SIMULATION ON TEMPERATURE FIELD OF FRICTION STIR WELDED JOINTS OF 2024-T4 Al

The thermal model of FSW based on the thermal elastic-plastic finite element method, and the transient temperature distribution of FS welded joints of 2024-T4 Al was simulated by using this model, which provides useful information for the investigation of FSW process. Simulation resuits show that the temperature distribution of the weld gradually decreases toward periphery in a radiate format, whose center is the probe, and the highest temperature in the weld can reach about 400℃. The initial terminal of the weld is a zone, in which the temperature gradient is great, and defects of the welding are easily produced in this zone. Temperature change at the end of the welded joint is as layer variation, the local serious defects are not easy to produce in this zone.

Artificial-neural-network-based storage method for three-dimensional temperature field data during friction stir welding

In this paper,a new storage method for the three-dimensional temperature field data based on artificial neural network(ANN)was proposed.A multilayer perceptron that takes the coordinate(x,y,z)as inputs and temperature T as output,is used to fit the three-dimension-al welding temperature field.Effect of number of ANN layers and number of neurons on the fitting errors is investigated.It is found that the errors decrease with the number of hidden layers and neural numbers per layers generally.When the number of hidden layers increases from 1 to 6,the maximum temperature error decreases from 74.74℃to less than 2℃.The three-dimensional temperature field data is obtained by finite element simulation,and the experimental verification is completed by comparing the simulation peak temperatures with the measured results.As an example,an ANN with 4 hidden layers and 12 neurons in each layer were applied to test the performance of the proposed method in storage of the three-dimensional temperature field data during friction stir welding.It is found that the average error between the temperature data stored in ANN and the original simulation data that stored point-by-point is 0.517℃,and the error on the maximum temper-ature is 0.193℃,while the occupied disk space is only 0.27%of that is required in the conventional point-by-point storage.

Evolution of residual stress field in 6N01 aluminum alloy friction stir welding joint

Based on the characteristics of friction stir welding( FSW) and Coulomb friction work theory,the residual stresses field of FSW joints of 6 N01 aluminum alloy( T5),which was used in high speed train,were calculated by using the ANSYS finite element software. During the FEM calculation,the dual heat source models namely the body heat source and surface heat source were used to explore the evolution law of the welding process to the residual stress field. The method of ultrasonic residual stress detecting was used to investigate the residual stresses field of the 6 N01 aluminum alloy FSW joints. The results show that the steady-state temperature of 6 N01 aluminum alloy during FSW is about 550 ℃,and the temperature mutates at the beginning and at end of welding. The longitudinal residual stress σ_x is the main stress,which fluctuates in the range of-25 to 242 MPa. Moreover,the stress in the range of shaft shoulder is tensile stress that the maximum tensile stress is 242 MPa,and the stress in the outside of shaft shoulder is compressive stress that the maximum compressive stress is 25 MPa. The distribution of the tensile stress in the welding nugget zone( WNZ) is obviously bimodal,and the residual stress on the advancing side is higher than that on the retreating side. With the increasing of the welding speed,the maximum temperature decreased and the maximum residual stress decreased when the pin-wheel speed kept constant. With the increasing of the pin-wheel speed,the maximum temperature of the joint increased and the maximum residual stress increased when the welding speed was constant. The experimental results were in good agreement with the finite element results.

Effect of Traverse/Rotational Speed on Material Deformations and Temperature Distributions in Friction Stir Welding

A fully coupled thermo-mechanical model was developed to study the temperature fields and the plastic deformations of alloy AL6061-T6 under different process parameters during the friction stir welding （FSW） process. Three-dimensional results under different process parameters were presented. Results indicate that the maximum temperature is lower than the melting point of the welding material. The higher temperature gradient occurs in the leading side of the workpiece. The calculated temperature field can be fitted well with the one from the experimental test. A lower plastic strain region can be found near the welding tool in the trailing side on the bottom surface, which is formed by the specific material flow patterns in FSW. The maximum temperature can be increased with increasing the welding speed and the angular velocity in the current numerical modelling.

Numerical analysis of joint temperature evolution during friction stir welding based on plastic deformation heat

3D numerical model for friction stir welding （FSW） was developed by using ABAQUS software considering the plastic deformation heat. Effects of the rotation and welding speeds on the temperature field of FSW 2024-73 aluminum alloy were systematicaUy investigated. The temperature measurement was performed to validate the reliability of the model. The simulation results are in good agreement with the experiments. Results show that changing the rotation speed has no influence on the time for reaching the peak temperature at certain point in the workpiece at a constant welding speed. While increasing the welding speed has significant effect on the time for reaching the peak temperature but the value of peak temperature changes little.

Thermal modeling of underwater friction stir welding of high strength aluminum alloy

The thermal modeling of underwater friction stir welding （FSW） was conddcted with a three-dimensional heat transfer model. The vaporizing characteristics of water were analyzed to illuminate the boundary conditions of underwater FSW. Temperature dependent properties of the material were considered for the modeling. FSW experiments were carried out to validate the calculated results, and the calculated results showed good agreement with the experimental results. The results indicate that the maximum peak temperature of underwater joint is significantly lower than that of normal joint, although the surface heat flux of shoulder during the underwater FSW is higher than that during normal FSW. For underwater joint, the high-temperature distributing area is dramatically narrowed and the welding thermal cycles in different zones are effectively controlled in contrast to the normal joint.

Effects of process parameters on microstructure and mechanical properties of friction stir lap linear welded 6061 aluminum alloy to NZ30K magnesium alloy

The microstructures and lap-shear behaviors of friction stir lap linear welded as-extruded 6061 Al alloy to as-cast Mg–3.0Nd–0.2Zn–0.7Zr(wt.%)(NZ30K)alloy joints were examined.Various tool rotation and travel speeds were adopted to prepare the joints.The analysis of temperature field indicates that the peak temperature for each sample can reach 450℃,which exceeds the eutectic reaction temperatures of 437℃ and 450℃ according to the binary phase diagram of Al–Mg system.The fierce intermixing can be found at the interface between Al and Mg alloys,forming the intermetallic of Al_(3)Mg_(2).Welds with the rotation speed of 900 rpm and travel speed of 120 mm/min display the highest tensile shear failure load of about 2.24 kN.The value was increased by 13%after the sample was heat treated at 400℃ for 0.5 h.

Numerical simulation of thermal field of FSW 2219 aluminum alloy thick plate

To investigate the influence of temperature field of friction stir welding(FSW)2219 aluminum alloy thick plate,and to achieve effective prediction of temperature field,the authors establish a three-dimensional numerical simulation model of FSW 18 mm thick 2219 aluminum alloy based on ABAQUS/CEL,considering the morphological characteristics of the tool pin.The simulations of plunging,dwelling,and welding stages are achieved.The distribution of temperature and temperature cycle curve of characteristic points in welding process are obtained.The validity of the simulation results is verified by experiments.The influence of the tool-rotational speed and welding speed on temperature field is explored.The work lays a foundation for the prediction and control of temperature field in FSW medium thickness 2219 aluminum alloy,and provides reference for selection of welding parameters to ensure high quality welding of fuel tank of heavy-lift rocket.

6061铝合金超声辅助搅拌摩擦焊温度场分析

为了分析超声振动对6061铝合金超声辅助搅拌摩擦焊接过程温度场的影响,采用解析建模和数值模拟的方法,建立了超声辅助搅拌摩擦焊过程中接触界面摩擦系数模型和热力耦合有限元分析模型,开展了6061铝合金超声辅助搅拌摩擦焊温度测量试验,结合有限元与试验结果进行对比分析.结果表明,仿真得到的工件表面温度分布曲线及取样点温度都与试验结果基本吻合,验证了建立模型的准确性;超声振动可以改变摩擦状态,降低焊接摩擦产热,减少峰值温度及高温区域的面积,振幅对焊接峰值温度影响的显著性高于频率.

一种利用自适应发射率模型补偿搅拌摩擦焊温度场的方法

针对目前搅拌摩擦焊温度场研究大多忽略热辐射作用或者采用固定发射率模型导致误差较大的问题,提出一种考虑粗糙表面的铝合金氧化膜生长过程的自适应发射率模型,对焊接温度场进行补偿研究。首先,考虑到搅拌摩擦焊过程中铝合金表面形貌的动态变化,采用二次曲面响应法确定焊接表面粗糙度及其与平均线单位长度平均值的交点数;随后,基于提出的自适应发射率,建立6061铝合金搅拌摩擦焊过程的完全耦合有限元模型进行数值模拟,并对模拟结果进行分析。结果表明:不同焊接条件下,基于自适应发射率模型所得结果与实验结果之间的最大绝对误差仅为11 K,表明采用自适应发射率的数值模型能够较好地再现焊接过程中的温度场,可为提高搅拌摩擦焊焊接质量提供支持。

搅拌摩擦焊过程热-力-流全耦合仿真:不同本构方程的仿真效果对比

本构方程是搅拌摩擦焊过程热-力-流全耦合仿真模型的重要部分。针对6 mm铝合金6061-T6板材FSW过程开展热-力-流全耦合仿真分析。为分析本构方程的形式对仿真效果的影响,在模型中分别采用Chen-Liu本构模型、Sellars-Tegart模型和Johnson-Cook模型,并对仿真结果进行对比分析。仿真结果表明,Chen-Liu模型计算得到的FSW温度场及流动场与实验结果的吻合程度均高于Sellars-Tegart模型和Johnson-Cook模型。究其原因,在搅拌头-工件界面附近的温度条件下,Sellars-Tegart模型和Johnson-Cook模型预测的流变应力较高,使得材料流动困难,搅拌头与工件之间的界面状态主要为滑动摩擦。相比之下,Chen-Liu模型能够体现材料在温度升高时的迅速软化现象,在搅拌头-工件界面附近的温度条件下,材料的剪切流变应力低于搅拌头/工件界面的摩擦应力,因而在摩擦作用下工件发生塑性流动,这降低了搅拌头/工件之间的滑动摩擦速度,从而使得滑动摩擦产热减少,且其减少量大于工件发生塑性流动产生的额外热量,从而使得采用Chen-Liu模型预测得到的焊接温度更低。综合来看,FSW过程温度场与材料流动速度场受材料本构模型影响归因于FSW的热-力-流全耦合效应。

Al/Ti异质合金回填式搅拌摩擦点焊数值模拟

采用耦合的欧拉-拉格朗日(CEL)算法对2 mm厚的5A02铝合金/TC4钛合金板异质金属回填式搅拌摩擦点焊过程展开模拟研究,分析了旋转速度和停留时间对焊点成型过程中温度场、等效塑性应变场以及材料流动的影响。结果表明,在扎入初期,热累积作用明显,升温速率相对较快,随焊接过程进行,产热会由摩擦产热转变为摩擦和塑性变形共同产热,升温速率放缓。当搅拌头转速为2000 r/min、扎入速度为1 mm/s、扎入深度为1.9 mm、回填速度为1mm/s、停留时间为0 s时,铝合金焊核区温度峰值达到558℃,等效塑性应变峰值达到120。在模拟的工艺区间内,焊核区峰值温度与旋转速度呈正相关,停留时间对温度的影响并不明显。

6061-T6铝合金高速搅拌摩擦焊数值模拟

基于耦合欧拉-拉格朗日方法,建立了6061-T6铝合金薄板的高速搅拌摩擦焊数值模型,研究高速焊接工艺条件下的温度场及变形场特点,采用示踪粒子方法研究焊接区材料塑性流动规律。开展高速搅拌摩擦焊试验,分别从温度场、宏观样貌和内部缺陷对数值模型进行验证。结果表明,采用该模型能够准确描述高速搅拌摩擦焊过程的温度场及变形场,也能精准预测焊接缺陷出现的位置及尺寸。相较于常规搅拌摩擦焊,高速搅拌摩擦焊在焊接方向和横截面都具有更密集的温度梯度,塑性应变区域也较为集中,其热影响区更小。

基于DEFORM-3D的纯铝快速冷却搅拌摩擦焊数值模拟和试验研究

采用DEFORM-3D软件建立了A1050纯铝传统搅拌摩擦焊(FSW)和快速冷却FSW焊缝的有限元模型,分析了冷却介质对焊缝温度场和微观组织演变的影响规律,并采用电子背散射衍射技术对两种FSW试验的结果进行分析,以验证模拟结果。结果表明:在焊接过程中通过添加冷媒介质,快速冷却FSW的峰值温度较传统FSW明显降低,在搅拌头后方快速冷却FSW的温度梯度明显大于传统FSW。快速冷却FSW焊缝的晶粒尺寸减小、小角度晶界比例增加且位错密度更高。模拟结果与试验结果基本吻合。

6061铝合金/AZ31镁合金异种金属搅拌摩擦焊温度场的数值模拟

使用COMSOL Multiphysics有限元软件建立了6061铝合金/AZ31镁合金异种金属搅拌摩擦焊的三维传热模型,实现了搅拌摩擦焊接温度场的模拟,并分析了焊接速度、搅拌头转速参数对温度分布的影响。结果表明:焊接过程中高温区域温度场呈椭圆状分布,温度最高处位于搅拌头后方镁板侧,且轴肩接触处的尤为突出。随着焊接速度的增加、搅拌头转速的减小,高温区域的面积减小,峰值温度明显降低。焊接速度比搅拌头转速对温度场的影响更为显著。

2219-T8铝合金搅拌摩擦沉积增材初始进料阶段数值模拟研究

研究了高强铝合金2219-T8在搅拌摩擦沉积过程中初始进料阶段的温度、应变和塑性流动,并深入探讨了主轴转速和进料速度对材料流动性的影响规律。采用Arrhenius材料定律建立了三维有限元热力学模型。实验结果表明,在不同的工艺参数下,同一区域的沉积时间存在差异。在当前工艺参数设定下,主轴转速为350 r/min,进料速度为0.2 mm/s时,沉积速度最快,增材效率最高;随着主轴转速的增加,进料杆的升温速率增大,材料发生塑性变形的最高温度增加,应变速率也增大;随着进料速度的增加,材料流动性减弱,填补中空旋转工具与基板之间的间隙所需时间增加。

基于SPH方法的搅拌摩擦焊数值模拟研究

光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)法是基于拉格朗日的一种无网格法,基于SPH方法使用ABAQUS软件进行AZ31B镁合金的搅拌摩擦焊数值模拟,通过改变搅拌头转速,研究残余应力和温度的分布。结果显示:焊缝两侧残余应力分布呈不对称,后退侧应力大于前进侧;应力曲线具有双峰特征,在焊接区域表现为拉应力;随着转速的增加,工件应力分布更加均匀;焊缝两侧的温度呈不对称分布,且前进侧高于后退侧,随着转速的增加,温度呈上升趋势;纵向温度曲线呈M形分布。模拟结果对实际焊接过程中焊接参数的选择具有一定参考意义。

差厚铝合金2024∕7075搅拌摩擦焊的温度场数值模拟

利用Abaqus有限元软件,建立差厚7075和2024铝合金的有限元模型和改进热源模型,进行模拟搅拌摩擦焊的焊接过程,分析了不同厚度比的温度分布,以及对焊核区和热力影响区的宽度变化的影响,并验证了所建模型应用的可行性。结果表明,铝合金焊件中的温度峰值随着厚度比的变化而改变,且温度在铝合金板上呈不对称的倒“V”形分布,板材上的温度峰值随着板材厚度变大而减小。焊接过程中温度越高焊件上的热力影响区就越宽。较大的厚度比会使得焊件的热力影响区宽度和焊核区宽度偏大。模拟得到的温度值和试验数据比较,两者的误差在8%以内,验证了模型的可行性。

大厚度铝合金搅拌摩擦焊接的仿真与实验研究

针对10mm大厚度7050铝合金板搅拌摩擦焊接需求,建立了任意拉格朗日–欧拉模型,结合仿真分析和实验研究,分析了转速、焊接速度及焊接时间下接头温度场分布规律。实测温度和特征点的热循环曲线吻合较好,说明数值模拟可以用来预测温度场的分布规律。结果表明:不同焊接参数下焊缝横截面温度场分布均呈碗状。各位置点的峰值温度随着转速增大及焊接速度减小而升高,其中转速对峰值温度影响更显著。最后,实验验证3组工艺参数下接头的力学性能,实验表明,转速为800r/min、焊接速度为1.6mm/s时,接头的力学性能较好。本研究方法为大厚度轻质合金搅拌摩擦焊接工艺的确定提供了参考和借鉴。

超声辅助搅拌摩擦焊接温度场与材料流动数值模拟

为了研究6061铝合金超声辅助搅拌摩擦焊接过程中温度场与焊缝区域材料流动等行为,采用耦合欧拉-拉格朗日方法,考虑超声振动对工件材料属性的影响,建立了6061铝合金超声辅助搅拌摩擦焊热机耦合数值模型,通过示踪粒子监测材料流动行为,开展超声辅助搅拌摩擦焊试验,并对模型准确性进行验证。研究结果表明:焊接过程中焊缝材料首先被压缩至工件底部,随后在搅拌头的作用下向工件上表面与搅拌头后方流动;工件表面温度场与焊缝区域的等效塑性应变场均呈不对称分布,塑性应变区域集中于焊缝两侧共约25 mm的区域内,区域温度均高于400℃;焊核区域的形状与尺寸及飞边的位置和尺寸的模拟结果与试验结果基本吻合,验证了建立的热机耦合数值模型的正确性。