Global and local mechanical properties and microstructure of Bobbin tool friction-stir-welded Al–Li alloy

AA2198–T851 sheets were welded by bobbin tool friction stir welding using a rotational speed of 800?rpm and welding speed of 42?mm?min^?1. The microstructure and precipitates within the joint were characterised by transmission electron microscopy. The global and local mechanical behaviour was determined using a digital image correlation system. Specific attention was given to the relationship between the local microstructure and properties across the joint, which govern the global strength and ductility of the welds. A lower global elongation of the joint is caused by the premature strain localisation in the softened zone.     

1.8万锭棉纱生产线的运行实践

探讨1.8万锭棉纱生产线的运行效果.分析阐述了采用高性能全流程纺纱生产线的必要性、设备性能特点、实际运行状况.从产品档次、配棉和用工成本方面分析了投资收益.认为:以进口清梳联、细络联为主的全流程纺纱设备可实现优质、高效、高产,明显提升产品档次,降低配棉和用工成本,创建企业品牌,提高市场竞争力,是棉纺厂技术升级改造的有效途径之一.     

Shear layer modelling for bobbin tool friction stir welding

Abstract

This study presents an approach to model the shear layer in bobbin tool friction stir welding. The proposed CFD model treats the material in the weld zone as a highly viscous non-Newtonian shear thinning liquid. A customised parametric solver is used to solve the highly non-linear Navier–Stokes equations. The contact state between tool and workpiece is determined by coupling the torque within the CFD model to a thermal pseudomechanical model. An existing analytic shear layer model is calibrated using artificial neural networks trained with the predictions of the CFD model. Validation experiments have been carried out using 4 mm thick sheets of AA 2024. The results show that the predicted torque and the shear layer shape are accurate. The combination of numerical and analytical modelling can reduce the computational effort significantly. It allows use of the calibrated analytic model inside an iterative process optimisation procedure.     

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φ1Gmm×1．5mm的蒸汽发生器传热管涡流检查的Bobbin探头（西11．0mm）的验收指标，为此类探头的性能测试和比较提供了参考。     

YJ19A卷烟机新型换纸器的设计与应用

通过对YJ19卷烟机原设计的换纸器结构的介绍 ,指出了原换纸器中存在的不足之处 :采用气缸及导向滑板机构 ,结构复杂 ,调整量大 ,可靠性及稳定性低 ,磨损后需要更换新零件 ,并需重新调整导向滑板。且外观笨重 ,给安装、维护及调整带来不便。新型换纸器新设计的换纸器装置采用导向气缸代替原设计的气缸滑板机构 ,简化了机械结构 ,减少了使用中的调整步骤 ,提高了可靠性和稳定性 ,同时也改善了卷烟外观质量 ,降低了生产成本     

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.     

Design features for bobbin friction stir welding tools: Development of a conceptual model linking the underlying physics to the production process

The effects of different pin features and dimensions of scrolled shoulder bobbin friction stir welding were tested for welding marine grade aluminium, Al6082-T6. Welds were created in longitudinal and transverse plate extrusion directions in thin plate aluminium clamped and supported at one side. Measured outcomes included visual inspection, plate distortion, mechanical properties, metallurgical examination, and hardness test. This study shows that tool features cannot be directly transferable from conventional friction stir welding technology without comprising process variables and tool part functionality. Process setting such as clamps, support arrangements, shoulder gap and welding direction create compression, vibration and heat distribution hence influence the weld quality. The best joint was produced by four flats tool pin followed by threaded tool pin with three flats. These findings were used to develop a conceptual theory representing the underlying physics of the friction stir welding process. The effects of pin features, specifically threads and flats, are identified. This model is useful for direct linking welding factors towards the expected consequences.     

A generalized likelihood ratio technique for automated analysis of bobbin coil eddy current data

This paper presents a generalized likelihood ratio technique for detection of defect locations from bobbin coil eddy current data. First a Neyman–Pearson (NP) decision rule for detection of known random signals (in presence of noise) is discussed. The result is then generalized to the problem of detection of unknown random signals that are commonly found in bobbin coil eddy current data. The performance of the proposed detection technique is tested on several real world data sets collected from the steam generator tubes of nuclear power plants. The experimental results indicate that the method is quite promising and useful for automated processing and classification of eddy current data.     

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 different 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 inter-face,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 difference between Guinier-Preston dissolution and Q phase precipitation leads to rare change of hardness in the heat affected zone(HAZ)at the AA6056 side.The increased hardness of the HAZ at the AA2219 side is attributed to avoidance of the dissolution of θ"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.     

干电池电芯粉pH值的控制与检测

笔者对锌锰干电池电芯粉的pH值控制范围和检测方法进行了探讨,认为检测拌粉处电芯粉的pH值并给予控制,效果较好。此方法简便迅速、测量准确,便于指导生产,有利于稳定产品质量,预防纸板电池早期结晶。