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Li J.-Z.,Dalian University of Technology | Luan J.-J.,Wuxi Micro Research Co. | Yu H.-L.,Dalian University of Technology | Zhang Y.-S.,Shanghai Spaceflight Manufacture Group Co. | Yu Z.-Y.,Dalian University of Technology
Dalian Ligong Daxue Xuebao/Journal of Dalian University of Technology | Year: 2011

To solve the electrode wear problem in three-dimensional micro-electrical discharge machining (3D micro-EDM), a new compensation method of combination of linear compensation method (LCM) with uniform wear method (UWM) is presented. The experimental results show that the machining efficiency and the roughness on the bottom surface are improved obviously in 3D micro-EDM, and the electrode wear is reduced using this new method. Compared with the UWM, the length of electrode wear decreases by 17.8%, the surface roughness reduces by 9.9% and the material removal rate increases by 10.1%. Source

Lu W.-W.,Nanchang Hangkong University | Chen Y.-H.,Nanchang Hangkong University | Xie J.-L.,Nanchang Hangkong University | Wang S.-L.,Nanchang Hangkong University | Feng X.-S.,Shanghai Spaceflight Manufacture Group Co.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2014

The welding joint of Ni47Ti44Nb9 shape memory alloy with thickness of 200 µm was achieved by Nd:YAG laser, and the laser process parameters were investigated by orthogonal experiment. The welding joint microstructure was observed by optical microscopy, the strength of extension of the joint was tested by precision stretcher, and the micro-hardness of the welding joint was tested with the precision hardmeter. The results shows that the best laser parameters of jointing Ni47Ti44Nb9 shape memory alloy with thickness of 200 µm are that the average power is 16.8 W, the width of pulse is 4.5 ms and the frequency is 4.5Hz. At this time, the tensile strength is 880 MPa, reaching 95% strength of the base metal. The horizontal surfaces appear uniform scales striate. And there is a phenomenon of layering on the cross-section, the center of the welding joint is ultrafine axis crystal. The heat affected zone is the column structure. The longitudinal section is exchange distribution of equiaxed grains and pseudoeutectic of NiTi-βNb. The average hardness of the welding joint is greater than that of the base metal. ©, 2014, Science Press. All right reserved. Source

Lu W.-W.,Nanchang University | Chen Y.-H.,Nanchang University | Chen Y.-H.,Harbin Institute of Technology | Huang Y.-D.,Nanchang University | And 2 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2015

Nd: YAG laser was used to weld hot-rolled-state NiTiNb shape memory alloy with thickness of 200 µm. The effects of main process parameters including average power of laser, pulse width of laser and frequency of laser to the morphology of the welding joint were studied, then the transformation law about the microstructure of heat-affected zone and mechanical properties of the welding joint were analyzed. The results indicate that a perfect welding joint needs a good match of average power, pulse width and frequency of laser. The highest tensile strength of welding joint reaches 95% of that of the base material obtained when average power of laser is 16.8 W, pulse width of laser is 4.5 ms and frequency of laser is 4.5 Hz. With increasing the average power and pulse width of laser, the width of heat-affected zone first increases, then decreases. The grains in the heat-affected zone continue to coarsen with increasing the frequency of laser. A gross dendrites area arises in the welding joint near the heat-affected zone when the frequency of laser is 27 Hz. The dimples in the parent material fracture is large and deep, which is classic ductile fracture. The dimples in the welding joint fracture are small and shallow, which look like roes. The micro-hardness of heat-affected zone is higher than that of the base material but lower than that of the centre area of welding joint. ©, 2015, Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals. All right reserved. Source

Cao J.Y.,Shanghai JiaoTong University | Wang M.,Shanghai JiaoTong University | Kong L.,Shanghai JiaoTong University | Guo L.J.,Shanghai Spaceflight Manufacture Group Co.
Journal of Materials Processing Technology | Year: 2016

A series of welds were produced at various processing parameters in friction spot welded of AA6061-T6 to investigate hook formation and mechanical properties. Two different types of hook defect were identified based on the locations, which were closely associated to the plunge depth. The weld strength had a negative correlation with the hook height. An increase in rotational speed, joining time or plunge depth increased the hook height and resulted in lower weld strength. Increasing plunge depth might also bring a positive effect of weld strength as a result of increased effective shear area. © 2015 Elsevier B.V. Source

Wang C.,Dalian Jiaotong University | Zhang X.,Shanghai Spaceflight Manufacture Group Co. | Tang C.,Shanghai Spaceflight Manufacture Group Co.
Advanced Materials Research | Year: 2011

Composite sandwich structures are extensively used in the aerospace, wind power, sports equipment, shipbuilding, automotive and train locomotive industries in order to improve structure rigidity and reduce weight. The molding process of sandwich structure using glass cloth and fibre materials as panels has been reported in many literatures. However, few researches are found relative to the molding process of large scale sandwich structure with the characteristics of thin-walled aluminum alloy panels and variable thickness of Polymethacrylimide (PMI) foam cores. This paper describes a preformed molding process that consists of thermoforming foam core blocks, assembling blocks into a whole sandwich core, CNC machining the sandwich core according to surface models of the thin-walled aluminum alloy panels, and finally, bonding and curing panels and sandwich cores. © (2011) Trans Tech Publications, Switzerland. Source

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