25 June 2009, Volume 28 Issue 6
    

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  • Guan Xinchun;Guo Pengfei;Ou Jinping;
    . 2009, 28(6): 1-5.
    Abstract ( 1871 ) Download PDF ( 763 )   Knowledge map   Save
    Firstly, the response time of a large-scale magnetorheological fluid damper (MRF damper) under different velocities and currents was tested. Then, the changing dynamic magnetic field inducted by changing electric current was simulated by finite element analysis (FEA). Based on variation of shear yield strength of MR fluid at gap between cylinder and piston, the response time of MRF damper was calculated. The response time between tested and calculated was also compared. Finally, the effects of eddy current and electric current response time on the damper’s response were also investigated. The researches show that, it is effective that using history curve of average effective shear yield strength of MR fluid at gap which calculated by FEA to study response time of MRF damper. The results also show that, electromagnetic response time is the most important factor which influence the response time of MRF dampers, and reducing eddy current is the key method to reduce response time of MRF damper. Moreover, the influence of eddy current is much higher at condition of current decreasing, and with the same skip of current, whether current increase or decrease, the smaller the initial current is, the greater eddy current affect the damper’s magnetic circuit and the longer damping force response time is. Shorten response of electric current, may induce higher eddy current, and not always reduce response time of damping force.
  • Li Lei;Huang Yi
    . 2009, 28(6): 6-7.
    Abstract ( 1465 ) Download PDF ( 608 )   Knowledge map   Save
    Abstract: On the basis of the nonlinear dynamical foundational equations, the big deflection equation and the nonlinear dynamic equation of the shallow spherical shells were established by the method of quasi-shells. Dimensionless quantity of shells with uniform thickness was introduced and simplified the foundational equations and the boundary conditions under the fixed boundary conditions. First the big deflection is taken as the initial imperfect of the system and a nonlinear dynamic differential equation including the second and third order is derived by the method of Galerkin. The critical conditions of that chaos motion are given by solution the Melnikov function. Using the digital simulation plotted the plane phase and it approved existence of the chaotic motion and controlled the chaos。 Finally, it is found that the natural frequency of shallow reticulated spherical shells considering initial imperfect becomes bigger and the critical value of chaotic motion is smaller.
  • Liu Jingbo;Yan Qiushi; Wu Jun
    . 2009, 28(6): 8-11.
    Abstract ( 1870 ) Download PDF ( 998 )   Knowledge map   Save
    Abstract: An explosion inside the tunnels would generate blast wave which transmits through the longitudinal tunnels. Because of the close-in effects of the explosion and the reflection by the confining tunnel structure, blast wave propagation inside the tunnels is distinct from which in air. When the explosion happens inside tunnel structure, the peak overpressure is higher than which the explosion happens in air. The duration of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for a experiment of the explosion inside the tunnels has been made. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strains problems. Compared with the experiment results, the simulation results have made the material parameters of numerical simulation model available. Making use of the model and the same material parameters, many results have been adopted by calculating the model under variety for different TNT explosion dynamites .Then the method of dimensional analysis has been used for the simulation results. As the explosion blast wave overpressures are the governing factor in the tunnels response, a formula has been suggested for calculating the blast wave peak overpressures at a certain distance from the detonation center point inside the tunnels by using the dimensional analysis theory. Compared the results computed by the formula with experiment results which had been done before board and in, the formula has been proved very applicable at some instance. The research may be helpful to rapidly estimate the tunnel internal explosion effects on the structure.
  • Li Zhinong;Fan Tao;Liu Lizhou;Lu Jifu
    . 2009, 28(6): 12-16.
    Abstract ( 1569 ) Download PDF ( 908 )   Knowledge map   Save
    Abstract:The traditional blind separation method of mechanical sources generally can not give a satisfactory separation performance under the unknown noise. Based on this deficiency, a new separation method of machine fault sources based on variational Bayesian independent component analysis (VbICA) is proposed. Compared with the traditional method, the proposed method has such unique characteristics, i.e. the unknown noise can not be regarded as an independent source. The denoising preprocessing is also neglected. The mechanical sources under the noisy environment can be directly separated. The simulation result shows that the proposed method is superior to the traditional method, the separation error is greatly reduced. The experiment results also verified the validity of the proposed method .
  • ZHOU Dai;MA Jun;LI Huafeng;ZHU Zhongyi
    . 2009, 28(6): 17-22.
    Abstract ( 1505 ) Download PDF ( 376 )   Knowledge map   Save
    Abstract: The wind pressure on the structural surface and the coupling wind-induced vibration effects of spatial flexible structure were studied. The fluid governing equations and the turbulent model of large eddy simulation (LES) were introduced and iteration solving process for the wind-structure coupling dynamic equations was established. Some accepts describing structural working states such as pre-stress loading state, stable state and coupling state were defined, while the uniform expression for both structural static state and dynamic state were developed. The time-history structural dynamic analysis technique, the unilateral coupling process and the coupling interaction process were applied to a series of computation and comparison on the wind effects of a typical spatial cable-membrane structure. The investigation shows that the structural mean displacements by time-history structural dynamic analysis technique basically accord with those by the unilateral coupling process; however, the greater structural wind-induced vibration coefficient was gotten by the former technique. Moreover, by the coupling interaction process, the structural mean displacements were less than those by the other two, while the greatest structural wind-induced vibration coefficients were gotten.
  • ZHENG Fei;YE Ji- hong
    . 2009, 28(6): 23-28.
    Abstract ( 1973 ) Download PDF ( )   Knowledge map   Save
    Abstract: The spatial variation of ground motion is affected by source rupture process, transmission route and soil condition. At present, the research on coherence of ground motion mostly based on array measured data, which doesn’t have universality. In this paper, using dislocation model of seismic source, theoretical seismogram of random earthquake motion field in homogeneous and single medium was simulated by numerical method. Spatial coherence of surface earthquake motion field is investigated, according to a lot of calculation data. The results show that the laws of spatial coherence of ground motion reflected in numerical simulation results basically tallies with those reflected in measured data, which indicates that the analysis method and model adopted in the paper is reasonable. Besides, anisotropy exists in spatial coherence of ground motion with propagation direction of seismic wave, and fault strike is an important influence factor of spatial coherence of ground motion. The method in this paper is just a attempt for coherence of ground motion.
  • XU Wei-hua;LIU Ji-ke;LV Zhong-rong
    . 2009, 28(6): 29-31.
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    Abstract: In this paper, finite element analysis is used for the forced vibration analysis of the string structure. The dynamic response sensitivity with respect to the physical parameter (elemental cross-sectional area) is then derived. In the inverse analysis, the local damages in the string are identified from dynamic response sensitivity-based finite element model updating method. It is found that the local damage(s) can be identified successfully from several dynamic response measurements. The effect of artificial measurement noise on the identified results is also discussed. Numerical simulation shows that the proposed method is insensitive to the measurement noise and with very good accuracy. And it has the potential for practical application.
  • Wang Yu;Chi Yilin;Wu Xing
    . 2009, 28(6): 32-41.
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    Abstract: On the basis of introducing the unified model of blind signal processing (BSP), the typical BSP algorithms are comprehensively concluded, and the present research status of BSP in machine noise monitoring and fault diagnosis are summarized. It is emphatically discussed that mixed models, blind source separation and blind deconvolution of mechanical noise, blind source separation combined with other technologies and machine noise monitoring and diagnosis system based on BSP. Finally, the future further main research is put forward.
  • TAN Ping;BU Guo-Xiong;ZHOU Fu-Lin
    . 2009, 28(6): 42-45.
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    Abstract: Considering insufficient space in installing TMD at high-rise tower structure in practical engineering application, a study on wind-resistant dynamic reliability of TMD with limited spacing is developed. Firstly, the wind-induced stochastic responses of the high-rise tower structure is calculated by using pseudo excitation method. Further, the wind-resistant dynamic reliability of TMD shock absorber within the acceptable level of TMD stroke is investigated for different returning periods wind loads, based on First Excursion Failure Criterion of random vibration. New Guangzhou TV Tower, which is the highest engineering structure in China, is employed as a numeric example herein. Results show that this study is of great engineering significance.
  • Li Chunxiang;Tan Yaya;Li Jinhua
    . 2009, 28(6): 46-51.
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    Abstract: The wind loading is one of the crucial loads in both the wind-resistant design and disaster prevention and reduction analyses for overpass bridges. Inasmuch as the wind-overpass bridge interaction is rather complicated, we can obtain the reliable data of wind velocity (loading) by resorting to wind tunnel tests, full-scale measurements, and numerical simulations. Notwithstanding this, we may gain an insight into the dynamic characteristics of vibrations of overpass bridges under wind loads via the time history analysis. The effectiveness of wind vibration control of overpass bridges can be intuitively displayed in the time domain. Therefore, the main objective of this paper is to simulate the fluctuating wind velocity time series of overpass bridges with resorting to the auto-regressive move average (ARMA) model in the white noise filtration method (WNFM). First, taking into account both the time and space correlativity of the wind speed of overpass bridges, the expressions of the ARMA model have been derived with the order of both the auto-regressive (AR) and move-regressive (MA) components being unequal. Then, based on Kaimal spectrum, the simulation of the wind velocity time histories of a real overpass bridge has been carried out utilizing the ARMA model. Eventually, through comparing the simulated values of wind speed spectral density, auto- and cross-correlation functions with the corresponding targets, the flexibility is then corroborated of simulating the fluctuating wind speed time series of overpass bridges using the ARMA model.
  • LI Wei;ZHU Xi;WANG Xiao-qiang;MEI Zhi-yuan
    . 2009, 28(6): 52-55.
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    Abstract: To study the ballistic performance of basalt fiber reinforced composites, ballistic tests were conducted on target samples made by basalt fiber reinforced composites with different resin matrix. Anti-penetration properties and typical damage mode were studied. Influence of different resin matrix and different stack sequence to targets’ bullet-proof effect was analyzed. Results show that penetrated by bullet, the main damage mode of composites was local damage, whose forms were shear lapse of fiber facing the ball and tensile failure behavior of fiber on the backside. In addition, new design mentality on defend structure was put forward adopting to light armor. So research results could supply reference to design of light composite armor.
  • YANG Chao FAN Shi-juan
    . 2009, 28(6): 56-59.
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    Abstract: Numerical analysis of fluid-structure coupling vibration of fluid-conveying pipe was carried out by method of characteristics (MOC). 14-function model is adopted in the numerical analysis, and the MOC is improved to get higher numerical analysis precision. Confirming conditions of time step, Dt and divided number of straight pipe, N are presented, self-adaptive-mesh-manifolding method of modifying mesh spacing Dz close to boundary is put forward to catch accurate change of fluid pressure. A numerical simulation research on coupled vibration response of a hydraulic system is carried out, the result shows that numerical result is consistent with experiment result, and the numerical method introduced is validated.
  • SHAO Yi-min;CHEN Zai-gang;ZHOU Xiao-jun;GE Liang
    . 2009, 28(6): 60-65.
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    Abstract: The impact energy of gears in meshing is produced by different excitation sources such as machining or mounting errors, time-varying stiffness, and damages in critical components. In order to find the relationship between contact interfaces and the vibration energy delivered to the gear-shaft-bearing-housing-casing multi-interfaces, the definitions of multi-interface, through which the vibration energy is delivered, are provided in this paper. The energy peak value and the energy root mean square (RMS) are investigated. The term energy-maintaining factor is proposed to illustrate the relationships between the contact interfaces and the vibration energy. Finally, a table of factors depicting the relationships between energy on multi-interface and energy-maintaining factor is obtained based on experimental studies. The results show that energy-maintaining factors and the energy relationships can be used to explain the decaying of shock vibration energy in mechanical transmissions.
  • Shen Jianhong;;Li Chunxiang;Li jinhua
    . 2009, 28(6): 66-70.
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    Abstract:Difficulties of selecting the accurate dynamic parameters will be increased in stages of building design for lack of the dynamic parameter data, especially damping ratios related to wind-induced responses of super tall buildings. Field measurements of dynamic responses of super tall buildings and subsequent modal parameter identification thus may increase and supplement these data and evaluate the design accuracy. In this paper, the strong wind-induced responses of Shanghai Jin Mao mansion via field measurements are analyzed by the wavelet transformation (WT) with a kernel function, namely the Morlet wavelet, combined with the random decrement technique (RDT), then identifying its natural frequencies and corresponding damping ratios. The numerical result shows that the identification of structural natural frequencies is considerably accurate and while with the increasing of order, the standard deviation of damping ratios is going up.
  • LIN Li;ZHAOiDe-you
    . 2009, 28(6): 71-74.
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    Abstract: In this paper we show the possibility of using local-wave to analyze the time-frequency feature of the acoustic emission signals produced by the crack in the offshore structure model. In the investigation, we used a local wave decomposition technique, allowing time series of acoustic emission signal being decomposed into a small number of intrinsic mode function components (IMF). Under the Hilbert transformation process, IMF can be translated into an expression called Hilbert spectra, which exhibits the amplitude-frequency-time distribution of the data. The marginal spectra, which present the energy-frequency distribution of the data, were obtained by integrating the Hilbert spectra with time. The feature of the offshore structure simulation acoustic emission signals could be extracted by applying local wave analysis. On the basis of local-wave analyzing, the characteristics of the crack acoustic emission signals in the offshore structure, was found which indicated the acoustic emission occurrence. Consequently, the experimental results show that the proposed approach is able to effectively capture the significant information reflecting the acoustic emission in the offshore structure, and thus has good potential in the field of acoustic emission signal feature extraction.
  • BAI Zheng-feng;ZHAO Yang;TIAN Hao
    . 2009, 28(6): 75-78.
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    Abstract: The contact phenomenon in flexible multi-body system is common in engineering, which always make great effects to system design and analysis. The contact condition is analyzed and then the contact model of flexible bodies is established using nonlinear spring model as well as the tangential friction is considered by Coulomb friction model. Then the contact model was associated with the equation of flexible multi-body system. So the flexible multi-body system dynamics model is established including contact model, which is applied to common contact multi-body system. The dynamic simulation of contact process of a flexible beam in gravitational field is made to proof the validity and correctness of the model. The dynamic response and the rule of the contact force are discussed in detail, which includes the angular displacement and angular velocity, the time course of contact force and the rule of terminal displacement and velocity. Finally the differences between flexible and rigid beam are compared and discussed in detail. The results show that the nonlinear spring model is availability for contact dynamics of flexible multi-body system.
  • Qin Zhiying; Lu Qqishao
    . 2009, 28(6): 79-81.
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    Abstract Nonsmooth factors widely exist in natural and engineering areas, so it is important to study in general by dynamics theories. For non-smmoth systems, there not only are general bifurcations in smooth systems, but also occur special bifurcations, which are named non-smooth bifurcations. These non-smooth bifurcations have important effect on system dynamic behavior, and provide more routes to chaos. This is hot and difficult point for non-smooth dynamics.
  • Gao Mei-juan;Zhang Wei;Yao Ming-hui;Yao Zhi-gang
    . 2009, 28(6): 82-85.
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    Composite laminated plates have many advantages such as unique electromechanical coupling, light weight, high strength, fatigue resistance, and it is widely used in modern engineering and especially in the aerospace industry. In the present study, based on the third-order shear deformation laminate theory of Reddy, we study the six-dimensional nonlinear system for the simply supported at the four-edge rectangular laminated composite piezoelectric rectangular plates, which are subjected to in-plane excitations, out-plane loads, thermal loads and piezoelectric excitations. Taking into account that the averaged equation has a double zero and two pairs of pure imaginary eigenvalues, we use the theory of normal form to simplify the six-dimensional averaged equation to a simpler form. The energy-phase method is employed to study the global bifurcations and chaotic dynamics of the six-dimensional nonlinear system for a composite laminated plate. The global analysis indicates that there exists the multi-pulse jumping of homoclinic orbits in the system. At the same time, numerical simulation is used to investigate the nonlinear characteristic of the plate. The results of numerical simulation demonstrate that the jumping phenomena of orbits can occur for the composite laminated plate.
  • ZHAO Demin;ZHANG Qichang;WANG Wei
    . 2009, 28(6): 86-89.
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    The 2-DOF airfoil system with freeplay nonlinearity in pitch, excited by longitudinal and vertical random turbulence, is investigated numerically. The random bifurcation including P-and D-bifurcation is studies in term of the Bi-dimension probability density function (PDF) and the largest Lyapunov exponent respectively. The power spectral density function is also obtained in the paper. The results show in two different aspects. First when the airspeed lies in pre- and post-flutter speeds regime, the shapes of the Bi-dimension PDFs change as the turbulence intensity change from low to high, which demonstrates that the P-bifurcation has happened at the both airspeeds regimes. However, the largest Lyapunov exponents show that the D-bifurcation has not happened in whatever pre- and post-flutter speeds regime regardless when the turbulence intensity is low or high. Second the power spectral density functions are obtained in different airspeed regimes, the conclusion presents that when the airfoil flutter occur, the more power of the system focus on the flutter frequency.
  • SHEN Jian-he;CHEN Shu-hui(
    . 2009, 28(6): 90-92,1.
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    The multiple scales method was used to calculate the normal forms of dynamical systems near the Hopf bifurcation point and the analytical formula regarding the amplitude and frequency of the controlled limit cycles and the
    feedback gains was obtained. Thus, the control of amplitude and frequency of limit cycleswas realized by choosing the suitable feedback gains. A three-dimensional system was chosen as an illustrated example. The efficiencies of some linear or nonlinear state feedback controllers were discussed and compared. The obtained analytical conclusions were verified bynumerical simulations.
  • YANG Feng-hong; ZHANG Wei
    . 2009, 28(6): 93-94,9.
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    A dynamical and nonsmooth model of two-degree-of-freedom for an automotive disc braking system is established. Herein, the effect of the velocity of the rotor on the system’s dynamical behavior is focused on by numerical method. The results indicate that there exist complicate nonlinear dynamical phenomena, such as chaos and period-adding bifurcation, in the automotive disc braking system.
  • JIN Ji-duo; ZHANG Yu-fei; YANG Xiao-dong
    . 2009, 28(6): 95-99.
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    The stability and critical flow velocity of a supported pipe conveying fluid are analyzed. The both ends of the pipe are held by the pinned supports with torsional spring constraints. The stability of the fluid-conveying pipe is analyzed using the eigenvalues and eigenfuntions of a beam that has the same boundary conditions as the pipe. Using some numerical method, it is shown that the supported pipe conveying steady flow with the boundary conditions under consideration loses stability first by divergence always. According to the explicit expression derived for the critical flow velocity of the pipe, the effect of some physical parameters of the system, such as the spring constant, gravity and tension, on the values of the critical flow velocity is discussed.
  • Jia-Zhong Zhang;Li-Ying Chen;Guan-Hua Mei;Zhi-Hong Zhou;Zhe Su
    . 2009, 28(6): 100-103,.
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    From viewpoint of nonlinear dynamics, the shallow arch under impact can be considered as a continuous dynamic system or dynamic system with infinite dimension. The governing equation for the shallow parabolic arch under impact is derived following the nonlinear shell theory. Then, a new nonlinear Galerkin method, namely, Inertial Manifolds with Time Delay, is developed and applied to the dynamic buckling analysis of shallow arch, which is governed by a set of nonlinear partial differential equations. By this method, the solutions of the governing equations are projected onto the complete space spanned by the eigenfunctions of the linear operator of the governing equations. In comparison with traditional Approximate Inertial Manifolds(AIMs), the relationship between the high and low modes is improved by Approximate Inertial Manifolds with Time Delay (AIMTDs), that is, not only the instantaneous relationship is considered, but also the past behaviors. Finally, the method is applied to the dynamics buckling analysis of the shallow arch under impact, and the comparisons between traditional Galerkin's procedure, traditional AIMs, and AIMTDs are given. It can be concluded that the methods presented are effective for the dynamic buckling analysis of continuous dynamic system.
  • Sun Wei-peng; Wu Bai-sheng
    . 2009, 28(6): 104-106.
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    A modified Newton-harmonic balance method is used to construct analytical approximate periods and periodic solutions to the singular oscillator describing certain phenomena in plasma physics. The Newton-harmonic balance method is modified by rewriting the original control equation and selecting the simple and suitable correction terms. Two new analytical approximate solutions obtained in this paper are effective for the whole range of initial oscillation amplitudes and parameters, and they can rapidly converge to exact solution. The percentage errors between two new analytical approximate periods and the exact one are lower than 0.92% and 0.09%, respectively, and the latter is more accurate than the existing results.
  • YU Kai-ping;MU Xiao-ming
    . 2009, 28(6): 107-109,.
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    Recursive least square (RLS) is an efficient approach to neural network training. However, for the classical RLS algorithm, during the iterations, its gain vector gradually decreases to zero and loses the ability of modification, which will lead to the so called “data saturation” phenomenon. This paper proposes an improved recursive least square (IRLS) and applies it to nonlinear time-varying system identification together with the feed forward neural network. Theoretic analysis and two simulation examples are given to demonstrate the effectiveness of the proposed IRLS. Simulation results show that the proposed IRLS can overcome the problem of “data saturation” and has higher accuracy and robustness.
  • ZHANG You-qiang; DING Wang-cai
    . 2009, 28(6): 110-112,.
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    A nonlinear dynamical model of the two-degree-of-freedom dry friction oscillators with symmetric clearance is established, semi-analytic and numerical simulation method are used to resolve the response of system and complicated Slip-stick-impact dynamic behaviors are investigated. In order to capture accurately dividing points of Slip-stick-impact motions, the theoretical method about decision of Slip, stick, and impact of system are given and their engaging conditions are put forward respectively. There exist rich symmetrical periodic motion, stick-slip-impact motion, quasi-periodic motion, chaos and the influences of dry friction on the system dynamics are discussed.
  • Wang Qi-shen Wang Da-jun; Wu Lei Liu Quan-jin Zhang Li-hua
    . 2009, 28(6): 113-117.
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    In this paper the difference discrete models of the beam with overhang are established, the stiffness matrices of above discrete system are determined and their sign-oscillating property are proved. On the basis of it, some qualitative properties of the frequencies and modes of the discrete system of the beam with overhang are obtained.
  • Chai Fangmao Fang Bo Liu Fang
    . 2009, 28(6): 118-121.
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    A method of establishing dynamical models of axial symmetry missiles with complicated dynamical coupling was presented in this paper. The effects of vibration characteristics and flexibility deformation on the trajectory of flexible missiles were considered. First, according to traditional flight dynamics theory, the approach of establishing dynamical models of rigid missiles and flexible missiles with control force and aerodynamical force coupling was proposed. Second, the deformation equation of flexible missiles with control force, aerodynamical force and vibration coupling was derived based on Timoshenko beam theory. Finally, the effect of the flexible deformation of missiles to ballistic parameters was analyzed.
  • Zhao Na; Cao Deng-qing;
    . 2009, 28(6): 122-125.
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    As the object of high-speed and heavy-load putting into effect, the nonlinear dynamic problem of freight trains’ bogie become serious. Various factors which can be the causes of faults are analyzed in order to construct the 39-degrees-of-freedom nonlinear dynamic model of vehicle with fault parameters, and the wearing fault of second suspending is described in detail. After a large number of numerical calculations, the result is used to investigate the relations between the dynamic behavior and the corresponding fault parameters. A novel approach of vehicle fault diagnosis might be set up in this way.
  • Liu Xiang-qiu; Wang Cong; Zou Zhen-zhu
    . 2009, 28(6): 126-130.
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    The dynamics model of weak coupling periodic antenna structure is established. Based on the dynamics model, vibration properties of the structure are studied. Active vibration control of the structure considering disorder is investigated by applying Linear Quadratic Regulator control method. Results of numerical examples show that small disorder of the structures can induce remarkable mode localization and ratio of the amplitude of perfect structure to that of disordered structure is about 30%. The disorder must be considered seriously while performing active vibration control of this kind of structure to avoid invalidation of vibration control system.
  • Hongkun Li Shuai Zhou Zhihui Sun
    . 2009, 28(6): 131-134.
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    In this paper, a new pattern recognition method for machine working condition based on gravity center of Hilbert time-frequency spectrum and support vector machine (SVM) is demonstrated in detail based on vibration signal analysis. Firstly, synchronous average is used on monitored signal for preprocessing, which is used to remove effect from cyclostationary characteristics. Vibration signal data information changes from time domain to angle domain, which is more suitable for rotary machine pattern recognition. Then, Hilbert time-frequency spectrum is obtained according to Empirical Mode Decomposition (EMD) and Hilbert transform. Thirdly, gravity center of Hilbert spectrum is calculated to construct a feature vector for machine working condition pattern recognition. In the end, different working condition can be classified by using support vector machine (SVM). Rolling bearing pattern recognition is as an example to verify the effectiveness of this method in the research. According to the result analysis, it can be concluded that this method will be helpful for the development of machine preventative maintenance.
  • CAO Deng-qing;ZENG Jing;CHENG Wei-wei;CHEN Min
    . 2009, 28(6): 135-138.
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    A 6 DOF railbogie model established here was used to investigate the time delay output feedback contro of rail-bogie dynamic system.A vibration control rule for the entire system was designed in terms of the measurable output of the system.The differential equation of motion of the system was transformed to a state-space model with time delay in the control input.Then, a transformation with a linear term and an integral term was employed to transfer the original time delay system into a form without time delays.Accordingly, a time delay semi-active control rule for the system was designed based on the principle of output feedback,a reasonable performance index, and the“on-off” control strategy.Finally,a rail-bogie model with a set of typical parameters was taken as an example to illustrate the application procedure of the control strategy proposed.The numerical results show that the time delay semi-active control strategy designed here is effective.
  • X. Y. Guo W. Zhang M.H.Yao L. H. Chen
    . 2009, 28(6): 139-144.
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    An analysis on the nonlinear vibrations of a simply-supported composite laminated rectangular plate with parametrical excitations and forcing excitations is presented. First, based on the Reddy’s high-order shear deformation theory and the model of the von Karman type geometric nonlinearity, nonlinear governing partial differential equations of motion are derived by using the Hamilton’s principle. The plate has linear external damping. Then, used the second-order Galerkin discretization approach, the partial differential governing equations of motion are transformed to nonlinear ordinary differential equations under parametrical excitations and forcing excitations, which deals with the periodic and chaotic oscillations. The method of multiple scales can be used to get four averaged equations. From the averaged equations obtained here, the theory of normal form is used to give the explicit expressions of normal form. Based on normal form, high-dimensional Melnikov method is utilized to analyze the global bifurcations and chaotic dynamics in composite laminated rectangular thin plates. The results obtained above mean the existence of the chaos for the Smale horseshoe sense in parametrically excited and forcing excited composite laminated plates. The chaotic motions of composite laminated plates are also found by using numerical simulation. Numerical simulations obtained in this paper indicate that there exist different shape of the chaotic responses in the nonlinear oscillations of the composite laminated plate under certain force excitations, parametric excitations, parameters and initial conditions.
  • Liu Li Chu Jiangwei Shi Shuming
    . 2009, 28(6): 145-149.
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    Vehicle cornering system is a complicated system, the nonlinear tire force makes cornering system present strong nonlinear. The nonlinear model of the vehicle cornering system is established and the theory of nonlinear dynamics is introduced in this paper. Through the analysis of the character of the singular point, the influence of the geometrical character of the tyre and the longitudinal acceleration to the handling stability is studied, and the longitudinal acceleration is added to the stability condition, which deepen the study of the handling stability.
  • ZHOU Xiaodong YAN Shaoze CHU Fulei
    . 2009, 28(6): 150-152.
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    a new type of exact element method for calculation of natural frequencies of tightly stretched cable network structures is presented. Some of the theoretical aspects of the dynamic element method (DEM) are considered. Then the element formulation of dynamic element method of taut string is presented. Only motions within the vertical cable plane are regarded. The global matrices are assembled by a summation process same as the conventional finite element method. Three illustrative cable network structures are discussed to demonstrate the implementation of the current method. Solutions show that the results from using the DEM were more accurate than with the conventional finite element method especially on high order frequencies.
  • Hao Yuxin Zhang Wei
    . 2009, 28(6): 153-154.
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    The nonlinear dynamic response of functionally graded (FGM) rectangular plates under combined transverse and in-plane excitations are investigated under the different internal resonance. The material properties are assumed to be temperature-dependent and vary along the thickness direction. The thermal effect due to one-dimensional temperature gradient is included in the analysis. The governing equations of motion for FGM rectangular plates are derived by using Reddy’s third-order plate theory and Hamilton’s principle. The Galerkin’s approach is utilized to reduce the governing differential equations to a two-degree-of-freedom nonlinear system including quadratic and cubic nonlinear terms, which are then solved numerically by using 4-th order Runge-Kutta algorithm. The resonant case considered herein are 1:1, 1:2 and 1:3 internal resonance and principal parametric resonance-1/2 subharmonic resonance. The effects of plate geometry parameters, in-plane excitations and temperature field on the internal resonance relationship and nonlinear dynamic response of FGM plates are studied. Numerical results show that in the case of 1:2 internal resonance and principal parametric resonance-1/2 subharmonic resonance, the vibration amplitude of the plate center is much greater than the other two cases of the internal resonance.
  • LI Shao-hua;YANG Shao-pu
    . 2009, 28(6): 155-158.
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    A model of three-dimensional heavy vehicle-pavement foundation coupled system was presented, which is drawn as a sevenDOF vehiclemoving along a simply supported double-layer rectangular thin plate on a linear viscoelas-
    tic foundation. Using Galerkin method and quick direct integration method, the dynamical behavior of the vehicle-pavement foundation coupled system was investigated numerically and compared with that of traditional vehicle system and pavement system. The effects of coupling action on vehicle body vertical acceleration, suspension deformations, tire forces and pavement displacements were discussed. The investigation shows that the coupling action should not be neglected and it is necessary to investigate dynamics of vehicle and pavement simultaneously based on the vehicle-pavement foundation coupled system.
  • Li zhong gang Kong da Jiao ying hou Chen zhao bo Li ming zhang
    . 2009, 28(6): 159-163.
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    The influence of the low induced force is evidence in the ultra supercritical and the supercritical steam turbine. The dynamic characteristics of the flow induced force acting on rotor-seal systems is investigated in the paper.The nonlinear dynamic model of the rotor-seal system is established with Muszynska model. And Floquet theory is applied to study stabilities and dynamic behaviors of the periodic solutions in the systems. The dynamic characteristics of the system at the certain rotating speed and the certain physic parameters are analyzed by the periodical responses, Poincaré maps, frequency spectrums chart, bifurcation charts, etc.
  • LI Changyou XU Minqiang
    . 2009, 28(6): 164-167.
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    Generally, industry equipment is composed of several subsystems, and criticality of the subsystems in the equipment are different so that assigning reliability in design phase, confirming the detection level in running phase, selecting the maintenance policy for each subsystem must be based on its criticality. The improved TOPSIS used to evaluating the criticality of each subsystem of industry equipment satisfies the requirement of practical engineering. TOPSIS is employed to evaluate the criticality after the weights of each attribute are assigned using the information-entropy method. It is shown by the instance——criticality analysis of plastic extruder that the proposed method is effective and applied for evaluating the equipment criticality.
  • Liu Xijun Liang Chenjie Guo Jiping Jia Qifen Teng Xiaojun Liu Longxia
    . 2009, 28(6): 168-170.
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    In this paper, the forced vibration test is taken in the Dragon Washbasin. When a certain frequency excitation force is excited on the shell of the Dragon Washbasin, different shapes gravity waves will appear. Because of the object is a water waves, the magnitude is large and water splashes, it asks more of the measurement. According to the crossed optical axis theory we designed the experiment system. The space between the raster is adjustable, and we use high speed camera taking pictures. By using median filter, Fourier transformation, frequency filter, Inverse Fourier transform etc, the 3D height information of the first-order and second-order gravity waves of any time is got. Through the processing of a series of pictures in one period we got the time histories of any point of the waves. The work of this paper is a new trial of the measurements of the free surface wave in the fluid-shell coupled system, and the experimental data are significant references for the further theoretical study.
  • Si Chundi Chen Enli Yang Shaopu Wang Cuiyan
    . 2009, 28(6): 171-174.
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    Microphone Array technology is to get sound field information by multiple microphones, to process sound field signals applying the beam forming technology and to be able to identify broad-band sound sources efectively. Using the microphone array system based on beam forming technology, the frequency and energy distribution property of the noise emission of vehicle were investigated in this paper, the frequency and exact noise poisitions were determined by means of the optical pictures automatically overlapping. The results show that the microphone array technology is an efective way for the noise diagnose and sound localization, it ofers the scientific basis for noise control of vehicle.
  • Dong Lei Zhang Jazhong Wei Yingjie Jin Daqiao
    . 2009, 28(6): 175-178.
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    The underwater two-phase ramjet is one kind of the new style jet which is based on the development of the two phase bubbly flow throughout the Laval nozzle. The working mechanism of the ramjet is studied numerically by using CFD commercial software FLUENT 6.2. A steady flow, non-compressible air and non-exchanging heat are considered. When the velocity of the ship and the aeration angle is steady, and the aeration speed is supersonic, the inner thrust of the ramjet increases as the aeration speed increases. The inner thrust fluctuates in a wide range when the aeration speed increases to a very high speed. When the air is aerated only, the temperature of the air doesn’t have effect on the inner thrust almostly. While the gas aerated is composed of air and vapour, and the volume flux of the gas remains invariable, that the humidity of the gas increases causes a drop of the inner thrust of the underwater two-phase ramjet.
  • WEI Yingjie WANG Jinghua ZHANG Jiazhong CAO Wei HUANG Wenhu
    . 2009, 28(6): 179-182.
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    Supercavitation can be viewed as a phenomenon that could boost the speed of underwater vehicles. The vehicle is entirely surrounded by the cavity while it is traveling underwater in the supercavitation stage. Thus, the vehicle actually travels in air and has very small skin friction drag. Hydrodynamics and stability of the supercavitating vehicle do not depend on the hydrodynamic coefficients as in the case of a fully wetted underwater vehicle. The contact of the aft of the vehicle with the cavity wall get rise to the nonlinear planning force. And it is really hard to control and moneuver a supercavitating vehicle. This paper analysed the hydrodynamic force of all parts of the supercavitating vehicle. The efficiency of fin while it is traveling underwater are computed. The nonlinear dynamics model of supercavitating vehicle is completed. The controller are designed by nonlinear switched control strategy.
  • WU Yuhua LOU Wenjuan
    . 2009, 28(6): 183-187.
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    The random seismic analysis of long-span concrete filled steel-tube (CFST) arch bridge under multi-support excitations of three-dimensional orthogonal earthquake motion was performed. The precise finite element model of a 308 m span half-through CFST arch bridge was established. The seismic response of the arch bridge under one-dimensional P-wave, one-dimensional SH-wave, one-dimensional SV-wave and three-dimensional considering cross-power spectrum of multi-support earthquake excitations were numerically simulated by the method of the three-dimensional and multi-support stationary random seismic response, and the influence of three-dimensional earthquake motion, traveling-wave effect and partial coherence effect on arch rib were studied. The results show that the internal forces of arch rib may be greatly changed by considering the spatial variation of seismic motion. The influence of the traveling-wave effect of the earthquake motion on the internal forces of arch rib is greater than that of the partial coherence effect. The internal forces of arch rib under three-dimensional earthquake excitations are greater than that under one-dimensional excitation. The random seismic analysis under three-dimensional and multi-support earthquake excitations must be performed for the long-span CFST arch bridge otherwise the seismic design forces of the structure are likely to underestimate seriously.
  • XU Wenju YANG Baoru SONG Minfeng
    . 2009, 28(6): 188-190.
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    Uncrimping energy is an important quality index to measure the crimping effect of cellulose acetate fibers. It is determined by both crimp cap force and crimp roller force. It is found by analyzing that umcrimping energy is determined directly by vibration of crimp cap. In order to evaluate the stability of uncrimping energy, we develop a real-time signal monitoring system which is used to detect vibration signals of crimping machine. The electric vortex sensor is used to measure the swing of crimp cap. Finally, the umcrimping energy of this system is calculated with Root-Mean-Square Value, Peak to Peak Value and Average Value. During the on-line application, the results indicated that the umcrimping energy data which measured by monitoring system were more stable than practical and could rapidly reflect the force changes of crimp cap and roller.