25 February 2009, Volume 28 Issue 2
    

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  • ZHANG Qinghua;GU Ming;HUANG Peng
    . 2009, 28(2): 1-4.
    Abstract ( 1464 ) Download PDF ( 549 )   Knowledge map   Save
    Abstract Latticed tower(LT) have been tested in TJ-1 wind tunnel in Tongji University using high-frequency-force-balance technique to investigate the characteristics of wind forces acting on the tower. The results indicate that the mean force coefficients have no practical variability with turbulence. And along-wind wind force is the major load on the LT for the static wind effects, along-wind fluctuating forces are larger than across-wind fluctuating forces, but the fluctuating torsional force can be ignoring. At same time, some exiting codes and standards about mean drag coefficients are compared. Based on the analysis of power spectrum densities (PSDs) of the forces, some conclusions are drawn that incoming wind turbulence has great contributions to the along-wind forces, and PSD of across-wind forces is more complicated, multiple excitations may be existed. In addition, the torsional PSD is a broadband frequency spectrum, and its value is smaller than PSD values of along-wind and across-wind force, with the increasing of turbulence, the torsional PSD value does not change remarkably. Furthermore, the coherence of across-wind forces and torsional moment is strong,and turbulence intensity has little influence on coherence.
  • ZHOU Wei;CHU Yan-dong;YU Jian-ning
    . 2009, 28(2): 5-7.
    Abstract ( 1428 ) Download PDF ( 617 )   Knowledge map   Save
    Abstract: In the context of a new generalized Lorenz system,the algorithm of calculating the optimal delay time was improved by use of the tesemblance degree of vectors to achieve reconstruction of phase space of the system.The numerical results show that the improved algorithm is effectuive and the optimal delay time can be chosen effectively.
  • WANG Rui;LIU Guo-zhi
    . 2009, 28(2): 8-11.
    Abstract ( 1871 ) Download PDF ( )   Knowledge map   Save
    Abstract Deployment optimization can improve the coverage and quality of service for wireless sensor networks (WSNs). A new deployment method based on fish-swarm algorithm was proposed for WSNs consisting of many mobile and stationary sensor nodes. The movement of mobile nodes was analogized to the follow and prey action of the artificial fish with the network coverage as object function, and the virtual force factor was introduced to direct the moving and updating status for artificial fish. Simulation results show that this algorithm can improve the network coverage and performance efficiently with the better ability on global searching.
  • LI Cheng;DING Tian-huai;CHEN Ken
    . 2009, 28(2): 12-15.
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    Abstract: A finite-differential model for the one-dimensional propagation of longitudinal waves along the drill string is established. The influences of acoustic transducer positions and carrier wave signals on acoustic transmission signals in the periodic pipe structure transmission channel are analyzed by the time and frequency domain simulation. An on-off keyed (OOK) modulation of time-delayed pulses is designed. Then, the narrow pulse modulated signal transmission experiments are performed by applying the longitudinal excitation to the length-limited simulated drill string in the axial direction of pipes. The results show that under the conditions of excitation power of 1W, transmission rate of 77 bit/s and 6.44-meter simulated drill string, the proposed transmission method can implement the data transmission and signal detection of test signals via low-frequency extensional waves in the laboratory. Moreover, the simulation and experimental research on acoustic wave propagation along the drill string provides the theoretical and trial foundation for the design of downhole acoustic telemetry system.
  • Zhou Yun Wang Dayang Deng Xuesong Chen Lin
    . 2009, 28(2): 16-21.
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    Abstract: Wind-induced vibration control of a super high-rise building was selected as an example in this paper. The dynamic characteristic of wind was introduced. Fluctuating wind-speed time series of both X-direction and Y-direction were simulated by improved AR model. According to natural characteristics of the building, three kinds of damping control plans of added viscous dampers and tuned mass damper(II), added viscous dampers(III), added tuned mass damper(IV) were put forward. Dynamic analysis of wind-induced vibration control for the building in different wind directions and different control plans was studied in once for 10 years, 50 years and 100 years. The control effect of different plans was analyzed in detail. The results show that the control plans of II and III can dissipate energy imported by wind, attenuate dynamic response, reduce mutation of story-acceleration response and inter-story displacement effectively. The maximum roof displacement and acceleration response can be respectively reduced by 33% and 51.4%. So, the control plans is feasible and effective to control wind-induced vibration, improve safety and comfort of structure. Some suggestions of wind-induced vibration control for high-rise buildings are put forward at last.
  • Yang Qiuwei Liu Jike
    . 2009, 28(2): 22-24.
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    Abstract: This study presents a simple and effective method to detect damages in reticulated structures. The developed theory approaches the damage location and extent problem in a decoupled fashion. First, the elemental stiffness matrix of the reticulated structure is decomposed to obtain the elemental stiffness connectivity vector. Then a damage localization criterion is defined as the dot metrix of the elemental stiffness connectivity vector and the eigenvector change. Subsequently the probable damaged elements can be determined according to the relatively larger values in the localization vector constituted by the damage localization criterions of all the elements. With the probable damage locations determined, the eigenvalue perturbation technique is employed to estimate damage locations and extents more accurately. The proposed method is demonstrated on a reticulated structure and its efficiency is demonstrated through a damage simulation. The results show that the proposed technique can give good predictions for both single and multiple damage cases even if noise is present. It has been shown that the presented procedure may be useful for detecting damages in reticulated structures.
  • YANG Zhi-chun;YANG Fei;ZHANG Ling-ling
    . 2009, 28(2): 25-27.
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    Abstract: A novel scheme for panel flutter suppression is proposed. In this scheme the panel is designed as a sandwich panel incorporated with distributed beam-type dynamic absorbers acting as it core layer. The frequency of the dynamic absorber is designed according to the first natural mode of the sandwich panel, the installation positions are determined according to the first three natural modes which are typically involved in the coupling of flutter mode. The dynamic properties and flutter characteristics of the dynamic absorbing panel are calculated and compared with these of the sandwich panel without absorber or sandwich panel installed with rigid beam. The results demonstrate that the proposed beam-type dynamic vibration absorber scheme is very effective in flutter suppression for this sandwich panel.
  • Duan Yong Chen Qian Zhou Hongwei
    . 2009, 28(2): 28-31.
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    ABSTRACT: The characteristic of energy dissipation for particle damper was investigated by simulation using 3-D discrete element method under harmonic excitation in vertical in this paper; the excitation level and frequency were controlled, respectively. For the excitation level, not only the acceleration amplitude was interested but the velocity amplitude and the displacement amplitude as well. As a result: the loss power depends on the excitation level and frequency. When the acceleration amplitude, velocity amplitude and displacement amplitude increase, loss power increases. When the acceleration amplitude is the same, loss power decreases with the excitation frequency increases. When the velocity amplitude is the same, loss power has almost nothing to do with the excitation frequency. When the displacement amplitude is the same, loss power increases with the excitation frequency increases. And as the excitation level increases, the percent of friction part of loss power decreases and the percent of the impact part increases. The result has been also obtained by experiment.
  • Shen Yong-jun Kong De-shun;Yang Shao-pu Zhang Guang-ming
    . 2009, 28(2): 32-35.
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    Abstract: The basic theory of fractional wavelet transform (FrWT), including the construction and fast computation of FrWT, is introduced at first. Then a new de-noising method based on the correlativity of fractional wavelet transform is presented, the core of which is due to different correlativity of different signals in FrWT field. Compared with the de-noising method by traditional wavelet packet transform, the excellent de-noising performance of this new method is illustrated through two simulated examples. At last, the possibility of application of this method is discussed.
  • Zeng Ben;Zhou Fu Lin;Xu Zhong Gen
    . 2009, 28(2): 36-39.
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    Abstract A transfer function of absolute acceleration response of NSC which is supported on a base-isolated structure is presented. Base flexibility has been assumed to be described by complex-valued impedance function which calculated by cone model. The proposed formulation is used to generate the FRS by PSDF according to random vibration theory, and compared with the FRS obtained by the time history analysis. The results show that PSDF provides satisfying FRS with far less effort and good agreement with current seismic code; The peak acceleration of NSC is appear in low frequency band(near base-isolated frequency), and the use of base-isolated device would weakening the effect of SSI, especially in the base-isolated frequency band.
  • ZENG Zhi-ping;YU Zhi-wu;CHEN Xiu-fang;ZHAO Guo-fan
    . 2009, 28(2): 40-44.
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    Abstract: Aiming at seamless turnout on bridge, the rail-turnout tie-bridge spring-damping vibration model was built by using finite element method. The train-turnout-bridge spatial vibration equation sets were formulated by using the principle of total potential energy with stationary value in elastic system dynamics and the “set-in-right-position” rule for formulating matrixes. Taking Tian-luo major bridge in Wenzhou-Fuzhou railway line for passenger as an example, it was assured that there was a crossover combined with two No.38 turnouts on the bridge. The train-turnout-bridge spatial vibration dynamic responses were analyzed when “China Star” high speed train with 1 locomotive and 4 passenger cars at the speed of 140km/h through turnout branch. The influences of train velocity, the lateral stiffness under rail, the lateral uniform stiffness under tie and the height of pier to the train-turnout-bridge system vibration were analyzed. The results show that bridge leads the displacement of rail and turnout tie increase very much, the dynamic responses of train increase a little, and it has little effect to the acceleration of turnout and wheel/rail force. The system responses increase with the increasing of train velocity, the decreasing of lateral stiffness under rail, the decreasing of lateral uniform stiffness under tie, and the increasing of pier height.
  • CHEN Hai-long;YAO Xiong-liang;ZHANG A-man;HUANG Fei;LIU Min
    . 2009, 28(2): 45-50.
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    Abstract: The dynamic design calculation method DDAM and time domain simulating method are introduced in this paper. Basic on the structure characteristic of the ship power package parts, the DDAM method and time domain load method are introduced respectively in frequency-domain and time –domain to analyze the shock resistance. The result indicates that the responses of different devices are relationship with the structure characteristic and the shock load direction. To the main turboset and the main reducing gear device, because of the connecting relationship between the parts, the dynamic response of the bolt, dowel and the connecting structure of them is more sensitively. The results can give certain reference to the analysis and calculation of the ship device shock resistance and the shock resistance design of the new ship device.
  • Dai Yu;Sun Heyi;Li Huipeng;Tang Wenyan
    . 2009, 28(2): 51-55.
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    Abstract: Utilizing the amplitude and phase of continuous wavelet transform (CWT) coefficient on ridge, weak nonlinearities on damping and stiffness are identified from the free decay response of a structural system in this paper. A new algorithm for the detection of ridge is introduced to eliminate the frequency-shift of CWT amplitude extreme. In order to minimize end-effect, the parameter selection of wavelet function is performed by using an optimization technique based on the fitting error of least squares. Both numerical and experimental studies are performed to demonstrate the proposed procedure and verify its accuracy. The experimental system is a high accuracy instrument for measuring moment of inertia. The results show the method works very well in identifying weak nonlinearities on damping and stiffness of structures.
  • Liu Shizhong Ren Wanming
    . 2009, 28(2): 56-59.
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    Abstract: The girder and arch combination bridge of continuous rigid frame with V-shaped Support is studied in this paper. This paper introduces the design of V-shaped piers of the beam-Arch Combination System Bridge of continuous rigid frame. Using SMAD finite element computing method, the author pays attention to the analysis of influences that the size of pier bodies and boundary conditions make to the whole structure. Through the optimization of computing, the author treats the adverse influences that shrinkage, creep of second internal force, Pre-stressed and temperature of second internal force make to the structure. The ratio of lateral stiffness is 1926:1 between the tie beam and arch rib of the bridge. After the completions of main shrinkage and creep, constructing the arch of main girder and the suspenders are double erected by supporting cable,this method treats effectively the lateral stability of frame arch bridges with flexible bars. Three-dimensional seismic responses of the bridge show that all upper parts of the bridge's seismic forces are not the control internal forces of the bridge, then illustrate the structural design of the bridge have a good seismic performance. This internal force analysis and conclusions are useful to construction and design of similar bridges.

  • WANG Xiong-jiang;QIN Xian-rong; GU Ming
    . 2009, 28(2): 60-63.
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    Abstract: Accurate determination of flutter derivatives for large-span bridges is of critical importance to ensure the reliability of the flutter analysis. Although much progress has been achieved both in the identification and testing methodologies of flutter derivatives, inadequate attention has been paid to the relationships among the flutter derivatives. In this paper, after a brief summary of the researches on the relationships among flutter derivatives, new relationships among flutter derivatives for the thin flat plate model was proposed based on Theodorsen’s aerodynamic force theory. The analytical formulas considering the influence of reduced frequency, were compared with the wind tunnel test results, determined by the covariance-driven stochastic subspace identification method. The validation of the relationships among flutter derivatives was experimentally verified and the possible application of them was discussed.

  • Zhiyi Zhang Junfang Wang Jianpeng Zhou Hongxing Hua
    . 2009, 28(2): 64-67.
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    Discussed are the adaptive control of vibration of systems that are excited by forces of periodically varying frequencies.
    The adaptive control is realized on the basis of tracking of time-varying frequencies and a method for online frequency estimation,filtering and control is proposed. Based on the principles of subspace identification, the time-varying frequencies are first estimated from the recursively computed autocorrelation of measured signals. Then a group of bandpass filters, the center frequencies of which are equal to the estimated ones, are given to track and filter signal components. Finally, the controller is synthesized on the LMS and constructed by independent parallel control units that cancel vibrations corresponding to those components. Given as well are the
    simulation and experimental results that demonstrate that the proposed method can obtain 10-25dB attenuation in vibration.
  • Liu Yameng;Wang Hao
    . 2009, 28(2): 68-71.
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    This article discusses extrapolation technology in structural topology optimization.The traditional extrapolation method in bidirectional evolutionary structural optimization method can only be applied on regular rectangle element or cuboidal element, the article introduces a new method. The method is based on a new idea. After the normal modes analysis, according to the known displacements of the nodes in the intra-domain, unknown displacements of the nodes on the boundary of the structure will be calculated by linear static method. The method can be popularized on arbitrarily elements. The example demonstrates that the method in this article is effective.
  • Wang Jiasheng;Zhu Sihong
    . 2009, 28(2): 72-76.
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    Based on the theory of thermomechanics and fluid dynamics, the state equations and dynamic equations of air spring, auxiliary chamber and orifice are established. In order to simplify the complex nonlinear model, supposing the amplitude of vibration is small, the dynamic equations are linear processed with small deviation linear method which based on Taylor series, then the linearied model for dynamic stiffness of air spring is deduced. In order to verify the precision of linearied model and analyze the effect of each parameter on dynamic stiffness of air spring, taking the Firestone 1T15M-2 air spring as example, the dynamics stiffness of air spring with varying parameters was calculated with the dynamic stiffness nonlinear model and the dynamic stiffness linearied model respectively. The results show that air spring pressure, area of orifice, frequency of vibration, volume of auxiliary chamber all affect dynamic stiffness of air spring. Under the affection of each factor, the change curves of linearied model and that of nonlinear model are closed on the whole.
  • Xie ping;Du yihao
    . 2009, 28(2): 77-81.
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    Aiming at complex features in rotor system running process, such as non-linearity, coupling, un-steady abrupt states etc., a new method based on information entropy feature extracting algorithm is proposed here to combine rotor system power analysis and parameter recognition method. Information entropy feature and change rule of respond parameters in typical rotor fault states are analyzed, such as crack, rub-impact, crack and rub-impact coupling etc., and a wavelet neural network model is established which can realize the recognition and diagnosis of different fault states. The validity of the proposed method is demonstrated by theoretical analyzing and testing experiment of the rotor system.
  • Wu Xing;Chi Yilin;Chen Jin
    . 2009, 28(2): 82-85,1.
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    A feature mining model is set up for rotating machine fault diagnosis, based on data mining. There are two problems in tranditional reduction of rough set. One is uniqueness of the best reduction; another is to spend much time for calculating redcution. This paper proposes a feature reduction algorithm of rough set (RS) based on entropy importance and genetic algorithm (GA). In the end of this paper, a feature mining tool, RMFMiner, is designed and implemented. This algorithm is employed to reduce the faults of rotating machinery and UCI data set. It is proved to be effective.
  • Y. Wang;B. J. Wu;Z. X. Li
    . 2009, 28(2): 86-91.
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    The monitoring of fatigue stress is a key issue of structural health monitoring and safety assessment of long-span bridges. For a mass of data recorded by health monitoring system, daily data differ in thousands ways. Data in local period of time cannot reflect whole strain character and in different types of bridges such as a cable-stayed bridge and a suspension bridge, responses due to vehicle load and environment load are diverse. In order to acquire roundly actual running state and stress level, statistical analysis of vast data recorded is needed. This paper is aimed at investigating the feature of fatigue stress spectrum on the steel box-girders under service loading on the basis of strain history data recorded by structural health monitoring system installed on Runyang Suspension Bridge and Cable-stayed Bridge. The probability density function of fatigue damage increments of each bridge is simulated. The result of parameter estimation of half-year-samples shows that, relative accumulative damage increments are submitted to lognormal distribution in both bridges. In the same environment and vehicle loads, fatigue damage due to vehicle and temperature varying in suspension bridge is twice higher than that in cable-stayed bridge. Damage increments induced by strain history containing noise is twice higher than those after getting rid of noise, and damage increments coupling with temperature deformation goes beyond 30% of those without regard to temperature deformation. Therefore, controlling sternly impacts of noise and temperature deformation, and picking-up actual dynamic strain messages to evaluate fatigue state of long span cable bridges are needed.
  • LI Wu;YAO Wen-juan;HUANG Xin-sheng;LI Xiao-qing
    . 2009, 28(2): 92-95.
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    The mechanical character of acoustic conduction for tympanic membrane(TM) was concerned since ear disease often resulted in conductive deafness. As TM belongs to physiologic anisotropic material, different material value should be given to corresponding element in finite element method (FEM), therefore, computing error are aroused due to the mutation of material character in the interface of different element. In this paper, TM is analyzed based on the meshless method(MM), and the results of the MM are compared with that of FEM and experiments as well. The results show that meshless method (MM) is feasible in simulating physiologic anisotropic material, and it is also more effective when calculating the amplitude of TM.
  • Zhang Qiang;Zhang Pin;Zhang Mingtong
    . 2009, 28(2): 96-98.
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    The spectrum correction is a promised approach to overcome the fence picket effect of the fast Fourier transforms (FFT); however the formula for the triangular window case is not available from references. Two approaches were proposed here to the triangular window case. The first one makes use of the first and second highest spectral lines, but needs iteration to solve a nonlinear equation numerically. The second one makes use of the second and third highest spectral lines that locate at two sides of the first highest spectral lines. The simulation examples show that, first; both approaches have much better performance than the conventional direct readings from the spectral lines. Second, the error can be ascribed to the interference from the negative frequency component.
  • Zhao Wei;Zhang Yimin
    . 2009, 28(2): 99-101,.
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    This paper is based on the Kronecker algebra, the matrix calculus, the generalized second moment technique of vector-valued functions and matrix-valued functions, the matrix perturbation theory, the probability and statistics. The effective approach for stochastic response analysis for vibration transfer path systems in time range is presented, and the random responses of the vibration transfer path systems with uncertain paths,which include mass, damping, stiffness and position, are analyzed theoretically and computed numerically, and the mathematical expressions of the first order and second order moments for the random vibration response of random path systems are obtained. Thus, in practical project, the most uncertain factors in vibration transfer systems can be considered so as to give the effective way for solving the vibration transfer path systems with uncertain factors. The results of calculation are consistent with the results of Monte-Carlo simulation by the numerical examples.
  • ZHANG Guan-hua;GE Yao-jun
    . 2009, 28(2): 102-106.
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    Based on the reinforced concrete box girder continuous pedestrian bridge, through vibration characteristics test and in-depth analysis of its significant vertical and lateral vibration with the finite element theory considering to the structure as a whole, according to the results with field test and calculation. The inadequacy of the existing evaluation methods of pedestrian bridge was provided, the comfort and quality of the bridge were evaluated, and suggestions on how to evaluate the footbridge comfort were put forward. The practical referential value and effects for the design and maintenance of this type of bridge are predicted.
  • LIU Qiang;Wang Xin-wei;CHEN Ren-wen;Liu Lin
    . 2009, 28(2): 107-110.
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    The advantages and disadvantages of Finite Impulse Response (FIR) filter and Infinite Impulse Response (IIR) filters were discussed in this paper, aiming at the disadvantages, some improvements on FIR filter were made using orthonormal basis functions. The improved filter has both advantages of FIR and IIR filters. Then, the feedforward control algorithm based on the improved filter was designed. Finally, simulation analysis and vertical tail experimental verification for the new algorithm were given. The results demonstrated that the feedforward control algorithm in this paper has good performances such as fast convergence and robustness, so it is feasible to practical engineering application.
  • Wan Quan;Jiang Wei-Kang
    . 2009, 28(2): 111-116.
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    The classical normal-mode theory about the steady-state sound field in a room proposed by the famous physicist named Morse P M is perfect in mathematical derivation. However, some domestic researches cast doubt on this theory since its solution about the steady-state sound field in a room is purely composed of normal modes, and the direct sound cannot be found directly in this normal-mode solution. Is this solution the complete solution that contains both the direct sound and the reverberant sound, or just a partial solution without containing the direct sound field? In this paper, the basic assumption about the sound source in Morse’s normal-mode theory is shown correct by one rigorous derivation, which indicates that one arbitrary sound source in a room with the addition of its all image sources resulted from wall reflection can be represented by discrete normal functions. This conclusion may interpret some researcher’s doubts about this basic assumption. Moreover, the ray solution is derived directly from the normal-mode solution in spatial domain, which demonstrates that Morse’s normal-mode theory is absolutely equivalent to the acoustical image source theory of room acoustics, in case of rectangular shaped room with rigid walls. Hereby, the present author thinks that Morse’s normal-mode solution for the steady-state sound field in a room is complete.
  • Liu Zhengshan;Wu Zhigang
    . 2009, 28(2): 117-120,.
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    This paper presents a parameter identification method for nonlinear dynamic systems. Firstly, the derivative of the unknown parameters is introduced into the output error cost function of the system. Then, difference equations for the unknown parameters are deduced by using of the discrete variational principle, and solved simultaneously with state equation of the nonlinear system. Lastly, the to-be-identified parameters are guided from given initial conditions to their true numerical values with an iterative procedure. In addition, simulations for parameter identification of linear and nonlinear vibration systems are also presented to verify the proposed algorithm. Numerical results show that the parameter identification method is effective.
  • HU Hui;GUO Yuan-jun;ZHENG Min-yi
    . 2009, 28(2): 121-123.
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    The method of harmonic balance is used to calculate analytical approximations to the periodic solutions of the nonlinear oscillator in which the restoring force is inversely proportional to the dependent variable. Unlike Mickens method, the second order nonlinear singular differential equation is directly solved. The Fourier series expansion coefficients of the nonlinear restoring forces corresponding to the first and second order harmonic balance solutions are easily calculated using corresponding integrals. The nonlinear algebraic equations for the second order approximate solution are solved by using symbolic computation software. The percentage error of the first approximate frequency in relation to the exact one is 12.8%, and the percentage error for the second approximate frequency is lower than 1.28%. A comparison of the first and second analytical approximate periodic solutions with the numerically exact solutions shows that the second analytical approximate periodic solution is much more accurate than the first analytical approximate periodic solution. It is usually rather difficult to use the harmonic balance method to produce higher order analytical approximations because it requires solutions of sets of complicated nonlinear algebraic equations. This difficulty may be overcome to some extent by using symbolic computation software such as Matlab or Mathematica. The derivation in this paper can be considered as a typical example.
  • LUO Zhi-gao;LI Ju;Wang Xiang;FAN Bin-bin;GUO Xiao-dong
    . 2009, 28(2): 124-127.
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    Saw blade is a thin plank with a large area. During the high-speed sawing, the vibration of the saw is a universal phenomenon. In order to improve its sawing performance and reduce its working vibration, on the basis of vibration analysis of circular saw and theoretical study of experimental modal, compares the inherent characteristics of two different structures of circular saws and analyses the changes of lts natural frequency and vibration mode, as well as concludes the effects of opening an damping hole which affect the overall performance, especially for the vibration. Experiment shows that opening an damping hole can reduce the vibration effectively. All these can provide theoretical guidance for the structure and optimal design to reduce the vibration of the circular saw blade.
  • Feng Wang;Hong-Nan Li;Ting-Hua Yi
    . 2009, 28(2): 128-131.
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    Abstract: A seismic design approach is presented where the design procedure attempts to create R.C. buildings with a specified limited objective under a specified level of seismic intensity. The limited objective may be directly defined by limiting damage state of the weakness storey. The famous Park-Ang damage model, constant ductility inelastic response spectra and the conventional seismic design method are combined to determine families of structures whose initial strength and stiffness characteristics will ensure that the desired limited damage performance objective for each seismic level is, as closely as possible, achieved. Furthermore, the applicability of using the parameter for storey response of multiple degree-of-freedom structures is analyzed, and the corresponding equation is established. Finally, a design example shows that the design approach is feasible and accurate.

  • Zhu Liang-kuan;Ma Guang-fu and Hu Qing-lei
    . 2009, 28(2): 132-136.
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    Abstract: A dual-stage robust design method is concerned for the rotational maneuver and vibration stabilization of a flexible spacecraft. Based on the backstepping-based adaptive technique, a new attitude control law for attitude maneuvering is derived to control the attitude motion of spacecraft, in which the asymptotic stability is guaranteed by using Lyapunov analysis. Furthermore, for actively suppressing the induced vibration, strain rate feedback control compensator is designed using piezoelectric materials as additional sensors and actuators. Numerical simulations are performed to show that both maneuvering and vibration suppression can be accomplished effectively.
  • WANG Kao;TAO Jun-yong;CHEN Xun
    . 2009, 28(2): 137-140.
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    Abstract:The early Repetitive Shock (RS) machine has some inherent flaws, such as energy uniformity in frequency domain, lower energy below 2KHz, and so on. These characters confine the application of RS machine in the Reliability Enhancement Testing of electronic assemblies. However, many key technologies of RS machine have not been studied in detail in our country because of lacking technology stuff. In this paper, vibrators which are crucial components of RS machine are regarded as the specific objects. Based on the generating mechanism of exciting signals produced by vibrators, the analysis formulas of power spectrum density and low frequency energy of exciting signals are concluded respectively, the relationships between the parameters of vibrators and the low frequency energy of exiting signals produced by vibrators are studied deeply, and the effective approach to improve the low frequency energy of vibration signal produced by RS machine is put forward at last. In a word, the results of this paper are useful not only to the optimization design but also to the self exploiture of RS machine.
  • JIANG Da-qiang;CUI Li-shan;ZHENG Yan-jun;JIANG Xiao-hua
    . 2009, 28(2): 141-144.
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    Abstract: The mechanical properties and transformation behavior of NiTi shape memory alloy under constant strain constraint with and without vibration were investigated by using tensile test machine, CSM002 type material test equipment and differential scanning calorimeter (DSC). With increasing the amplitude of vibration, the two-stage recovery strain of NiTi alloy obtained during free heating decreased. With increasing the time of vibration, the recovery stress of NiTi alloy generated under constraint also decreased. The DSC results showed that the second reverse transformation peak temperature of NiTi alloy after vibration under constraint increased slightly during the subsequent heating. The transformation heat of the two reverse transformation peaks had an opposite change, the first one increased, while the second one decreased. All these results indicated that the recovery stress of NiTi alloy generated under constant constraint decreased due to vibration. These could be caused by microscopic plastic deformation during vibration.
  • XU Wan-hai;ZENG Xiao-hui;WU Ying-xiang;LIU Jia-yue
    . 2009, 28(2): 145-150.
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    Abstract: The tendon is simplified as nonlinear beam, the equations of motion and boundary conditions of a Tension Leg Platform (TLP) with a single tendon undergoing planar motion are obtained using Hamilton’s principle; employing two different tendon models(nonlinear beam and massless elastic spring) under different flow field conditions, the difference of the dynamic response of TLP was investigated; it is concluded that when the flow field conditions are different, the difference of the dynamic response of TLP using two different tendon models are quite obvious. Finally, explaining the reason why the difference of the dynamic response of TLP is so large.
  • PAN Xiao-yong;;CHAI Guo-zhong;SHANGGUAN Wen-bin;XU Chi
    . 2009, 28(2): 151-154.
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    Abstract An approach for calculating the dynamic characteristics of rubber isolators based on hyperelastic-viscoelastic model is investigated. The fundamental theory for frequency domain viscoelasticity is reviewed, and the experimental method for obtaining the viscoelastic parameters of rubber material is presented. A hyperelastic-viscoelastic model of rubber is proposed. The model parameters for viscoelastic model are obtained using dynamic simple shear test, and the model parameters for hyperelastic model are estimated using uniaxial and planer tension tests. The dynamic properties of the simple shear specimens for obtaining model parameters are calculated with the proposed material model. The calculated results match well the measured data. It is shown that the proposed methods for obtaining model parameters are effective. Taking a suspension bushing as a studying example, the dynamic and static characteristics of the rubber bushing with different diameter-shrinking are calculated, and the results agree well with the experiment. The proposed methods for estimating dynamic performances of rubber isolators in this paper can be used for calculating the dynamic properties of elastomeric mounts and bushings in automotive industry.
  • CHEN Jin-xin;WANG Yu
    . 2009, 28(2): 155-161.
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    Abstract: Through concluding the structure and characteristics of existing megnetorheological fluid dampers, a new type of magnetorheological fluid damper is proposed. The new one can be applied in the field of small size mechanical structure on the ground and the vibration isolation system in microgravity conditions. To verify the validity of the damper, there are six aspects discussed in the article, which are structure design, fluid design, magnetic circuit analysis, mechanical analysis, theoretic result and error analysis. It is found that it can be used when the damping force is small, and therefore, it widens the applied field of the magnetorheological fluid damper.
  • A DENOISING METHOD BASED ON HANKEL MATRIX AND SVD
    ZHANG Bo LI Jianjun
    . 2009, 28(2): 162-166.
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    Hankel matrix is combined with SVD for denoising fight flutter testing data corrupted by noise, in order to improve the precision of identifying flutter modal parameters. Firstly Hankel matrix made of measured data is used in SVD; then on the basis of the extent of mastering the statistic property of noise, two different methods respectively based on the statistic property of noise and a sudden change of singular value varying curve are used, the Hankel matrix is divided into two uncorrelated spaces, real signal space and noise space; finally the denoising singal is constructed with a average algorithm in real signal space. According to the results of numerical simulation and application in fight flutter testing data, the influence of different dimensions of Hankel matrix on division of spaces and denoising effect is analyzed and studied , feasibility and effectiveness of the denoising methed are showed.
  • Yao Tingqiang Chi Yilin Huang Yayu Tan Yang
    . 2009, 28(2): 167-171.
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    This paper brought out a new dynamic modeling and analysis method on rigid-flexible coupling of gear meshing. Based on Multi-body Dynamics Theory and Compliant Contact Dynamics, we proposed three dimensional contact dynamic model of gear meshing with factors such as flexible deformation between teeth and gear body, discrete contact surface with discrete involute profile and geometrical parameters. Apply numerical simulation and vibration analysis to research on contact vibration of gear meshing with the effect of single surface contact, double surface contact of meshing teeth and characteristics of rigid and flexible coupling. We got contact force and moment in full surface of meshing teeth and speed of driven gear and so on. The results revealed that the new method and dynamic model brought out in this paper could effectively deal with vibration response analysis of gear meshing with the effect of flexible and three dimensional contact of gear meshing. The method and simulation results provide basic data and valuable theoretical basis for further research on dynamics characteristics of gear transmission systems.
  • Tang Wei Shi ZhongKe
    . 2009, 28(2): 172-177.
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    A flutter modal parameters identification method using continuous wavelet transform is presented, which is applied to flight flutter testing excited by linear sweep. This method firstly employs fractional Fourier transform to filter noisy data, and then derives the impulse response from estimated frequency response function. Lastly, Continuous wavelet transform is used to extract modal parameter from impulse response. For reasons of local property of linear sweep in fractional Fourier domain and bandwidth property of Morlet wavelet, the proposed method is particularly efficient when dealing with significantly noisy data. The performance and the required conditions of using this method are discussed. Finally, the efficiency of this method is illustrated by real flight data.
  • PU Dayu ZUO zhengxing FENG Huihua LIU Xiao
    . 2009, 28(2): 178-180.
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    Research on room acoustics shows that the proper position for the absorptive material is the region with modes’ maximum pressure gathered. It is seen that the proper position contributes greatly to the flatness of the acoustic pressure curves. Based on the research, the method is proposed to improve transmission loss of air cleaner by placing absorptive material. Applied finite element method, a simplified air cleaner is modeled. The shape likes the rectangular room with smaller sizes. The mode analysis results shown that the modes’ maximum pressure occurs in the corners and the edges in the rectangular air cleaner. For improved the transmission loss, the absorptive material were paced in the corners and edges, it is seen that transmission loss improved greatly in mid and high frequency, and it is better than the method adding filter thickness. Applied this procedure to a real design of air cleaner, the absorptive material was placed in the position where the modes’ maximum pressure gathered. The results testified the procedure is reasonable and feasible; it can be applied in air cleaner design to increase the mid and high frequency of transmission loss of air intake systems.
  • Wang Sujuan Lei Zhengbao Zhao Jian
    . 2009, 28(2): 181-186.
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    For insuring the automobile collision process steady, and improving the degree of automation of energy-absorbing equipment, the energy-absorbing equipment added a new bumper system by cutting the screw thread teeth for automobile collision are aimed at, the control system with a microcontroller core is used, the collision energy can be calculated by the wheel-velocity from the sensors, according to the collision energy, the required energy-absorbing capability of energy-absorbing equipment can be adjusted. Thus, the energy-absorbing equipment will have different energy-absorbing capability for different vehicle speed, it is realized that the energy-absorbing capability can be controlled automatically.
  • Yu Ben Gang Lin Han Sun Yu Wu Yuan Xing Ou Jun Hui
    . 2009, 28(2): 187-190.
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    Based on accurate droptest simulation of microwave oven with explicit dynamics tool, the structure of the foam package was optimized and the optimum design was proved to be effective by virtue of virtual tests. It was shown that the optimum design provided better protection to the microwave oven, while the production cost was lowered due to less package material used.
  • KANG Xiaomin LI Guixuan
    . 2009, 28(2): 191-195.
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    According to work conditions of coal plough, considering stochastic cutting resistance by coal, single-degree-of-freedom nonlinear stochastic dynamic model of coal plough is presented , at the same time considering chain pretension and polygon effect. With certain parameters MATLAB/Simulink is used to get numerical solution and simulation. Each factor effect on the change of plough body velocity and chain tension is found. It indicates that cutting resistance and chain pretension have significant effects on plough body velocity and chain tension, and polygon effect of sprocket is smaller。It provides references for coal plough working and the reliability of chain.