Effects of postweld aging on the microstructure and properties of bobbin tool friction stir-welded 6082-T6 aluminum alloy

Samples of 6082-T6 aluminum alloy were subjected to bobbin tool friction stir welding (BT-FSW), and the joints were treated by postweld natural aging (PWNA) and postweld artificial aging (PWAA). The microstructure, microhardness, and tensile properties of the aged and as-welded specimens were investigated. Transmission electron microscopy (TEM) observations revealed that a large number of Guinier–Preston (GP) zones precipitated in the form of a network on the stir zone (SZ) after PWNA for 60 d, and a large number of β'' phases precipitated in the matrix for after PWAA for 6 h. As the aging time increased, the microhardness of the SZ and the thermomechanically affected zone (TMAZ) increased significantly, and the hardness of the SZ after PWAA for 6 h was close to that of the base metal (BM). With increasing PWNA time, the strength and strain increased slightly. When the PWAA time increased, the strength clearly increased, with a maximum value of 279.9 MPa after 6 h, while the strain decreased.

涡流Bobbin探头性能评价参数试验

为了评价和比较传热管涡流检查使用的Bobbin探头,通过对于影响检测结果的基本要素的分析,提出涡流Bobbin探头的性能评价参数。采用自制探头和进口探头进行了比较试验。通过对试验结果的分析,总结出涡流Bobbin探头的性能评价方法,并最终给出了对材料为08X18H10T不锈钢、尺寸为φ16 mm×1.5 mm的蒸汽发生器传热管涡流检查的Bobbin探头(φ11.0 mm)的验收指标,为此类探头的性能测试和比较提供了参考。

Assessment of self-reacting bobbin tool friction stir welding for joining AZ31 magnesium alloy at inert gas environment

Research work presented in this study has the primary target of exploring joint attributes of AZ31 magnesium alloys using friction stir welding process with a modified tool referred as bobbin tool.Effects of inert and open atmosphere on mechanical properties are evaluated over a wide range of welding speed and tool rotation speed.Comparison of the research findings from the inert atmosphere bobbin tool were made with the traditional process of friction stir welding.The results depicted improved joint properties for inert atmosphere welding.Low and intermediate range of tool rotational speed is found to be favorable for bobbin tool friction stir welding without and with an inert medium,respectively.Controlled atmosphere due to inert medium leads to less oxidation of the AZ31 Mg alloy leading to superior joint properties.Microstructural investigations are also made with the aim of evaluating the impact of bobbin tool and inert medium on joint properties.In each aspect for joining of AZ31 Mg alloy,bobbin tool with inert medium is found to be an effective solution for joining with improved mechanical properties compared to without inert bobbin tool as well as conventional tool friction stir welding.

涡流Bobbin探头的性能对比试验

为了评价自制Bobbin探头的性能,通过与进口探头进行对比试验的方式,设计加工了系列样管,检测了探头阻抗、中心频率、有效扫查区域宽度、填充系数、深度系数、轴向长度系数、周向宽度系数、相位-伤深曲线、永磁饱和强度、信号对称性等性能指标。对比结果表明,自制探头与进口探头的性能相当。

Enhanced Fatigue Properties of 2219 Al Alloy Joints via Bobbin Tool Friction Stir Welding

In the present study,2219-T87 Al alloy plates,4 mm in thickness,were subjected to bobbin tool friction stir welding(BTFSW)under relatively high welding speeds of 200 and 400 mm/min,with the aim to analyze the effect of welding speeds on fatigue properties of the joints.The results showed that the tension–tension high-cycle fatigue performance of the BT-FSW joints at room temperature was significantly enhanced compared to that of other joints of 2xxx series Al alloys counterparts.Particularly at a high welding speed of 400 mm/min,the fatigue strength of the joint reached 78%of the base material together with a high tensile strength of 311 MPa.It was found that the joint line remnants had no effects on the fatigue properties of the BT-FSW joints due to the elimination of root flaws under the action of the lower shoulder.Most of the samples with the welding speed of 200 mm/min failed at the thermo-mechanical zone(TMAZ)during fatigue tests,attributable to the coarsened grains and precipitates,but all of the samples with high welding speed of 400 mm/min randomly failed at the nugget zone due to the improved hardness value in the TMAZ.

基于逆投影变换的纱筒纱线余量检测算法

纱筒纱线余量检测是纺织行业自动化生产过程中的重要一环,针对目前纱线余量检测算法检测精度低的问题,提出一种基于三点逆投影变换模型的纱筒纱线余量检测技术。根据实际生产过程中相机与纱筒的位置关系,建立三点逆投影变换模型进行初步矫正。为得到更好的图像矫正结果,设置补偿矩阵并根据内外筒位置信息优化变换矩阵,最后将逆投影变换后的图像按照改进的椭圆坐标变换模型展开为矩形,根据余量计算准则计算得到纱筒纱线余量。在自主搭建的检测平台上进行实验,结果表明,本文算法检测精度在5 mm以内,基本满足实际生产要求,可为纺织产业自动化生产提供依据。

基于改进残差网络的空纱筒识别模型

针对纺织车间背景复杂、纱筒种类多导致利用传统机器视觉识别空纱筒准确率低、模型参数量大的问题,设计了一种基于改进残差网络的空纱筒识别模型。该模型借鉴ResNet系列的模型结构,进行卷积核轻量化,改进经典的残差模块并加入SENet注意力机制,以达到提高检测空纱筒的准确率,减少模型参数的目的。最后通过数据增强,创建了适合工厂实际生产的纱筒数据集。实验结果表明:在消融实验中,应用SENet注意力机制可以提高3.86%的准确率,利用优化残差模块不仅减少了650%的模型参数还提高了1.22%的准确率。在原数据集的验证集上,改进模型的准确率为99.6%比ResNet-18模型高4.46%,与VGG-16和AlexNet相比提高了7.05%~9.41%。在增强的数据集上,识别模型的准确率都有了较大的提升,但改进模型的准确率变化不大,说明该模型的鲁棒性较好,不易受到样本不足的影响。改进模型的参数数量缩小到原模型参数数量的1/10左右,为嵌入式设备部署空纱筒识别模型提供了思路。

适应多类型纱筒的换筒末端执行器关键技术

为解决现有换筒夹持机构无法适用于不同规格纱筒抓取的问题,根据针织生产车间纱架结构特征和纱筒更换工艺流程,设计了由夹爪机构、刹车机构、离合机构、推纱机构、翻转机构等组成的换筒末端执行器,该末端执行器可通过外扩电动机和外张气缸分别调节夹爪收缩尺寸以及夹爪间角度,以适用于不同类型的纱筒抓取。在机构设计过程中,不仅对各组成部分及其运动原理进行分析,还通过ANSYS Workbench软件对不同直径和不同长度的夹爪进行了静力学仿真,得出夹爪的直径为18 mm、长度为58 mm时可满足设计要求。同时研制样机,并进行了不同规格圆柱筒和圆锥筒的抓取实验。实验结果表明:该换筒末端执行器能够稳定、快速抓取内径为20~65 mm、质量不大于6 kg的纱筒,可应用于圆型纬编针织生产线。

Research Progress of Bobbin Tool Friction Stir Welding of Aluminum Alloys:A Review

Bobbin tool friction stir welding(BT-FSW)is a variant of conventional friction stir welding(FSW).It can be used to weld complex curvature structures and closed sections by adding an extra shoulder instead of a rigid backing anvil,which expands the potential application of FSW in aerospace,railway,automotive and marine industries.BT-FSW has some signifi cant advantages over conventional FSW such as no root fl aws,full weld penetration,low stiff ness requirements for machines and fi xtures,balanced heat input,lower distortion and thus has broad prospects for development.At present,there have been numerous research reports on BT-FSW,but its widespread use is still restricted due to various factors such as tool life,process stability,control complexity and implementation cost.In this paper,the domestic and foreign research progress of BT-FSW is reviewed from four aspects of bobbin tool design and classifi cation,temperature fi eld and fl ow fi eld during welding,microstructure and mechanical properties of welded joints as well as industrial application,and then the possible research hotspots of BT-FSW in the future are pointed out.This paper mainly aims to help researchers have a comprehensive and in-depth understanding of BT-FSW.

基于改进遗传算法的换纱筒机器人路径规划

为了解决针织换筒机器人顺序换筒耗时长、功耗高问题,首先综合考虑换筒机器人移动距离和翻转等待时间,建立具有时空约束的换筒路径数学模型;其次基于自适应遗传算法,提出一种改进的近邻度初始种群算子和按位变异的局部搜索算子,得到改进的遗传算法。结果表明,改进遗传算法规划的换筒机器人路径所消耗的生产时间相对于人工排序缩减55.5%,改进算法收敛速度相对于传统遗传算法提升48.3%,改进算法最优解质量也优于其他几种传统启发式算法,提升了系统效率,证明改进遗传算法应用在换筒机器人路径规划优化问题中的可行性和有效性。

Effects of traverse speed on weld formation,microstructure and mechanical properties of ZK60 Mg alloy joint by bobbin tool friction stir welding

ZK60B(Mg-6%Zn-0.6%Zr)alloy joints fabricated by bobbin tool friction stir welding(BTFSW)with various traverse speeds were investigated.The sound joint fabricated by the BTFSW was possible under the appropriate welding parameters.The severe plastic deformation during BTFSW resulted in dispersion and segregation of the Zr-rich particles within the stirred zone(SZ)followed by evolution of a bimodal grain structure with distributed bands of 0.8-1.7μm ultrafine grains and 4.1-7.1μm equiaxed grains.Micro-hardness of SZ is substantially reduced in contrast to that of parent metal(PM)in spite of the finer grain size owing to dissolution of Mg-Zn based precipitates having hardening effects on alpha-Mg matrix.With the decrease in traverse speed,randomization degree of the plasticized metal flow increases,which is evidenced by the randomized arc line pattern at the low traverse speed.Among all defect-free joints,the 200 mm/min joint exhibits the weakest isotropy of texture within SZ and the best tensile properties,which has reduced ultimate tensile strength and yield strength by 5.4% and by 22.2%,respectively,as compared to the PM.The randomized texture hinders the joint fracturing within SZ at low elongation.Therefore,a relatively high elongation of 10.8% was achieved,which corresponded to 72% of the PM value.

Improving weld formability by a novel dual-rotation bobbin tool friction stir welding

A novel dual-rotation bobbin tool friction stir welding （DBT-FSW） was developed, in which the upper shoulder （US） and lower shoulder （LS） have different rotational speeds. This process was tried to weld 3.2 mm thick alunlinum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formabiliW. Experimental results show that compared to conven- tional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process.

Comparative study on local and global mechanical properties of bobbin tool and conventional friction stir welded 7085-T7452 aluminum thick plate

7085-T7452 plates with a thickness of 12 mm were welded by conventional single side and bobbin tool friction stir welding （SS-FSW and BB-FSW, respectively） at different welding parameters. The temperature distribution, microstructure evolution and mechanical properties of joints along the thickness direction were investigated, and digital image correlation （DIC） was utilized to evaluate quantitatively the deformation of different zones during tensile tests. The results indicated that heat-affected zone （HAZ）, the local softening region, was responsible for the early plastic deformation and also the fracture location for SS-FSW samples, while a rapid fracture was observed in weld nugget zone （WNZ） before yield behavior for all BB-FSW specimens. The ultimate tensile strength （UTS） of SS-FSW joints presented the highest value of 410 MPa, 82% of the base material, at a rotational speed of 300 rpm and welding speed of 60 mm/min, much higher than that of BB-FSW joints, with a joint efficiency of only 47%. This should be attributed to the Lazy S defect produced by a larger extent of heat input during the BB-FSW process, The whole joint exhibited a much higher elongation than the slices. Scanning electron microscopic （SEM） analysis of the fracture morphologies showed that joints failed through ductile fracture for SS-FSW and brittle fracture for BB-FSW.

Assessing the Bonding Interface Characteristics and Mechanical Properties of Bobbin Tool Friction Stir Welded Dissimilar Aluminum Alloy Joints

This study focuses on the bonding interface characteristics and mechanical properties of the bobbin tool friction stir welded dissimilar AA6056 and AA2219 aluminum alloy joints using diff erent welding speeds.Voids arise solely in the stir zone at the AA2219 side.A distinct boundary with limited material mixing develops at the middle section of the bonding interface,while excellent material mixing with an irregularly jagged pattern forms at the top and bottom sections of the bonding interface.Increasing the welding speed,the material mixing is rarely changed at the middle section in comparison with the bottom section.Furthermore,a small diff erence between Guinier–Preston dissolution and Q phase precipitation leads to rare change of hardness in the heat aff ected zone(HAZ)at the AA6056 side.The increased hardness of the HAZ at the AA2219 side is attributed to avoidance of the dissolution ofθ’’phase precipitates.A maximum tensile strength of 181 MPa is obtained at 300 mm min-1.Fractures occur at the AA6056 side near the top and bottom surfaces and at the bonding interface in the middle section of the joints.The regions close to the top and bottom surfaces of the joints show a better ductility.

基于移动终端的全自动管纱溯源系统研发

为了更好地实现纺纱生产过程中细纱环节的质量追溯,针对目前管纱溯源繁琐低效等缺点,将移动终端与无线射频识别技术相结合并利用网络与数据库技术,设计出基于移动终端的全自动管纱溯源系统。采用固定式RFID标签读写检测装置将细纱机台号和锭子号自动写入到对应的纱管电子标签后,利用移动终端对络筒工序中被剔除的疵管电子标签上的生产信息进行读取、保存与处理,实现了对管纱的质量追溯和实时移动管理,还可及时维护修理问题纱锭,对管纱问题形成了闭环管理。系统在20台JWF1579型和100台FA506型细纱机上稳定运行9个月,纱疵数量明显减少。认为:该系统具有操作简单方便、溯源精准等特点,有利于降低人工成本,提高细纱追溯效率,进而提高生产效率和经济效益。

5083铝合金搅拌摩擦焊缝多区域力学性能研究

对12 mm厚的5083铝合金双轴肩搅拌摩擦焊接头不同区域进行金相组织观察、拉伸试验、硬度测试和疲劳试验,对疲劳试验后的试样断口进行SEM观察。结果表明:焊核区晶粒明显细化,热影响区晶粒粗化,热机影响区晶粒发生严重变形并带有方向性。接头整体硬度近似呈非对称的“W”形分布。从母材到焊核区硬度先减小后增大。母材硬度值最高,焊核区次之。母材、焊核区、热影响区的疲劳寿命差别较大,母材疲劳性能最好,焊核区次之,热影响区最弱。各区的疲劳裂纹源位于疲劳试样的表面,扩展区中可以看到疲劳条带,瞬断区断裂形式均为韧性断裂。

JWF0083型棉卷运输系统电气控制分析

为了解决传统条并卷机与精梳机之间物料运输效率低、用工量大等问题,介绍JWF0083型棉卷运输系统要求,以及使用人机界面、可编程控制器、变频控制系统、传感器、编码器、磁感应开关、气缸等整机控制系统配置方案,剖析棉卷筒管运输、条并精梳联通信、双定位等模块主要功能。指出:JWF0083型棉卷运输系统是实现条并精梳联的关键系统,能实现精梳机与条并卷机之间物流的自动输送,且结构紧凑、操作方便、运行稳定,具有高度智能化和良好的经济性。

基于机器视觉的空纱筒口定位方法

为实现换筒桁架机器人空纱筒口定位功能,提出一种深度学习与传统图像处理相结合的定位方法。首先通过改进的Yolov5模型框定图片中纱筒口的位置;然后利用Sobel边缘检测、阈值分割、滤波、闭操作处理框定区域的图像,并通过最小二乘法拟合得到空筒口径及中心坐标;最后利用单目相机小孔成像原理完成纱筒口的定位。结果表明:改进后的模型在检测准确率上达到99.2%,检测速度可达54.3帧/s,同时模型参数量减小到3.71 M,X轴、Y轴、Z轴方向的定位误差分别控制在1.3、1.9、0.7 mm以内,本文研究结果可满足换筒桁架机器人空筒口定位功能需求。

新型缫丝成筒技术的工艺优化

为缩短生丝加工流程并改进现有的缫丝成筒技术,在自动缫丝机基础上,借鉴络筒机的络交卷绕和张力控制等方法,开发出了一种新型的缫丝成筒设备及技术。通过正交分析法优化了缫丝成筒技术的工艺参数,并考察该缫丝成筒技术制备的缫丝成筒生丝与自动缫丝机制备的小生丝和小生丝经复摇、整理、泡丝、络筒等传统工序制备的传统筒装生丝在结构和性能上的差异。结果表明:对于选用的原料茧,当选择卷绕速度130 m/min、超喂比1.15、干燥温度90℃、油剂体积分数5%作为工艺参数时,该技术制备的缫丝成筒生丝同时具有相对较好的断裂强度、断裂伸长和抱合性能。缫丝成筒生丝的分子基团和结晶结构等微观结构、断裂伸长率、柔软性等力学性能与传统筒装生丝相近,而断裂强度、抱合指标要明显优于传统筒装生丝。新型缫丝成筒技术制备的筒装生丝优异的性能表明该技术具有良好的应用前景。

基于灰色系统理论的筒子纱卷绕密度测量误差预测

为提高采用激光扫描建模的筒子纱卷绕密度测量方法的测量精度,提出基于灰色系统理论的测量误差预测方法。通过灰色关联分析脉冲频率、采样周期和参数K与测量误差的相关性,获得满足灰色建模要求的建模参数。根据实际建模结构为非线性和建模因子序列中元素变化幅度较大的特点,基于传统多变量GM(1,N)幂模型,引入背景值优化和分数阶累加生成得到优化后的GM(1,N)幂模型,然后结合粒子群优化算法通过幂指数自适应寻优建立PSGM(1,N)幂模型,利用实际采集数据进行建模精度验证。结合测量误差预测值对卷绕密度测量值进行校正,得到更精确的卷绕密度值。结果表明,相比于传统多变量GM(1,N)幂模型,PSGM(1,N)幂模型的卷绕密度测量误差预测精度提升了48.6%,激光扫描建模方法的测量精度提高了11.7%。