25 December 2011, Volume 30 Issue 12
    

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  • Yu Hechun;Ma Wenqi;Zhao Guang;Wang Zuwen;Chen Longxing;Liu Haiyan
    . 2011, 30(12): 1-6,27.
    Abstract ( 1167 ) Download PDF ( 554 )   Knowledge map   Save
    This paper is focused on the aerostatic bearing-rotor system based on ship turbocharger. One quasi-dynamic interaction method between flow field and rotor dynamics is proposed. CFD software is used to calculate the flow field with the varying of eccentricity and rotor speed. Based on the calculation results, one nonlinear fitting function of the bearing load capacity related to eccentricity and rotor speed is deprived. The finite element method and coupled method are used respectively to build the kinetic model of the rotor system and to calculate the kinetic response of it under the influence of the gravity, the unbalanced force and the gas film force. The critical speed and the response characteristics are followed obtained. The computed numerical results are certified by the experiments which show that the coupled method based on the calculation results of CFD calculation can describe the kinetic characteristics of the system with a good accuracy.
  • Nie Zhen-hua;Cheng Liang-yan;Ma Hong-wei
    . 2011, 30(12): 7-13.
    Abstract ( 825 ) Download PDF ( 418 )   Knowledge map   Save
    The method of hierarchical visualization and visualization fusion of vibration-based structural damage detection is put forward creatively. This method can display the structural damage information visually using visual images. Taking the simple beam for example, the hierarchical images are obtained using four currently maturely applied indexes for the conditions of one damage and two damages, respectively. The hierarchical images are fused with auto-adaptive weighted least squares method, which can solve the weakness that the visual image of a single index only contains limited damage information. So, the results are more accurate. The visualization of vibration-based structural damage detection will provide a new display platform for damage detection and structural health monitoring.
  • ZHOU Da-xing;YAN Wei-ming;CHEN Yan-jiang;TANG Zhen-yun;LI Zhen-bao
    . 2011, 30(12): 14-18.
    Abstract ( 1221 ) Download PDF ( )   Knowledge map   Save
    Studying on time delay is an important aspect in real-time substructure testing with shaking table. Time delay will affect the accuracy and the stability of the system, and even cause divergence. In modern control theory, neural network is the effective way to compensate time delay. So, it can be used to predict the signal applied to the actuator of the shaking table. According to the simulation, the effect of compensation is significant.
  • YANG De-sen;DONG Lei;SHI Jie;LAN Chao-feng
    . 2011, 30(12): 19-21,6.
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    Through multiple scale method, analyses characteristics of amplitude-frequency response of Duffing system. Multi-frequency excitation changes the main resonance domain of Duffing system under the single-frequency excitation , and the main resonance curve of the system shifts. Through analysis, we can see that multi-frequency excitation amplitude and frequency decide the change extent of Duffing system amplitude-frequency curve. Through numerical simulation, the example of the hard spring Duffing system is calculated, the results show that the multi-frequency excitation change the vibration state of Duffing system under single-frequency excitation. The vibration state of system under different paramaters of multi-frequency excitation are compared , and the theoretical analyses are verified with numerical simulation.
  • Jing Lin;Wang Zhi-hua;Song Yan-ze;Zhao Long-mao
    . 2011, 30(12): 22-27.
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    The plastic dynamic response of clamped cellular metallic sandwich panels was investigated experimentally by using metal foam projectile. The deformation and failure modes of sandwich panels subjected to impact load are exhibited. Experimental results show that sandwich panels under impact loading can fail in several modes: indentation failure, penetration failure, core compression and core shear. Based on the experiments, corresponding finite element simulations have been undertaken using the LS-DYNA software. A good agreement has been obtained between the numerical and experimental results. The effects of face thickness, core thickness, relative density of core and applied impulse on the shock resistance of sandwich panels were studied. Structural response of sandwich panel is sensitive to its configuration and the permanent deflection of back face can be decrease by increasing face-sheet and core thickness. The experimental results are of worth to optimum design of cellular metallic sandwich structures.
  • SUN Jin-shan;JIAN Qing-hui;JIN Li;Zhou Chuan-bo;LU Wen-bo
    . 2011, 30(12): 28-34.
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    The mechanism of jointed rock mass loosing caused by the transient adjustment of in-situ stress is analyzed. The Mathematical model to simulate the dynamic unloading process of jointed rock mass is induced. With this model it is found that the rock mass joints would loose when the normal stress unloaded transiently. And the loosing process of jointed rock mass in a circular tunnel is analyzed with distinct element method (UDEC 4.0). It is proposed that the radial stress of rock blocks adjustment process direct and simple, and tangential stress is more complicated. A loosing zone is formed in the jointed rock mass, which is probably much larger than the static plastic zone. The mechanical parameters of joints in the loosing zones such as strength and permeability are decrease. Transient adjustment of in-situ stress will induce the particle vibration, which is an important damage source of jointed rock mass.
  • GONG Ha-ijian;HUANG Wei-guo;ZHAO Kai;LI Shuang;ZHU Zhon-gkui
    . 2011, 30(12): 35-38.
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    Time-frequency distribution provides signal features in the joint time and frequency domain. Wigner-Ville distribution and wavelet scalogram, as two methods of time-frequency analysis both have inherent defects, because Wigner-Ville distribution suffers severe interference terms, while wavelet scalogram has low time-frequency concentration. This paper proposes a time-frequency fusion algorithm based on Wigner-Ville distribution and wavelet scalogram, which aims at eliminating interference terms and keeping good resolution. Simulation study shows that the time-frequency fusion algorithm is effective in suppressing the interference terms while keeping high resolution in time and frequency plane, and it also inhibits the disturbance of the weak noise. The comparison of the proposed method with Cohen’s idea of time–frequency analysis reveals that the fusion algorithm is superior. Application in time-frequency representation of bearing vibration signals, the fusion algorithm eliminates interference terms of time-frequency representation and keeps good time-frequency aggregation, which represents that the fusion algorithm is effective in time-frequency feature representation.
  • YANG Dong;REN Wei-Xin;
    . 2011, 30(12): 39-43.
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    Vibration signal extended to higher dimensional phase space by phase space reconstruction algorithm, and study the distribution and movement characteristic of neighborhood points of signals in high dimension, and proposed the methods of recurrence plot and recurrence quantification analysis used for studying noise and non-stationary of the signals. Based on principal component analysis, the evaluating feature of non-stationary is the correlation coefficient of first principal component of recurrence quantification analysis of the sample matrix. The analysis of numerical simulated signal and vibration signal of a bridge cables show that the recurrence plot based stationary evaluation method is fast and intuitive; the proposed non-stationary feature can be effectively.
  • JIA Bai-long;LIU Ying;KOBAYASHI Yukinori
    . 2011, 30(12): 44-48.
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    To study the motion and vibration of Flexible Master-Slave System, in this study a new adaptive hybrid controller is designed. In order to improve the performance of the system, a dynamic model is established, parameters sensitivity is analyzed based on the experimental results, and then the adaptive bilateral controller and the adaptive servo controller based on LQR are designed, in both of which the parameters can be changed according to the real-time tracing error. Finally the adaptive hybrid controller is built, which combines the adaptive bilateral controller and adaptive servo controller based on LQR with the gauge of real-time tracing error. Experimental results indicate adaptive hybrid controller has improved the motion stability and vibration suppression performance significantly.
  • wang ru-bin;zhou yi;zhang zhi-kang
    . 2011, 30(12): 49-53,7.
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    in order to deeply understand working priciple of cochlea. influences of motion of basilar membrane on resolving power for different frequencies and sound pressure levels were studied. because the original model for vibration of basilar membrane didn't consider influences caused by different moving speeds of outer hair cells in the course of their own motion on frequnency response of basilar membrane, it could not completely describe active respnance effect of outer hair cells. therefore, time-delay characteristic of outer hair cells in mechanical process of incereasing frequency selectivety of basilar membrane was induced. according to results of simulation calculation, the corrected model absolutely accorded with physiological features of mechanism of action of outer hair cells and it explained the effect of outer hair cells's motion on viration of basilar membrane.

  • LI Xiao-zhen;LIU Xiao-han;LIU De-jun
    . 2011, 30(12): 54-58.
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    The effect of soil-structure interaction on the coupled vibration of continuous rigid-frame bridges and vehicles under high speed vehicle load was discussed. With BDAP V2.0(Bridge Dynamic Analysis Program), the natural frequencies and dynamic responses of the bridge under vehicle load are calculated by using a new bridge model(whole-pile model), which can take account of the interaction of lateral displacement and bending angle on group-piles. Comparing with commonly used consolidation model and equivalent-stiffness model, the dynamic response of bridge, especially the lateral dynamic response, varies a lot by considering soil-structure interaction. While the maximum dynamic accelerations get lower, the maximum dynamic displacements become much higher, the maximum error reaches 31%. For a high speed railway bridge located in soft ground with high-pile cap foundation, whole-pile model is proposed to analysis the coupled vibration of vehicle and bridge.
  • LUO Bing-hua;GAO Yue-fei;LIU Rong-hua;Zhao Peng
    . 2011, 30(12): 59-63.
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    A finite element model of an axially moving beam under a moving load was established, and a method called node’s life and death was put forward to describe the state of nodes on a moving beam. This method let the number and length of the elements on the model to be constant, the parameters of nodes under different time steps transfer with less error, and thus it overcomes the shortcomings leaded by methods that change the number or length of elements. Finally, finite element dynamic model of gun firing in two different ways was established by this method and lateral dynamic response of muzzle points were calculated. Compared with previous algorithm, the result shows this method more in line with the actual condition.
  • Si Jing-ping;Ren Qing-shuang;Liang Hong-bo;Zhang Bao-wei
    . 2011, 30(12): 64-68.
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    Taking the DA462 engine as the object, this research adjusted the valve clearance artificially to different values to simulate the fault of abnormal engine valve clearance, and obtained cylinder head vibration signals in normal and abnormal states separately, in order to do analysis in time domain. Also, this research decomposes the combustion excitation signals and the exhaust valve shut excitation signals through wavelet packet. The frequency bands of the excitation signals were determined by calculating the Root Mean Square (RMS) values of vibrational energy of reconstruction frequency bands. In order to achieve satisfying results, this research determine whether the valve clearance is normal or not, by comparing the RMS values.
  • Liu Yong; Wen Li-hua
    . 2011, 30(12): 69-73.
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    Based on the LuGre dynamic friction model,a model reference adaptive controller (MRAC) is proposed to solve the vibration isolation problem of frictional structures with undetermined parameters. The dynamic model of the single-degree-of-freedom (SDOF) frictional structure is established using the LuGre dynamic friction model to describe the friction force. With choosing the ideal Skyhook structure as the reference model, a dual-observer is used to estimate the state of the friction, and a MRAC active controller is designed. It is proven by the Lyapunov method that the closed-loop system is asymptotically stable, and that both the displacement tracking error and the velocity tracking error converge to zeros. The simulative study is carried out and the results show that this kind of controller not only greatly decreases the response of frictional structures near the resonance frequency, but also improves the system’s vibration isolation performance at higher frequency.
  • Lu Yu-hua;Wang Zhong-sheng;Jiang Hong-kai
    . 2011, 30(12): 74-77,1.
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    An improved Time-Varying Autoregressive model is established for rolling bearing fault diagnosis based on combination of forward and backward estimation. By adopting time-varying forgetting factor, mean squared error based on forward and backward estimation error is defined and partial derivative is taken with respect to weighting coefficients of basis functions to obtain its calculation formula. Then, recursion formula of the weighting coefficients is derived using Recursive Least Squares (RLS). Time-frequency analysis on analog and experimental signal of faulty inner ring is conducted using improved and unimproved model. The result shows that, the improved model can overcome the unavailability of frequency estimation at the initial time, has more accuracy in temporal and frequency estimation, and better anti-noise performance. So the improved model can withdraw fault feature frequency of rolling bearing more efficiently.
  • Li Xiao-long;Leng Yong-gang;Fan Sheng-bo;Shi Peng
    . 2011, 30(12): 78-84.
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    The adjustment process of the parameter for stochastic resonance (SR) is quite complicated. And to achieve stochastic resonance, the sampling frequency is more than 50 times of the signal frequency .By means of the idea of non-uniform sampling, we propose a method of periodic non-uniform sampling SR. The sampling data in different sampling frequencies is first operated through SR, and then processed with non-uniform sampling flourier transformation. The proposed method can give the signal frequency in spectrum analysis simply by fixing a group of resonance parameters. It can also provide the characteristic signal frequency components when the sampling frequency is less than 50 times of the signal frequency. The numerical simulation and the fault diagnosis experiment verified the potential applicability of this method.
  • Zheng Hao-zhe
    . 2011, 30(12): 85-87,1.
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    A real domain pseudo-excitation method (PEM) is proposed for computing the power spectral density (PSD) of the linear time variant systems subjected to stationary stochastic external excitations. This method consists of that in accordance with relationship between the Hartley transform and Fourier transform to construct the real pseudo exceptions and to determine the real transfer function, to compute the real pseudo response of structure, and to calculate the PSD of random vibration responses. The results show that the statistical relevancies and coherences among the excitations can be easily evaluated; compared with the traditional complex field PEM, using real pseudo excitations and real pseudo responses to evaluate the PSD of structural random vibrations responses, this method is simpler and practicable.
  • WEI Hao-dong;AO Hong-rui;JIANG Hong-yuan;PI Ya-dong
    . 2011, 30(12): 88-92.
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    in order to study the dynamic characteristics of hard disk drive subject to external shock, a dynamic model was established to describe the system of head/disk interface with slider suspension and the lift-tab/ramp interface. The dynamic performance of the system subject to external shock with half-sinusoidal shape for different durations and amplitudes were simulated. The dynamic response of the head slider under the shock and factors affecting the air bearing force were discussed. The simulation results indicate that during the shock, the squeezing effect of the thin film at head/disk interface influences the air bearing force, and the variation of the shock duration and amplitude determines the stability of the slider. The simulation results provide beneficial theoretical reference and analytical method for the design of the hard disk drive with good anti-shock performance.
  • BAI Zhi-hai;JIANG Zhi-gang;YAN Bo;SONG Dian-yi
    . 2011, 30(12): 93-97,1.
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    3-D numerical simulations of stiffened metal plates' dynamic responses under close-range localized blast loading are carried out with the finite element software LS-DYNA, and the blast loading on the stiffened plates is analyzed primarily. The rationality of simulation technology is verified by comparing the simulation results to the published experiments. The main influencing factors of blast loading are analyzed. The numerical results show that the blast loads increase with the increase of equivalent rigidity of stiffened plates, and the stiffeners' configuration and plates' fracture have little influence on the impulsive loading. Based on the simulation results, a loading model for stiffened metal plates under close-range localized blast is proposed.
  • Gu Yin;Yu Zhi-min
    . 2011, 30(12): 98-102,.
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    The problem of semi-infinite space with layered medium in the finite element model and corresponding Rayleigh wave input was solved by using equivalent viscous-spring artificial boundary elements. Based on the secondary development of the interface program, an example of two-dimensional finite element model of even and layered medium had been developed. The results indicated that finite element method had excellent estimation precision compared with theory. The dynamic response of pile-soil-bridge structure dynamic interaction under Rayleigh waves was analyzed. A typical rigid frame bridge had been included in this case study. The influence of different site conditions, changes in the location of the soft interlayer, different Rayleigh wave input and pile length on Rayleigh wave propagation and seismic response are considered. The influencing factors of the rigid frame bridge structure are also discussed.
  • He Wei;Chen Jian-wei;
    . 2011, 30(12): 103-107.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the LuGre dynamic friction model,a model reference adaptive controller (MRAC) is proposed to solve the vibration isolation problem of frictional structures with undetermined parameters. The dynamic model of the single-degree-of-freedom (SDOF) frictional structure is established using the LuGre dynamic friction model to describe the friction force. With choosing the ideal Skyhook structure as the reference model, a dual-observer is used to estimate the state of the friction, and a MRAC active controller is designed. It is proven by the Lyapunov method that the closed-loop system is asymptotically stable, and that both the displacement tracking error and the velocity tracking error converge to zeros. The simulative study is carried out and the results show that this kind of controller not only greatly decreases the response of frictional structures near the resonance frequency, but also improves the system’s vibration isolation performance at higher frequency.
  • HAO An-min;ZHOU De-yuan;LI Ya-ming;ZHANG Hui
    . 2011, 30(12): 108-113,.
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    Damping modification factors (DMF) are used in modern seismic codes to adjust elastic response spectral values corresponding to 5% of viscous damping to other damping levels. However, codes have the disadvantage of neglecting the impact of pulse-type motions. This study examined the influence of moment magnitude, site classes and distance on pulse periods by representative forward-directivity ground motion records with distinct velocity pulses. Furthermore, Pulse periods were confirmed to possess better linear relationship with periods corresponding to the peak values of pseudo-velocity spectral. Finally, Nonlinear regression analyses were conducted with the Levenberg–Marquardt method. The resulting equations, as a function of both normalized periods and damping ratios, for DMF successfully represented data distribution. The results show that,with the decrease of pulse periods, periods corresponding to DMF peak values reduce and DMF approach 1.0 at middle and long period range. In contrast to the considerations of current seismic codes, DMF are strongly dependent on pulse periods, the periods of structural vibration and damping ratios, and that in comparison with the DMF proposed by the authors, current DMF are shown to be either too low or too high, depending on pulse periods, period range, damping ratios.
  • Liu Qing-kuan;Zhang Feng;Ma Wen-yong;Wang Yi
    . 2011, 30(12): 114-119.
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    Dry cable galloping is a new vibration type of stay cables which was found in recent years. It has become an important factor that should be considered in bridge design because of large amplitude and serious demage. Three different surface roughness cable models were investigated by high frequency balance technique and displacement meter in wind tunnel. Based on analyzing on drag forces, lift forces and vibration amplitudes under different Reynolds number, it is found that asymmetric and unstable flow field appears under critical Reynolds number; cable balance position are changed and large amplitude vibration are induced due to unstable lift forces in the flow field. Critical Reynolds number decrease with the increase of surface roughness. For prototype cables with smooth surface, as wind velocity corresponding to critical Reynolds number is rather high, the possibility of large amplitude vibration induced by forces of citical Reynolds number is small. However, cables surface will becomes rough under environment such as sunshine, wind, rainfall, floating dust adherence, thus large amplitude vibration becomes possible under common high wind velocity. This is one of the possible mechanisms of dry cable galloping for prototype cables.
  • XIE Quan-min;LONG Yuan;ZHONG Ming-shou;HE Yang-yang;LI Xin-hua;MAO Yi-min
    . 2011, 30(12): 120-124,.
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    Based on the comparability of wavelet and fractal technology, wavelet and fractal combination technology is proposed to analyze blasting vibration signals. According to the variation law of fractal dimen-sion for vibration waveform after different scales wavelet threshold de-noising, the optimum wavelet de-composition scale was got. Through the similarity between blasting vibration signal and its wavelet vectors, and self-similarity for the wavelet vectors, fractal characteristics of blasting vibration signal were verified. Based on comparison analysis of corresponding box-counting dimension for the wavelet vectors of blasting vibration signal, the fractal dimension variation law with different frequency components was got. Fractal box-counting dimension of blasting vibration signals was put forward as a new parameter, which can reflect their frequency composition. The whole band fractal dimension analysis model of blasting vibration signal was set up by wavelet and fraction portfolio analysis, and the report will provide important reference for more detailed research on blasting vibration effects and their fractal characteristics.
  • WANG Zhao-qiang;LIU Hai-li;XU Tian-zhu;CHEN Jia-lang;HUANG Zhen-yu
    . 2011, 30(12): 125-128.
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    Piezoelectric stack has the advantages of high longitudinal electro-mechanical coupling coefficient and strong fatigue resistance, but its electro-mechanical conversion efficiency is not high under low frequency vibration, which limits its applications in vibration energy harvesting. A novel oscillator piezoelectric energy conversion system (OPECS) is presented to enhance conversion efficiency of OPECS nearby resonant frequency, through attaching an oscillator onto the surface of piezoelectric stack. The parameter model of the OPECS is built at first. According to the model electro-mechanical conversion efficiency is evaluated by ratio between longitudinal force and exciting force. Then the relationship between effective working bandwidth and structure parameters are ascertained, thus the design principles of structure parameters are given out. Experimental results show that OPESC can effectively increase the electro-mechanical conversion efficiency in low frequency vibration and enhance the output voltage of piezoelectric stack.
  • WANG Hong-yan;XIE Tao;SHAN Xiao-biao;YUAN Jiang-bo
    . 2011, 30(12): 129-134.
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    The strain distribution characteristic of a piezoelectric cantilever with a tip mass in the multimode vibration is studied in this paper. The effect of the location of electrode pairs on the voltage output of the piezoelectric cantilever is analyzed by the coupled piezoelectric-circuit finite element method. With the aim to measure the electricity generating capacity of the piezoelectric cantilever using the configuration with the segmented electrodes and the continuous electrodes around the first and second resonant frequency, an experiment measuring system was established, and the amplitude of the power output is compared. The results show that the power output of the segmented electrodes is closed to the power output of the continuous electrodes at the first vibration mode, but the peak power output of the segmented electrodes is increased about 900% at the second vibration mode. Compared with the continuous electrodes configuration, the segmented electrodes configuration can result in a significant increase of the electricity generating capacity of the piezoelectric cantilever at high frequency vibration.
  • XU Feng;LIU Yun-Fei
    . 2011, 30(12): 135-140.
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    In order to reduce the random noises and pulse disturbances in acoustic emission (AE) signals and to enhance the quality of useful signals, A new method combining median filter and singular value decomposition was proposed. Firstly, the outliers in the original AE signals were suppressed by median filter. Secondly, signal sequences removed outliers was reconstructed in phase space, and the attractor track matrix was decomposed by singular value decomposition (SVD). Finally, the concept of energy difference spectrum of singular value was put forward to determine reconstruction order of singular value according to its major peak position. The numerical simulation results and measured data of degumming and surface fracture of five-plywood show that the method proposed in the paper can retain the original signal characteristic efficiently, and can eliminate noise and enhance the signal-to-noise ratio in a maximum extent.
  • LIN Wei;CHEN Shang-hong;Qi Ai;ZHANG Gen-ming
    . 2011, 30(12): 141-146.
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    It is an effective solution to install MR damper on adjacent structure to mitigate seismic responses and prevent pounding during earthquake. In this paper, trust-region based instantaneous optimal semi-active control algorithm (TIOC) is introduced to earthquake excited adjacent structure installed with MR damper. Based on the equation of motion, the optimization equations of the semi-active control problem are first proposed. And then TIOC optimization problem subjected to a bound constraint is deduced, and optimal semi-active control forces are calculated at every time step. Finally, simulation is carried on adjacent structures installed with MR dampers applying TIOC algorithm. The results show that the seismic responses of adjacent structures can be reduced effectively; compared with Clipped-optimal control algorithm, TIOC algorithm is more capable of controlling the relative displacement between the structures; it is found that TIOC algorithm has great adaptability, the controller’s behavior can be significantly changed with the objective function and thus should be decided carefully.
  • Yang Qiu-wei;Liu Ji-ke
    . 2011, 30(12): 147-153.
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    Structural damage identification using measured static or dynamic data has emerged as a new research area in civil, mechanical and aerospace engineering communities. A large number of approaches have been proposed for detecting structural damage in recent years. In these existing approaches, the flexibility-based method is one of the promising techniques since the flexibility can be constructed easily from the measured static or lower frequency modes and is very sensitive to structural damage. This paper presents a general summary and review of the flexibility-based damage identification methods in the past two decades. These flexibility-based techniques can be divided into six groups by the different calculation methods and data used. The basic idea of each group is briefly illustrated and the main formulas are given, respectively. The advantages and shortcomings of these approaches are also discussed and compared in detail. In the end, several key issues related to flexibility-based damage identification methods are emphasized and future study aspects are pointed out.
  • BU Jian-qing;WANG Hai-yun
    . 2011, 30(12): 154-159.
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    A BP neural network method is presented to identify the effective prestress for simply-supported PRC beam bridges with eccentrically straight tendons based on the mode frequencies and dynamic responses of the bridge in this paper. The modal frequencies and dynamic responses of the simply-supported PRC beam bridge with different prestress levels are calculated by using the MATLAB software after setting the model of the vehicle-bridge coupled vibration system, and the calculated modal frequencies and dynamic responses are made use to identify the effective prestress. Three-layer BP networks were adopted, and the convergence of iterative sequence was admissible through 14 groups of training samples. The identified results agree with the true values very well, it shows that the trained BP networks have strong recall memory and interpolation ability, and can be adaptable to the noised dates. The effective prestress identification can be performed conveniently by the proposed method.
  • DU Yan-chen;WANG Shu-lin
    . 2011, 30(12): 160-163.
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    Impact damping with fine particles as damping agent (IDFPDA) exhausts vibration energy by means of the plastic deformation of fine particles. In order to quantitatively study energy dissipation in the impact damping, equivalent parameters are used in the existing model of impact between two balls to rapidly predict the energy dissipation in particle clamping in a single period. FEM analysis on the impact between two balls covered by fine particles show good agreement with the results from the equivalent parameter method. Further results from the equivalent parameter method show that the energy dissipation in particle clamping is much more than that in collision without particles under the same initial conditions, which implies that the performance of the IDFPDA is better than the conventional impact damping and agrees well with the existing experimental results. By means of FEM, we discuss the effects of parameters, including diameter ratio of particle to ball, particle material and particle amount in collision area, on the energy dissipation of impact between two balls with fine particles, and further demostrate the rationality of the equivalent parameter method. The study provides a useful tool to predict the damping analysis for IDFPDA and simulate the vibro-impact damping system.
  • CHENG Mei;MENG Guang;WU Bing-yu
    . 2011, 30(12): 164-169.
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    Under the conditions that both the nonlinear ball bearing force and Alford force, the dynamic model of the rotor system was set up. Then nonlinear dynamic properties of rotor-ball bearing with Alford force were studied by means of numerical stimulation. The nominal contact angle of the ball bearing was introduced in the improved ball bearing method. And the result of the present method was in good agreement with the previous conclusions, so it was feasible using this method to predict the dynamic characteristics of rotor system. By using the numerical value integral method, the influences of a series of factors on the nonlinear dynamic behaviors of the coupled system were studied.By changing the values of the rotation speeds, the ball bearing clearance and the rotor eccentricity, the bifurcation diagram was obtained respectively. Meanwhile the pictures of some typical Poincare maps and frequency spectra were also given. From the results of the numerical simulation, it is found that the stability of the coupled rotor system could be improved under combined Alford force and ball bearing.
  • LI Yu-chuan;WU Xing;CHI Yi-lin;LIU Chang
    . 2011, 30(12): 170-174.
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    In order to separate the compound faults from rolling bearing, and improve diagnosis accuracy, a method based on morphological filtering (MF) and sparse component analysis (SCA) was proposed to deal with the blind source separation (BSS) problem of rotation machines in the case of nonlinear, noisy source mixing and the number of failure sources are unknown. The morphological filtering was used to extract modulation features embedded in the observed signals and to ensure signals presented in sparse mode, and then SCA was used to separate unknown sources from mixed signals. In the over-completed and underdetermined condition, the method was applied to analyze the faulty rolling bearing acceleration signals. Analysis results show that this method can separate and extract the rolling bearing’s fault characteristic efficiently.
  • zhu yue;zhang ling-mi;guo qin-tao
    . 2011, 30(12): 175-180,.
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    because of the complicated engineering structures using finite element models are more uncertain parameters and uncertain parameters varied greatly, its slow convergence when the target parameters are updated. for this issue, introducing the hierarchical model of thinking, the complex characteristics of engineering structures by connecting decomposed into several sub-structure, then the sturcture is divided into several sub-parts, respectively, parts, sub-structure of the updating;. finally do not neet to modify the overall structure of an acceptable project generated finite element model, through the model validation techniques in the field of stratified amendment benchmark. the results show that thinking based on hierarchical finite element model updating method has high precision, with great engineering value.
  • Zhang Yu-xin;Sim S H;Spencer B F
    . 2011, 30(12): 181-184.
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    Based on the basic idea of Natural Excitation Technique (NExT) and Eigen Value Realization Algorithm (ERA), the solution process are formulated for NExT/ERA conducting multiple reference channels; and the strategies for determining the reference channels are suggested and investigated in the mean time. First, two evaluation criteria concerning modal frequencies and mode shapes are proposed to evaluate the identification results; then according to the criteria, the strategies for multiple references selection are proposed and discussed herein. The strategy can be used to exclude the bad references, which is more important for complex structures for which more sensors could be on the nodes of the natural modes so that more sensors are excluded and only a few sensors may survive. By applying the method to the Bill Emerson Bridge who is well known as it has been used worldwide as the ASCE benchmark model for the structural control problem of cable-stayed bridges, the work in this paper is proved to be meaningful. The work can also provide helpful reference for the system identification of general cable-stayed bridges.
  • YAN Dong-jin;SUN Chuan-huai;ZHANG Hai-ming
    . 2011, 30(12): 191-194.
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    Frame structure when subjected to horizontal vibration is usually simplified as shear beam model or bending beam model. The accuracy of each model is not quite clear until now. A typical 3-stories concrete frame structure is analyzed with shear beam model and bending beam model respectively. Vibration frequency equations are derived and first three vibration frequencies are solved. On the comparison of these frequency values with the corresponding calculation results of finite element analysis of the 3-stories structure, it can be seen that bending beam model is more accurate than shear beam model.
  • Gao Guang-fa; Li Yong-chi; Zhao Kai; Pang You-chao
    . 2011, 30(12): 195-200.
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    Aimed at anti-explosion design in defense engineering, attenuation mechanism and evolution law of stress waves in defense layer which cavities or cylindrical shells were embedded in were focused on. Based on theoretical analysis and numerical simulations, it was found that dispersion and diffraction effect of stress waves were occurred in the concrete material, which significantly weakened the strength of stress waves behind the cavity or shell, and the structure embedding shell has better protection than the structure embedding cavity. Numerical calculations for different radius of the shells were preformed. The results show: the protect effect and scope is amplified as the radius of the shells are increased; and when several shells were horizontally equispacedly arranged in defense layer, the stress peaks of the measure points are obviously less than the minimum of stress peaks of corresponding measure points in the structure that single cylindrical shell was embedded in. all those can be referred to design of advanced defense layer in anti-explosion engineering.
  • Yang Tao;Zhong Xin-gu;Shen Ming-yan
    . 2011, 30(12): 201-204,.
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    In order to solve a widespread problem that the vertical prestress applied widely in the webs of large-span concrete box girder bridges loses efficacy seriously, authors built concert box girder web-models in lab and installed vertical prestressing anchor system as field do. On the basis of the lateral vibration signals when an acceleration sensor was fixed at the tip of the uncased part of vertical tendon, we applied single-pulse-impact method to study the frequency properties of the uncased part of vertical prestressing anchor system in this paper, which proposed a model that takes the uncased part of the bar as a cantilever with fixed end and variational flexural rigidity, and then identified the flexural rigidity of anchorage zone stiffened by nut at uncased part of the bar, moreover, provided theoretical basis for testing effective tension retained in the vertical tendon.
  • YAO Hao-ping;ZHANG Jing
    . 2011, 30(12): 205-208.
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    The model of sound field of a rigid cylindrical enclosure with a middle flexible panel is deduced by using Hamiltonian function and sound modal theory. The model allows the consideration of a wide variety of boundary conditions by means of continuous distributions of artifical springs along boundary of flexible panel. A general formulation considering the full coupling between the two cavities and the panel with different boundary conditions is developed. Analytical results intended to investigate two main issues are presented. One is that the rotational stiffness has less influence on the structural-acoustic coupling of the model and the panel velocity than the translational stiffness has,the other is that the sound response of cavity 2 caused by panel increases with the increase of the translational stiffness. The contribution of this paper is that it provides some supporting theoretically in engineering.
  • Wang Jia-ying; Zhang Shi-lian; Wu Shao-bo
    . 2011, 30(12): 209-215.
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    To enhance the warship vitality, the double-bulkhead was set on the latest Europe warship. Numerical simulation method was adopted to study the structure response of ordinary double-bulkhead module under internal explosion. The blast wave propagations in the cabin, the impact loads on the bulkhead and structure plastic responses were discussed. The double-bulkhead damage pattern under internal explosion was researched. Corresponding to this pattern, the anti-explosion design of double-bulkhead was discussed preliminarily and the improved design plan is proposed. The bulkhead corner plate thickness was increased and longitudinal bulkheads were added between two bulkheads. Through the analysis, the improved double-bulkhead design plan can effectively increase the anti-internal-explosion capability.
  • Chen Lingkun; Jiang Lizhong; Yu Zhiwu; Luo Bofu;
    . 2011, 30(12): 216-222.
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    In recent years, along with fast development of high-speed railway, research on dynamic response of high-speed railway bridge under earthquake has raised great concern among common people and researchers. The finite element method is employed to establish the beam element space analysis model of the high speed railway bridge and solid model of single pier in this paper, by means of finite element software and bending moment-curvature relationship program, the elastic-plastic earthquake responses of high-speed railway bridge under different earthquake intensity and effect combination is calculated under different earthquake strength, different speeds and soil-structure interaction (SSI). The calculation results show that influence of the SSI on seismic responses is little under good geology condition, the simplified method can be adopt to consider the SSI; the seismic responses increase with the increase of earthquake strength, train speed and pier height; the frequency character of seismic wave have great effects on the seismic responses of structure; the piers bottom step into elastic-plastic stage and plastic hinge will be developed at the bottom of piers under the rare earthquake action, the stirrup densification should be taken into account to enforce the elastic-plastic deformation capacity of piers.
  • ZHANG Jian-tao; JIN Jia-mei; ZHAO Chun-sheng
    . 2011, 30(12): 223-225,.
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    A novel multi-DOF ring-shaped standing-wave type ultrasonic motor is proposed. It is composed of a spherical rotor and a ring-shaped stator. The motor using the second in-plane vibration mode can rotate in three directions. In this paper, the motor operation and driving mechanism is analyzed in detail. A prototype motor is fabricated according to results of finite element design. The motor, whose stator is 25.7 mm (length) × 25.6 mm (width) × 25.7 mm (height), operates at 26.76 kHz. The rotational speeds in three directions are 12r/min、10 r/min and 12r/min respectively. The motor have the advantages of small volume, simple and compact structure, avoiding considering the frequency consistency of different modes of composite mode ultrasonic motors. It may find applications in various fields: small robots, robot eyes, robot hands, attitude adjustment of mechanisms.
  • SHEN Xiao-wei;YAO Min-li;CHANG Rui-hua
    . 2011, 30(12): 226-229,.
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    Due to the classical wavelet had the shortcoming of computation complexity and constant decomposition levels in inertial sensors de-noising, a thresholding de-noising method based fuzzy logic and lifting wavelet transform was brought out. Firstly, the motion type was determined by a fuzzy expert system, and the bandwidth of true motion dynamic was chosen accord to the spectrum estimation base on the priori knowledge. Then, a suitable wavelet decomposition levels for each axis of inertial sensors was automatically chosen in accordance with the relationship between wavelet decomposition levels and cut-off frequency. Finally, a discrete wavelet transformation was obtained under lifting scheme, and the signal was de-noised by compresses the coefficients of wavelet transform of signal at a threshold value. Test results prove that the proposed de-noising method can distinguish the motion type correctly, and has a better results and higher computational efficiency than classical wavelet de-noising with the constant decomposition levels.
  • LI Xiang-peng;ZHANG Chun-hui;WANG Shi-ying
    . 2011, 30(12): 230-234.
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    Gear was simplified to three medium thick annular plates with the outer diameters of reference circle, addendum circle and dedendum circle respectively,according to the structural characteristics of a cylindrical gear with a hole in the center and its ratio of the thickness to radius beyond the scope of the classical thin plate theory. The frequency equations for transverse vibration of the medium thick annular plate were derived with the free boundary conditions based on Mindlin’s theory and solved computationally with the help of MATLAB. The solutions are in best agreement with those from the finite element method and also with the experimental results only when the diameter of gear equals to one of its reference circle. The conclusion has certain theoretical significance to guide to design the vibration system of ultrasonic gear honing.
  • KANG Qiang; ZUO Shu-guang; ZHANG Shi-wei
    . 2011, 30(12): 235-240.
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    A significant problem of fuel cell vehicles is high-frequency noises caused by air support system, and the air compressor generates the maximum noise. The vortex blower is adopted as the compressor. The noise of the vortex blower at the front and outlet was measured and analyzed under steady and unsteady conditions. It is concluded that there are discrete peak frequencies and the 10 times, 42 times, 84 times frequencies are the most significant. By simulation of interior pressure fluctuation of the vortex blower using Fluent, the cause of the harmonic frequencies is explained.
  • Wang Hai-wei;Yang Hui-xia;Liu Geng;Wu Li-yan
    . 2011, 30(12): 241-244,.
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    This paper simply introduces the concept and application of virtual prototype technology, and analyses the veracity program of complex multi-body system simulation. The rigid-flexible couple virtual prototype model of complex multi-body system including impact is built with multi-body dynamics software Virtual Lab, and the accuracy of virtual prototype simulation is evaluated combining with the test data. Revising some key system parameters by sensitivity and perturbation method, the simulation results of scattering degree have better consistency with test results, and the reality of virtual prototype model is improved.
  • CAO Hua-jin;; LI li;; JIANG wei;; CHEN yuan-kun;
    . 2011, 30(12): 245-249.
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    Galloping of overhead transmission conductor which is a low-frequency, high-amplitude self-induced vibration. The transmission tower-cable-insulator model in consideration of coupling effect was established based on ANSYS in this paper. The vertical, horizontal and torsional three directions galloping of the transmission conductors was detailed using the restarting technology and the validity of the restarting technology is verified based on the typical case. Under the condition of different wind velocity, the galloping analysis is performed and the amplitude of the transmissions and the dynamic response of the towers. Different galloping control measures of using inter spacers and multi-point loading were performed. Various layouts projects of the galloping control measures are carried out and the conclusions are got that weighting-added is a good measure for galloping control, multi-point weighting is better than single point weighting, and increment of weight in an appropriate range is conductive to anti-galloping.
  • HUANG Chong;WU Xiao
    . 2011, 30(12): 250-252,.
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    In this paper ,the natural vibration of mlti-spans cable with supports in different lines was studied.The modal function of single-Span was derived and the characteristic equation of frequency of multi-spans cable was derived based on the boundry condition and continuous condition of single-Span and the natural frequrncy of multi-spans cable was decided. Through the FEM analysis of mlti-spans cable, the correctness of the method was verified. In the analysis of example, the influence of angle to natural frequrncy was discussed.
  • ZHU Hai-peng;ZHU Hai-chao;MAO Rong-fu;DU Xiang-hua
    . 2011, 30(12): 253-256,.
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    The common near-field acoustic holography (NAH) can not be utilized to analyze modulating component of the modulated sound source. In this paper, a method to analyses the modulated sound source with statistically optimal near-field acoustic holography (SONAH) technology was applied, that is, Hilbert transform was introduced to demodulate the sound signal and pick-up the modulating component, and then the modulating component was reconstructed by SONAH technology. Its effectiveness in engineering was proved by the loudspeaker experiment and the air compressor experiment.
  • Shi Lin-suo;Shen Jin-wei;Zhang Ya-zhou;Niu Wu-ze
    . 2011, 30(12): 257-260.
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    the Auto-Regressive (AR) model was an important tool for stationary signal analysis. The optimum AR model order was determined by the Maximum Kurtosis Criterion, and then this AR model was used to pre-processed the fault signal which obtained from rolling element bearing. As a result, it eliminated the liner predictable stationary part and achieved the residual error, which only contained the noise and the non-stationary part of the signal. Consequently, the difficulty of following signal analysis was eased. Spectral Kurtosis(SK) was sensitive to non-stationary signals, it could extract the non-stationary part from the noisy background, and so, aiming at a more efficient result of the rolling element bearing diagnosis, this essay combined the AR model and Spectral Kurtosis to detect the fault. And the expected result was achieved.
  • Hu yan-chao;Chen zhang-wei
    . 2011, 30(12): 261-264.
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    Due to second harmonic electromagnetic force, the end winding coil was subject to vibration damage,which is an important part of F4 three-phase synchronous motor stator for precision bar steel in Bao steel. A modal testing has been carried out on the winding coil, and of which some first modes acquired. The test shows us some appropriate positions for fixtures and where the maintenance should pay attention or on which the short circuit and damage happen more
  • Che Hong-kun;Lu Fu-zai;Xiang Zhan-qin
    . 2011, 30(12): 265-269.
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    Problems of signal recognition in ultrasonic inspection are analyzed. A new fusion recognition method base on multiple features extraction is researched, which compounds with support vector machine theory and Bayes reasoning. The principles of SVM method and the Bayes reasoning are introduced. Fusion recognition method base on maximum a posteriori(MAP) are designed to identify the signals of different flaws with features extracted from different ways. Four feature extraction methods from different spatial domains of a signal are presented for fusion recognition. Experiments with both SVM method and SVM-Bayes method are carried out to identify the flaw signals of oil casing pipe. The result shows that flaws can be identified effectively by SVM-Bayes method, and both recognition correct rate and generalization are better than a single feature SVM method.