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Li J.,Harbin Institute of Technology | Xu C.,Harbin Institute of Technology | Xu C.,University Of Science And Technology Liaoning | Yao Y.,Harbin Institute of Technology | And 2 more authors.
Precision Engineering

Wire sheave drives are used as transmission elements in docking mechanisms for their excellent flexibility, light weight and high intensity performance. The synchronous accuracy of sheave drives is vital to the docking of spacecraft and is achieved mainly by manual assembly. Due to the lack of further research in this aspect, assembly workers have to operate it for several cycles, which leads to lower assembly efficiency and quality. This paper takes two sheaves of serial drives as a typical example and establishes a prediction model for their synchronous accuracy based on the classic sheave equation. Then the prediction model is modified because of large error between the predicted values and the experiment results. The modified model captures the dominant trends under various operating conditions, and the predicted values also agree well with the experiment results. Thus, the modified model can be used to predict synchronous accuracy of wire sheave drives, to analyze the effect of dominating parameters and to test whether the preset parameters imposed on rope is appropriate or not. This lays a foundation for the study of serial drives and for further improving assembly efficiency and quality of docking mechanisms. © 2014 Elsevier Inc. Source

Li J.-Z.,Dalian University of Technology | Zhang Y.-S.,Shanghai Aerospace Equipments Manufacture | Luan J.-J.,Wuxi Micro Research Co. | Yu Z.-Y.,Dalian University of Technology
Dalian Ligong Daxue Xuebao/Journal of Dalian University of Technology

The diameter of micro-hole varies proportionally with the length of electrode when a micro-hole with high aspect ratio is drilled by micro-electrical discharge machining (EDM) even under the same machining conditions. To explain this phenomenon, the theory of classic Bernoulli-Euler rod is used to study the relationship between the reaction force during micro-hole drilling by micro-EDM and the deflection of electrode under three reaction force conditions. Theoretical values are very close to experimental results. It is clarified that the bending of an electrode increases with an increase of the electrode length, resulting in different diameters of micro-holes using the same diameter of electrode but in different lengths. Source

Xu C.T.,Harbin Institute of Technology | Xu C.T.,University Of Science And Technology Liaoning | Li J.G.,Harbin Institute of Technology | Ding J.,Harbin Institute of Technology | And 2 more authors.
Proceedings - 2013 IEEE International Symposium on Assembly and Manufacturing, ISAM 2013

The androgynous peripheral driving mechanism is a flexible series multi-body system, of which assembly precision is primarily dependent on worker's experience. In order to improve the assembly efficiency and reduce the assembly cost, a system used to predict the synchronous accuracy for guide assembly is developed based on Matlab-GUI. This system consists of three modules, i.e., data management module, accuracy prediction module and animated simulation module. Each module is briefly investigated in this paper. By predicting the driving mechanism, the theoretical data have been compared with the experimental data. And the synchronous errors of the simulation and animation are also shown on the interface. The results indicate that the predicted values are within the permitted deviation range and agree well with changes of the synchronous errors. Moreover, the prediction system is also of good reliability and stability which can be used to guide the workers for assembly. © 2013 IEEE. Source

Shen Z.,Tianjin University | Yang X.,Tianjin University | Yang S.,Tianjin University | Zhang Z.,Tianjin University | Yin Y.,Shanghai Aerospace Equipments Manufacture
Materials and Design

Friction spot welding (FSpW) is a relatively new solid state joining technology developed by GKSS. In the present study, FSpW was applied to join the 6061-T4 aluminum alloy sheet with 2. mm thickness. The microstructure of the weld can be classified into four regions, which are stir zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and the base material (BM), respectively. Meanwhile, defects such as bonding ligament, hook and voids are found in the weld, which are associated to the material flow. The hardness profile of the weld exhibits a W-shaped appearance and the minimum hardness is measured at the boundary of TMAZ and SZ. Both the tensile/shear strength and cross-tension strength reach the maximum of 7117.0. N and 4555.4. N at the welding condition of the rotational speed of 1500. rpm and duration time of 4. s. Compared to cross-tension strength, the tensile/shear strength were stable with the variation of processing parameters. Three different fracture modes are observed under tensile/shear loading, which are plug type fracture, shear fracture and plug-shear fracture. There are also there different fracture modes under cross-tension loading, which are plug type fracture (on the upper sheet), nugget debonding and plug type fracture (on the lower sheet). © 2013 Elsevier Ltd. Source

Li J.,Harbin Institute of Technology | Du J.,Harbin Institute of Technology | Yao Y.,Harbin Institute of Technology | Hao Z.,Changchun University of Technology | Liu X.,Shanghai Aerospace Equipments Manufacture
Journal Wuhan University of Technology, Materials Science Edition

An attempt was made to investigate the machinability of SiCp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center using integrated abrasive cutting tool. The effects of combined machining parameters, e g, cutting speed (vs), feed rate (vf), and depth of cut (ap), with the same change of material removal rate (MRR) on the mill-grinding force and surface roughness (Ra) were investigated. The formation mechanism of typical machined surface defects was analyzed by SEM. The experimental results reveal that with the same change of material removal rate, lower mill-grinding force values can be gained by increasing depth of cut and feed rate simultaneously at higher cutting speed. With the same change of MRR value, lower surface roughness values can be gained by increasing the feed rate at higher cutting speed, rather than just increasing the depth of cut, or increasing the feed rate and depth of cut simultaneously. The machined surface of SiCp/Al composites reveals typical defects which can influence surface integrity. © 2014, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg. Source

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