25 April 2009, Volume 28 Issue 4
    

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  • Zhao Yang; Cao Shuyang; Yukio Tamura; Duan Zhongdong; S.Ozono
    . 2009, 28(4): 1-3.
    Abstract ( 1653 )   Knowledge map   Save
    Abstract: In order to study the aerodynamic characteristics of the structure undergoing sudden change flow, this paper introduced the test on the simulation of sudden change flow by active control wind tunnel. Firstly, a gust velocity profile of Downburst was simulated by the wind tunnel. Subsequently, time history of wind speed changes was simulated by step flow method. Finally, high-rise structure models were prepared in the sudden change flow, and the variation characteristics of wind pressure on surface and aerodynamic parameters in the flow were observed and studied in this paper. The results showed that the identities between the gust velocity profile simulated by the wind tunnel and the theory formula were above ninety percent, and sudden change flow could generate a high unsteady lift on the whole high-rise structure and a big unsteady wind pressure on the surface of structure meanwhile.
  • Liu Tao
    . 2009, 28(4): 4-9.
    Abstract ( 1421 ) Download PDF ( 742 )   Knowledge map   Save
    Abstract:Through a steel beam damage experiment, the validity of the structural damage alarming method based wavelet packet energy spectrum is proved. This experiment has four cases, one of which is the initial case and others are three damage cases. Dynamic responses of a steel beam are measured and decomposed by wavelet packet and energy varieties of characteristic frequency bands are investigated. Experimental results reveal that three damage cases can be alarmed by the damage alarming indices ERV and ERVD and that ERVD varies slightly along with different measurements of the same damage case. The structural damage alarming indices based on wavelet packet energy spectrum are sensitive to damages, robust to noise and can be applied to actual structures.
  • PAN Li-jian
    . 2009, 28(4): 10-13.
    Abstract ( 811 ) Download PDF ( 218 )   Knowledge map   Save
    Abstract: The dynamic mechanical properties of viscoelastic material embedded in composites and that co-cured with composites was investigated by dynamic mechanical thermal analysis (DMTA). The effects of co-curing process, the thickness of viscoelastic layer and the composite flexible layer on the damping characteristic of co-cured composites was studied by finite element method. The results show that, the value of damping crest is 54% of idealized value due to the interaction of the resin and the embedded viscoelastic material during the process of co-curing. Increasing the thickness of the embedded viscoelastic layer or inserting some flexible layers near the viscoelastic layer not only results in the increasing the value of damping crest of co-cured composites but also can widen the temperature range of damping in co-cured composites.
  • He Zhi-yong;Lv Zhong-rong;Chen Wei-huan;Chen Shu-hui;Liao Wei-yang
    . 2009, 28(4): 14-17.
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    Abstract: Taking the Guangzhou New TV Tower under construction as a test bed, this paper presents a case study of monitoring the dynamic characteristics of high-rise building under typhoon and normal wind excitation using GPS measurement. Dynamic displacement time histories of one measuring point on the top of the TV Tower are obtained. From the FFT analysis of the displacement time histories, the lower few natural frequencies of the TV Tower are obtained. The identified natural frequencies from GPS measurement are compared with those from acceleration measurement and from finite element analysis, good agreements are found. This indicates that it is practical to monitor the dynamic characteristics of high-rise building using GPS measurement.
  • . 2009, 28(4): 18-24.
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    Abstract: Considering the engine’s foundation excitation and nonlinear oil film force, the dynamic model of turbocharger rotor-bearing system is established, and the nonlinear dynamic behavior of eccentricity is investigated. The response is simulated by numerical calculation. The bifurcation disciplinarian of nonlinear rotor dynamics with different rotational speeds under foundation excitation is studied, and the influences of foundation excitation are evaluated. The result shows that foundation excitation will remarkably affect the rotor dynamic behaviors through the nonlinear oil film force, and foundation excitation will lower the rotational speed at which the oil whirl occurs. However, the influences of foundation excitation are more distinct on the low rotational speed stage of rotor than on the high speed stage.
  • Shuai;Li Bin;Wen Jinpeng;Tan Dewei;Yang Zhichun
    . 2009, 28(4): 25-28.
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    Abstract: A normal soft landing process using a gas-filled bag can be decomposed into two physical stages: the first is the adiabatical compressure of airbag, then the second is the release of landing shock energy. Based on the thermal dynamic and rigid dynamic equations, the analytical model of soft landing airbag is developed, thus a simple and quick numerical solving method of cushioning response is presented. As an example, the parameters determination method of a vertical cylinder soft landing airbag for an unmanned aircraft is proposed, and these parameters refer to the height of airbag, the bottom area of airbag and the area of vent orifices. The cushioning time history of the soft landing airbag with different types of vent orifices including no gas bleed, with a constant-area orifices and with a controllable orifices, are calculated by a Matlab program. Compraring with these simulation results, the advantages and disadvantages of different soft landing airbags are concluded, and some improvement advice on the design of a soft landing airbags are proposed to help the engineering applications.
  • LI Fanghui;NI Zhenhua;SHEN Shizhao;GU Ming
    . 2009, 28(4): 29-32.
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    Abstract: Proper orthogonal decomposition (POD) is an effective technique for data reduction and feature extraction of the random field. This paper introduces the basic theory of the POD and main advantages of its applications to wind engineering of structures, these include that the original pressure field can be accurately reconstructed with a limited number of modes; the prediction of the wind pressure field increases the pressure tap resolution, the POD technique can be used to predict pressure time series in the regions without pressure taps by using the existing pressure time series. Taking the pitched roof as an example, mentioned contents above which include reconstruction and prediction of wind pressure field was investigated by using the wind pressure data which are measured simultaneously in a wind tunnel test. The effectiveness and practicability of POD was illustrated by comparing with original data in the time domain and frequency domain.
  • Tao Xin-min;XU Jing;DU Bao-xiang;XU Yong
    . 2009, 28(4): 33-37.
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    ABSTRACT: In order to avoid the practical problems that traditional wavelet energy spectrum as the characteristics is insufficient for the diagnosis infer in bearings fault detection, a novel fault detection method based on the wavelet histogram signatures which capture all the first order statistics using a model based on hidden Markov model (HMM) is presented. In this approach, the statistics features of the multi-scale wavelet coefficients generated by the wavelet decomposition of the signals are analyzed, the detail wavelet histogram of the bearing vibration signals can be modeled by the hidden Markov model. The parameters of this model as diagnosis features are introduced to completely describe the wavelet coefficients’ first-order statistics. The scale and shape parameters of the model are estimated by the maximum likelihood method. Comparison of the performance of detection of the proposed approach with the method based on the wavelet energy spectrum and wavelet energy spectrum entropy is experimented. The results show the relative effectiveness of the introduced feature sets in the detection of the bearing conditions with some concluding remarks. The effects of the wavelet base selection, window width and classifier on the proposed method are conducted in the experiments, which evaluate the stability and robustness of the proposed method.
  • Wang Miao;Meng Guang
    . 2009, 28(4): 38-41.
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    Abstract:Based on the Mead-Markus assumptions,the assumed mode method(AMM)was used to model a partially ACLD beam.And the validity and effectiveness of AMM were examined by comparing the results with those of FEM.Furthermore,the geometrical effects of a ACLD patfch as ,PZT thickness,VEM thickness,its location and length on matural frequencies and modal loss factors of the beam were also atudied.It seemed that it is useful for damping efffct to increase PZT thickness,reduce VEM thickness and exted the ACLD patch.
  • 王修勇;宋璨;陈政清;孙洪鑫;陈丕华
    . 2009, 28(4): 42-46.
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    Abstract: Magnetorheological damper is a new kind of smart device for vibration control. Through characteristic testing of MR damper, force-displacement and force-velocity relationship at different current is researched; the main features of friction-type MR damper are analyzed. A forward model and an inverse model of MR damper are established by using BP neural network. Simulation results show that the neural network model can accurately predict force and current of MR damper, so the approach is effective. Comparing with the existing model, the features of the model built in this paper are high accuracy and easy calculation.


    *国家自然科学基金项目(50578063) 国家自然科学重点项目(50738002)
  • Xue-wen;DING Xu-jie;HUA Hong-xing;SHEN Rong-ying
    . 2009, 28(4): 47-50.
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    ABSTRACT: Vibration and acoustic radiation characteristics of a finite cylindrical shell with a floating raft are investigated in this paper. A FEM/BEM model is established for the complex dynamic system composed of machineries, floating raft, and the shell, with which three projects, i.e., one cabin, three cabins, and whole submarine, are considered for the prediction of the underwater sound level. Discussions are presented for the influences of three different projects on the shell’s surface vibration velocity and the far-field acoustic radiation, which indicate that below the resonance frequency for the first bending mode of the submarine cabin, it’s improper to simulate the dynamic characteristics of a whole submarine with one cabin model, and above this frequency, it’s acceptable for using a cabin model to predict the shell surface velocity of a whole submarine.
  • Jiang Li;Li Lin;Dong Hui
    . 2009, 28(4): 51-53.
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    Abstract: Empirical mode decomposition (EMD) is a local, fully data driven and self-adaptive analysis approach. It is a powerful tool for analyzing multi-component signals. Aiming at the reduction of scale mixing and artificial frequency components, an improved scheme of EMD is proposed for the analysis and reconstruction of nonstationary and multicomponent speech signals. The improved EMD method uses higher order extrema and then the optimal envelope mean can be obtained by an inverse EMD scheme. A new sifting stop criterion is proposed based on the index of orthogonality. And finally, the mean square error criterion is used for performance evaluation. Experiments on simulation signals and actual sound signals prove the correctness and validity of the modified method. An exact decomposition result can be obtained by the improved EMD method with less scale mixing than the standard EMD method. The proposed method has broad application potential in processing of speech signals, mechanical vibration signals and radar signals, etc.
  • Xian Rong;Liao Hai-li;Li Ming-shui
    . 2009, 28(4): 54-58.
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    Abstract The flexible long-span bridge girder is easy to occur Vortex-Induced Vibration(VIV), which is influenced by cross-wind at relative low speed. Although VIV may not be catastrophic, it may be fatiguing to structure and disconcerting to users. The first-order approximate theoretic solution on lock in is deduced by using Scanlan’s nonlinear VIV model and Wilkinson’s correlation function of vortex shedding force to describe vertical and torsional vibration of girder. Moreover, the method is discussed to identify aerodynamic parameters from section model test. Lastly, the spanwise vertical and torsional VIV response of a long-span cable stayed bridge girder are calculated from girder’s section mode VIV test.
  • GAO Shang-han LONG Xin-hua MENG Guang
    . 2009, 28(4): 59-64.
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    Abstract: A six-degree-of-freedom (DOF) model is presented for the study of the bifurcation of the machine-tool spindle-bearing system in the paper. The dynamics of machine-tool spindle system supported by ball bearings can be described by a set of second order nonlinear differential equations with piecewise stiffness and damping due to the bearing clearance. Numerical results show when the inner race touches the bearing ball with a low speed, grazing bifurcation occurs. The solutions of this system evolve from quasi-periodic to chaotic orbit, from period doubled orbit to periodic orbit, and from periodic orbit to quasi-periodic orbit through grazing bifurcations. In addition, the route of the period-doubling bifurcation to chaos and the tori doubling process to chaos which usually occurs in the impact system are also observed in this spindle-bearing system. These researches rich our understanding to chaos and promote the investigation into nonlinear dynamics theory in the spindle-bearing system and application.
  • Lin li-guang Chen jian-jun
    . 2009, 28(4): 65-69.
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    Abstract:A new interval stochastic finite element method based on the interval factor method and random factor method is given and the analysis of structural dynamic characteristic for interval stochastic truss structures is presented. Considering the interval randomness of the structural physical parameters and geometric dimensions simultaneously, the structural stiffness and mass matrices were constructed based on the interval factor method and random factor method;from the Rayleigh’s quotient of structural vibration,the structural interval random dynamic characteristic was obtained by means of the interval arithmetic;the interval numeric characteristics of dynamic characteristic were then derived by using the random variable’s moment function method and algebra synthesis method.Two numerical examples were provided to illustrate the validity and feasibility of the present method.
  • Chen Siyu Tang Jinyuan
    . 2009, 28(4): 70-75.
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    Impact and nonlinear dynamic behaviors of gear pair system with combining time varying stiffness and friction is developed. Firstly The phase plane is divided into three different part to construct the Poincare mapping structure of piecewise linear gear pair system. And then the influences of load parameters and initial values on the impact and nonlinear dynamic behaviors of gear pair system are analyzed in numerical method. The results show that: 1) with the increasing of constant load , the interval of off meshing and the impact velocity are decrease, and the gears has steady movement. The initial value of appearance of grazing bifurcation is increase, 2)inversely with the increasing of fluctuating component of load , impact velocity is increase and the interval of off meshing is decrease, and the gears has instability movement.

  • LU Bo;ZHU Caichao;SONG Chaosheng;WANG Haixia
    . 2009, 28(4): 76-80.
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    In this paper, a 3-D finite element model of a gear-rotor-bearing-box coupling system is developed by coupling transmission subsystem and structure subsystem with the support of bearing for the analysis of the kinetic characteristic of large burden marine gearbox. Based on the research on the change of contact line of helical gears, a method of calculating the time-variant stiffness is proposed. Considering the effect of internal and external excitation on the transmission subsystem, its kinetic characteristic is dealt with by numerical simulation. The kinetic evaluating indexes of structure subsystem, such as vibration displacement and velocity, and the structure preestimated noise are obtained. The research results lay down a theoretical basis to optimize the dynamic performance of large burden marine gearbox.
  • GUO Shu-qi;YANG Shao-pu
    . 2009, 28(4): 81-85.
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  • Haoyu Li;Shaopu Yang Shaohua Li
    . 2009, 28(4): 86-89,1.
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    A three-dimensional vehicle-road-foundation interference system is modeled. A moving vehicle is simplified to a “quarter-vehicle” model. A 3-D model of asphalt pavement is established based on the elastic layered theory. The time-dependent deflection and stress of the asphalt pavement are obtained by linking together the characteristics of a road profile, a moving vehicle, and a multiple layered pavement structure. A detailed model parametric study then follows to show the effect of vehicle velocity, suspension stiffness, suspension damping, tire stiffness, and tire damping on the road dynamic response. The study is conducted with program ANSYS. The results show that in the three-dimensional pressure, the failure of asphalt concrete is mainly caused by shear stress. The maximal horizontal tensile stress and the maximal transverse tensile stress all emerge in joint region of base course and subbase. The influences of the vehicle speed on the pavement dynamic responses is complicated, which should be further discussed considering road profile and vehicle model . The pavement dynamic responses decrease with the increase of suspension stiffness, suspension damping, and tire stiffness .These conclusions may be useful for further analysis of the dynamic responses and damages of road structure, as well as the interference effect between vehicle and road.
  • MA Chunsheng ZHANG Jinhuan DU Huiliang HUANG Shilin
    . 2009, 28(4): 90-92.
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    In order to optimize the design parameters of seat-bumper on the spacecraft, it’s necessary to develop the numerical model of the expanding-tube bumper. The formula of the axial force during press expansion was deduced on the basis of plastic mechanic theory. The finite element model of seat-bumper was developed by introducing the virtual contact surface using the LS-DYNA software. These two numerical models were validated by comparing the simulation and test results under static and dynamic loads. These two models can be used for the optimization design of bumper parameters. The method of developing numerical models can be as a reference for other related studies.
  • Liu Yunchuan; Wang Xuguang Dou Jinlong;
    . 2009, 28(4): 93-96.
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    Dynamic response of the Chinese white poplar is investigated using modified Kolsky (split Hopkinson pressure) bars. Analysis based on the elementary one-dimensional wave theory indicates that the stress uniformity in specimens tested dynamically by the SHPB method can be achieved notwithstanding the lower mechanical impedance of woods, no additional incident-pulse shaping technique is required as usually proposed for soft materials. The dynamic data are discussed and compared to those of quasi-static experiments. Results show that the Chinese white poplar has typical properties of all cellular solids. Concerning the longitudinal samples, both the initial failure strength and the plateau (crushing) stress are sensitive to the strain rate, while the degree of the plateau stress enhancement is lower compared with the former. For the tangential samples have no distinct initial failure stress, the plateau stress is regarded as the initial failure stress. It is shown that the plateau stress is very sensitive to the loading rate. The effect of strain rate on the initial failure stress of Chinese poplar wood has the logarithm law exponent.
  • Xie Gen-quan;Sen Zhong-yuan;Hu Bang-nan
    . 2009, 28(4): 97-102.
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    Dispersion of surface wave in an electro-magneto-elastic compositons layered plate is investigated by hybrid numerical method. Material properties, electric coefficient and magnetic coefficient are supposed to vary linearly in the thickness direction. The electro-magneto-elastic compositons layered plate is first devided into strip elements. the governing equations of an element are obtained, and then the governing equations of the elements are assembled into the total equations. The dispersion of waves can be obtained by solving eigenvalue equation of the system. Effect of electric and magneto field on the dispersion of waves is investigated
  • Yang Fuchun;Zhou Xiaojun;Zhang Zhigang
    . 2009, 28(4): 103-105,.
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    The weak impulse component is always contained in the mechanical fault vibration signal, and the impulse signal possesses the remarkable non-Gaussian characters. The kurtosis could depict the departure degree away from the Gaussian distribution, so a new method was proposed for the weak impulse characteristic based on the sliding kurtosis algorithm. Firstly, a new time series, kurtosis series, is obtained by sliding kurtosis computation of the original signal; then FFT of the kurtosis series is done to extract the frequency of the weak impulse signal. The simulation was done by the new method to the strong signal and noise signal with weak impulse components, and the results illustrated that the method has strong ability for extraction of the weak impulse component. In practice, a broken gear vibration signal was analyzed by the method and the weak impulse component was extracted effectively.
  • YU Mei
    . 2009, 28(4): 106-109.
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    Based on the research of uncertainty source and magnitude, the experimental results and experience, the measurement uncertainty of magnitude and phase shift of sensitivity is analyzed and evaluated according to ISO 16063-11:1999 for high precision low frequency accelaromter with amplifier at Secondary Standard for Vertical Low frequency Vibration. Therefore, it will provide a reference data to emending the nation vibration dissemination system. The relative expanded uncertainties of magnitude and phase shift of sensitivity are 0.30% and 0.19 at reference condition (16Hz), 0.66% and 0.65 over the complete frequency range from 0.1Hz to 120Hz.
  • ZHENG Guo-yong;YANG Yi-ren
    . 2009, 28(4): 110-112.
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    The dynamic response of two-dimensional wing to atmosphere turbulence is investigated. The aerodynamic force is resolved into two parts, free vibrating aerodynamic force and fluctuating aerodynamic force. The fluctuating pressure can be obtained by using trigonometric series composition method of random field. The root of mean square of response of system is calculated with the random theory. It is the focal point to analyze the influences of the mean velocity, the strength of turbulence and the integral measure of turbulence on the root of mean square of structure response. The results show that the root of mean square of response slowly and linearly increases when the flow velocity is low the flutter critical speed. But, when the flow velocity is over the flutter critical speed, the root of mean square of response prominently and linearly increases with the increasing of the flow velocity. However, the root of mean square of response is insensitive to the change of the integral measure of turbulence.
  • LI Jia-quan;WANG Yong
    . 2009, 28(4): 113-116.
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    Feedforward damping compensation method, a realization of damping compensation of secondary path, is studied, and it can be used to improve the performance of filtered x-LMS algorithm. Then, by combining the feedforward compensator and the adaptive feedforward controller, an improved filtered x-LMS algorithm based on feedforward damping compensation is designed. The improved algorithm still holds the virtues of filtered x-LMS algorithm, such as simple structure, excellent robustness, etc. A simulation of active control on a flexible cantilever’s first two modal vibration is carried out, in which standard and improved filtered x-LMS algorithm are respectively used. Simulation results show that the improved algorithm is capable of suppressing the first two modal vibration of cantilever in far less time than standard one.
  • Zhang Sheng Cong Wang Ai Lun
    . 2009, 28(4): 117-120.
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    A coupling dynamic model of disk rod fastening rotor is established by using bond graph in this paper. Coupling properties of the component parts of disk rod fastening rotor are depicted and its effects are analyzed. The natural frequencies of the disk rod fastening rotor are calculated by using the model presented here and by using the integral rotor model at the same time. The study shows that the calculative results of the model presented here are much closer to the experimental results than that of the calculative results of the integral rotor model.
  • Li Qingya;Ye Jihong
    . 2009, 28(4): 121-126,.
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    Based on FLUENT soft platform with Reynolds Stress Model (RMS) and Large Eddy Simulation (LES), the wind pressure distributions on the structures such as dome, cylinder, catenoid, saddle and elliptic hyperbolic paraboloid are obtained in steady and unsteady numerical simulation. The auto-regressive model is adopted to generate the time history of pulse wind speed. The time series satisfy the target spectrum and spatial correlations. Then the time series of pulse wind speed are imposed on the inflow boundary of omputational zone. The steady numerical results conform to the experimental data much at one. The unsteady numerical results match the experimental data a little worse, and the simulation precision of positive Gaussian structures is better than that of negative Gaussian structures.
  • WANG Le;YANG Zhichun;WANG Hui;DANG Xiaojuan;DING Yan
    . 2009, 28(4): 127-131.
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    Using the cross correlation function of the vibration responses under white noise excitation, a novel concept of inner product vector (IPV) is introduced. Based on the conception of IPV, a new damage detection method is proposed, and the measuring noise resistant ability of the proposed method is also analyzed theoretically. It is proven that the IPV can be easily formed using the inner product of the time domain vibration responses; the value of IPV is dependent on the mode shapes of the structure and the influence of measuring noise on the damage detection results can be adaptively eliminated in the calculation of IPV. Numerical simulation examples of delamination damage detection for a composite laminated beam demonstrated the effectiveness and the anti-noise ability of the proposed method.
  • Lv Lei Han Lei
    . 2009, 28(4): 132-136.
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    Surrogate-data method of phase-randomized based on correlation dimension was proposed to surrogate the data of the amplitude transformer terminal in the axial direction, which were tested in different pressures, and then the nonlinear dynamic theory was checked whether the data contained the nonlinear factor. The result indicate there are nonlinear factors in the axial direction of the amplitude transformer terminal, after calculating the correlation dimension of the tested data, when ultrasonic bonding system is loaded different pressures. It is helpful for understanding of transducer and provides analytic science instrument for further study of the vibration in ultrasonic wire bonding with the nonlinear time series method.
  • Zhang Ying Tan Ping Zhou Fulin
    . 2009, 28(4): 137-141.
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    This paper establishes the energy balance equation of a story isolation structure at the moment that the maximal seismic responses occur. The maximal deformation ratio between the isolation layer and the sub-structure is solved by RSS(root sum square) method. The expressions of the total elastic vibration energy, the hysteretic damping dissipated energy by the lead dampers in isolation layer and the viscous damping dissipated energy of the sub-structure are presented. Through introducing the concept of design energy spectrum, the formulas to predict the seismic responses are derived based on the energy balance equation. Finally, the 12-story story isolation structures with three various isolation layer locations are used as a numerical example to validate the accuracy of the predicted responses. Results indicate that the response prediction curves can match well and envelope most of the time history responses for a class of earthquake records.
  • WANG Cheng ZHANG Peilin FU Jianping
    . 2009, 28(4): 142-144.
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    The whole working process of artillery counter-recoil mechanism was divided into four different stages. By this way the high-pressure gas thermodynamic characters in counter-recoil mechanism under the action of recoil impulsive and the actual performances of this mechanism were studied. Because of the recoil impulsive, the thermodynamic characters of the gas in counter-recoil mechanism would deviate from ordinary pneumatic mechanisms and the ploytropic processes of it were not always between the isothermal process and the adiabatic process. This would affect the performance of counter-recoil mechanism. The results of experiments were coincident with theoretical analyses. Since the effects of internal friction and heat transfer were taken into account, the analysis results would make the theoretical calculations more closing to the facts.
  • LiLin Zhang Yongxiang Ming Tingtao
    . 2009, 28(4): 145-148.
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    Three different conditions of a gear, normal condition, crack in root of tooth, broken-tooth, are diagnosed by calculating the correlation dimension in the fractal theory. In order to weaken the effect of the noise on the precision of calculating , a new approach to filter based on EMD is put forward to pre-conduct the signal sampled. Through experiment with a gear box, this method is proved to be feasible and valid.
  • WANG Shuchao ZHANG Hang YE Zhixiong LI Li
    . 2009, 28(4): 149-152.
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    The facade of one high rise building is designed as Pipa tower, which used steel-concrete composite structure. The middle part of Pipa tower is concrete shear wall tube, and around columns are steel columns with box-section. The height width ratio of this bulding is severe out-of-codes. By means of ANSYS program two kinds of dynamic stabilities excited by earthquake of this building are studied by the method of time history response analysis. The first definition of dynamic stability is essentially dynamic buckling based on the definition of Lyapunov, which is analyzed by a modified time freezing method and dynamic eigenvalue method; the second one is the problem of dynamic ultimate load carrying capacity, which is obtained by combing Incremental Dynamic Analysis (IDA) with Budiansky & Roth (B-R) criteria. Results show that this building is of a poor performance of dynamic stability, some parts must be reinforced. Therefore, the presented method can supply a reliable and feasible computing approach for the stability analysis of such super tall and complex buildings.
  • CHI Qinglei Han Wei He Xianlong
    . 2009, 28(4): 153-156.
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    In the present article, the characteristics and the composition of the vibration-measuring system are introduced. The vibration-measuring system is composed of passive servo vibration pickup. This article focuses on the analysis of the nature of feedback and the principle on which the passive servo vibration pickup works. We also compared the characteristic difference of the system before and after feedback. some test data and examples of application are given. Anti-jamming problem of vibration-measuring system is analyzed. In addition, some conclusions are given.
  • Lai Fei Deng Zhaoxiang Dong Hongliang Zhang Lishuang
    . 2009, 28(4): 157-160.
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    Depending on the two important components of vehicle chassis—steering subsystem and suspension subsystem, lateral dynamics submodel, suspension dynamics submodel and the integrated dynamics model with their interactions were built up. Then the performances of the vehicle system with four different control strategies were investigated, including the passive suspension and front wheel steering system, the active anti-roll bar control system, the active anti-roll bar and four wheel steering control system and the active suspension and four wheel steering integrated control system. It can be concluded that the integrated control system of active suspension and four wheel steering can take the advantages of active suspension and four wheel steering into account, while improving the vehicle’s handling and riding performance greatly.
  • GUO Rong Zhou Hong Yu Zhuo-ping Chen Yang
    . 2009, 28(4): 161-163.
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    Fuel cell vehicle (FCV) is a sort of clean energy vehicle with zero emission. And its noise source layout spread out the front and rear part of the FCV. As a result, it is called distributed noise source. Because the interior noise of the FCV is composed of multiple noise sources, the linearity of the interior noise of the FCV is worse than that of the conventional cars. Therefore, the sound quality of the FCV should be improved so that the customers can enjoy the clean energy and comfortable environment simultaneously. Spectral characteristics of noises measured inside the FCV at idle are analyzed. The loudness value is used to evaluate the interior noise of the FCV. Based on evaluation results, the frequency ranges for improving the sound quality of interior noise are put forward. Combined with the spectral analysis results, the parametric filtering method is used to prepare 29 sound samples to find the critical frequency which affected the human ear’s subjective sensation seriously. A virtual validation about the effect of the design parameters on the improvement of the sound quality can be achieved by this method with advantage of time-saving and cost effective and without modifying the physical structure. Hence, the tendency of better solution will be found. To convert the sound quality problem identification into physical problem identification, the noise sources identification experiment is carried out by a single run method to quantify the noise sources which mainly contribute to the critical frequency of the interior noise spectrum. As a consequence, the main noise sources are identified as fuel cell auxiliary system.
  • Pan Yu na Chen Jin
    . 2009, 28(4): 164-167.
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    Bearing is an important unit in rotary machinery, performance degradation assessment is more effective than fault pattern recognition for proactive maintenance realizing near-zero downtime. Wavelet package decomposition (WPD) can depict signal finer, statistical learning theory (SLT) based support vector data description (SVDD) is a one-class classification method holding excellent computing ability. Here, we propose a bearing performance degradation assessment method based on them. This method uses nodes energy of WPD to compose feature vectors, and just needs normal data to build knowledge database using SVDD, then qualitative degradation for test data can be realized. Application results for bearing with different defect size and its whole life time of accelerated life test validated this method’s feasibility and validity.
  • Lanzhu Zhang
    . 2009, 28(4): 168-172.
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    Experimental Techniques and Identification of dynamic properties of flexible polyurethane foam used in automotive seats were described. In the experimental fixture a rigid block was mounted on a 3 inch cube of foam material, which served as the only flexible component. The dynamic system was molded as a single degree of freedom system. The experimental fixture was excited by a small impulse at the top of the block and by shaker on the basement. For the first situation the foam was simplified as a linear viscoelastic material. By exciting with shaker the nonlinear and viscoelastic properties of foam materials were considered. For these two different cases the system response was measured and the corresponding system parameters according to the experimental data were identified.
  • Cheng lijun Zhang yingtang Luo liang Ding junfang
    . 2009, 28(4): 173-176.
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    The acoustic pressure signal near the engine valve cover contains many useful information which can diagnose the fault of diesel engine, these information includes combustion, the valve open and close information. But this signal also contains many interfere noise, like exhaust noise and other noise eradiated from the other part of the diesel engine, and the frequency composition of useful signal and interfere noise are largely overlapped in the frequency band under 20KHz. So how to abstract the useful signal is very important. In this paper,1CM outside the valve side of the engine valve cover was selected as the measure point. Four kinds of signal processing methods: wavelet decomposition, FIR filter, wavelet denoise and FIR divided frequency bands threshold valve denoise was investigated . We find wavelet denoise can reserve useful signal and eliminate interfere noise in the same time, have the obvious advantage in cylinder head acoustic signal processing. After the cylinder head acoustic signal was denoised, the misfire and valve clearance related fault could be diagnosed through the cylinder head acoustic signal.
  • Zhang Xiangdong Yan Weiming Rren min Liu Meng
    . 2009, 28(4): 177-179.
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    Environment effects due to traffic transmit is paid more and more attention nowadays. In suit experiment is one primary approach to this problem, but because of mass background vibration, the testing data can not represent the vibration characteristic of source and promulgation. In order to obtain ideal data, two methods to remove background vibration were presented in this paper, one was Fourier Amplitude Revised Method, the other was Acceleration Vibration Level Revised Method, the two methods were tested in measured data, the result showed that the two methods were effective. Basic principles to banish background vibration were discussed in the end.
  • XU Lin-shan;ZHAO Lin;GE Yao-jun
    . 2009, 28(4): 180-184,.
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    Under action of stochastic wind loading, dynamic responses of a cooling tower show small deformation and weakly nonlinear characteristics. Its natural frequencies centralize in a lower frequency band, coupling effects between various modes are obvious. With help of syrface aerodynamic pressure of a 1B200 reduced-scale cooling tower model which was measured in TJ-3wind tunnel,the stochastic response ofa full scale cooling tower was calculated using pseudo-excitation method and super position method, considering the coupling effects between modes. The contributions of background components and resonantones were quantified and the effects of different parameters, such as, modal numbers,cross terms of force spectra, damping ratio etc, were systematically studied.The numerical calculation results were in good agreement with the dynamic responses measured on the 1B200 reduced-scale cooling tower aeroelastic model.
  • LUO Zhi-gao;LI Ju;WANG Xiang;WANG Mang-mang
    . 2009, 28(4): 185-187.
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    On basis of theoretical analysis of a shell stiffness and deformation, vibration and warping deformation of back cover of a computer display were analyzed with modal shapes of the first 20 modes, a revision proposal was given. It could solve the problem that it was difficult to perform accurate analysis of stiffness and strength of a shell plastic part due to finite element simulations with many theoretical assumptions and boundary conditions. The proposal could provide an important guide for correcting its structural design to reduce its unreasonableness and increase its stiffness.
  • CHEN Haiwei ZHANG Qiuju SU Gaofeng
    . 2009, 28(4): 188-193.
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    This paper details pendulum characteristic linked with a vertical automatic washing machine. At first, a non-linear mode provided in [2] is linearized at its static equilibrium position and ingredients of its Jacobian matrix are analyzed. Second, the pendulum mode born with the machine is obtained by an eigensolution, and factors contribute to this mode are discussed. Third, relationships between the pendulum mode and a damp coefficient in the suspenders are found based on simulation results and pendulum characteristics are analyzed. The existence of the critical damp coefficient is discussed based on energy, factors affect it are then considered. Fourth, the bisection method is employed to determine the critical damp coefficient in a particular washing machine; relationships between the damp coefficient and radius of unbalance under different rotation speed are then fitted by several second order polynomials. The existence of the critical damp coefficient is supported through experiment and effect of the hydraulic balancer is finally discussed.
  • Hong Jin Jing Zu
    . 2009, 28(4): 194-197.
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    Impact acceleration is a vital parameter to airdropped mine system design, which has strong relation to the mechanical parts’ action. Airdropped mine’s drop, parachute release, water entry will generate slow and fast accelerate signals. Overrun of data memory will occur with constant frequency sample. Traditional data compression methods can not be used in a tiny storage test and measurement system due to its limited hardware and power supply. The paper introduces a variable time interval of data storage algorithm which can be fit into a low power CPLD chip. The algorithm analyzes data’s change from a ADC at high speed sampling, and changes the time interval of data storage automatically. It reduces the data storage capacity while keep enough information for both slow and fast accelerate signals. An airdropped mine’s accelerate build-in measurement system based on this algorithm has been build. Test results show that it works well and can be used for other dynamic measurement applications