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Analysis of vibration and frequency transmission of high speed EMU with flexible model

Acta Mechanica Sinica 2014年第6期30卷 876-883页

作者： Zun-Song Ren Guang Yang Shan-Shan Wang Shou-Guang Sun School of mechanical Electronic & Control EngineeringBeijing Jiaotong University

When the operation speed of the high-speed train increases and the weight of the carbody becomes lighter,not only does the sensitivity of the wheel/rail contact get higher,but also the vibration frequency range of the vehicle system gets enlarged and more frequencies are transmitted from the wheelset to the *** is important to investigate the vibration characteristics and the dynamic frequency transmission from the wheel/rail interface to the carbody of the high-speed electric multi-uint（EMU）.An elastic highspeed vehicle dynamics model is established in which the carbody,bogieframes,and wheelsets are all dealt with as flexible body.A rigid high-speed vehicle dynamics model is set up to compare with the simulation results of the elastic *** the rigid vehicle model,the carbody,bogieframes and wheelsets are treated as rigid component while the suspension and structure parameters are the same as used in the elastic *** dynamic characteristic of the elastic high speed vehicle is investigated in time and frequency domains and the di ff erence of the acceleration,frequency distribution and transmission of the two types of models are *** results show that the spectrum power density of the vehicle decreases from the wheelset to the carbody and the acceleration transmission ratio is approximately from 1%to 10%for each suspension *** frequency of the wheelset rotation is evident in the vibration of the flexible model and is transmitted from the wheelset to the bogieframe and to *** results of the flexible model are more reasonable than that of the rigid model.A field test data of the high speed train are presented to verify the simulation *** shows that the simulation results are coincident with the field test data.

关键词： High-speed EMU Vibration transmission Flexible model Acceleration Power spectrum density

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Rolling element bearing instantaneous rotational frequency estimation based on EMD soft-thresholding denoising and instantaneous fault characteristic frequency

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Journal of Central South University 2016年第7期23卷 1682-1689页

作者：赵德尊李建勇程卫东王天杨温伟刚 School of mechanical Electronic and Control engineering Beijing Jiaotong University

The accurate estimation of the rolling element bearing instantaneous rotational frequency(IRF) is the key capability of the order tracking method based on time-frequency analysis. The rolling element bearing IRF can be accurately estimated according to the instantaneous fault characteristic frequency(IFCF). However, in an environment with a low signal-to-noise ratio(SNR), e.g., an incipient fault or function at a low speed, the signal contains strong background noise that seriously affects the effectiveness of the aforementioned method. An algorithm of signal preprocessing based on empirical mode decomposition(EMD) and wavelet shrinkage was proposed in this work. Compared with EMD denoising by the cross-correlation coefficient and kurtosis(CCK) criterion, the method of EMD soft-thresholding(ST) denoising can ensure the integrity of the signal, improve the SNR, and highlight fault features. The effectiveness of the algorithm for rolling element bearing IRF estimation by EMD ST denoising and the IFCF was validated by both simulated and experimental bearing vibration signals at a low SNR.

关键词： rolling element bearing low signal-to-noise ratio empirical mode decomposition soft-thresholding denoising instantaneous fault characteristic frequency instantaneous rotational frequency

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Frequency Loss and Recovery in Rolling Bearing Fault Detection

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Chinese Journal of mechanical engineering 2019年第2期32卷 145-156页

作者： Aijun Hu Ling Xiang Sha Xu Jianfeng Lin Department of mechanical engineering North China Electric Power University

Rolling element bearings are key components of mechanical equipment. The bearing fault characteristics are a ected by the interaction in the vibration signals. The low harmonics of the bearing characteristic frequencies cannot be usually observed in the Fourier spectrum. The frequency loss in the bearing vibration signal is presented through two independent experiments in this paper. The existence of frequency loss phenomenon in the low frequencies, side band frequencies and resonant frequencies and revealed. It is demonstrated that the lost frequencies are actually suppressed by the internal action in the bearing fault signal rather than the external interference. The amplitude and distribution of the spectrum are changed due to the interaction of the bearing fault signal. The interaction mechanism of bearing fault signal is revealed through theoretical and practical analysis. Based on mathematical morphology, a new method is provided to recover the lost frequencies. The multi-resonant response signal of the defective bearing are decomposed into low frequency and high frequency response, and the lost frequencies are recovered by the combination morphological filter(CMF). The e ectiveness of the proposed method is validated on simulated and experimental data.

关键词： Rolling element bearing Signal processing Frequency loss Fault detection Morphological filter

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Development process of muzzle flows including a gun-launched missile

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Chinese Journal of Aeronautics 2015年第2期28卷 385-386页

作者： Zhuo Changfei Feng Feng Wu Xiaosong School of mechanical engineering Nanjing University of Science and Technology

Numerical investigations on the launch process of a gun-launched missile from the muz- zle of a cannon to the free-flight stage have been performed in this paper. The dynamic overlapped grids approach are applied to dealing with the problems of a moving gun-launched missile. The high-resolution upwind scheme （AUSMPW ＋） and the detailed reaction kinetics model are adopted to solve the chemical non-equilibrium Euler equations for dynamic grids. The development process and flow field structure of muzzle flows including a gun-launched missile are discussed in detail. This present numerical study confirms that complicated transient phenomena exist in the shortly launching stages when the gun-launched missile moves from the muzzle of a cannon to the free- flight stage. The propellant gas flows, the initial environmental ambient air flows and the moving missile mutually couple and interact. A complete structure of flow field is formed at the launching stages, including the blast wave, base shock, reflected shock, incident shock, shear layer, primary vortex ring and triple point.

关键词： Blast flow field Chemical reaction Computational fluiddynamics Dynamic overlapped grids Gun-launched missile Muzzle flows

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Direct capture efficiency of range hoods in the confined kitchen space

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Building Simulation 2022年第10期15卷 1799-1813页

作者： Changsheng Cao Wuhao Xie Yunfei Xia Jun Gao School of mechanical engineering Tongji UniversityShanghai 200092China

Range hood is a local ventilation device applied widely in residential kitchen for maintaining healthy environment. This study firstly defines the direct capture efficiency (DCE) based on the two-zone model in a confined kitchen space. A mass flux ratio of the secondary captured pollutant to the entrained pollutant from the room zone is proposed for the determination of DCE, where the distribution coefficient is firstly solved, and then its sensitivity analysis on the DCE is carried out. To validate the mass flux ratio and concisely identify the DCE, a virtual purification method that artificially sets the escaped pollutant to zero, is further applied. Compared with the newly developed DCE, the existing indexes, such as contaminant removal efficiency (CRE), total capture efficiency (TCE), fail to differentiate the direct capture from the total capture. Finally, the effects of such factors as makeup airflow pattern, exhaust flow rate, cooking source temperature and the individual occupied/unoccupied on the DCE are fully studied. It is confirmed that different makeup airflow pattern results in distinguished airflow distribution, which makes a significant difference of more than 30% in DCE. Over 50% increase of DCE can be achieved when the exhaust flow rate is increased from 300 to 600 m3/h. About 30% decrease of DCE is observed with the increased cooking source temperature from 100 to 300 °C, and 10% increase of DCE is appeared in the individual occupied case. This reasonable definition and determination of DCE would help to improve the real capture performance of range hoods.

关键词： kitchen ventilation capture efficiency air distribution local exhaust makeup airflow

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New Method to Measure the Fill Level of the Ball Mill I——Theoretical Analysis and DEM Simulation

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Chinese Journal of mechanical engineering 2010年第4期23卷 460-467页

作者： HUANG Peng JIA Minping ZHONG Binglin School of mechanical engineering Southeast University Nanjing 211189 China

The accurate measurement of the fill level in the ball mill has not been resolved because of the interplay of many variable factors, which led the mill to be operated under the uneconomical condition and lost a lot of energy. At present, some methods, such as vibration method and acoustic method, have been applied for measuring the fill level by the researchers. Aiming at the problem of the traditional methods for measuring the fill level, that is, the feature variables of the fill level suffer the influences of the ball load and the water content of the coal, a novel method to measure the fill level is proposed and a possible relation between the fill level and the angular position of the maximum vibration point on the mill shell is investigated. The angular positions of the maximum vibration point on the mill shell for different fill level cases are calculated theoretically under two assumptions, respectively. Meanwhile the charge motions of the mill for different fill level cases are simulated with the discrete element method （DEM）. And the simulation results are verified by comparing the motion trajectories of steel balls and power draft of the mill. The simulated movement trajectories of the outmost layer steel balls in the mill are monitored and analyzed to obtain the angular positions of the maximum vibration point on the mill shell. Both the results of the theoretical calculation and the 3D DEM simulation show that the position of the maximum vibration point on the mill shell moves to a lower angular positions as the fill level decreasing, which provides a new idea for measuring the filllevel accurately.

关键词： ball mill fill level discrete element method (DEM) simulation

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Influence of welding speed on corrosion behaviour of friction stir welded AA5086 aluminium alloy

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Journal of Central South University 2016年第6期23卷 1301-1311页

作者： Kamran Amini Farhad Gharavi Department of mechanical engineering Tiran Branch Islamic Azad University

The plates of AA5086 aluminium alloy were joined together by friction stir welding at a fixed rotation speed of 1000 r/min various welding speeds ranging from 63 to 100 mm/*** behavior of the parent alloy(PA),the heat affected zone(HAZ),and the weld nugget zone(WNZ)of the joints were studied in 3.5%(mass fraction)aerated aqueous Na Cl solution by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The corrosion susceptibility of the weldments increases when the welding speed increases to 63 and 100 mm/***,the value of corrosion rate in the weldments is lower than that in the ***,the corrosion current density increases with increasing the welding speed in the HAZ and the *** the contrary,the corrosion potential in the WNZ appears more positive than in the HAZ with decreasing the welding *** WNZ exhibits higher resistance compared to the HAZ and the PA as the welding speed *** results obtained from the EIS measurements suggest that the weld regions have higher corrosion resistance than the parent *** increasing the welding speed,the distribution and extent of the corroded areas in the WNZ region are lower than those of the HAZ *** the HAZ region,in addition to the pits in the corroded area,some cracks can be seen around the corroded areas,which confirms that intergranular corrosion is formed in this *** alkaline localized corrosion and the pitting corrosion are the main corrosion mechanisms in the corroded areas within the weld *** pits are observed within the weld regions.

关键词： friction stir welding aluminum alloy corrosion properties welding speed

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Vibration analysis of a single row angular contact ball bearing with the coupling errors including the surface roundness and waviness

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Science China(Technological Sciences) 2020年第6期63卷 943-952页

作者： LIU Jing PANG RuiKun XU YaJun DING ShiZhao HE QuBo State Key Laboratory of mechanical Transmission Chongqing UniversityChongqing 400044China college of mechanical engineering Chongqing UniversityChongqing 400044China Chongqing Materials Research Institute Co.Ltd. Chongqing 400707China

Roundness and surface waviness are main manufacturing errors on the components of single row angular contact ball bearings(ACBBs).An analytical study for vibrations of the ACBBs with coupling errors including the roundness and waviness can be useful for the vibration control of the rotating ***,most previous works only focused on the single error modelling *** this paper,an improved time dependent displacement excitation(TDDE)model is proposed to consider the coupling errors including the roundness and waviness on the inner and outer races of an *** TDDE model for the roundness and waviness is established by using a combination of several sinusoidal functions.A dynamic model in the previous study is improved to consider the influences of coupling errors including the roundness and *** Hertzian contact theory and Dowson’s method are adopted to calculate the bearing contact *** time-and frequency-domain vibrations for the experimental and simulation results are compared to show some model *** influences of roundness orders and waviness amplitudes on the vibrations of the ACBB are *** obtained results show that the coupling errors including the roundness and waviness have some influence on the time-domain impulse waveform and frequency-domain spectrum characteristics of the bearing *** differences of the vibrations between the coupling errors and sing error are from 4%to 42%.This paper can provide a useful guidance for the accurate diagnosis of surface imperfections in the ACBBs.

关键词： angular contact ball bearing(ACBB) roundness error waviness error vibration dynamic model

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Effect of Sodium Chloride on Enhanced Performance of Chitosan-Based Ion Actuator

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Journal of Harbin Institute of Technology(New Series) 2024年第6期31卷 24-36页

作者： Zhaoyang Cui Xiaoli Zhao Weikun Jia Yueming Ren Yan Xu Yanzhuo Lv college of Material Science and Chemical engineering Harbin Engineering UniversityHarbin 150001China college of mechanical and Electrical engineering Harbin Engineering UniversityHarbin 150001China

In this work, an actuate membrane and an electrode membrane were prepared by a sol-gel method. And then, they were physically pressed to form a chitosan-based ion actuator(CSIA). Importantly, the effect of sodium chloride on CSIA was *** mechanical properties of CSIA were tested by establishing an output force test platform and a displacement test platform while testing its porosity. And, the electrochemical performance was tested by electrochemical workstation. At the end, the surface morphology and functional groups were measured by scanning electron microscopy and infrared spectrogram, respectively. The results indicated that the molar concentration of the sodium chloride was the best at 0.06836 mol·L^(-1) for CSIA. Its mechanical properties could reach an output force of 2.939 mN and a deflection displacement of 4.025 mm, and the maximum porosity of 12.98 % at the same time. The specific capacitance of the electrochemical performance was up to 0.07719 F·g^(-1), and the minimum resistance reached 13.48 Ω. From the surface morphology and functional groups, the appropriate doping ratio of NaCl into CSIA was helpful for increasing the transport space of internal ions. The effective internal ion concentration and significantly reduced internal stress provided excellent performances under the appropriate voltage conditions. The doping of inorganic ion sodium chloride improved the internal electron transport efficiency of chitosan ion actuator, and it advanced the mechanical properties of the actuator. Hence the enhancement of NaCl output force in CSIA had a good significance for the development of inorganic salt ion strengthened ion actuator.

关键词： sodium chloride chitosan doped ion actuator

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A robust shell element in meshfree SPH method

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Acta Mechanica Sinica 2013年第2期29卷 241-255页

作者： Fu-Ren Ming A-Man Zhang Xue-Yan Cao college of Shipbuilding engineering Harbin Engineering University

With the incorporation of total Lagrangian smoothed particle hydrodynamics（SPH） method equation and moving least square（MLS） function,the traditional SPH method is improved regarding the stability and *** on Mindlin-Ressiner plate theory,the SPH method simulating dynamic behavior via one layer of particles is applied to plate＇s mid-plane,i.e.,a SPH shell model is ***,through comparative analyses on the dynamic response of square,stiffened shells and cylindrical shells under various strong impact loads with common finite element software,the feasibility,validity and numerical accuracy of the SPH shell method are ***,further researches on SPH shell may well pave the way towards solving problems involving dynamic plastic damage,tearing or even crushing.

关键词： SPH shell Total Lagrangian equation Moving least square (MLS) Stability Consistency Stress point

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