25 January 2009, Volume 28 Issue 1
    

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  • Zhang YuanYuan;Xu KeJun;Xu Yaohua
    . 2009, 28(1): 1-3.
    Abstract ( 1709 ) Download PDF ( 1023 )   Knowledge map   Save
    In this paper, the dynamic linear model of sensor is founded based on the improved particle swarm optimization (PSO) algorithm and function link artificial neural network (FLANN). According to measurement data in dynamic calibration ,the weights of network is used to initialize one particle station of whole particel swarm when the training of FLANN has finished.Then the improved PSO algorithm is applied ,the global best particle station of particle swarm is the coefficient of sensor’s dynamic model what we need. The experiment results show that this approach has excellence of both PSO and FLANN, meanwhile it has better precision.

  • TAN Changjian; ZHU Bing
    . 2009, 28(1): 4-8.
    Abstract ( 1446 ) Download PDF ( 913 )   Knowledge map   Save
    Abstract: To investigate the characteristic of coupled vibration of high speed train and bridge under seismic excitation, the effect of the railway track irregularity, different seismic excitation were compared and investigated by analyzing the coupled vibration of the JR300 high speed train-bridge system under seismic excitation. The results show that the vertical acceleration of train will be increased and approach the limit value ,but the vertical response of the bridge will not be affected obviously ,when the railway track irregularity is considered. The level of influence of the different seismic excitations is much different.
  • Xiaodan SUN and Jinping OU;
    . 2009, 28(1): 9-13.
    Abstract ( 1416 ) Download PDF ( 935 )   Knowledge map   Save
    Abstract: As a key problem of the vibration-based damage detection, many damage indexes was developed in recent years, but a systematic and effective method to evaluate those damage indexes is not available till now. Therefore, a new assessment method including sensitivity analysis of damage indexes to stiffness, robustness to noise, ability of correct identification based on incomplete information and capacity of indicating locations of damage precisely is proposed in this paper to reflect various main problems in the damage detection for guiding choice of the proper damage index. The numerical example results show that conclusions drawn from proposed method as a foreordain way are consistent with common conclusions of previous study, which means it has strong reliability. The assessment method containing four indexes to quantify characteristic of indicators has bright prosperity in large scale structures for all the pacing factors in practice are considered.
  • Li Jin-hua Li Chun-xiang Shen Jian-hong
    . 2009, 28(1): 18-23.
    Abstract ( 1637 ) Download PDF ( 499 )   Knowledge map   Save
    Abstract: For the numerical simulation of non-stationary fluctuating wind velocity, the critical factor is to obtain time-varying power spectra (referred here to as the TVPS). According to the theory of evolutionary power spectra (referred to as the EPS), TVPS, namely EPS, can be acquired through this way using a deterministic modulating function (referred to as the DMF) to modulate a known power spectra of stationary fluctuating wind velocity such as Kaimal spectra, Davenport spectra or Simiu spectra. But there is not a DMF that can be universally acknowledged currently, so that the simulation of non-stationary fluctuating wind velocity can be scarcely paid attention to. In order to acquire a DMF to stimulate the non-stationary fluctuating wind velocity, firstly this paper assumes that a non-stationary fluctuating wind velocity during the time is made of segments of stationary fluctuating wind velocity with a very short time ; then, TVPS can be obtained by connecting each power spectra from segments of stationary fluctuating wind velocity when ; finally, DMF has been deduced through the relation that TVPS is equal to EPS, and the simulations of the non-stationary wind velocity for three spatial points has been carried out using harmony superposition method.
  • YANG Ziyou;GU Jincai;CHEN Anmin;Xu Jingmao
    . 2009, 28(1): 24-27.
    Abstract ( 1546 ) Download PDF ( 1065 )   Knowledge map   Save
    Abstract: The different influence degrees of anti-blast of wall rock reinforced by two kinds of rock bolts which have the different length around two underground openings are studied by the method of model experiments under the effect of explosive stress waves produced by focus charging. The distinctions produced by the different length of the rock bolts of stress in wall rock,surface strain of two underground openings,the roof-to-floor relative displacements of two underground openings,accelerations of roof, floor, ribs and macroscopical damage forms are compared and analyzed. The results indicate that when the wall rock of underground openings is reinforced by the longer rock bolts, the reinforcement range can be enlarged and the stressed state of wall rock of vault can also be modified, the distortion of the wall rock is restricted efficiently and the stability of underground cavern is maintained in good condition. When the rock bolts’ intervals reach a given size, the damage cracks are produced and extended outside the reinforced zone The experiment’s results provide the references of the reinforcement methods of wall rock of protection projects and tunnels.
  • Zhang-Limin Dong-Tiejun
    . 2009, 28(1): 28-31.
    Abstract ( 1457 ) Download PDF ( )   Knowledge map   Save
    Abstract: Dynamics model of railway vehicle systems are presented with constant differential equations, expressions of eigenvalue parameters sensitivity of a railway vehicle has been deduced. Eigenvalue sensitivity analysis are executed about the railway vehicle with 6-DOF. The elements in stiffness matrix which influence eigenvalues have been discussed. The result can be used to guide to modify suspension parameters, which provide an effective method of dynamic design on railway vehicle suspension system.
  • Ning Xiang-liang Tan Ping Ye Mao Zhou Fu-lin;
    . 2009, 28(1): 32-35.
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    Abstract: Semi-active control algorithm for MR damper based on adaptive fuzzy control (AFLC) is proposed in this paper for dealing with nonlinearity and uncertainty of structure and external loadings. Equivalent control law is approximated by the adaptive fuzzy control system by adjusting the membership functions of conclusion part in rules on line. Lyapunov stability theorem is employed to design the adaptive law. AFLC is integrated with clipped optimal control algorithm for MR damper. Benchmark control problem for a seismically excited highway bridge developed recently is simulated, results show that active and semi-active control strategy based on AFLC reduce response quantities of structure effectively when suffered to seismic loadings with different soil type and different amplitude, semi-active achieve almost the same control performance of active control, this superiority promises a very high value in popularization and application of MR semi-active control strategy.
  • CAO Shu-qian;FU Yao-dong;HE Wei-bo
    . 2009, 28(1): 36-41.
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  • Yang Yujun; Chen Jianjun
    . 2009, 28(1): 42-45.
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    Abstract: In order to increase the computational efficiency of the interval eigenvalues, the monotone property of the design parameters of the structure matrix is studied firstly. Then a fast methodology for calculating the eigenvalues of structure matrix with interval parameters is put forward, which is based on the Rayleigh quotient and the theories of the interval mathematics. As the deviation of the interval factors of the design parameters are similar and close to unity, it shows that the computational error of the fast methodology are determined by the dispersion between the interval factors, and the error come up to zero if all the interval factors are equal. Finally, two numerical examples are given, which proves that the presented method is more feasible and efficient than the global optimization algorithm and the interval stepped dividing method for engineering applications.
  • Xu Jinyu;;Li Weimin;Fan Feilin;Bai Erlei
    . 2009, 28(1): 46-49.
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    Abstract: The industrial wastes, slag and fly ash, were used to produce geopolymeric concrete (GC). The impact mechanical properties of GC, including compressive strength, deformation and energy absorption capacities, were studied using a 100-mm-diameter split Hopkinson pressure bar (SHPB) apparatus. The experimental results show that the impact properties of GC exhibit strong strain rate dependency, and the transition point from low strain rate sensitivity to high sensitivity occurs at 42.7 s-1. The critical strain decreases with the increase of dynamic compressive strength. GC is a type of quasi-brittle material. The energy absorption property should be paid more attention to than strength or deformation capacity.

  • FANG Pingzhi;;DU Mingxia ;GU Ming
    . 2009, 28(1): 51-55.
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    Abstract: By virtue of a code for solving aeroelastic problems developed by the authors based on loosely coupled method, vortex-induced vibration of an elliptical cylinder at high Reynolds number is simulated. The ratio of major to minor axis for the elliptical cylinder approaches to 2, and the incident flow is perpendicular to major axis. Numerical results show that the lateral vibration dominates the vibration of the cylinder although the streamwise and lateral dynamic parameters are different. The vortex-induced vibration of the cylinder with two degree-of -freedoms exists streamwise and lateral lock-in phenomena, and with the increasing of the reduced velocity, the vortex shedding mode switches from out-of-phase 2S to in-phase 2S, which are the same as those for circular and square cylinders.

  • SU Chang-qing;ZHANG Yi-min;LV Chun-mei;WEN Bang-chun
    . 2009, 28(1): 56-59.
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    Abstract The relation criterion of difference not beyond special value of the natural frequency and driving frequency is proposed. The reliability mode and the safety probability of the rotor system are defined as series mode, and the frequency reliability analysis method for avoiding the resonant is carried out. The reliability sensitivity analysis method for resonant problem of the rotor systems is studied by using the random perturbation technique, reliability theory and sensitivity technique. A numerical example has demonstrated that the proposed method is efficient and accurate.
  • Yanhui Wei;Jieqiong Xu;Longsheng Huang
    . 2009, 28(1): 60-63.
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    Abstract In this paper, a two-degree-of-freedom vibro-impact system is investigated. By using a constant phase surface in the pre-impact instantaneous as the Poincaré section and introducing the local maps, the Poincaré section is constructed and the corresponding Jacobi matrix is obtained. Using the Gram-Schmidt ortho-normalization and the iterative method, we obtain the method for calculating the spectrum of Lyapunov exponents of the vibro-impact system. The numerical simulation shows that the sequence of the spectrum of Lyapunov exponents of periodic attractor and chaotic attractor can converge well. The numerical simulation also shows that the largest Lyapunov exponents agree with the attractors behavior observed in the corresponding global bifurcation diagram.
  • ZHANG Yi-min;ZHANG Shou-yuan;LI He;WEN Bang-chun
    . 2009, 28(1): 64-67.
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    Abstract:There are lots of rotating machines in mechanical engineering field,which make input excitations don't meet the requirement of operational modal analysis(OMA).A simple and effective method of distinguishing the forced harmonic resonse from the measured vibration signal was presented through analysis of atatistical properties of stochastic signal and harmonic signal.This made OMA applicable to the situation existing harmonic excitation.An OMA and an experimental modal andlysis of a steel plate excited by a motor were carried out the harmonic components were succcessfully separated from the overall response with the proposed method.The comparison of the two experiment results proved the effectiveness of this method which provides a new way to distinguish the pseudo modes in an OMA.

  • He Qinxiang Tian Xiaohong Song Dan
    . 2009, 28(1): 68-71.
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    The seismic performance evaluation of a high-pier long-span continuous rigid frame bridge is an interesting and formidable issue in seismic analysis of bridges. An elastic-plastic seismic response analysis was put forward based on its characteristics. The simulation of the seismic response of bridge under severe earthquake was carried out by using the plastic hinge element in the text and finite element program on hand. With the intensity of earthquake up to which caused the fracture of the bridge, the elastic-plastic seismic response analysis of a high-pier long-span continuous rigid frame bridge in the west was realized, and some available conclusions such as the failure mode, the greatest intensity that bridge could afford were got, which were useful to the seismic design.
  • XIA Yu-hong;JIANG Hong-yuan;WEI Hao-dong;YAN Hui;А.М.Уланов
    . 2009, 28(1): 72-75.
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    The shock protection characteristics of Metal Rubber isolator are studied theoretically and experimentally. Based on the primary loading line and the hysteresis loops of isolators, the calculation method of maximum response of nonlinear shock protection system with dry friction damping on the short and long shock impulses is proposed. The stepping integration of the maximum response is programmed by using Matlab software. The effects of the structural parameters, the load, and the shock acceleration level on the shock protection performance of metal rubber isolators are researched experimentally to testify the theoretical calculation method. The results are beneficial to the engineering application of metal rubber isolators.
  • Hu JiaShun;Feng Xin;Zhou Jing
    . 2009, 28(1): 76-80,8.
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    Fatigue crack is one of the main damages existing on the structural members, which can lead to structure failure due to repeated loads. The nonlinear dynamic characteristics of a cantilever beam with a non-propagating asymmetric fatigue crack subjected to a harmonic load at the tip are studied. A breathing crack model is introduced to describe the nonlinear dynamic behavior of fatigue crack and can be simulated as a frictionless contact plane problem. Meanwhile, the quarter-point element is used to simulate the crack tip effects. Based on the proposed model, the effects of various factors, such as the excitation frequency, crack depth and crack position on nonlinear dynamic characteristics are discussed in detail. A relatively amplitude of system frequency is proposed to detect the crack severity based on the analysis of the sub-harmonics and super-harmonics at the crack interfaces. The results provide theory and reference for damage identification of cracked structure at some extent.
  • WANG Zheng-ying;XU Yong-gang;LI Qiang;WANG Tai-yong
    . 2009, 28(1): 81-83.
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    Aiming at nonstationary property of mechanical vibration signals,Empirical mode decomposition(EMD) can adaptively decompose signals to several intrinsic oscillation modes,and different mode contains different status information of an equipment.By means of approximate entropy(ApEn),the complexity of the original signal and its intrinsic oscillation modes can be quantified,thereby the intrinsic mode comlexity of mechanical vibration signals can be quantitatively evaluated. One can use this method to understand the complex dynamic behavior of rotors ,and monitor the change of running conditions of a mechanical equipment to prevent deterioration of fault.The engineering application results showed that this method can extract the fault information of a mechanical equipment ,and provide an effective technology for condition monitoring and fault diagnosis of a mechanical equipment.

  • LIU Qi-neng
    . 2009, 28(1): 84-87.
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    For studying the influence of impurity absorption on the 1D photonic crystal filter, the complex wave number is adopted, the transfer matrix of the impurity-doped 1D photonic crystal is inferred ,and variety feature of attenuation coefficient with the transmission coefficient in the impurity-doped 1D photonic crystal is calculated. Worth biggest of the defect mode lowers quickly with the attenuation coefficient increment, FWHM of the defect mode increases with the attenuation coefficient increment. The worth biggest and FWHM of defect mode lowers with the impurity thickness increment. Have to consider the absorption of the impurity quality while design filter, the attenuation coefficient should less than 0.0005k and the impurity thickness should less than a wavelength.
  • Chen Bo-wang;WANG Hai-bo
    . 2009, 28(1): 88-91,9.
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    Combining the precise integration method and Adams-Bashforth-Moulton’s predict-correct multi-step method, we put forward a precise integration method for nonlinear dynamic equations, which is implicit predict-correct, four order accuracy and multi-step method avoiding calculating the inversion of the state matrix. Based on the advanced multi-step method of nonlinear precise integration, a new applied numerical integration method for pseudodynamic test of structures is raised. Its accuracy is superior to center difference method by enlarging time step twice or fourfold and its stability is better. Thus, the testing work would be largely reduced. Finally, a pseudodynamic test of combined tube structure has been executed with the explicit multi-step method.
  • LI Yiliang XIE Danmei ZHANG Hengliang QIAN Yong ZHAO Xianbo DONG Chan
    . 2009, 28(1): 92-94,1.
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    In order to study the influence of the transverse crack models on the shafting`s torsional shearing stress calculation, this paper deduces and analyzes the mode Ⅲ stress intensity factor in the crack deepest point of the transverse straight crack model and the transverse semi-elliptical crack model. The calculating result indicates that: the relative distinction of the torsional shearing stress by using these two models might be great and the biggest distinction can reach about 60%. But in a particular range, the distinction is rather small. In addition, this paper has defined a critical relative distinction concerning the torsional shearing stress of the two models, and then confirmed the corresponding critical elliptical parameters with different crack depth ratios. At last, this paper has fitted an equation, with regard to the critical elliptical parameters under different crack depth ratios, so as to build up a theoretical background for scientifically selecting models.
  • Shi Yu;Xiao Yougang;Kang Zhicheng
    . 2009, 28(1): 95-98.
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    A series of models, namely the vehicle-track coupling dynamics model, the finite element model of train head, the acoustical boundary element model of passenger room of high speed train, have been established. The interior noises of passenger room caused by track irregularities have been calculated, and the distribution characters of the internal noise of passenger room have been ascertained and reached the following conclusion: The noise in passenger room changes in the range of 61.9~69.6 dBA. At the frequency of 40 Hz and 200 Hz, the sound pressure levels in passenger room are greater. To reduce the biggest noise in the passenger room, measure must be adopted at 40 Hz and 100 Hz, which are the decisive frequencies. At 40 Hz, it is better to add stiffened ribs or a layer of damping material on the panel with biggest acoustics contribution; At 200 Hz, it will more suitable to coat with viscoelastic layer on the panel with the biggest acoustical contribution.
  • LIU Hui-xun;DING Hong-yan
    . 2009, 28(1): 99-103.
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    Cavity beneath slab, which is the chief reason of the cement concrete pavement slab rupture, is the general disease of the concrete pavements. After transient impact by hammer, the vibration frequency of slab relates to the destruction or not, the destruction degree, etc. Therefore, vibration-frequency-based method, namely vibrating image, on cavity beneath concrete slab detection is presented. The fundamental principle of the vibrating image detection is introduced. The modal analysis and model experiment of slab are conducted, and its vibration characteristic in different conditions is obtained. Based on the factor analysis on vibration frequency and the frequency spectrum analysis on transient vibration signal of slabs, the fact that the slab vibration frequency is sensitive to cavity beneath slab is obtained. Thereby, the vibration-frequency-based detection criterion of cavity beneath slab is established. It is concluded that, if the cavity beneath slab is serious, the natural frequency is less than 50 . If the subgrade can support the slab well, the natural frequency is more than 200 generally. The vibration signal of slightly cavity beneath slab is between two conditions above, the natural frequencies both less than 50 and more than 200 exist at the same time.
  • LIU Shu-yong;ZHU Shi-jian;YU Xiang
    . 2009, 28(1): 104-108.
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    Based on the phase space reconstruction of chaotic time series, an adaptive prediction method of chaotic vibration is presented and the adaptive algorithm of model parameters is derived. The effect of the neighborhood size, embedding dimension on the prediction is studied and results show that when the parameters are reasonable, the method can be use to predict chaotic time series efficiently. Finally, this method is applied to predict experimental signal of the X- type nonlinear vibration isolation system successfully.
  • Chen JianGuo
    . 2009, 28(1): 109-111,.
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    If the ratio of signal’s energy and frequency is much larger than some value, this paper presents the new integrated method of Empirical Mode Decomposition and Independent Component Analysis. It can seprate the Overlapped information, decompose accurately the Intrinsic Mode Functions. recover the character of the Intrinsic Mode Function, and perfect the deficiency of Empirical Mode Decomposition’s capability. This method can ensure the validity of Empirical Mode Decomposition. The feasibility of this method is demonstrated by the application of simulated signals and practical signals. The results show that this method has wide application prospect in the condition signal procession and fault diagnosis of mechanical equipment.
  • Fang Rui;Xiao Xinbiao;Jin Xuesong
    . 2009, 28(1): 112-117.
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    In order to investigate the effect of wheel web shape and contact position on the sound radiation characteristic of the railway wheel, a hybrid FEM-BEM vibro-acoustic model is developed. A 3D solid finite element model (FEM) is developed. In the FEM model, the eigenfrequencies and mode shapes of the wheel are calculated by using a “Block Landzos” method. The frequency responses of the wheel due to a normal unite force excitation are determined using modal superposition method. The dynamic response is used as velocity boundary condition in acoustic boundary element model (BEM) for noise radiation analysis. In the numerical simulation, three types of web shapes (s-type, straight-type, and corrugated-type) and three contact positions (flange contact, nominal contact, and field side contact) are considered. The numerical results indicate that the web shape and contact position have a significant effect on the sound radiation of the wheel. Moreover, the sound radiations from different web shapes of wheels are different for the same contact position. The investigation can help optimize design of low-noise railway wheel. The theory and the algorithm of the artificial neural network are applied in the research of the technique and the composition, the gross mass fraction of element, the thickness of surface alloying layer as well as the absorption rate is built. The calculation results are in good agreement with the experimental results.
  • Lin Tengjiao;Rong Qi;Li Runfang;Shao Yimin
    . 2009, 28(1): 118-122.
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    Considering the effect of the radial load and rotational speed of bearing, the finite element model for dynamic contact problem of deep-groove ball bearing was established by the software--ANSYS/LS-DYNA. Based on explicit dynamic finite element method, it adopted fully integrated element algorithm to control the hourglass and set the mass scaling time step size to reduce the calculating time. A dynamic contact analysis of the deep-groove ball bearing was made with the same radial load and different rotational speeds imposed on inner ring, and obtained the dynamic response of bearing and the stress distribution of the rolling element during the running process. The maximum and the minimum linear speed of the rolling element occurred at the contact point with the inner ring and the outer ring respectively. The dynamic stress between the rolling element and inner ring was basically the same, while the dynamic stress between the rolling element and outer ring increased with the increasing of the rotational speed. The reaction force fluctuation between the rolling element and the outer ring was bigger than that with inner ring, while the force between the rolling element and the cage was relatively small. The Research showed that ANSYS/LS-DYNA software is a very useful tool for analyzing dynamic contact of rolling bearing in motion process.
  • Xu Wen;Ye Jihong;Shan Jian
    . 2009, 28(1): 123-130.
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    The fluid-solid interaction can not be neglected in the analysis of the membrane structures due to its sensitivity to wind. The flow is treated as incompressible and potential in this paper. Firstly, the wind pressure on the structure is determined by means of the boundary element method (BEM). Afterwards, the structure deformation under the pressure of wind is calculated and then the shape of the membrane structure is modified. Subsequently, using the BEM to calculate the wind pressure, one obtains the deformation of the structure under the pressure that time. This procedure is repeated until the solution is satisfied the convergence criteria. Typical examples have been analyzed which illustrate the method and demonstrate its efficiency and accuracy as compared with other numerical methods. The analysis of the wind-structure interaction has been performed with the method mentioned above, by considering parameters, such as rise-span ratio, prestress and the wind velocity. The results have practical application in wind resistant study and engineering.
  • SHI Liang;HE Lin
    . 2009, 28(1): 131-133.
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    According to the modified Dahl model, the method of integral energy is given to derive the relationship of applied current and the model parameters. A method for evaluating the model parameters is presented to transform the nonlinear parameters identification for hysteretic system to the linear parameters identification and it exhibits high precision.
  • Hu Li Huang Qibai Wang Jianliang
    . 2009, 28(1): 134-137.
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    The particle damping technology has been used successfully in many fields for vibration reduction. However, it is difficult to predict the damping characteristics due to complex collisions in the dense particle flow. In this paper, the micromeritics model is established here to study the effect of the geometry on the characterization of particle dampers. The nonlinear characteristics of particle dampers are also studied experimentally to model the nonlinear damping of particle dampers as equivalent dampers that can be applied directly to engineering structures at the design stage.
  • wang ping li xiaoliang liu qiang
    . 2009, 28(1): 138-142.
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    On the base of magneto-elastic theory and the theory of random vibaritions of continuous systems with distributed parameters, the magneto-elastic random vibration equations of a random-current-carrying plate in a magnetic field is obtained. And the Lorentz force and torque are expressed in the concrete form. The thesis analysis the random displacement response of the elastic body on the assumption that the coupled part of Lorentz force is a kind of damp of the elastic body and the other Lorentz force is random distributing load .And as examples of a rectangular plate simply supported at each edge, the mathematical expectation, correlation function, power spectral density function of the random displacement response of the elastic body with the stationary or nonstationaty random current in the magnetic field are derived. At last, through specific examples, as examples of elastic body with stationaty random current of white noise in the magnetic feild, calculate the power spectral density function and the mean square value function of the random displacement response. The changes of the curve indicate the effect on the random displacement response of the coupled part of the Lorentz force.
  • Li Xiangbin Li Guo Li Xueren
    . 2009, 28(1): 143-145.
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    Cockpit voice recorder (CVR) in aircraft records many cockpit voices, such as speaker voices, noises, background sounds with special meanings. Cockpit voices’ complexity exacerbates analysis difficulty through traditional differentiating & hearing methods, so that more cockpit voices’ characteristics are not resolved easily. According to the shortage in cockpit voice hearing and analyses by traditional short time Fourier transformation (STFT), the united time-frequency analysis, which is introduced into airplane cockpit voice
    analyses, expands CVR analysis method. Compared with these methods, time-frequency distributions and reassigned versions each has its strong point at time-frequency resolution and immunity of cross term interference, and are adapted to analyze non-stationary cockpit background sounds, and offer a method as a reference for flight accident investigatations.
  • PENG Wei LI Jian-zhong
    . 2009, 28(1): 146-151.
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    Based on non-classical damping problem during simplified analysis process of seismic response for isolated continuous girder bridges, taking lead rubber bearing(LRB) for example, direct integration time-history method and modal time-history method after forced uncoupling are employed to study the effect of non-classical damping on seismic response, and structural modal damping ratios are obtained from equivalent damping ratios of isolators according to linear hysteretic damping model, then compared with non-linear time history analysis, simplified analysis based on response spectra method is adopted to calculate the seismic response. The results indicates that non-classical damping produced by seismic isolation devices changes the overall damping characteristics of structure and its contribution to structural seismic response rises with increased equivalent modal damping ratio, and seismic response obtained by simplified analysis after equivalent linearization of isolators is not safe for lower estimate of pier force and beam displacement.
  • MEI Zhiyuan LUO Zhong ZHOU Xin MAO Liang
    . 2009, 28(1): 152-155,.
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    The eccentricity vibrator system and electromagnetic vibrator system. was designed through the analysis of vibration isolation theory. The relationship between vibration level difference and insertion loss was discussed in different vibrator system. By the vibrator experiment of the vertical brace sandwich base and the crooked brace sandwich base, the property character of composite sandwich base was analyzed. The isolation effect of sandwich base was discussed in different vibrator. The result indicated that the sandwich base had superiority vibration isolation effect and can restrain the resonance in high frequency.
  • HAN DeBao SONG XiGeng
    . 2009, 28(1): 156-160.
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    The experimental research of dynamic characteristics of rubber isolator was conducted, and the signals which collected from experiment were analyzed by using FFT. The neural net that the feasibility was verified by the curve reconstructed method, was used to fit the experimental curves. Based on the data exporting from the neural net, the parametric identification for polynomial model to describe the dynamic characteristics of rubber isolator was processed by employing the method of optimized least square. It is indicated that the relationship between damping, stiffness and the amplitude, frequency is surface. The least square method was used to fit the surface of damping and stiffness, and the constitutive relationships for describing the damping and stiffness of rubber isolator was obtained.
  • Mao Yongfang Qin Shuren Qin Yi
    . 2009, 28(1): 161-165.
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    Reassigning the spectrogram is able to enhance the time frequency concentration of the spectrogram and reduce the cross-term, however, it causes great estimation variance. Multiple window spectrum is of satisfying estimation accuracy, while poor of time frequency concentration. Combining the two methods enables to further enhance the readability of the spectrogram. The method of combined reassigned spectrogram and multiple window spectrum is adopted to analysis the fault signal of a shaft, a gear box and a bearing, and the results is compared with that of reassigned spectrogram, which shows the method is of good time frequency concentration, small estimation variance, able to remove the noise in the signal and reduce the cross-term, hence doing better in mechanical fault diagnosis.
  • wang zhifeng zhou xianyan yan banfu xiao yunfeng
    . 2009, 28(1): 166-169.
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  • Wan shuting Lv Luyong He Yuling
    . 2009, 28(1): 170-173.
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    In order to overcome the shortcomings of the traditional wavelet transform in the signal decomposition, and according to the undecimated discrete wavelet transform theory, an undecimated discrete wavelet transform method based on lifting scheme is put forward. Then according to the fault characteristics of rolling bearings, a rolling bearing fault diagnosis method based on the undecimated discrete wavelet transform of lifting scheme is proposed. Moreover, an experiment on the ADBE-56-N4 AC machine is taken to actually measure the vibration signal of the 6305 rolling bearing under the condition of normal operation, the outer ring fault and the inner ring fault. The results shows that this method can diagnose the rolling bearing faults more effective than the traditional wavelet transform.
  • Fan Xuanhua Hu Shaoquan Zhang Zhixu Song Qiong
    . 2009, 28(1): 174-176.
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    Random vibration test simulation of a specimen with rubber vibration isolations was carried out based on the integral finite element model of a vibration, a clamp and a specimen. Obvious attenuation phenomena of responses in mid and high frequency areas over several hundred hertz were found for thin shells and rubber vibration isolations during simulation process. Further investigations indicate nonlinearity of dynamic stiffness in the mid and high frequency areas is the main factor that results in the attenuation. Then the dynamic stiffness of the thin shells and the rubber vibration isolations were updated combined with real test results. The updated results show that dynamic stiffness of the thin shells and the rubber vibration isolations is enhanced with the increase of frequencies, the trend of which was described by graphs. Based on the updated dynamic stiffness, the attenuation problems were solved and the simulated results are in accordance with the real test ones.
  • YI Tinghua LI Hongnan GU Ming
    . 2009, 28(1): 177-181.
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    To satisfy the requirement of wind resistance for the Shenyang Tiexi gymnasium, the wind tunnel test for wind pressure distribution is performed. Firstly, the technical parameters used in the test and the basic data processing methods are introduced in detail. Then, the contour curves of mean wind pressures for the most unfavorable conditions, which show clearly the characteristics of wind pressure distributions on the roof of the structure, and the variations of wind pressure for typical measuring points under different wind angles are given to analysis the effect of with and without the interference of the surrounding building. The results show that the upstream interfering building may decrease the mean wind load on the roof of the gymnasium, so do the downstream interfering building, while the parallel interfering building may increase the load. The conclusions may be used as reference for the analysis of wind induced effect of the similar structures.
  • XU Xueyong WANG REN WU Jingping SUN Xuejun 
    . 2009, 28(1): 182-185.
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    This paper aims to monitor and analyze the vibration effect due to squeezing silt by blasting according to engineering example at the special terrain. Results show that the measured vibration velocity is in the safety-judging standard that norm demands, and the decay law of blasting shock wave obtained by linear regression method is mostly consistent with that of norm. At the same time, the results discover that the main vibration frequency of blasting shock wave which is due to squeezing silt by blasting is low. This means that spread medium has great decay action on shock wave, and the high frequency of shock wave measured decays quickly. Natural frequency of blasting area surroundings is on average lower than 10Hz, so in order to avoid the damage caused by resonance, it is necessary to strictly control blasting vibration velocity and increase the numbers of times of monitoring.
  • JIANG Xianghua ZHANG Hui
    . 2009, 28(1): 186-190.
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    Violent vibration with component broken appeared in the scuttles of a thermal-electric power station. By the help of the industrial accident record and on-spot inspection, transient response induced by some kind of impaction was initially deduced to be the cause of this vibration. Using FEM, transient dynamic analysis as well as static analysis was carried out to study this scuttle system. Result shows the scuttle vibrates and breaks in the same way with the actual ones, which reveals that the initial deduction is reliable. Result also indicates this broken is caused by the stiffness asymmetry in the braced frame. Based on this, it was inferred that the vibration was excited by the impulsion to the scuttle of the falling coal which is previously jammed and now collapsing. Many factors of coal jamming were analyzed, including the structure features, reduction of area, coal humidity and friction factor. Two treatments, high polymer material hyperbolic inner lining and anti-drop device, were finally presented in order to reduce the impaction and vibration