Time filter

Source Type

Yingfei G.,Nanjing Institute of Technology | Jiuhua X.,Nanjing University of Aeronautics and Astronautics | Hui Y.,Beijing Precision Engineering Institute for Aircraft Industry
Wear | Year: 2010

The wear pattern and its mechanisms of single crystal diamond (SCD) and polycrystalline diamond (PCD) tools have been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced 2009 aluminum matrix composite under wet machining conditions. The results showed that microwear, chipping, cleavage, abrasive wear and chemical wear were the dominating wear patterns of SCD tools, and PCD tools mainly suffered from abrasive wear on the rake face and adhesive wear on the flank face. The local temperature increase in the workpiece material adjacent to the contact surface of SCD tool was approximately as high as 505. °C. The combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix caused the severe graphitization of SCD tool with (rake face 1. 1. 0-flank 1. 1. 0) crystal orientation. The adhesive wear on PCD tool was induced by the intermittent growth and breaking off behavior of build-up-edge. SCD tool with the crystal orientation of (rake face 1. 1. 0-flank 1. 0. 0) had the best cutting performance among the three types of tools, by which the machined surface roughness Ra was less than 49 nm after cutting for over 9 km. PCD tool had a steady and favorable cutting performance and could produce acceptable surface quality when the cutting distance was less than 6 km, during which the value of Ra was less than 46 nm and varied in the range of 12-15 nm. For this tool, adhesive wear on the rake face and abrasive wear on the flank increased gradually with the increase of cutting distance. The flank wear value of PCD was only 50 μm which was slightly higher than that of straight-nose SCD (40 μm) when cutting for 6.22 km. For all the three types of tools, with the increase of cutting distance, the machining induced defects such as craters and scratches increased too. Especially, when cutting distance was long enough to cause severe tool wear, material swelling on the machined surface was severe due to the plastic side flow. The chips formed by PCD tool were more discontinuous and fragmentary than that for straight-nose SCD tool. © 2009. Source

Qu S.-D.,Beijing Mentougou District Hospital | Qu S.-D.,Capital Medical University | Hai Y.,Capital Medical University | Su Q.-J.,Capital Medical University | Qu S.-P.,Beijing Precision Engineering Institute for Aircraft Industry
Chinese Journal of Tissue Engineering Research | Year: 2015

BACKGROUND: The Coflex is widely used in China, but it has a high complication rate of spinous process fracture. OBJECTIVE: With the help of finite element analysis, to verify if rigid restriction of spinous process contacts in modified Coflex design is semi-rigid restriction so as to reduce the stress of spinous process in spine flexion and extension, lateral bending and rotation and to decrease the risk of spinous process fracture. METHODS: The images were extracted from patients who had undergone abdomen CT scans in the Beijing Chaoyang Hospital affiliated to Capital Medical University. Three-dimensional finite element model of lumbar spine was established. The Coflex model and the corresponding modified Coflex model were established and then simplified in the SolidWorks software of CAD. Tensile force, shearing force and axial rotating force in resting state were analyzed in ANSYS software. RESULTS AND CONCLUSION: Under tensile force, transversal shearing force and axial rotating force, compared with Coflex system, the stress of spinous process model was reduced in the modified system (P < 0.01). These findings indicate that the forces of the modified model are superior to the force of Coflex. It can reduce stress in the spinous process under stresses and diminish the occurrence of spinous process fractures. © 2015, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved. Source

Ge Y.-F.,Nanjing Institute of Technology | Xu J.-H.,Nanjing University of Aeronautics and Astronautics | Yang H.,Beijing Precision Engineering Institute for Aircraft Industry
Binggong Xuebao/Acta Armamentarii | Year: 2015

Single crystal diamond and polycrystalline diamond tools are selected for ultra-precision turning of SiC particulate reinforced aluminum matrix composites (SiCp/2024Al and SiCp/ZL101A). The appearance and the metallurgical microstructure of chip are observed in order to investigate the formation mechanisms of chip using micromechanics and metal cutting theory analytical methods. The chip formation process models are also established. The results show that a saw-toothed chip with semi-periodic thickness is formed. It is pointed that the dynamic behavior of microcracks and the periodic variation of shear angle are the two main mechanisms for this type of chip. A great number of microcracks and microvoids are produced on this kind of material during machining due to the inherent defects and, non-uniformity of the materials and the presence of the reinforcement particles. The periodic variation of shear angle is determined by the workpiece microstructure and the mechanical properties and the periodic slip-stick phenomenon. Volume fraction of reinforcement, cutting speed, feed rate and tool edge radius are the main factors that affect the chip formation. ©, 2015, China Ordnance Society. All right reserved. Source

Gao Y.,Jilin University | Wang R.,Jilin University | Gao L.,Jilin University | Shen S.,Beijing Precision Engineering Institute for Aircraft Industry
2010 International Conference on Intelligent Computation Technology and Automation, ICICTA 2010 | Year: 2010

The crosstalk coupling for wiring harness in vehicle has great influence on electromagnetic compatibility (EMC), it is necessary to estimate it at the beginning of EMC design of system. The relative position between wires in harness is random, the deterministic methods based on constant harness geometry are inappropriate to estimate crosstalk, while the statistical methods can reflect the actual crosstalk coupling, reveal random nature of crosstalk. The paper described three kinds of statistical models of crosstalk, and each model has its own characteristic and scope of application: the worst case method is appropriate to find potential crosstalk quickly, both probabilistic model and segmentation method catch the quantitative statistical characteristics of crosstalk i.e. mean value and standard deviation, the segmentation method can estimate the crosstalk in non-uniform wiring harness particularly. © 2010 IEEE. Source

Yuan J.,Hunan University | Zhang F.,Harbin Institute of Technology | Dai Y.,National University of Defense Technology | Kang R.,Dalian University of Technology | And 2 more authors.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2010

Ultra-precision machining is essential method for obtaining the highest quality in terms of form accuracy, surface finish Ultra-precision machining is essential method for obtaining the highest quality in terms of form accuracy, surface finish and surface integrity. As the higher requirements of quality and diversifications for products are put forward, it is essential to improve the precision and efficiency of ultra-precision machining. Ultra-precision machining has become a complicated systems engineering, which involves more and more last research fruits. The conception, application fields, present research status, development tendency, and the key issues of future researches on scientific and technological of ultra-precision machining are introduced in this paper. Some advanced and typical ultra-precision machine tools, ultra-precision cutting, grinding, and polishing are reviewed and compared in terms of machining accuracy, quality and efficiency. The main problems and miss distance from the advanced technologies of China in ultra-precision machining field are analyzed. In the same time, the probable further trend of ultra-precision machining is forecasted, and the developing countermeasure and strategy of fundamental research, technologies and industry in China are given. © 2010 Journal of Mechanical Engineering. Source

Discover hidden collaborations