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 aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional 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.     

Thermal models for bobbin tool friction stir welding

This study presents three thermal 3D models for bobbin tool Friction stir welding (FSW) implemented in Comsol and Matlab. The models use thermal pseudo-mechanical (TPM) heat sources and include tool rotation, an analytic shear layer model and ambient heat sinks like the machine and surrounding air. A new transient moving geometry approach has been implemented. It includes the full tool motion along the weld line, while the other two models use fixed geometry with and without moving heat source.The computational effort is small for all three models. The steady state model can be solved in approximately 5 min on a state of the art workstation. Experiments on the FlexiStir experimental welding unit have been carried out to validate the models’ outputs. The predictions of all models are in excellent agreement with each other and the experiment.     

电芯粉中总锰的测定

本文提出了一种简便的处理方法,使乙炔黑转化成二氧化碳排出,并利用指示剂准确地指示终点,用氧化还原滴定法测定电池电芯粉中总锰含量。     

Effect of rotation speed on microstructure and mechanical properties of bobbin tool friction stir welded AZ61 magnesium alloy

The 5-mm-thick AZ61 magnesium alloy was friction stir welded by using the specially designed bobbin tool with various rotation speeds. Defect-free welds were successfully obtained with rotation speed ranging from 550 to 600?rev?min^?1. Grain size in different regions of the joints varied depending on the rotation speed. The hardness value of the joint is uniform. The defective joint fractured in the weld nugget zone with the lowest tensile strength, while the fracture location of the defect-free joints changed to the heat affected zone. The impact energy of weld nugget zone is higher than that of the heat affected zone, and the impact energy of the two zones in defect-free joint both decreased with increasing rotation speed.     

长城卷接机组盘纸控制系统的改造

长城卷接机组原盘纸控制系统存在故障率高且原器件老化的问题,将该系统的直流调压调速改造为交流变频调速,不仅可以满足卷接机组对盘纸的控制要求,也降低了备件成本,维修方便。     

光电式断纱检测头性能试验研究

探讨环锭纺纱过程中光电式断纱检测头应用性能。分析了光电式断纱检测原理,并根据管纱卷绕特点,分别对管底和管身两个卷绕阶段的钢丝圈信号进行监测,对比分析了不同卷绕阶段升降动程底部、中部、顶部的检测信号波形特征。结果表明:管底成形阶段中升降动程的顶部,钢丝圈信号检测波形的峰值最低并接近阈值。认为,该位置的波形信号状态是判定检测器性能的一个关键因素,以此位置的信号峰值水平作为检测头的重要评估参数,可对检测头综合应用性能进行正确评估,以获得准确、可靠、性能良好的检测装置。     

高速包装机械供纸系统的动态拼接与控制

自动供纸和动态自动接纸是当代轻工包装机械设计的关键技术和重要特征之一。它不仅要求包装机械供纸系统能够随机器的工作速度变化而自动改变供纸速度,而且要求在“在用盘纸”即将用完时,能够自动拼接“待用盘纸”,从而保证在不停机条件下自动换用盘纸。本文以高速卷烟机为对象,分析ＰＡＳＳＩＭ卷烟机供纸系统的工作原理,重点介绍盘纸动态拼接的设计技术,并讨论相应的电气控制过程     

提高糊式电池容量与均匀率的途径

本文通过一系列生产工艺试验、放分试验的验证和生产实践的总结,论述了影响不包扎电池放分、均匀率的诸因素,并且提出了提高电容量与均匀率的方法。     

再论粗纱机"恒离心力纺纱"

对棉纺高速粗纱机采用翼导卷绕方式，在减小离心张力、降低能耗等方面的机理进行了理论分析。分析表明：翼导卷绕方式的筒管转速始终比管导卷绕方式的筒管转速要低；当粗纱定量较重时，翼导卷绕方式能显著地减小粗纱机纺纱时粗纱的离心张力。解决高速粗纱机大纱时卷绕层易崩裂的问题，不能局限于降低粗纱机的纺纱速度，以求“恒离心力”纺纱的模式。由于现代高速粗纱机大都采用微型计算机控制，断头时易发生乱头和飞花的问题是可能解决的。由于采用翼导卷绕方式替代管导卷绕方式可提高生产率、减轻磨损、降低能耗，因而值得认真开发和研究。     

Bobbin tool friction stir welding: a review

ABSTRACT

Friction stir welding is a solid-state welding technique for joining similar and dissimilar material. Bobbin tool friction stir welding (BTFSW) is a variant of the conventional friction stir welding process (CFSW). Compared with conventional FSW, BTFSW eliminates all limitations of CFSW using a two shoulders configuration. Now, the need has arisen to review the work done on BTFSW to provide broader aspects of the technique to researchers. This paper aims at providing comprehensive insight on the BTFSW. The paper pays critical attention to tool material selection, design features of shoulder and pin surfaces, microstructure evolution, mechanical characterisation, derivatives, and challenges in this technique. Further, welding defects and future scope of BTFSW are also addressed in this paper.