6005A-T6铝合金型材搅拌摩擦焊与MIG焊的数值分析

以轨道车辆用铝合金车钩面板为研究对象,应用数值分析技术,分别模拟了车钩面板MIG焊与搅拌摩擦焊的焊接过程,得到2种焊接方法的焊后变形与残余应力,并进行对比分析。结果表明:采用MIG焊的车钩面板焊接变形呈马鞍状,最大变形量为-1.515mm;较大的焊后残余应力主要集中在焊缝区,最大应力值为248 MPa。搅拌摩擦焊后的车钩面板为反马鞍状变形,变形最大值为-0.72 mm,焊缝区残余应力最大值为225 MPa。经对比可知,采用搅拌摩擦焊的车钩面板焊后变形小于MIG焊的,且焊道中的残余应力较小,为较优的焊接方法。研究结果对促进搅拌摩擦焊在铝合金轨道车辆上的应用具有十分重要的现实意义。     

6005A-T6铝合金搅拌摩擦焊焊缝相控阵超声波检测

分析了6005A-T6铝合金搅拌摩擦焊接头缺陷特征,研究了6005A-T6铝合金搅拌摩擦焊焊缝缺陷相控阵超声波检测技术的原理和特点,采用相控阵超声波检测方法对典型的搅拌摩擦焊焊缝缺陷进行了检测,并通过X射线对检测结果进行了验证和对比分析。结果表明,针对6005A-T6铝合金车体搅拌摩擦焊对搭接焊缝的特点,采用相控阵超声波无损检测技术能够有效地检测出隧道孔、未焊透等典型搅拌摩擦焊焊缝缺陷,是一种切实可行的搅拌摩擦焊焊缝缺陷无损检测方法。     

6005A-T6铝合金型材搅拌摩擦焊工艺参数优化

针对某型号地铁侧墙板6005A-T6铝合金型材搅拌摩擦焊进行焊接工艺参数优化。根据前期试验拟定搅拌头转速为1 000~2 100 r/min、焊接速度为500~2 200 mm/min,通过对比焊缝外观成形质量,确定搅拌头旋转速度为1 500 r/min和焊接速度为1 100 mm/min。对不同顶锻力获得的接头进行金相检验和拉伸弯曲试验。当工艺参数为ω=1 500 r/min、v=1 100 mm/min、F=13.5 k N时,接头无缺陷,抗拉强度可达母材的80%,180°弯曲试验无断裂。     

铝合金搅拌摩擦焊温度场的数值模拟分析

基于粘着摩擦理论,建立了4 mm厚7075铝合金FSW过程中的产热模型,对同种铝合金对接焊中的温度场进行了数值模拟,并得出了焊接过程中温度场的分布规律:高温区位于轴肩的正下方焊核区,且在沿焊缝方向的横截面上整体呈现"碗状";搅拌头前方的温度梯度比后方的温度梯度大,高温区相对于后方也较窄;对于所有焊接工艺参数下的温度峰值均未超过母材熔化点,表明搅拌摩擦焊接过程一直处于固相连接状态;旋转速度与焊接速度对峰值温度有一定的影响。     

6005A-T6铝合金厚板单面与双面搅拌摩擦焊的性能比较

采用搅拌摩擦焊对35 mm厚的6005A-T6铝合金分别进行单、双面对接焊接,对焊缝的微观组织、焊缝整体和沿厚度方向上的力学性能变化、焊缝的腐蚀电流密度和电位进行了研究。结果表明,单面焊焊核区的平均晶粒尺寸为9.14μm,双面焊为6.33μm。单、双面FSW焊缝前进侧与母材有明显的界面,两种焊缝接头均出现明显的软化;沿焊缝厚度方向单面焊的硬度最低点出现在焊缝根部,双面焊则出现在两次焊接的重合部位。单面焊接头的平均抗拉强度为182 MPa,为母材的65.9%;双面焊接头的平均抗拉强度为209 MPa,为母材强度的75.7%;双面焊焊缝的腐蚀电流密度低于单面焊而电位高于单面焊。     

6005A-T6铝合金搅拌摩擦焊接头 微观组织及耐应力腐蚀性能

利用光学显微镜、透射电镜以及四点弯曲应力腐蚀方法研究6005A-T6铝合金搅拌摩擦焊接头的微观组织及其应力腐蚀性能。结果表明,6005A-T6铝合金搅拌摩擦焊接头硬度分布呈"W"型,其中热影响区的硬度最低,焊核区的硬度有所升高,母材硬度最高;铝合金母材的主要强化相为含铜Q'相,而焊核区大部分强化相消失,存在大量位错,主要强化机制为细晶强化、位错强化和固溶强化;搅拌摩擦焊接头表现出良好的抗应力腐蚀性能,但仍出现点蚀现象,其中热影响区为接头耐蚀性的薄弱部位。     

5A06铝合金搅拌摩擦焊温度场数值模拟

采用热量自适应热源模型,利用ANSYS有限元软件对5 mm厚5A06铝合金搅拌摩擦焊接过程温度场进行模拟,研究不同转速、焊接速度对搅拌摩擦焊温度场的影响。结果表明:当焊接速度提高或搅拌头旋转速度降低时,焊接过程中的峰值温度降低;焊接过程进入稳态后,峰值温度稳定在420°C左右;沿焊缝两侧温度场分布不完全对称,前进侧温度略高于返回侧温度。     

铝合金搅拌摩擦焊温度场数值模拟及参数影响分析

对10 mm厚6061-T6铝合金,应用有限元软件COMSOL建立了搅拌摩擦焊有限元模型,模拟搅拌摩擦焊稳态温度场并分析焊速、转速变化对温度场影响。结果表明:温度分布曲线在x、y方向呈非对称的M型,返回侧峰值温度比前进侧峰值温度低约10℃,搅拌头后侧峰值温度比搅拌头前侧峰值温度高约25℃;焊接速度越大,峰值温度差值越大,转速越大,峰值温度差值也越大。焊接速度不变,转速等值增加时,x、y方向温度分布曲线等值上移,具有一定的平行性和相似性。转速不变,焊接速度等值增加时,x、y方向温度分布曲线以越来越小值下移。与转速相比,焊接速度改变对椭圆形的热影响区改变大,对椭圆率改变明显,对温度场影响显著。     

2024铝合金搅拌摩擦焊初始温度场数值模拟与分析

搅拌摩擦焊下压过程中温度场的建立对工件的焊接质量有重要的影响。在搅拌摩擦焊接过程中,搅拌工具与焊接工件的摩擦接触关系及焊接工艺参数的选取,决定了焊接过程中工件的温度场分布。基于修正的库仑摩擦定律,建立了火箭燃料贮箱所用3 mm厚2024铝合金材料搅拌摩擦焊接下压过程的热量输入模型,通过有限元分析得到了整个过程中的温度场分布。分析结果表明,该模型的下压阶段温度场计算精度较高。模型的计算结果对指导铝合金焊接初始下压过程中转速、下压速度及顶锻力的大小等焊接工艺参数的选取具有重要意义。     

列车地板6005A-T6铝合金搅拌摩擦焊接头疲劳性能研究

对4 mm列车地板6005A-T6铝合金搅拌摩擦焊接头进行高周疲劳性能研究。采用优化的工艺进行焊接,对试样进行轴向高周疲劳试验,得到了焊接接头疲劳性能的平均S-N曲线和疲劳极限。用扫描电镜观察疲劳断口的微观形貌并分析了疲劳断裂机理。结果表明:列车地板6005A-T6铝合金FSW接头疲劳试样,其起裂位置包括试样上、下表面及侧面区域,其断裂位置大部分在距离焊缝中心3~7 mm的范围内,即接头的热机影响区及热影响区。接头疲劳断口的裂纹扩展区存在比较明显的疲劳裂纹,该区域主要以脆性解理断裂为主,瞬时断裂区主要为韧性断裂。     

焊接速度对6005A-T6铝合金双轴肩搅拌摩擦焊接头力学性能的影响

文中研究了转速和热输入特征值WP一定两种条件下焊接速度对6005A-T6铝合金双轴肩搅拌摩擦焊接头力学性能的影响. 结果表明,转速一定时,接头抗拉强度随焊接速度的增加呈先增大后减小的趋势;热输入特征值WP一定时,随着焊接速度的增加,接头的抗拉强度持续减小;接头呈现出三种断裂方式,分别为发生于热影响区的Ⅰ型断裂、发生于焊核区的Ⅱ型断裂和发生于热力影响区的Ⅲ型断裂;Ⅰ型断裂和Ⅱ型断裂为韧性断裂;Ⅲ型断裂为包含韧性断裂和脆性断裂的混合型断裂;接头拉伸断裂位置并非总出现在硬度最低处;焊接速度小于1 000 mm/min时,WP ≤ 1有利于提高接头力学性能,而焊接速度大于1 000 mm/min时,WP > 1更有利于提高接头力学性能.     

高速列车铝合金车身双热源搅拌摩擦焊仿真

高速列车采用超长铝合金型材作为车身新材料。搅拌摩擦焊以固相连接原理成为高铁车身制造新工艺。针对单热源模型不足,考虑搅拌轴肩转动摩擦生热和搅拌头塑变剪切生热,建立搅拌摩擦焊双热源有限元模型。基于传统熔焊方式,实现满足搅拌焊特征的双面挤压型材接头变形设计。通过ANSYS二次开发,完成该工艺移动瞬态热交换数值仿真,获得焊接全程三维温度场分布,仿真结果与试验数据吻合良好。结果表明,该仿真模型可行．仿真结果合理,为高铁车身国产化制造工艺吸收和工艺优化提供参考。     

高速列车6005A-T6铝合金型材激光-双丝MIG复合焊

分别利用双丝MIG焊和激光-双丝MIG复合焊进行了高速列车6005A-T6铝合金型材的焊接试验研究,对比分析了两种焊接方法的焊缝成形、焊接变形、接头力学性能及其接头微观组织.结果表明,激光-双丝MIG复合焊接6005A-T6铝合金型材时的焊接速度可达4.5 m/min,焊接过程具有较好的搭桥能力,对接间隙达到1.4 mm时,仍可以获得良好的焊缝成形.当焊接速度大于或等于4 m/min时,复合焊接头的焊接变形量仅为常规双丝MIG焊的40%左右,其抗拉强度达到了母材强度的83%,比常规双丝MIG焊接头的抗拉强度提高了9%左右.     

高速列车6005A-T6铝合金焊接接头软化分析

测试了6005A-T6铝合金双丝MIG焊和激光-双丝MIG复合焊的焊接热循环曲线,并利用热处理方法进行了焊接软化的热模拟试验,探讨了6005A-T6铝合金焊接接头的软化问题.结果表明,焊接热循环峰值温度超过260℃时热影响区开始软化,当峰值温度达到350℃左右时软化最为严重,晶内的非稳态强化相β"相及β'相转变为平衡态的β相(Mg₂Si)并聚集长大是造成软化的根本原因;受热温度在260~500℃的热影响区,焊后经简单的时效处理后,硬度无法恢复至原始状态;复合焊的焊接热循环曲线在260℃以上的高温停留时间相对较短,这是造成复合焊接头软化程度低于常规MIG焊的直接原因.     

Numerical simulation of friction stir spot welding process for aluminum alloys

Thermo-mechanical simulations of the Friction Stir Spot Welding (FSSW) processes were performed for AA5083-H18 and AA6022-T4, utilizing commercial Finite Element Method (FEM) and Finite Volume Method (FVM) codes, which are based on Lagrangian and Eulerian formulations, respectively. The Lagrangian explicit dynamic FEM code, PAM-CRASH, and the Eulerian Computational Fluid Dynamics (CFD) FVM code, STAR-CD, were utilized to understand the effect of pin geometry on weld strength and material flow under the unsteady state condition. Using FVM code, material flow patterns near the tool boundary were analyzed to explain weld strength difference between welds by a cylindrical pin and welds by a triangular pin, whereas the frictional energy concept using the FEM code had a limited capacity to explain the weld strength difference.     

搅拌摩擦焊接过程温度场数值模拟

在深入考虑搅拌摩擦焊的具体焊接过程后,提出了简化的热输入模型。利用ANSYS有限元分析程序建立了随热源一起移动的坐标系,采用分步加载的方法对搅拌摩擦焊过程的温度场进行了模拟。得到了3mmLY12硬铝合金薄板在整个焊接过程中焊缝区每一时刻的瞬态温度场以及焊缝区各点的焊接热循环曲线,确立了温度场空间分布和时间变化的规律,并且通过测量特征点的实际温度验证了计算结果的准确性。     

Sequential modeling of local precipitation,strength and strain hardening in friction stir welds of an aluminum alloy 6005A-T6

A novel microstructure-based strain-hardening model for precipitate hardening materials is developed, accounting, in addition to the usual contributions, for the influence of a supersaturated solid solution as well as for a dependence of dynamic recovery on the yield strength and on the presence and stability of Orowan loops. This model is the third step of a chain involving: (i) a precipitation model which predicts the evolution of precipitate radius distribution and volume fraction with thermal cycles, and (ii) a model which predicts the yield strength as a function of the microstructure. The model parameters are identified from quantitative characterizations and tensile tests performed after isothermal heat treatments of AA 6005A-T6 samples. A critical assessment of the sequential three-steps model is made by predicting, based on local thermal history measurements, the local microstructures and flow properties in two friction stir welded joints generated with different advancing speeds. The predicted results show very good agreement with the local experimental data. This analysis leads to a better understanding of the competing factors controlling the strength profiles and ductility of the friction stir joints.     

Effect of pin rotating speed on lap shear strength of stationary shoulder friction stir lap welded 6005A-T6 aluminum alloy

Stationary shoulder friction stir lap welding (SSFSLW) was successfully used to weld 6005A-T6 aluminum alloy in this paper.Effect of pin rotating speed on cross section morphologies and lap shear strength of the SSFSLW joints were mainly discussed.Results show that joints without flash and shoulder marks can be obtained by the stationary shoulder.Cross section of the SSFSLW joint presents a basin-like morphology and little material loss.By increasing the rotating speed from 1 000 rpm to 1 600 rpm,both effective sheet thickness and lap width increase,while lap shear failure load firstly decreases and then increases.The maximum failure load of 14.05 kN is attained when 1 000 rpm is used.All SSFSLW joints present shear fracture mode.     

Numerical simulation of friction stir butt-welding of 6061 aluminum alloy

A two-dimensional computational fluid dynamics model was established to simulate the friction stir butt-welding of 6061 aluminum alloy. The dynamic mesh method was applied in this model to make the tool move forward and rotate in a manner similar to a real tool, and the calculated volumetric source of energy was loaded to establish a similar thermal environment to that used in the experiment. Besides, a small piece of zinc stock was embedded into the workpiece as a trace element. Temperature fields and vector plots were determined using a finite volume method, which was indirectly verified by traditional metallography. The simulation result indicated that the temperature distribution was asymmetric but had a similar tendency on the two sides of the welding line. The maximum temperature on the advancing side was approximately 10 K higher than that on the retreating side. Furthermore, the precise process of material flow behavior in combination with streamtraces was demonstrated by contour maps of the phases. Under the shearing force and forward extrusion pressure, material located in front of the tool tended to move along the tangent direction of the rotating tool. Notably, three whirlpools formed under a special pressure environment around the tool, resulting in a uniform composition distribution.