25 May 2009, Volume 28 Issue 5
    

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  • an QIU Mian-hao WANG Zi-ying AN Gang LIU Dong-li
    . 2009, 28(5): 1-5.
    Abstract ( 1366 ) Download PDF ( 823 )   Knowledge map   Save
    Abstract:, A method was proposed based on combination of KPCA with ECOC-SVM to enhance accuracy of fault diagnosis of gear. Firstly, original sample vector was preprocessed based on KPCA to eliminate noise and redundancy. Secondly, some uncorrelated SVMs were constructed based on ECOC matrix to improve whole performance of fault tolerant of classification model. Finally, the new vector got through KPCA was used as training and testing sample of ECOC-SVM to recognize different fault state of gear. The result shows this method can extract better sample vector for classification, and has better effect of fault diagnosis.
  • LEI Zhengbao;PENG Zuo;LIU Lan;HOU Shijing
    . 2009, 28(5): 6-9.
    Abstract ( 2370 ) Download PDF ( 789 )   Knowledge map   Save
    ABSTRACT:The road with a Curve radius less than 400 meters has the highest rate of traffic accidents, and we have to use the straight-road barrier on curve-road for the lack of research on curve -road barrier. To change this unreasonable situation, we must obtain the optimal parameters of concrete barrier with curve radius of 400 meters. Therefore, this paper takes barrier with safety grade of the SS into account base on the research of parameters of the NJ-concrete-barrier. The total mass of research bus model is 18 t, the collision speed is 80 km / h, and the collision angle is 20 °, based on the ETA / VPG and LS-DYNA software platform and " vehicle – barrier – curve-road" integration vehicle - road system dynamics model, the research use combination of orthogonal experimental design methods and dynamic explicit finite element method. The research sets the rear wheel elevation as criteria for the evaluation and creates six cross-section shape design variables. The application of L25(56) Orthogonal table for simulation and the using of SPSS statistical package helps the variance analysis of simulation results, we find out the results of various factors on the degree of influence, then determine optimal parameters of concrete barrier. 25 Groups of the simulation results show that overturn accident occurred to all when large bus collide concrete barrier with a radius of 400 meters, and then bus run out of concrete barrier and fall down to cliff outside of the barrier. The optimal design results showed that the increasing in height of the concrete barrier is a important way to protecting bus from running out of barrier, and a concrete barrier with reasonable parameters can control the overturn-accident occurs inside, then avoid the occurrence of major badly-damaged accidents. The six cross-section variables which determined the sharp of the barrier have impact on the accident, the existence of priorities as following: height of lower slope> height of flange at the bottom > height on the upper slopes> top width> width of the lower slope > width of the upper slope, and the influence of height factors is greater than that of width, the height of lower slopes impact more significantly than that of the upper.
  • Yang Zhichun Yan Linjuan
    . 2009, 28(5): 10-12.
    Abstract ( 2102 ) Download PDF ( 636 )   Knowledge map   Save
    Abstract: In this paper, we aimed at the impact responses of human body during aircraft force-landing by studying the seat-to-body transmissibility using the 11-DOF seated human body model. The impact responses of human body under the vertical impact excitation are examined by numerical simulation approach. The results show that the lumbar spine would be more easily injured than the other part of the body because of more evident response. Moreover, it was indicated that the passenger seat stiffness had obvious influence on the responses of the human body under vertical impact excitation and the appropriate design for the passenger seat stiffness can reduce the impact responses of human body significantly.
  • Cheng Junsheng;Zhangkang;Yang Yu;Yu Dejie
    . 2009, 28(5): 13-16.
    Abstract ( 1659 ) Download PDF ( 1101 )   Knowledge map   Save
    Abstract A new nonstationary signal analysis method,namely, the local mean decomposition (LMD) is introduced in this paper. By using LMD, any complicated signal can be decomposed into a set of product functions whose instantaneous frequencies own physical sense and each of which is a product of an envelope signal and a purely frequency modulated signal, thereby the complete time-frequency distribution of the original signal can be obtained. In this paper, firstly the LMD method is introduced, and then the simulated signal is analyzed by LMD and satisfied results have been obtained. At last, the LMD method is compared with EMD method and the results indicated that the LMD method is superior to the EMD method in some respects, as in boundary effect and iterative times.
  • Yu Hua Wu-DingJun Xiang-HaiFan
    . 2009, 28(5): 17-21.
    Abstract ( 1910 ) Download PDF ( 749 )   Knowledge map   Save
    Abstract:In this paper,precise-time step integration method is used to solve the dynamic equation of bridge under moving loads.The moving property of moving load is simulated as equivalent joint loads by Hermite function.The Duhamel integration format of moving load during a time interval is derived,including the moving load at the start time and at the end time on the same element,neighboring elements,or non-neighboring elements.Numerical example shows that highly accurate solution from the proposed method can be obtained by maximum time step in comparison with other numerical methods.
  • Lou Menglin;Zhang Jing
    . 2009, 28(5): 22-26.
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    Abstract: The dynamic response history of a 420 meters long span bridge under the excitation of seismic wave was analyzed. The computation results using Rayleigh and Caughey damping models were compared with the exact solution, and the differences between the effects of the two damping models were pointed out. Further discussions were made about the applicability and validity of different damping models. Finally, some caveats about the application of Caughey damping model were proposed at the end of the paper.
  • Zhiyi Zhang Yong Chen Hongxing Hua
    . 2009, 28(5): 27-31.
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    Abstract: Discussed are the influence of output saturation on active vibration isolation and sound radiation control and the method for saturation alleviation. A time domain model describing the coupled vibration of fluid-structure systems is first established by the FEM/BEM approach, in which the added mass of fluid is modified to ensure the accuracy of the natural characteristics of the coupled system. With the time domain model, an adaptive vibration control strategy with saturation alleviation is constructed. Simulation is conducted with a single-degree-of-freedom model connected to a simply supported stiffened plate, which is rigidly baffled and coupled with water at one side. The results have demonstrated that the scheme for saturation alleviation can substantially improve the performance of active isolation of vibration and reduce the radiated sound from the stiffened plate.
  • SUN Shao-ming;REN Lu-quan;MEI Tao;Zhang Yong-zhi
    . 2009, 28(5): 32-34.
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    Abstract: The long-eared owl wing surface with noise reduction characteristics was remarkable influence on its flight noise,analysing the characteristic of shape and configuration by the reverse restructure technology. The design on the bionics volute tongue will control the air current noise of the centrifugal fan. Through the experimental study, the bionics volute tongue reduce air noise of centrifugal fan in entire frequency band total acoustic pressure level LA, the average sound pressure level decreased 2.3 dB. The primary and secondary influence factors of the noise reduction effect on bionics volute tongue are: non- smooth unit spacing t, non- smooth unit integer n, highly unit h. The computer simulation analysis indicated that, the bionics volute tongue surface shape noise reduction mechanism mainly is: reduced the impact of air current to the volute tongue; causes the volute tongue surface turbulent boundary pressure oscillation to weaken and to delay the eddy shedding to fall off from the tail section of the volute tongue; causes the speed of pulsating air flow on the volute tongue surface which flows out from the air blower impeller distribute even, the speed changes suddenly reduce. The flow stability enhancement is advantageous to reduce the production of the centrifugal fan air current noise.
  • ZHANG Jian-dong;CHU Yan-dong;YU Jian-ning;LI Xian-feng;YANG Li-xin
    . 2009, 28(5): 35-40.
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    The complex dynamic behavior of the mechanical centrifugal flywheel governor system was studied.The dynamical equation of the sysablished using lagrangian and Newton's second law,The chaotic behavior of the system was analyzed by means of bifurcation diagram and Lyapunov exponents.The evolution from Hopf bifurcation to chaos was shown by the shown by the bifurcation diagrams and a series of Poincaré sections under different sets of system parameters,and the bifurcation diagrams were verified by the related Lyapunov exponent spectra.Based on Lyapunov stability theory theory,a method of non-linear control was proposed for synahronization between Duffing system and mechanical centrifugal flywheel govvernor system was realized by aonstructing the appropriate non-linear controller.Numerical simulation shows the effectiveness and feassibility of the proposed method.
  • Zhang Xinguang;Li Zhinong;Wang Xinyi;Yuan Zhenwei
    . 2009, 28(5): 41-43.
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    Abstract: Combining the advantage of order analysis and blind identification of time series model, a new blind identification algorithm of AR model on order domain is proposed. The proposed algorithm includes two parts: (1) Preprocessing, the non-stationary signal is resampled by order sampling, i.e. constant angular interval, and transformed into stationary signal at the angular domain. (2) Blind identification, the stationary signal at the angular domain is identified by the blind identification of AR model. The proposed algorithm not only inherits the advantages of traditional blind identification of AR model, but also overcomes the deficiency of raditional blind identification of AR model. The simulation result shows that the proposed algorithm is very effective, and can be a powerful tool for processing non-stationary signal.
  • Li Shunming;CHENZhao;LI Yan
    . 2009, 28(5): 44-48.
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    Abstract:The Squeeze Film Damper (SFD) has great importance to reduce the vibration of rotary machines. The work characteristics are different for different SFD. The numerical methods of loop arithmetic and curve intersection methods are compared. Next the dynamic characteristic experiments are researched on a SFD. The experimental condition and the methods are introduced. Tree excitation forces are used and the displacement admittance curves are drawn. And then the results of amplitude-frequency characteristic and phase-frequency characteristic on displacement admittance gotten from calculations are compared to experimental results. On the last the conclusions of practical value have been educed.
  • Acoustic Stealth Design on the Underwater (. College of Naval Architecture and Power;Naval Univ. of Engineering;Wuhan 00;China; . Department of Training;Naval Univ. of Engineering;Wuhan 00;China)
    . 2009, 28(5): 49-54.
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    Abstract: Replace the added structure steel shell with acoustic stealth sandwich composite, the acoustic models of underwater acoustic stealth sandwich composite structure was built. The corresponding transition matrixes, reflection coefficient and absorption coefficient of oblique incidence in planar were deduced from the acoustic wave equation. The acoustic frequency response of stealth added structure with water layer in vertical incidence was measured by experiment, and the results of transition matrix method were matched to the experimental data. The influence in different oblique incidence angle was analyzed. The effects of acoustic stealth on the thickness, density, loss factors of absorption layer and the thickness of water were calculated, the acoustic stealth structure of underwater sandwich composite added structure was designed, and the reflection coefficient and absorption coefficient frequency response were analyzed by numerical method in different material parameter and different geometrical parameter.
    Keywords:acoustic stealth; oblique incidence; sandwich composite; added structure; transition matrix
  • Yang Zhichun;Gu Yingsong;Li Bin
    . 2009, 28(5): 55-58.
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    Abstract: Classical linear flutter analysis is based on the solution of flutter eigenvalue problem, and needs to track the root loci to determine the correct flutter boundary but sometimes may fail. To solve this problem, a new flutter solution called μ-ω method is presented by utilizing modern robust control theory. Based on the frequency-domain μ analysis, this method is established by applying dynamic pressure perturbation to the flutter equation with frequency domain unsteady aerodynamics. It is found that the continuity of the real μ analysis is crucial to this method, so a two dimensional wing model with steady aerodynamics is adopted to explore the continuity of real μ analysis. It is proven that the μ value obtained by real μ analysis is not a continuous function of frequency, but if complex perturbation is introduced, the complex μ analysis does guarantee the continuity of μ analysis. According to this conclusion, the algorithm of the μ-ω method is extended with complex μ analysis. Numerical results demonstrate that the complex perturbation μ-ω method is a useful frequency domain flutter solution with good convergence and accuracy.
  • Zhu WeiGuo; Bai XiangZhong
    . 2009, 28(5): 59-62.
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    Abstract The problem of bifurcation and chaos of a four-side fixed thermo-electromagnetic-mechanic coupling rectangular thin plate is studied. Considering the effect of temperature, the vibration equations of the rectangular thin plate under the action of mechanic field, the temperature and steady transverse magnetic field are derived. By Melnikov function method, the chaos condition and judging criterion of the system under the condition of Smale horseshoe map are given. The vibration equations are simulated numerically. By some examples, the bifurcation diagram, the Lyapunov exponents diagram, the displacement wave diagram, the phase diagram and the Poincare section diagram of the system are obtained. The influences of electromagnetic field and the temperature on system vibration properties are analyzed. From the simulation, we can control the characteristics of the vibration system and can make the system become chaos motion or avoid chaos motion by changing the temperature and electromagnetic parameters.
  • Lin Jie-qiong;Zhou Xiaoqin;Kong Fansen;Wang Wencai;Yu Junyi
    . 2009, 28(5): 63-68.
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    Abstract: Both regenerative cutting and mode-coupling principles are taken into consideration to model the delayed dynamics of regenerative machining system under stochastic excitation. The influencing of the orientation of principal stiffness axes on machining instability lobes is analyzed. The dynamic responses of machining system are sampled as the observation data. The cross fourth-order cumulant based ESPRIT approach to jointly estimating harmonic parameters is proposed, which is applied to investigate the influence of the orientation of principal stiffness axes into the harmonic parameters of dynamic response in mode-coupled regenerative machining system. Several novel dependent characteristics of the harmonic parameters on the orientation of principal stiffness axes is disclosed, these harmonic parameters includes the frequency, phase shift and cross power of the dynamic machining responses.
    Key words: machine tool; regenerative machining; mode-coupling principle; dynamic stability; cross high-order cumulants.
  • Li Zhongwei Long Xinhua Meng Guang
    . 2009, 28(5): 69-73.
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    In this paper, a set of delay differential equations (DDEs) are setup to describe the dynamics of milling process. An improve semi-discretization method based on Magnus-Guassian truncation is presented for analyzing the stability of periodic orbit of the DDEs. By comparing the stability charts obtained by zero-order semi-discretization method with the stability charts obtained by the improved semi-discretization method, one can say the computational efficiency, convergence, and accuracy are improved by the semi-discretization method based on Magnus-Guassian truncation.
  • LIAO Chang-Jiang;;JIANG Wei-Kang;WANG Yun;DUAN Hao
    . 2009, 28(5): 74-79,8.
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    The coupled vibration equation of axially stiffened finite cylindrical shell is derived, in this equation additional impedance caused by the axial stiffeners is added to the coupled vibration equation. As a result, the vibration and sound radiation of shell depend on the mechanical impedance of shell, the radiation sound impedance and the additional impedance. Based on the numerical simulation, the influencing factors for sound radiation characteristics of submerged simply-supported thin finite length cylindrical shells excited by external force were investigated. It is found that the axial stiffener number just has a slight influence on radiated sound power, whereas structural damping has a great influence on radiated power and radial quadratic velocity on the surface of shell. This study can give some guidelines for noise reduction of this kind of shell.
  • Liu wei-hua Ding wang-cai Tian hai-yong
    . 2009, 28(5): 80-83.
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    In this paper, the question about parametric identification of nonlinear vibrating system based on time-frequency combination is studied. Firstly , the mechanical model of a single-degree-of-freedom vibrating system with nonlinear parameter is established , and the chaotic response of a known nonlinear system is used as an excitation for parametric identification, it is assumed that the system consists of several unstable periodic orbits, the nearly periodic orbits are extracted from the state space of chaotic response based on recurrence property , and the harmonic balance identification method is used to identify the parameters of nonlinear system. And then the error of identified parameters are analysed. It is indicated that using chaotic signal as driving source for identifying the nonlinear system is feasible by numerical simulation.
  • LIN Wen-jing;CHEN Shu-hui;LI Sen
    . 2009, 28(5): 84-86.
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    The free vibration of circle membrane is studied in this paper. Firstly, the governing differential equation of membrane is set up by Hamilton’s principle. Then, by employing the method of separated variables, two second order differential equations regarding the time t, the radial direction coordinate r and one Bessel equation regarding the circumferential direction coordinate are derived. These equations are solved respectively. Therefore, the analytical solution of natural frequencies and modals of circle membrane and fan-shaped membrane are obtained. Finally, the numerical calculations are also taken by using the finite element software ANSYS. Two examples show that the theoretical results are pretty good agreement with those numerical results obtained by ANSYS. The theoretical results are lower limits of the numerical results.
  • WANG Donghua;LIU Zhansheng;DOU Wei
    . 2009, 28(5): 87-91.
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    Critical speeds are important factors during the design process of rotating machinery. If the critical speeds do not comply with the requirements of operation safety, the rotor system configuration must be adjusted. How to adjust the rotor system configuration to get the desired critical speeds and change the configuration least at the same time is a focus of rotordynamics. An improved model for optimally design the critical speeds of a rotor system is presented, not need to consider the relationship between the number of critical speeds and that of design variables, and whether the desired critical speeds could be approached to. Aiming to solve the complicated model, a genetic-complex shape combined algorithm is designed with better search speed and higher accuracy. The result of a case study on a rotor system shows that the improved model can get the optimal solution and may be applicable in practical rotor system design process.
  • SHI Wen-Ku;LONG Yan;LU Yu-Dong
    . 2009, 28(5): 92-96.
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    Based on the structure of dual-mass flywheel(DMF) arc spring, design an innovation damping spring structure and makes stiffness of DMF from single-class to multistage. Established parameter selection principle and design process of multistage DMF,and also established a discrete model of a domestic car,evaluated the multistage nonlinear DMF torsional vibration control in the transmission and idling conditions. Simulated the multistage DMF damping properties by ADAMS. Finally optimized the design parameters.
  • Ju Ping-hua;Qin Shu-ren;Qin yi;Ding zhi-yu
    . 2009, 28(5): 97-101.
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    Time domain averaging is a common method to extract the fault characteristics of vibration signal of rotating machineries. However, when rotating machineries occurring earlier faults, time averaging will not be applicable because of the influence of the strong background noise. It also can’t distinguish the different faults from rotating machineries effectively. Via the comparative analysis of wavelet transform、Hilbert-Huang transform and Multi-resolution Hilbert-Huang transform, based on the analysis of time synchronous averaging, a new method which combines the method of Multi-resolution Empirical Mode Decomposition (MEMD) and Frequency Domain Geometrical Average is proposed. The application results show that the proposed method can realize the earlier gear fault detection effectively.
  • JIANG Bo;TIAN Mao-cheng;LENG Xue-li;CHENG LIN;CAO Bing-yang
    . 2009, 28(5): 102-105.
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    Experimental research and numerical simulation were carried on to study the flow and heat transfer characteristics outside a circular and an elliptical tube under vibration condition. The orthogonal design method was used to analyze the effect of amplitude, frequency and shape of the tube on heat transfer performance, and a fitting correlation between heat transfer and vibration parameters was obtained in the low-frequency area. Based on the field synergy theory, the dependence of the cosine value of synergy angle on the vibration frequency and amplitude was gained for the near-wall region. It is shown that heat transfer is significantly enhanced while the frequency increases, and rises to a peak value when resonance condition appears. Comparison between different kinds of vibration tubes indicates that heat transfer of elliptical tube with vibrating direction the same as its short axis is the best, round takes second place, and elliptical tube with vibrating direction the same as its long axis is the worst. And it is obtained that tube type is also an important factor affecting the heat transfer under vibrating condition.
  • HOU Liqun;OU Jinping;Zhao Xuefeng;Li Hongwei
    . 2009, 28(5): 106-110.
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    Modal parameter of bridge is very important for finite element updating, damage identification and bridge condition assessment. Dynamic test is the necessary approach to obtain the modal parameter of bridge. Finite element model of Harbin Sifangtai Bridge was established, eight accelerometers with force feedback was applied to measure acceleration of bridge deck by the way of group test, piezoelectric accelerometer was applied to measure acceleration of cable, the combined method the NExT and ERA was applied to identify cable-stayed bridge modal parameter and the identification result was compared with the calculated result of finite element, frequency difference fitting method was introduced to identify frequency and tension of cable and the result was compared with the design cable tension of real bridge.
  • Li Xue Li Hong-nan  Huang Lian-zhuang
    . 2009, 28(5): 111-114.
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    In this paper, based on the principle of collapsed steel tower design for Guajing transmission line, the finite element model of multi-tower-line coupled system has been established according to the original data of engineering. The curve of ice increasing with time has been given according to the data of icing record. Considering the high deference, ice increasing, asymmetry between ices of conductors and wind load, nonlinear buckling analysis of transmission tower-line system under ice load and wind load has been carried out. The ultimate load of tower structure has been studied by using nonlinear buckling analysis and the cause of the tower falling down is analyzed in this paper. It can be concluded that wind load and unbalanced tension caused by overload and asymmetry between ices of conductors are the main reasons why the steel towers fell down, and technical code of design overhead transmission line in heavy icing area needs to be modified.
  • ZHANG Xiao-min;JIN Xian-long;CHEN Xiang-dong
    . 2009, 28(5): 115-118.
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    Dynamic characteristics of flexible container under wind load is typical problem about fluid-structure interaction under multiphase flow. Mutil-material ALE method is used to build the finite element model of the flexible container and wind. Dynamic characteristics of this structure under the different velocities of wind are compared. Numerical tests show that the the maximum principal stress and the deviation of the mass center become greater with respect to the increasing wind velocity untill the velocity achieves some certain value and the structure starts to slide on the ground, which provide important references for the research on wind-inducing response of flexible container.
  • BU Guo-Xiong;TAN Ping;ZHOU Fu-Lin
    . 2009, 28(5): 119-123.
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    Considering the uncertainties of practical civil engineering structures, the Neural Network Response Surface Method optimized by Genetic Optimization Algorithm has been proposed to calculate the dynamic reliability of stoch- astic structure with TMD and MTMD. This method has both of the advantages of Neural Network Response Surface Method and the global search of GA, which can approach to optimum solution accurately of the performance function. And the iteration steps of JC method can be reduced effectively. The results of instance show that this method is effec- tive and accurate. For the stochastic structure the MTMD can greatly improve the dynamic reliability than TMD.
  • LI Zhi-quan;DU Cheng-bin;YU Guo-jun;Sun Li-guo
    . 2009, 28(5): 124-126,.
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    The experiments on magnetorheological fluid damper(MRD) are carried out to investigate the characteristics of SG-MRD40 and RD-1005-3 dampers. Considering that the existing nonlinear hysteretic biviscous model can not be used to fit the curve of damping force vs. damper velocity well at low frequency, two parameters and are adopted in the model. is used to describe the characteristics of damper at yield phase when the absolute value of velocity is increased, otherwise, is used when the absolute value of velocity is reduced. The yield force is also introduced in this model. The improved model describes the characters of MRD under different states at yield phase. The results show that the improved model is more excellent than the existing nonlinear hysteretic biviscous model. It can be used to describe the characteristics of MRD at yield phase well, and is applicable at more large range of frequency.
  • Peng Tian-bo;Zhang Hua;Li Jian-zhong;Li Wen-xiao
    . 2009, 28(5): 127-130.
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    FRP rubber isolators are composed of rubber layers bonded to interleaving reinforcing plates. Former experimental studies have shown that the equivalent damping, shear deformation capacity and vertical loading capacity of FRP rubber isolators are superior to those of other isolators, so broad application prospects of FRP rubber isolators should be expected. Because former theoretical investigations of the isolator focus on the vertical compression and bending performances and investigations of horizontal shear characteristic and its mechanism are insufficient, practice application of the isolator is limited therefore. In this paper, a theoretical research on the horizontal shear behavior of rectangular FRP rubber isolators is conducted and the relation between total horizontal shear force and the shear strain of rectangular FRP rubber isolators is presented. The nonlinear characteristic of the horizontal shear force and its formation cause are investigated then, and it’s found that the horizontal shear stiffness would descend with the increase of shear strain. At last, it is shown with a numerical example that vibration isolation efficiency of FRP rubber isolator is enhanced along with the increase of shear strain.
  • ZHANG Qiang;WU Qing-ming
    . 2009, 28(5): 131-136.
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    A new method of parametric identification based on wavelet transform and bootstrap theory is proposed in this paper to identify modal parameters of multiple-DOF system. With modified Morlet continuous wavelet transform, measured responses are represented in time-frequency domain, after the analysis of time and frequency resolutions, the optimal parameters of wavelet function are determined by Shannon entropy. The statistical confidence intervals on modal parameters are estimated by bootstrap theory. A simulation and an experiment were carried out on a vibration platform to validate the proposed method.
  • WU Jian DAI Jiyang Sun Xiuxia
    . 2009, 28(5): 137-141.
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    For the nonstationary vibration signal of rotating machinery, when the rotative speed can be known, we can use degree area resampling method in speed tracking order analysis, so as to change the vibration signal into fixed order signal. Then, we can use the wavelet demodulation analysis’s functions as bandwidth filter and demodulation analysis, so as to pick up each order signal and to obtain its analytical signal at the same time. The method successfully solves the serious nonstationary vibration’s analysis problem of rotating machinery, and it can easily be expanded to the other nonstationary signal’s analysis problem. The expansion method has the similar frame as HHT, so it has a wide applied area. With zoom analysis as well as fast deconvolution based on FFT & IFFT, the thesis gives the corresponding numerical calculation method, which ensures the calculation to be stabile, accurate and rapid, and which overcomes the HHT’s deficiency of bad stability. Finally, by the comparison of the different methods’ analytic answer to the vibration signal during an aero engine’s test drive process, the validity of the thesis’s method is proved.
  • QI Hui SHI Yong ZHAO Jiaxi
    . 2009, 28(5): 142-145.
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    A series solution of two-dimensiona1 scattering of Plane SH waves by a circular inclusion in an infinite strip region is presented using the wave functions expansion. The Solution is reduced to solving a set of infinite linear algebraic equations using the interior region form of Graf’s addition theorem. Numerical solutions are obtained by truncation of the infinite equations and the accuracy is ensured by the extent to which the numerica1 results fit the exact boundary conditions with the increasing of the truncation order. Finally, the dynamic stress concentration factors around the circular inclusion are discussed to the cases of different thickness of strip region and geometry location of circular inclusion in numerical examples. The calculating results show that the existence of free boundary of strip region has great effect on incident plane SH-wave, and the variation of thickness of the infinite strip region can remarkably change the dynamic behavior of circular cavity.
  • FANG Jianyu HAN Xiaoyun CAI Li YU Dianlong
    . 2009, 28(5): 146-149.
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    The idea of periodic stucture of phononic crystals is introduced to the physical design of the beam, and the propagation of coupled flexural-torsional vibration in the periodic Timoshenko beam composed of two kinds of materials including warping effect is investigated. Based on the equation of coupled flexural-torsional vibration of beam, the band structure of such a beam are presented by making use of the transfer matrix theory. The transmission characteristic of vibration of the finite periodic beams is simulated by using finite element method, which shows vibration attenuation in the range of frequency agrees well with the band gap. Comparing with the band structure obtained from the condition ignoring the warping effect, the result has shown that it may be getting the meaningless result if igoring the warping deformation.
  • Yu’e Zhang Bao hong Bai Min Xiang
    . 2009, 28(5): 150-152.
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    Elements with concentrated plastic hinge were adopted for the analytical mode1,study of seismic behavior of continuous beam bridge was performed with dynamic elastic-plastic analysis method, The analysis results show the variation of force and deformation under seismic load, the seismic resistance performance evaluation of each pier also were discussed in this paper, the results can provide references to the seismic design of similar bridge.
  • LI Jing HAN DaJian
    . 2009, 28(5): 153-159.
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    Wind load is the critical load applied to cable-membrane roof structures because of the special properties such as light weight, large flexibility, and small damping. In design of cable-membrane structures, the dynamic coefficient is a major parameter for determination of the wind load. In this paper, the wind-induced response statistics and the dynamic coefficients are firstly defined, then a new method that the nonlinear finite element analysis combines with the artificial neural network technique is proposed to find the relations between dynamic coefficient with the mean wind velocity and with the structural prestresses. A large scale cable-membrane roof structure is taken for example to show the validity of the proposed method. The rules of variation of dynamic coefficients with mean wind velocity and with the structural prestresses are obtained, which provide a scientific basis for wind-resistant design of cable-membrane structures.
  • Li Wei Hu Xiangpeng
    . 2009, 28(5): 160-162.
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    For crane loads swing problems, mainly discussed the effect of vertical movement of the load on shimmy, established the mathamatical model of crane load sway under permitted supposed conditions.,through coordinate transformation, transformd differential equation into the standard form of Hill equation, and with research on Hill equation we can get the condition about damped oscillation. Finally, with the introduction of the parameter plane, the stable map of Hill equation can be drawed, i.e. the map of crane load damped oscillation.The results show that, if control of the pendulum length is used to realize the anti-sway of crane,three parametrics including initial pendulum length、amplitude of variation and periodic variation of pendulum length should be considered comprehensively, a coordinate point can be calculated by these three parametrics in the parametric plane,if this point is in the area of damped oscillation in the parameter plane, the anti-sway of crane can be realized.
  • Tian Hao Tang Liwei Tian Guang ZHANG Yan
    . 2009, 28(5): 163-164.
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    the ICA is a kind of signal processing method based on high order statistic, it can recover the source signals from the linearly mixed signals, but there are disadvantages in processing non-linearity signals, and the KICA, which is based on nonlinear function space, can solve this problem effectively. Compared to current ICA algorithms, the KICA is notable for its flexibility and robustness. We presented the principle of KICA, and illustrated it with simulations. Finally, through the analysis of transient acoustic signal on gearbox combined with order envelope spectrum analysis, we found the fault characters, thus showed its effectiveness.
  • Wang Ailun Luo Zhou
    . 2009, 28(5): 165-168.
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    A rod fastening rotor used to be treat as a continuous integral rotor, so the model is not very precise. By considering the contact effect of discontinuous interfaces, a dynamic model of rod fastening rotor’s torsional vibration is put forward by using bond graph. The influencing factors of equivalent torsional stiffness have been analyzed. The theoretical results and the experimental results of an experimental rod fastening rotor’s torsional vibration have been contrasted. The natural frequency of rod fastening rotor and continuous integral rotor’s torsional vibration has been analyzed under different pretightening forces. The vibration mode of continuous integral rotor and rod fastening rotor whose pretightening force is 4000N have been contrasted. The contrast results show that the model of rod fastening rotor is not only more precise than continuous integral model, but also it represent the essential difference between rod fastening rotor and continuous integral rotor, it can settle the foundation of the further research on rod fastening rotor.
  • Sun Jiedi Wen Jiangtao Jin Shijiu
    . 2009, 28(5): 169-171.
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    Aimed at the widely existing peripheral security problems around the oil and gas pipeline, the characteristic of seismic signals generated by the ground moving targets was investigated. The seismic signals which were acquired by many geophones and detection system appeared at different time. The target localization principle based on the arrival time difference is proposed. The seismic signal is typical non-stationary signal. As a new time-frequency method, Hilbert-Huang transform was used to process these signals and obtained the eigenvalue frequencies, the amplitude and the different appearance time. The ground moving localization was achieved. An experiment system was designed and the seismic signals were collected by sensors. Then these signals were processed by HHT method and acquired the different appearance time of target eigenvalue frequency. The arrival time difference, the sensor array location and the relative position of target and sensors were analyzed and the target localization can be achieved. The processing method above was verified through the real experiments data analysis.
  • WANG Bo XU Feng ZHANG Hailong
    . 2009, 28(5): 172-175.
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    To investigate the non-linear vibration behavior of spatial inclined cables subjected to harmonic displacement excitation at beam end or tower end, based on Newton's laws of motion and the tension forces of cable, the three-dimensional non-linear coupling control oscillatory differential equations in loosening and non-loosening state with the arbitrary direction excitations are derived. Runge-Kutta subsection integration method is applied to obtain those equations. The research results show that the cable will present coupled vibration characteristic of the out-of-plane and in-plane in three-dimensional spatial coordinates, the coupled vibration amplitude is relation with the matching ratio of natural frequencies of cable and excitation frequencies; in in-plane displacement excitation, the out-of-plane auto-parametric vibration will be found by increasing the excitation amplitude; with the accretion of the initial sag and the excitation amplitude, the alternate variation processes between loosening and non-loosening state are exposed during cable vibrations.
  • Xing Haijun Yang Shaopu Shen Yongjun
    . 2009, 28(5): 176-179.
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    Based on Bingham model,the equation of Magnetorlogical fluid through a slot valve is derive. The relationship between the damper force ,the structure parameters of MR damper and the performance parameters of MR fluid is shown as a quartic algebraic equation. The equation is solved and effect of the MR viscosity,yield stress and the structure parameters of MRFD on damper performance is analysed.The research in this paper can instruct MR damper design.
  • WANG Yong DING Weiping Shen Du Li Jianfeng Yang Lingmin
    . 2009, 28(5): 180-183.
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    Based on the cavity acoustic characteristics of dynamic subsystem modification methods, treating the automotive powertrain mounting systems as subsystems attached to the body, revealed the direct ration relationship of interior noise pressure and the stiffness, damping characteristic parameters of mounting elastic component. And in order to ensure efficiency and reduce the solution of environmental requirements, response surface methodology used to approximate treatment. Furthermore, to reduce vehicle interior noise pressure as the objectives and the stiffness, damping characteristic parameters of mounting elastic component for the design variables, established the mounting characteristic of acoustic optimization design model. Finally, taking 5t rough terrain container forklift truck for example, showed that the optimization of the design method is effective.
  • LIU Yaozong WANG Ning MENG Hao YU Dianlong WEN Jihong
    . 2009, 28(5): 184-187.
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    Excitation of the longitudinal modes of hull by the fluctuating thrust from propeller-shafting system is a major source of the radiated noise at low frequencies of submarines. Based on the four-pole parameters method, a simple model for analyzing the axial vibration of submarines is proposed, which accounts on the elasticity of the hull, thrust bearing and shafts. The axial transmission of powerflow from shafting to the hull is investigated. It is found that the fluctuating thrust will induce resonances of the shafting and the hull because they are elastically coupled, which will result in powerflow peaks. Such resonances are more significant while their frequencies are around the axial modes of the shafting. Dynamic vibration absorbers are designed to depress such powerflow peaks. It is found that absorbers could reduce the powerflow more effectively when they were tuned to resonances around the axial modes of shafting than tuned to others.
  • ZHANG XueBing RAO ZhuShi Ta Na SHAO YuYing
    . 2009, 28(5): 188-191.
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    Transformer tank is the main target of on-line transformer monitoring system. In this paper, a finite element model is presented to research the power flow of tank vibration which is transmitted by core. Consequently power transmission and its distribution of tank is acquired which provides theoretical and experimental foundation of on-line transformer monitoring system using non-electrical method.
  • Fang Zheng Yang Zhao Liu Yuntao Chen Yiguang
    . 2009, 28(5): 192-198.
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    The problem brought by noise becomes an impediment to make GEHP commercialized. The paper establishes three-dimensional model of acoustic enclosure and model of double chamber fastness muffler on the bases of acoustics spectrum analysis coupled with acoustic theory. And the simulation of the noisy level of a GEHP with and without acoustical enclosure by the RAYNOISE software has been finished. Then the sound insulation device is designed according to the practical situation of the GEHP. And it can be concluded from experiment that the sound pressure level is sharply reduced to 77.8 dB (A) after fixed the sound insulation device, which improves the validity of the design about the noise control of GEHP.