology existed as the thermomechanical characteristics affected by pins with various flats number have not been understood comprehensively. Therefore, the present work employs a 3-dimensional computational fluid dynamics(CFD) model to have an integrated observation of the FSW process with the effect of polygonal pin profiles. Both the heat generation modes due to contact friction at the tool–workpiece interface and volumetric viscous dissipation in the vicinity of the tool are considered. The model is utilized to give a quantitative analysis of the heat generation, temperature distribution, plastic material flow and welding loads during the FSW process for various tools with polygonal pin profiles, as well as a variety of shoulder diameters, welding speeds and tool rotation speeds. The calculated results of thermal cycles, tool torques and joint cross sections for some typical polygonal pins and welding parameters are all found to be compared well with the experimental ones, which demonstrates the feasibility and applicability of the present numerical model. Particularly, a methodology is developed for the optimization of the flats number by identifying the torque components in both parallel and vertical direction of the pin-side flat region. The results show that the optimized pin flats number increases with increasing tool rotation speed, while the influence of both welding speed and shoulder diameter can be supposed to be insignificant. Moreover, the dependability of the optimized results is also discussed by considering wear tendency and service life of the pin for multiple welding conditions.     

Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys

Workpiece material flow and stirring/mixing during the friction stir welding (FSW) process are investigated computationally. Within the numerical model of the FSW process, the FSW tool is treated as a Lagrangian component while the workpiece material is treated as an Eulerian component. The employed coupled Eulerian/Lagrangian computational analysis of the welding process was of a two-way thermo-mechanical character (i.e., frictional-sliding/plastic-work dissipation is taken to act as a heat source in the thermal-energy balance equation) while temperature is allowed to affect mechanical aspects of the model through temperature-dependent material properties. The workpiece material (AA5059, solid-solution strengthened and strain-hardened aluminum alloy) is represented using a modified version of the classical Johnson-Cook model (within which the strain-hardening term is augmented to take into account for the effect of dynamic recrystallization) while the FSW tool material (AISI H13 tool steel) is modeled as an isotropic linear-elastic material. Within the analysis, the effects of some of the FSW key process parameters are investigated (e.g., weld pitch, tool tilt-angle, and the tool pin-size). The results pertaining to the material flow during FSW are compared with their experimental counterparts. It is found that, for the most part, experimentally observed material-flow characteristics are reproduced within the current FSW-process model.     

AA5083铝合金的搅拌摩擦焊接工艺参数对搅拌头受力和热输入的影响(英文)

采用系统实验设计方法研究AA5083铝合金搅拌摩擦焊接工艺参数对搅拌头受力和热量输入的影响,得到了用来设计搅拌摩擦焊搅拌头和焊机的经验模型。当采用计算机来控制搅拌摩擦焊接时,这些模型可用来确定AA5083这类铝合金的摩擦焊接工艺参数、编制焊接程序及工艺参数控制。结果表明:影响轴向力和热量输入的重要参数是搅拌头转速、焊接速度和搅拌头轴肩直径,而影响纵向应力的重要参数是焊接速度和探头直径。