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Wang H.-D.,Shanghai Spaceflight Precision Machinery Institute | Luan Q.-L.,Zhejiang University | Chen Z.-W.,Zhejiang University | He H.-N.,Hangzhou ECON Science and Technology Co.
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2015

Through studying the control algorithm for multi-exciter PSD (power spectral density) replication vibration tests, an identification strategy for the frequency response matrix of a vibration test system based on partial coherence analysis was designed. For situations of singular points existing in a system frequency response matrix and the matrix being rectangular, different system decoupling algorithms were desgined based on the solutions to the matrix generalized inverse and its Moore-Penrose inverse with the minimum norm and least square methods. Aiming at the situation that the system APSD (auto-power spectral density) might be negative or zero in the traditional difference correction of the drive spectral control algorithm, an improved PSD equalization control strategy was designed by introducing a proportional RMS feedback correction algorithm. The algorithm could effectively avoid the APSD being negative and zero in the process of PSD equalization. The multi-exciter PSD replication vibration tests showed that the improved PSD equalization control strategy can achieve a reliable, high-precision control effect on a multi-exciter vibration system. ©, 2015, Chinese Vibration Engineering Society. All right reserved. Source


Yu Y.,Harbin Institute of Technology | Zhang W.,Harbin Institute of Technology | Dong W.,Shanghai Spaceflight Precision Machinery Institute | Han X.,Aerospace Research Institute of Materials And Processing Technology | And 3 more authors.
Materials and Design | Year: 2015

Heat treatment with different parameters were performed on the hot-hydrostatically extruded and swaged 3.5. vol.% TiBw/Ti6Al4V composites tubes. The results indicate that the primary α phase volume fraction decreases and transformed β phase correspondingly increases with increasing solution temperatures. The α. +. β phases will grow into coarse α phases when the aging temperature is higher than 600. °C. The hardness and ultimate tensile strength of the as-swaged TiBw/Ti6Al4V composite tubes increase with increasing quenching temperatures from 900 to 990. °C, while they decrease with increasing aging temperatures from 550 to 650. °C. A superior combination of ultimate tensile strength (1388. MPa) and elongation (6.1%) has been obtained by quenching at 960. °C and aging at 550. °C for 6. h. High temperature tensile tests at 400-600. °C show that the dominant failure modes at high temperatures also differ from those at room temperature. © 2015 Elsevier Ltd. Source


Zhao Y.,Harbin Institute of Technology | Zhao Y.,Shanghai Spaceflight Precision Machinery Institute | Lei Z.,Harbin Institute of Technology | Li L.,Harbin Institute of Technology | Chen Y.,Harbin Institute of Technology
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2013

In order to study the mechanism of laser induced stabilization and compression of arc during laser-arc double-sided welding(LADSW) for aluminium alloy, the method of comparative study and the technique of infrared temperature-measuring and arc spectroscopic measurement are dedicated to investigate the physical essence of the laser effect on arc plasma. The results show that laser supplying arc with the anode spot which is caused by the high temperature gradient of laser is the ultimate reason for the laser induced stabilization and compression of arc when the keyhole is not fully penetrated, and the high energy density of laser and high thermal conductivity of aluminium alloy are indispensable. While the keyhole is fully penetrated, the arc spectral intensities of Ar lines during conventional arc welding are strongest, much weaker during LADSW for stainless steel and weakest during LADSW for aluminium alloy. It is indicated that the laser produces more laser plasma at the bottoms of the keyhole due to the higher saturated vapor pressure, which offers the easier electric channel for the arc. Therefore, the arc roots the laser induced plasma. © 2013 Journal of Mechanical Engineering. Source


Wen L.,University of Science and Technology Beijing | Yuan Y.,Shanghai Spaceflight Precision Machinery Institute | Wang Y.,Harbin Institute of Technology | Jin Y.,University of Science and Technology Beijing
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2015

The pure and Fe-containing nanocrystalline layers were fabricated on the surface of 2024 Al alloy by surface mechanical attrition treatment (SMAT) using ceramic balls and steel balls, respectively. The friction and wear properties of 2024 Al alloy before and after SMAT were investigated by sliding against a GCr15 steel ball of 5 mm in diameter at a load of 1.5 N. The results demonstrate that the surface nanocrystalline layers with average grain sizes of 49.2 and 52.1 nm can be obtained by using ceramic balls and steel balls, respectively, when treated for 30 min. Moreover, a 5 μm thick surface layer containing Fe is also introduced into the Al nanocrystalline surface when treated using steel balls. The wear resistance of 2024 Al alloy is improved due to the combination of grain refinement, increased hardness and lubrication effect of iron-containing layer. Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved. Source


Xu X.,Shanghai Spaceflight Precision Machinery Institute | Li J.,Harbin Institute of Technology
Harbin Gongye Daxue Xuebao/Journal of Harbin Institute of Technology | Year: 2014

To promote the defective craft in non-circular grinding NC system, a special NC system for non-circular grinding is presented based on CPAC. First, on the basis of piecewise cubic spline fitting as mathematical foundation, the cutter center coordinates of X-Y is calculated. Second, the importance of constant speed grinding is produced, and two algorithms based on constant length of arc interpolation are put forward to realize constant speed grinding. Third, the method of error measuring and compensation is given. Finally, integrated system is completed and applied to three-axis milling machine. The experiment proves that the system can meet the needs of non-circular grinding. ©, 2014, Harbin Institute of Technology. All right reserved. Source

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