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Wang H.,Nanjing University of Aeronautics and Astronautics | Zhang L.,Nanjing University of Aeronautics and Astronautics | Zhou L.,AVIC Chengdu Aircraft Industry Group Co. | Liu S.,Nanjing University of Aeronautics and Astronautics
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2014

The batched complex blanks with same structure and certain deviations in geometry often needed to be reconstructed. The repeated process wasted a lot of labors and extended the production cycle. An efficient reconstruction method was proposed based on the structural template and the reverse design table. Firstly, the feature of the blank's structure was analyzed. A template representing the structure features, as well as a reverse design table based on open knowledge representation, was established. Secondly, the elements in the template and the steps in the design table were utilized to segment the cloud points automatically. Thirdly, different types of surface were reversely reconstructed and post processed orderly. The experimental results validate the method's high efficiency.


Zhou W.,Nanjing University of Aeronautics and Astronautics | Liao W.,Nanjing University of Aeronautics and Astronautics | Tian W.,Nanjing University of Aeronautics and Astronautics | Wan S.,AVIC Chengdu Aircraft Industry Group Corporation Ltd. | Liu Y.,AVIC Chengdu Aircraft Industry Group Corporation Ltd.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2013

For the absolute positioning accuracy of industrial robots used in aircraft flexible automated assembly cannot meet assembly precision, a neural network-based integrated accuracy compensation approach taking into account ambient temperature change factor was proposed based on robot spatial grid accuracy compensation method. Neural network's initial weights and thresholds were optimized by using particle swarm optimization method in order to prevent from falling into local minima in training. The experimental results show that the maximum value of the robot positioning error is as 0.32mm, and the mean value is as 0.19mm with the temperature in the range of 20°C to 30°C, which are much more better than the previous values 1-3mm, the absolute positioning accuracy can satisfy the requirements of aircraft automatic assembly.


Wang D.,Northwestern Polytechnical University | Li H.,Northwestern Polytechnical University | Yang H.,Northwestern Polytechnical University | Ma J.,Northwestern Polytechnical University | Li G.,AVIC Cheng du Aircraft Industry Group Co.
Chinese Journal of Aeronautics | Year: 2014

The H13 hot-working tool steel is widely used as die material in the warm forming of Ti-6Al-4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti-6Al-4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods (chromium plating, TiAlN coating, surface polishing and nitriding treatment) were applied to the H13 surfaces. Taking the coefficient of friction (CoF) and the wear degree as evaluation indicators, the high-temperature tribological behavior of the surface modified H13 steel was experimentally investigated under different tribological conditions. The results of this study indicate that the tribological properties of the TiAlN coating under dry friction condition are better than the others for a wide range of temperature (from room temperature to 500 °C), while there is little difference of tribological properties between different surface modifications under graphite lubricated condition, and the variation law of CoF with temperature under graphite lubricated is opposite to that under the dry friction. © 2014 Production and hosting by Elsevier Ltd.


Li X.,Shanghai JiaoTong University | Lei K.,Beijing Institute of Technology | Song P.,Beijing Institute of Technology | Liu X.,Beijing Institute of Technology | And 3 more authors.
Journal of Materials Engineering and Performance | Year: 2015

Strengthening of aluminum alloy 2219 by thermo-mechanical treatment has been compared with artificial aging. Three simple deformation modes including pre-stretching, compression, and rolling have been used in thermo-mechanical treatment. The tensile strength, elongation, fracture feature, and precipitated phase have been investigated. The results show that the strengthening effect of thermo-mechanical treatment is better than the one of artificial aging. Especially, the yield strength significantly increases with a small decrease of elongation. When the specimen is pre-stretched to 8.0%, the yield strength reaches 385.0 MPa and increases by 22.2% in comparison to the one obtained in aging condition. The maximum tensile strength of 472.4 MPa is achieved with 4.0% thickness reduction by compression. The fracture morphology reveals locally ductile and brittle failure mechanism, while the coarse second-phase particles distribute on the fracture surface. The intermediate phases θ″ or θ′ orthogonally precipitate in the matrix after thermo-mechanical treatment. As compared to artificial aging, the cold plastic deformation increases distribution homogeneity and the volume fraction of θ′′ or θ′ precipitates. These result in a better strengthening effect. © 2015 ASM International


Zhou W.,Nanjing University of Aeronautics and Astronautics | Liao W.,Nanjing University of Aeronautics and Astronautics | Tian W.,Nanjing University of Aeronautics and Astronautics | Li D.,AVIC Chengdu Aircraft Industry Group Corporation Ltd. | Liu Y.,AVIC Chengdu Aircraft Industry Group Corporation Ltd.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2012

This paper studied a positioning accuracy compensation method of 6-DOF KUKA robot. Through the establishment of conversion relationship between the robot and laser tracker coordinate system, the absolute positioning errors were obtained by comparing the actual positioning coordinates measured by laser tracker with the corresponding theoretical coordinates. Firstly, the robot's work space was divided into many three-dimensional grids with a certain step, then for any point within the workspace, its absolute positioning error can be estimated by the absolute positioning errors of eight vertices of the three-dimensional grid which contained it in. Finally, the robot's absolute positioning accuracy was improved by inverse compensation of estimated positioning errors to the theoretical coordinates. The results show that the maximum value of the robot positioning accuracy is as 0.386 mm, and the mean value is as 0.156 mm, which are much more better than the previous values 1~3 mm. The robot can satisfy the requirements of aircraft automatic assembly.

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