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2012 Vol. 31, No. 3 Published: 2012-02-15        论文 1 beat vibration of ertan arch dam under ambient excitation Lian Ji-jian;Li Cheng-ye;Liu Fang;Song Ming-fu DOI: Researching on the vibration time interval curve of Ertan arch dam under flood discharge excitation, we can see the phenomenon that the wave envelope increases or reduces along with the time. Firstly, the effects caused by initial phase difference, frequency ratio and amplitude ratio have been discussed. Secondly, dominant frequency of measured data has been collated and analyzed with the Auto Regressive Modal, obtaining the first four vibration mode based on SSI. Lastly, combined with special features of beat vibrations itself, beat vibrations of Ertan arch dam under discharge flow has been researched. The result shows that the main cause forming beat vibration is the former two orders vibration mode whose frequency is similar. In addition, a vibration component whose frequency band is during 1.27~1.39Hz also gives rise to forming “beat”. The component is considered at present that it is caused by nonlinear contact between dam sections. 2012 Vol. 31 (3): 1-7 [Abstract] ( 611 ) HTML (0 KB)  PDF (2853 KB)  ( 291 ) 8 Dynamic analysis of tapping mode atomic force microscopy under random noise excitation Wu Jie;Zhang Wen-ming;Meng Guang;He Yu-hang DOI: Nonlinear dynamic behavior of tapping mode atomic force microscope(AFM) under bounded random noise excitation is investigated. The microcantilever is modeled with a lumped-parameter model and the interaction between the microcantilever and sample is described by the Lennard-Jones (LJ) potential. Effects of the density of the random disturbance and contact angle of the meniscus force on the dynamic system are analyzed and discussed. The results indicate that various periodic and chaotic motions occur in the coupled dynamic AFM system, the dynamic system goes through a complex nonlinear behavior. As the density of the random disturbance and contact angle of the meniscus force increase, more and more chaotic components occur in the dynamic AFM system. It demonstrated that the effect of random noise cannot be ignored for the optimization design of tapping mode AFM. 2012 Vol. 31 (3): 8-12,4 [Abstract] ( 1121 ) HTML (0 KB)  PDF (1910 KB)  ( 335 ) 13 Three-dimensional flutter analysis of a suspension bridge with a pc slab stiffening girder ZHU Zhi-wen;HE Shu-lin;HUA Xu-gang DOI: Based on a tentative design of suspension bridges with a PC slab stiffening girder in Guizhou Province, the sectional model wind test has been carried out to identify flutter derivatives of the stiffening girder, by using the Forced Vibration Technique at the wind angle of attack -3°,0°and 3°. With a second development of the software ANSYS, full-mode flutter analysis of the bridge in frequency domain is implemented, considering the influence of wind angle of attack under construction stage and in-service state. It is found that the presented handrail on the stiffening girder apparently enervates bridge flutter instability at zero angle of attack; for both the construction stage and the in-service state, the flutter onset wind speeds of the bridge are significantly decreasing under negative wind angle of attack; while very high flutter onset wind speeds occur at positive angle of attack in both construction stage and in-service sate. Because of the very sensitive flutter instability of such kind of bridge to wind angle of attack, studies on the suitable selection of the handrail shape as well as the wind environment at bridge site should be highlighted. 2012 Vol. 31 (3): 13-17 [Abstract] ( 1022 ) HTML (0 KB)  PDF (1601 KB)  ( 238 ) 18 Investigation on interface friction model in split hopkinson pressure bar tests for engineering materials LU Yu-bin;SONG Dan-lu;LI Qing-ming;MENG Hui DOI: Dynamic behavior of engineering materials at high strain-rates is frequently investigated by split Hopkinson pressure bar (SHPB) technique. The uniaxial stress state within an SHPB specimen is one of the fundamental assumptions which determine the accuracy of an SHPB test. However, the uniaxial stress state is not always satisfied within the SHPB specimen in an actual SHPB test due to the existence of some unavoidable negative factors, e.g., interface friction constrains on the contact surface between the SHPB specimen and the end of pressure bars. A kinetic interface friction model was proposed based on kinetic friction tests to describe the variation of kinetic friction coefficient with the maximum radial relative velocity between the SHPB specimen and steel pressure bars. It shows that the proposed kinetic interface friction model can fit the kinetic friction results well. 2012 Vol. 31 (3): 18-22 [Abstract] ( 1484 ) HTML (0 KB)  PDF (1879 KB)  ( 628 ) 23 orthotropic dynamic damage constitutive model for concrete CHEN Shi-hai;ZHANG An-kang;DU Rong-qiang;ZHANG Zi-huai DOI: In order to establish orthotropic dynamic damage constitutive model for concrete, dynamic increase factors (DIF) were first used for considering strain effects, then based on Sidoroff’s energy equivalent theory, the dynamic damage elastic matrix of elements was found., and Mazars’ damage model was used for calculating damage scalars of principle axial directions, and orthotropic Hoffman failure criteria was adopted, which intensities was modified for damage and DIF. The model was proved by a destroying experiment of a structure under blasting vibration. 2012 Vol. 31 (3): 23-26 [Abstract] ( 625 ) HTML (0 KB)  PDF (954 KB)  ( 352 ) 27 Rotordynamic analysis of a micro gas turbine overhung rotor system supported on floating ring bearing Shen Na-wei;Chen Zhao-bo;Jiao Ying-hou;Ma Wen-sheng DOI: the rotor dynamic performance of overhung rotor supported on floating ring bearings (FRBs). The Reynolds equation and bushing motive regulation of FRB are established. The forces of two oil films are calculated using 4-node isoperimetric h-version refining FEA method by Galerkin approximation. The equivalent stiffness and damping coefficients of the FRB are obtained combining with the dynamic equations. This paper also presents the rotodynamic simulations of the critical speed, unbalance response by using the commercial software Ansys 12.1. By contrast with test results, this proposed model of overhung rotor system is of good validity and practicability in design work for future. 2012 Vol. 31 (3): 27-31 [Abstract] ( 929 ) HTML (0 KB)  PDF (1593 KB)  ( 744 ) 32 Study on Vibration Characteristics of 2 DOF nonlinear torsional vibration system of rolling mill and its conditi ons of instability HOU Dong-xiao;LIU Bin;SHI Pei-ming;LIU Fei;liu yun-jing DOI: A kind of 2 DOF nonlinear torsional vibration tion of rolling mill which considers iffness and nonlinear friction damping is esta under load torque of motor is studied. Firstly the equivalent ation under load torque of moto n. Then the main resonance amplitude-frequency equation by averaging method, and transition set of system and its ngularity theory. At last, according to actual parameters of g mill, the amplitude frequency resonance characteristics under different nonlinear factors are studied and torsional vibration of ror is obtained by means of coordinate transformatioof system under external periodic excitation is obtaineddifferent bifurcation behaviors are analyzed by using sidynamic equan onlinearst blished, and the vibration racteristics of equation torsional vibration equrollin the instability conditions of self-excited vibration are elicited. The results supply theoretical bases for suppressing lling mill. 2012 Vol. 31 (3): 32-36 [Abstract] ( 645 ) HTML (0 KB)  PDF (1679 KB)  ( 743 ) 37 Dynamic environment research of soft landing for lunar lander ZHAO Jun-feng;LIU Li;ZHOU Si-da;YANG Wu DOI: For the purpose of the mission of soft landing in the second lunar probe of China, a research on landing impact dy¬namic environ¬ment for lunar lander was carried out. The characteristics of the excitation loads were obtained by analyzing the force data col¬lected in the stability experimentation. According to the characteristics of the excitation loads, finite element method was employed to calcu¬late the struc¬tural response. Shock response spectra was used to describe the impact dynamic environment, and maximum expected envi¬ronment was formulated by adding a safety factor to the wrap of the spectrum. The results show that the dynamic environment during soft landing stage is not severer than during other stages in the frequency band above 10Hz, which indicates that the design of the buffer¬ing system is appropriate. The amplitude of the response blow 10Hz is large, so special test should be implemented in this fre¬quency domain. 2012 Vol. 31 (3): 37-42 [Abstract] ( 1289 ) HTML (0 KB)  PDF (1759 KB)  ( 479 ) 43 Impact dynamics model of long span high voltage transmission lines subjected to iced wire breakage LIU Chun-cheng;;CHU Zheng-yu;SUN Xian-he;ZHANG Wei DOI: In order to theoretically reveal the impact dynamic responses of long span high voltage transmission lines subjected to iced wire breakage, the impact dynamics model for long span high-voltage transmission lines with iced bundled conductors is developed comprehensively by using the equivalent single-iced conductor instead of bundled conductors.The impact dynamics model of iced wire breakage is derived by using energy method. Taking a typical tension section of long span high-voltage transmission line as an example, the impact responses under iced wire breakage and non-iced wire breakage are computed by using this model and a good agreements are achieved. The results show that: the impact dynamic response under iced wire breakage is larger than that under non-iced wire breakage, so the impact dynamic response due to iced wire breakage should not be ignored, and the model can provide a theoretical basis for experiments and numerical simulations of long span high voltage transmission lines under iced wire breakage. 2012 Vol. 31 (3): 43-48 [Abstract] ( 1370 ) HTML (0 KB)  PDF (2081 KB)  ( 610 ) 49 Monitoring dynamic characteristics for Guangzhou New TV Tower under different excitation CHEH Wei-huan;LU Zhong-rong;CHEN Shu-hui;Ni Yi-qing;LIAO Wei-yang DOI: The SHM system of Guangzhou New TV Tower has monitored the structural responses after having completed its construction under different excitation events (the typhoon, the earthquake and normal wind excitation conditions). Firstly, the time history and PSD of the acceleration response under different excitation events have been compared. Secondly, the modal properties (modal frequencies, mode shapes, and damping ratios) of the structure under different excitation events have been identified and compared using the acceleration responses. At last, the HHT technique is applied for obtaining the instantaneous frequencies and energy distribution under different excitation events in the time-frequency domain by use of the monitoring data and compared with the result of the wavelet scalogram. The results of this paper supply some references for better understanding the dynamic characteristics of supertall under different excitation. 2012 Vol. 31 (3): 49-54 [Abstract] ( 1087 ) HTML (0 KB)  PDF (2534 KB)  ( 296 ) 55 Identification of modal parameters based on wavelet transform and back propagation network DAI Yu;ZHANG Jian-xun DOI: In order to reduce the influence of edge-effect of continuous wavelet transform on the identification of modal parameters, artificial neural network is introduced to extend free decay response signal in both directions. A multiple-input and single-output back propagation network is devised to predict the signal at the next time step using a finite number of current samples. The training samples are obtained by simple combination of the original signal. Both numerical and experimental studies are performed to demonstrate the proposed procedure and verify its practicability. The experimental system is a force sensor developed for minimally invasive surgery robot. The results show the method works very well in identifying damping ratios and undamped natural frequencies from short signal. 2012 Vol. 31 (3): 55-59 [Abstract] ( 1055 ) HTML (0 KB)  PDF (967 KB)  ( 254 ) 60 Structrues damage detecting using singular entropy of recurrence matrix Dong Yang;;Wei-Xin Ren; DOI: The Recurrence plot’s recognizing performance was applied in this paper. Signals, recorded at different locations on the structure, are using to reconstruct the phase space of the system’s dynamics and subsequently generate the multivariate recurrence matrix. Multivariate recurrence matrix is then used to construct a novel feature detecting damage combined with singular entropy. It is using for strucure damge identification. Numerical experimentation verified this feature’s validity. 2012 Vol. 31 (3): 60-63 [Abstract] ( 679 ) HTML (0 KB)  PDF (1867 KB)  ( 747 ) 64 Field measurements of wind characteristics on roof of the national stadium LUO Yao-zhi;CAI Peng-cheng;SUN Bin;TONG Ruo-fei;Shen Yan-bin;WANG Qia-qin DOI: With the aid of measurement system which was self-developed based on Wireless Sensor Network, field measurements of wind characteristics were conducted on the roof of the National Stadium. Boundary layer wind characteristics such as mean wind speed and direction, turbulence intensity, gust factor and power spectrum density of longitudinal wind speed etc are revealed in this paper. Analysis results show that there are remarkable differences between the characteristics of the wind on the roof and the nature wind, which represent in high non-Gaussian characteristic, high turbulence, the peaks of the PSD function appeared in high frequency domain, and weak correlation among the oscillation of the different points in space; this paper proves that the theory of quasi-steady state is not applicable to the large-span roof structure . 2012 Vol. 31 (3): 64-68,7 [Abstract] ( 1165 ) HTML (0 KB)  PDF (2507 KB)  ( 1074 ) 69 MDOF packaging system cushioning optimization design of Polyethylene foam GAO De;LU FU-de DOI: Based on drop shock test, nonlinear dynamics constitutive relation of Polyethylene foam is established and the parameters in the formula are identified successfully; then the constitutive relation of the foam is used in the multi-DOF packaging system of Polyethylene foam, and the dynamics formula is constructed under the given height. Based on response acceleration of the items smaller than the allowable value and minimal material consumption of polyethylene, the object optimization function of the cushion package structure is determined. The optimization solutions of multi-DOF packaging cushion system are obtained by the optimization model; based on the optimization results, the response accelerations of the falling masses in the packaging system are tested. The numerical results in this paper show that the relative errors between measured and calculated values of the response accelerations are less than 0.8% so that the model can be used to directly designing cushioning packaging structure, and avoid excessive or less packaging. This method is effect because the maximum acceleration-static stress curves cannot be available in designing cushioning packaging. The methods and process can be meaningful to cushioning design, and also provide relevance for other cushion packaging material. 2012 Vol. 31 (3): 69-72 [Abstract] ( 797 ) HTML (0 KB)  PDF (1277 KB)  ( 861 ) 73 The method of roller bearing fault comprehensive diagnosis based on LMD Chen Ya-nong;Gao Pu-gang;He Tian;Liu Xian-dong DOI: LMD (Local mean decomposition) is a new kind of adaptive time-frequency analysis method, which exhibits a good application prospect in filed of bearing fault diagnosis. In this paper, the LMD is advanced to improve it calculation speed. Then, the synthetic signal is used to illustrate the effectiveness of the proposed method by processing multi-component modulated characteristics of the signal. In view of the modulation characteristics of the vibration acceleration signal of the faulty bearing and the impact of background signals, LMD method is proposed to diagnose the bearing with outer-race fault, inner-race fault and the elements fault. The results indicate that the characteristic frequencies can be extracted effectively using the LMD method and they are coincidental to the fault type. 2012 Vol. 31 (3): 73-78 [Abstract] ( 1186 ) HTML (0 KB)  PDF (2573 KB)  ( 930 ) 79 Research on the mechanism of control spillover of the decoupling of the Active Structural Acoustic Control based on the theory of radiation modes Tian Xiao-guang;JIANG Zhe DOI: Decoupling control methods can be achieved by arranging the position of the actuator, the control effects of the two control methods are discussed based on the theories of Active Structural Acoustic Control and radiation modes. The decoupling method needs less input control energy and more stable, it has obvious advantages compared with the non-decoupling method. Both of them can achieve well control effect in the low frequency range and occur control spillover in the high frequency range. The mechanism of control spillover is discussed by analyzing the feature of the radiation efficiency of the radiation modal and the correspondence between the symmetrical forms of the actuator positions and the radiation modals. 2012 Vol. 31 (3): 79-83 [Abstract] ( 1085 ) HTML (0 KB)  PDF (2142 KB)  ( 441 ) 84 Spectrum sensing based on fractal box dimension and myriad filter in impulse noise Zhao Chun-hui;Ma Shuang DOI: To achieve the spectrum sensing in the impulse noise background, a spectrum sensing method based on Myriad filter and fractal box dimension is proposed in this paper. Alpha-stable noises affect the fractal box dimension of the signal. The Myriad filter can suppress the Alpha-stable noise. So the signal with Alpha-stable noise was processed by Myriad filter, and then the fractal box dimension of the filtered signal was calculated as test statistics. Simulation results show that this method has good spectrum sensing performance in the Alpha-stable noise background. 2012 Vol. 31 (3): 84-87 [Abstract] ( 1040 ) HTML (0 KB)  PDF (1225 KB)  ( 291 ) 88 Vibration cutting mechanism and its application WU Ji-mei; HOU Yu-peng; MA Li;e DOI: The relative movement between the cutting tool and the paper stack was compared based on the kinematics analysis of the ordinary and vibratory cutting process respectivly. The prerequisite of realizing the vibratory cutting effect is that the cutting speed is smaller than cutting tool's maximum vibration velocity, which is known from the analysis, and the relative size of the two parameters decides the cutting time in a vibration cutting cycle. The smaller the cutting speed is and the higher the vibration frequency is, the smaller the cutting length is in a vibration cutting cycle. The impulsive cutting force, which is created in the vibratory cutting process, is related to the paper shearing strength, vibration cutting cycle, cutting time as well as cutting length. The reason of the vibratory cutting effect surpassing the ordinary cutting effect is obtained as follows. The slight division effect of impulsive cutting force reduces the cutting area in a vibration cutting cycle, thus reduces the cutting resisting force, and the cutting surface quality is improved. 2012 Vol. 31 (3): 88-91,9 [Abstract] ( 779 ) HTML (0 KB)  PDF (1234 KB)  ( 214 ) 92 Synchronization between excitation and response signals in frequency response function estimation for mimo random vibration test CUI Xu-li;CHEN Huai-hai;HE Xu-dong;JIANG Shuang-yan DOI: The estimation of frequency response functions (FRFs) is necessary in MIMO (Multiple Input and Multiple Output) random vibration test control. The actual excitation signals for the shaker tables are always not sampled during the vibration test. The FRFs are estimated by the actual response signals and the excitation signals in the computer memory. Because there is a phase lag between the signal in the memory and the actual signal on the shaker table, the response signal is not synchronal with the memory excitation signal. So, it is very difficult to estimate the FRFs with these signals. Based on the relationship between the excitation and the response in linear system and the random decrement technique, a Dual Correlation Method (DCM) is presented in the paper to estimate the FRFs without measuring the actual driving force signals. One only needs to sample the response signals to estimate FRFs. A comparing test between DCM and the convention method which needs to sample the excitation and response signals simultaneously is accomplished on a 3-axis vibration table. The result shows that the presented DCM is correct. 2012 Vol. 31 (3): 92-96 [Abstract] ( 1346 ) HTML (0 KB)  PDF (1655 KB)  ( 454 ) 97 Muti-parameters sensitivity analysis of impact factors for rigid-continuous combined bridge ZHOU Yong-jun;ZHAO Yu;SHI Qi-bin;SONG Yi-fan DOI: In order to study the sensitive influence parameters of the impact factors for rigid-continuous combined bridge, finite element model was set up based on the bridge-vehicle coupled vibration, the vehicle of which adopted three axles half-car model. The influence parameters included the ratio of bridge and vehicle frequency, the roughness of deck, the mass of vehicle, the damping ratio of vehicle, the velocity of vehicle, the driving mode of vehicle, the rigidity of bridge, the arrangement of bridge and the soil-structure–interaction mode, then orthogonal test table was employed to study the structural impact factors of deformation and bending moment in the critical sections under those parameters respectively, thus the sensitive parameters could be found. The results show that the impact factor of the combined bridge calculated by impact formula of General Code for Design of Highway Bridges and Culverts is relatively lower, and the ratio of bridge and vehicle frequency, the roughness of deck, the velocity of vehicle are the sensitive parameters affecting the impact factors. Therefore the impact factor should be interpreted as the function of muti-parameters rather than only one parameter. 2012 Vol. 31 (3): 97-101 [Abstract] ( 998 ) HTML (0 KB)  PDF (1546 KB)  ( 364 ) 102 Vibration property analysis of an axially moving cantilever beam with the effect of a moving mass LIU Ning;YANG Guo-lai DOI: The projectile-barrel launching system is simplified as an axially moving cantilever beam system under the effect of a moving mass. The vibration equation of the axially moving beam is derived. The modified Galerkin’s method is employed to truncate the governing partial differential equation of the translating beam to a set of second order time-varying ordinary differential equations. Then the equations are calculated based on Newmark-β time integration method. The results show that the first order mode of beam is inspired by the moving mass. The magnitude of the moving mass and its moving speed have an important effect on the beam vibration response and the beam shows instable vibration state in spite of constricting or extending. After the moving mass disengages the constricting beam, the beam instantaneous vibration frequency and vibration displacement are decreased while the vibration speed are increased and the movement of the beam is in the instability state too. However, while the beam are extending, the unrestricted vibration rules of the beam are reverse. 2012 Vol. 31 (3): 102-105 [Abstract] ( 1195 ) HTML (0 KB)  PDF (1228 KB)  ( 866 ) 106 Flutter and dynamic analysis based CFD/CSD coupling method Xie Liang;Xu Min;Li Jie;Cai Tian-xing DOI: CFD/CSD coupling algorithm research was conducted, and CFD based nonlinear aeroelastic simulation code was developed for complex aeroelastic system analysis. In order to meet the demand of rapid analysis, a reduced-order model based on Volterra series for nonlinear unsteady aerodynamics is developed. This model is validated on AGARD 445.6 wing which is a standard aeroelastic configuration, and used to the Flutter analysis of a plate wing with regula. CFD/CSD coupling is employed to calculate the aeroelastic response under the flight dynamic pressure, the result shows that even when the flight dynamic is below the flutter boundary, the aeroelastic response also has the possibility to go into Limit Cycle Oscillations(LCO).Then the dynamic load is analyzed in this case. The result shows that CFD/CSD Coupling Method can credibly simulate the aeroelastic response, and it can give accurate information about dynamic load in such response. 2012 Vol. 31 (3): 106-110 [Abstract] ( 796 ) HTML (0 KB)  PDF (1562 KB)  ( 347 ) 111 unsteady aerodynamic response and aeroelastic stability of oscillating compressor cascade ZHENG Yun;YANG Hui;TIAN Xiao DOI: An accurate and efficient numerical method is developed for the aeroelastic analysis of turbomachinery blading in unsteady transonic flows. The unsteady Reynolds-averaged Navier-Stokes equation with the Spalart-Allmaras turbulence model is solved with an implicit dual-time stepping technique. The blade passages were discretised using finite volume method with multi-block. The unsteady aerodynamic responses and the aeroelastic stability of the 10th standard configuration undergoing bending blade vibration were calculated in subsonic and transonic flows. The effect of the flow conditions, reduced frequency and inter-blade phase angle on the cascade aeroelastic stability is analyzed. The results indicate that the shock destabilizes the cascade and the influence of the inter-blade phase angle is enforced under the higher reduced frequency. 2012 Vol. 31 (3): 111-116 [Abstract] ( 823 ) HTML (0 KB)  PDF (2217 KB)  ( 327 ) 117 nonlinear dynamics of compound planetary gear sets based on incremental harmonic balance method Wu Shi-jing; Liu Zhen-hao; Wang Xiao-sun;qian bo DOI: A purely rotational model of Ravigneaux compound planetary gear sets including time-varying mesh stiffness, synthetical mesh errors and backlashes is developed. Incremental harmonic balance method is applied to obtain the steady state response of fundamental frequency. The influence of the system parameter on dynamic characteristics is analized by changing the value of time-varying mesh stiffness, backlashes, external excitations. It is showed from the research that multiple value and amplitude jump discontinuities are presented on the dynamic curves with the existence of backlashes. More abundant dynamic behaviors are existed in compound planetary gear sets by the coaction of the system parameters. Incremental harmonic balance method can be used in more complex systems to obtain the approximate solutions of arbitrary-precision, which lay the foundation of controlling vibration and noise of the system to achieve the dynamic design of compound planetary gear sets. 2012 Vol. 31 (3): 117-122 [Abstract] ( 742 ) HTML (0 KB)  PDF (1042 KB)  ( 382 ) 123 Gas Flow Noise from the pump chamber of Rolling Piston compressors Based on CFD YUE Xiang-ji;BA De-chun;SU Zheng-yu;JI Kai;LI Ai-ming DOI: In order to analyze gas flow noise from the chamber of rolling piston compressors, an effective method was presented based on computational fluid dynamics (CFD). Through the flow simulation of pump chamber by using dynamics mesh technology, the vortexes with larger turbulence intensity were found, and the location and mechanism of vortexes formation were analyzed. Then amplitude and frequency of vibration excitation were evaluated by gas force on the wall from CFD. The comparative results with or without silencer hole explained the principle of noise reduction, and validated the method. The proposal has also been arise to control flow and noise. 2012 Vol. 31 (3): 123-126 [Abstract] ( 897 ) HTML (0 KB)  PDF (2072 KB)  ( 562 ) 127 Characteristics of sound propagation in a buried pipe for leak detection YAN Jin;LIU Jing-xi;ZHANG Juan DOI: Since the loss of large amounts water through leak pipework system is both environmentally and economically damaging, accurate location of buried leakage pipes is a subject of waterworks and city planning construct in the worldwide major urban areas. For a buried pipe, it is a typically coupling system including three phases, i.e., soil, pipe and fluid. As the surrounding soil treated as elastic medium, characteristics of sound propagation are studied analytically for a fluid-filled pipe surrounding by elastic medium. Pipe coupling equations for n=0 axisymmetric wave motion are derived, and complex wavenumber solutions are obtained by numerical method for both s=1 wave and s=2 wave, which correspond to a predominantly fluid-borne wave and a compressional wave in the shell, respectively. The results show that the wavenumber of fluid-borne wave will decrease while nearly have no effect on compressional wave due to the existing of surrounding soil. Since the coupling between the pipe and the soil will result in energy radiation, larger attenuation arises for both s=1 wave and s=2 wave. It will give some help for leak detection of buried pipes. 2012 Vol. 31 (3): 127-131 [Abstract] ( 673 ) HTML (0 KB)  PDF (1064 KB)  ( 636 ) 132 Research on Weak Signal Detection Based on the Modulated Stochastic Resonance XIA jun-zhong;LIU yuan-hong;MA zong-po;LEN yong-gang;AN xiang-bi DOI: In engineering signal processing, parameters of the signal often beyond the requirements of adiabatic approximation or linear response theory of stochastic resonance. The paper discusses the mechanism and condition requirements of stochastic resonance of nonlinear bistable system, and the frequency modulation combined with the theory of stochastic resonance. Modulated stochastic resonance is used to achieve weak signal detection in engineering applications, the numerical simulation is conducted to prove its effectiveness, and the method is also used to detect pitting corrosion of bearing inner race. 2012 Vol. 31 (3): 132-135, [Abstract] ( 752 ) HTML (0 KB)  PDF (1549 KB)  ( 579 ) 136 Piecewise linear model of shape memory alloy and its damping characteristics ZHENG Ji-zhou; ZHANG Yan DOI: It is important to establish a simple and effective constitutive model of shape memory alloy (SMA) for engineering applications and theoretical analysis. The nonlinear constitutive relation between stress and strain of superelastic SMA was simplified and a piecewise linear one was derived with the effect of martensite content during the phase transition considered. Based on this model, expressions of loss factor and other characteristic parameters were given. Finally, the model was applied to a single degree-of-freedom system and the effects of shape memory alloy on vibration isolation were analyzed. The results of numerical simulation show that strain amplitude and temperature both affect these parameters with different degrees, and the stiffness of parallel spring has an influence on the damping effect of SMA wire. 2012 Vol. 31 (3): 136-140 [Abstract] ( 810 ) HTML (0 KB)  PDF (1600 KB)  ( 469 ) 141 Structure damping of thin-walled composite one-cell beams Ren Yong-sheng; Du Xiang-hong; Sun Shuang-shuang; Teng Xiang-meng DOI: This paper presents a theoretical study of the damping of thin-walled composite one-cell beams.The equations of motion of the beams are derived using Hamilton’s principle. A variational asymptotically approach(VAM) is employed in the cross-sectional analysis. The Galerkin’s method is used in order to solve the coupled differential equations. Analytical formulas of the modal damping of the beam are derived on the basis of maximum strain energy theory. Comparison of the theoretical solutions has been made with the results obtained from the finite element method. Numerical results are obtained for two box beams: Circumferentially Uniform Stiffness(CUS) and Circumferentially Antisymmetric Stiffness (CAS), and one airfoil profile beam, respectively. The effects of fiber orientations, box section aspect ratio and length aspect ratio on modal damping are investigated. 2012 Vol. 31 (3): 141-146 [Abstract] ( 593 ) HTML (0 KB)  PDF (1316 KB)  ( 691 ) 147 synchronous vibration system of multi-hammer and synchronous control strategy LAI Xin;WU Jian-zhong;ZHANG Zhen;ZHENG da-bing DOI: The development of pile is moving in bigger diameter and longer length, a single vibration hammer is difficult to meet power requirement for large-diameter pile, synchronous vibration control of multiple vibrating hammer is an effective method to solve the problem. The basic principles of synchronous vibration control and methods are analyzed. Synchronous control system base on field bus was designed, and an open distributed control network was built. Considering the working characteristics and mechanical properties of vibrating pile hammer, speed and phase synchronization controller was designed. The simulation research and experimental results show that control method is effective with rapid response speed, strong robustness and good stability, and synchronous vibration of multiple vibration pile hammer is achieved base on controller area network, velocity and phase differences are satisfy engineering demands. 2012 Vol. 31 (3): 147-152 [Abstract] ( 421 ) HTML (0 KB)  PDF (1929 KB)  ( 547 ) 153 Vibration analysis of cracked rotor with initial deflection ZOU Jian;DONG Guang-ming;CHEN Jin DOI: Based on the simple hinge crack model, the dynamic equation of a cracked rotor with initial deflection was modelled in dimensionless form, which can be applied to the vibration analysis of cracked rotor with different parameters at stationary, transient and nonlinear state. By analytical solution, the frequency components of the cracked rotor with initial deflection were compared with those without initial deflection. The participation factors of the crack and the initial deflection were obtained, and the subcritical resonance was discussed. The stability of the cracked rotor with initial deflection was investigated using Floquet theorem, and the influence of different stiffness variation and damping ratio on stability was analyzed, which can provide a basis for identification of cracked rotor. 2012 Vol. 31 (3): 153-156 [Abstract] ( 567 ) HTML (0 KB)  PDF (936 KB)  ( 206 ) 157 Bearing fault diagnosis under varying load conditions based on individual feature selection and relevance vector machine Zhou Yong; HE Chuang-Xin DOI: An intelligent fault diagnosis model based on individual feature selection (IFS) and relevance vector machine (RVM) is proposed for bearing fault diagnosis under varying load conditions. First, vibration data measured under no-load (0hp) and full-load (3hp) is combined and used for training. Second, Statistical characteristics in time domain and node energies in full wavelet packet domain are extracted as candidate features. Third, an improved Fisher feature selection method is proposed and used to select individual best feature subset for each pair of classes. Fourth, using one-against-one (OAO) approach, several RVM binary classifiers are trained for each pair of classes. Finally, the IFS_RVM multi-class fault diagnosis model is constructed by combining all RVM binary classifiers using max-probability-win (MPW) strategy. Vibration data measured under untrained load conditions (1hp and 2hp) are used for testing, resulting in very high accuracy of 99.58%. Experimental results demonstrate that the proposed model is very effective and robust for online fault diagnosis under varying load conditions. 2012 Vol. 31 (3): 157-161 [Abstract] ( 1042 ) HTML (0 KB)  PDF (711 KB)  ( 773 ) 162 The mid-frequency IL research of the sound package under structure excitation Lu Zhao-gang;Hao Zhi-yong;Zheng Xu Yang-ji DOI: The hybrid FE-SEA model to predict the Insertion Loss of the sound package in mid-frequency under the structural excitation was proposed, and the model turned to be good predictions compared to the results compared to experiments. Based on the model, the parameters of the sound package was changed and the relatively IL were calculated. A rule was presented that the most sensitive parameters to the IL dips frequency characteristic was those parameters affect the whole structure mode characteristic mostly. Finally, the conclusion was got that the most effective sound package applied on the structure when the structure-borne sound was the main sound transmission path was the Septum-backed carpet. 2012 Vol. 31 (3): 162-167 [Abstract] ( 1041 ) HTML (0 KB)  PDF (1828 KB)  ( 321 ) 168 higher-order nodal discontinuous galerkin method for aeroacoustics Chen Er-yun;Zhao Gai-ping;Yang Ai-ling;Zhuo Wen-tao DOI: Numerical schemes that have minimal dispersion and dissipation errors are desired for direct simulation of noise propagation. Dispersion and dissipation properties of nodal discontinuous Galerkin(DG) method for the linearized Euler equation are investigated by utilizing an eigenvalue analysis technique. It is found that for any given order of the basis functions, there are m+1 mode of numerical waves. But only one represents propagating mode of physical wave corresponding to the partial differential equations, the rest are numerical parasite modes. The directions of propagation of these two numerical modes are opposite. Moreover, the comparisons of dispersion properties among the nodal discontinuous Galerkin method, DRP schemes and compact finite difference schemes with the same order show the solvable wavenumber range lying between DRP schemes and compact finite difference schemes. Finally, a test problem of wave propagation with initial disturbance consisting of a Gaussian profile is solved. The quality of solution obtained by nodal DG method with less grid number are analogous to that of compact finite difference schemes, but better than that of DRP schemes, which indicate this method is very appropriate to direct numerical simulation of aeroacoustics. 2012 Vol. 31 (3): 168-171 [Abstract] ( 779 ) HTML (0 KB)  PDF (1058 KB)  ( 313 ) 172 new approach for predicting the wind-induced response – generalized coordinates synthesis method Chen Kai;Fu Long-biao;Qian Ji-hong;Jin Xin-yang DOI: The wind-induced structural responses are usually predicted by the complete quadratic combination (CQC) method as well as its improved forms on the basis of the power spectral density matrix of the excitation-source. However on the condition that the excitation time history is already given by the wind tunnel test, a preferred approach named generalized coordinates synthesis (GCS) method can be more efficient and less time-consumption. The single-degree-of-freedom generalized coordinate equations are firstly solved in frequency domain and the response time history or covariance matrix is accordingly obtained by the mode superposition. The acceleration response also can be predicted from acceleration time history of the generalized coordinates. If only the response covariance matrix is required, the computational cost and resource of GCS method is generally less than 10% of the traditional and improved forms of CQC method while the results are mathematically equivalent with them. Another significant advantage of GCS method is the response time history can be derived readily from the generalized coordinates, which provides convenience for the study on the components of the response and the probability distribution of response. It is demonstrated and verified by two typical examples that the GCS method is efficient, fast and accurate. 2012 Vol. 31 (3): 172-178 [Abstract] ( 1156 ) HTML (0 KB)  PDF (1347 KB)  ( 1224 )

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