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Rolling Element Bearing Diagnostics by Combination of Envelope Analysis and Wavelet Transform

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Journal of university of Science and Technology beijing 2001年第1期8卷 69-74页

作者： Ying Tang, Qiao Sun mechanical engineering {2., university of Science and Technology beijing, beijing 100083, china Department of mechanical engineering, university of Calgary Calgary Alberta T2. 1N4, Canada mechanical engineering {2. Univ. of Sci. and Technology Beijing Beijing 100083 China

Rolling element-bearing diagnostics has been studied over the last thirty years, and envelope analysis is widely recognized as being the best approach for detection and diagnosis of rolling element bearing incipient failure. But one of the on-going difficulties with envelope technique is to determine the best frequency band to envelop. Here, wavelet transform technique is introduced into envelope analysis to solve the problem by capturing bearing defects-sensory scales (i.e. frequency bands). A modulated Gaussian function is chosen to be the analytical wavelet because it coincides well with bearing defect-induced vibration signal patterns. Vibration signals measured from railway bearing tests were studied by the proposed method. Cases of bearings with single and multiple defects on inner and outer race under different testing conditions are presented. Experimental results showed that the proposed method allowed a more accurate local description and separation of transient signal part, which were caused by impacts between defects and the mating surfaces in the bearing. The combination method provides an effective signal detection technique for rolling element-bearing diagnostics.

关键词： continuous wavelet transform envelope analysis rolling element bearing diagnostics

Quasi-equality constrained risk-sensitive filtering for nonlinear discrete-time systems

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控制理论与应用（英文版） 2012年第2期10卷 229-235页

作者： Linfeng SHEN, Yan LIN school of automation Science and Electrical {2., beijing university of Aeronautics and astronautics, beijing 100191, china school of automation Science and Electrical {2. Beijing University of Aeronautics and Astronautics Beijing China

More and more data fusion models contain state constraints with valuable information in the filtering process. In this study, an optimal filter of risk sensitive with quasi-equality constraints is formulated using the reference probability method. Through recursion processes of probability density acquired from the probability measure change, the derived algorithm is optimal in the sense of the risk sensitive parameter. The system and constraint models are Consistent in statistics. Simulation results show that it is more robust and efficient than projection filters for the worst-case of noises and model uncertainty.

关键词： Optimal estimation Risk-sensitive filtering Constraints

Improvement on strip flatness of cold temper mills by modifying roll contour shape

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Journal of university of Science and Technology beijing 2004年第3期11卷 251-255页

作者： Xiaoyan Li Jie Zhang Xianlin Chen Jianguo Cao Haixia Li mechanical engineering {2., university of Science and Technology beijing, beijing 100083, china Mech. Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

A study on roll gap profile (strip profile) control was accomplished in a1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contourcaused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finiteelement model, the effects of roll contours (ground and wear) on strip profile were *** roll bending effect on strip thickness was also analyzed. It is pointed out that there are somespecial features of flatness control in the temper mill: during temper rolling, roll deformation isslight due to small rolling load, and the loaded roll gap profile mainly depends on work rollcontour, while the backup roll has a little effect on gap crown; the effect of bending force ongauge can not be ignored due to the coupling between flatness control and gauge control. A new rollcontour arrangement adaptable to the mill was presented and has been put into practical *** application of the new set of rolls showed some good results: larger crown control range of workroll bender, higher rolling stability, better strip profile and flatness quality.

关键词： cold rolling temper mill strip shape control roll contour arrangement bending

Effects of silver powder particle size on the microstructure and properties of Ag-Yb_2._3 electrical contact materials prepared by spark plasma sintering

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Rare Metals 2010年第4期29卷 366-370页

作者： CHEN Xiaohua,JIA Chengchang,and LIU Xiangbing school of Materials Science and engineering,{2. of Science and Technology beijing,beijing 100083,china school of Materials Science and engineering University of Science and Technology Beijing Beijing China

mg-Yb2.3 electrical contact materials were fabricated by spark plasma sintefing （SPS）. The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope （OM）, and the fracture morphologies were observed by scanning electron microscopy （SEM）. The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder （5 ktm）, homogeneous and fme microstmcture was obtained by fine silver powder （_〈0.5-1am）. At the same time, the electrical conductivity, microhardness, and tensile strength of the sin- tered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples （both by free and coarse silver powders） is more than 95%. The fracture characteristics are ductile.

关键词： composites electrical contact materials spark plasma sintering particle size microstructure physical properties mechanical properties

Temperature distribution in the tool-chip-workpiece system during the orthogonal cutting process

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International Journal of Minerals,Metallurgy and Materials 1997年第3期11卷 30-34页

作者： ZHENG Chun GU Tong (Department of mechanical engineering, McMaster {2., Canada) (Applied Science school, {2. of Science and Technology beijing, beijing 100083, china) McMaster Univ Canada

The temperature distribution in the tool, chip and workpiece was studied during the orthogonal cuttingprocess Under several different cutting conditions. The temperature distribution is calculated by the finite differencemethod. and the variation of the material properties with temperature was taken was taken into account The results obtained arecoincident with both previous published results and experimental measurements.

关键词： temperature distribution orthogonal cutting FDM tool-chip-workpiece system

Impact of Modal Parameters on Milling Process Chatter Stability Lobes

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武汉理工大学学报 2006年第S1期28卷 190-195页

作者： LI Zhongqun,LIU Qiang (school of mechanical engineering and automation,BeiHang university,{2. 100083,china) school of mechanical engineering and automation BeiHang UniversityBeijing 100083China

Modals of the machine/tool and machine/part system are the principal factors affecting the stability of a milling process. Based on the modeling of chatter stability of milling process,the influence of modal parameters on chatter stability lobes independently or jointly has been analyzed by simulation. Peak-to-valley specific value,lobe coefficient and the corresponding calculation formula have been put forward. General laws and steps of modal simplification for multimodality system have been summarized.

关键词： milling process chatter stability lobes dynamic stiffness modal parameter

Application of intelligent control theory in AC servo system

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International Journal of Minerals,Metallurgy and Materials 1997年第3期11卷 43-45页

作者： WANG Zhiliang XIE Lun IJ Chongjian (Information engineering school, {2. of Science and Technology beijing, beijing 100083, china) (automation Research institute of Metallurgical Industry, beijing 100071, china) Univ of Science and Technology Beijing Beijing China

An AC servo system based on neuron control theory is presented. Experimental results show that the neuralcontrol mode doesn't need the Precise model of the system, therefore, it has many advantages, such as simple designand high response performance. The simulation research of the AC servo system which is non-linear, *** on neuro-fuzzy controller is done. The results of the simulation show that the performances of the system areconsiderably improved and it is one of the novel pathways to realize intelligent control of servo system.

关键词： servo system fuzzy control neural networks neuro-fuzzy networks

Microstructure Evolution of Semi-solid Processed Hyper-eutectic Al-30%Si Alloy

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International Journal of Minerals,Metallurgy and Materials 1999年第4期13卷 259-261页

作者： Yanjun Li Weimin Mao Xueyou Zhong(Material Science and engineering school, {2. of Science and Technology beijing, beijing 100083, china) Material Science and engineering school University of Science and Technology Beijing Beijing 100083 China

An investigation was made on the influences of mechanical stirring on microstructure of hyper-eutectic Al-30%Si alloy (inmass fraction) during solidification. The primary Si crystals formed in the alloy melt were gradually changed from elongated platelets tonear-spherical shapes by mechanical stirring. The spheroidization of primary St crystals occurs by the mechanism of bending and fractureof Si platelets, wear and collision between Si crystals, and coalescence of small Si particles. The influence of under-cooling and coolingrate of the alloy melt on primary Si crystals of semi-solid processed alloys is investigated as well. The increase of under-cooling andcooling rate decreases the size of primary Si crystals.

关键词： semi-solid state process solidification structure mechanical stirring hyper-eutectic Al-Si alloy

Laser Shock Processing of an Austenitic Stainless Steel and a Nickel-base Superalloy

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Journal of Materials Science & Technology 2003年第5期19卷 402-404页

作者： Huaming WANG, Xijun SUN and Xiaoxuan LILaboratory of Laser Materials Processing and Surface engineering, school of Materials Science and engineering, Beihang university (formerly beijing university of Aeronautics and astronautics), beijing 100083, china Lab. of Laser Mat. Proc. Sch. of Mat. Sci. and Eng. Beijing Univ. of Aero. and Astron. Beijing 100083 China

An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-strengthened Ni-base superalloy GH30 were shock processed using a Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the laser shock processed surface were investigated as functions of laser processing parameters. Results show that high density of dislocations and fine deformation twins are produced in the laser shock processed surface layers in both the austenitic stainless steel and the nickel-base superalloy. Extensive strain-induced martensite was also observed in the laser shock processed zone of the austenitic steel. The hardness of the laser shock processed surface was significantly enhanced and compressive stress as high as 400 MPa was produced in the laser shock processed surface.

关键词： Laser shock processing Austenitic stainless steel Nickel-base superalloy Surface mechanical properties Residual stress