25 September 2009, Volume 28 Issue 9
    

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  • LIU Zhangjun;LI Jie
    . 2009, 28(9): 1-4.
    Abstract ( 2550 ) Download PDF ( 1557 )   Knowledge map   Save
    Employing the orthogonal expansion method, earthquake acceleration process is represented as a linear combination of deterministic functions modulated by 10 independent random variables. So, it is natural to combine the probability density evolution method (PDEM) and the orthogonal expansion of seismic ground motion to study the nonlinear stochastic earthquake response. Furthermore, the aseismatic reliability of structures is assessed using the idea of equivalent extreme-value, which can be used accurately to evaluate structural systems under compound failure criterion. A hysteretic nonlinear structure is taken as an example. The failure probability and reliability of the nonlinear shear frame structure with 10 degrees of freedom subjected to stochastic ground motions are investigated. The result indicates the system reliability of the structure is lower than the reliability of each story. The investigation shows that the proposed approach is of fair accuracy and acceptable efficiency for seismic reliability.
  • Li Jinhua Li Chunxiang Shen Jianhong
    . 2009, 28(9): 5-8.
    Abstract ( 2837 ) Download PDF ( 1167 )   Knowledge map   Save
    In the simulation of wind loads, it is mostly hypothesized that wind loads are stationary Gaussian stochastic processes. But, inasmuch as the wind pressure fluctuations measured at corners as well as other separation flow regions of roofs of buildings are found to be highly non-Gaussian, the Gaussian assumption is not appropriate for the generation of the wind pressure time history in these local regions. In order to simulate the non-Gaussian fluctuating wind pressure, the following framework is proposed in the present paper. Firstly, the power spectral density (PSD) function of fluctuating wind pressure is deduced rigorously by resorting to the relationship between the wind pressure and velocity. Then, an efficient yet practical method by which the fluctuating wind pressure may be reproduced with the designated skewness and kurtosis is presented based on the derived PSD function, Johnson translator system, and digital filter. Finally, in order to corroborate the feasibility and correctness of the present methodology, a numerical example of simulating one-dimensional uni-variate non-Guassian fluctuating wind pressure is taken into consideration. Numerical results indicate that the statistical parameters, such as the skewness and kurtosis, of the simulated fluctuating wind pressure are in remarkably agreement with their targets. Likewise, the PSDs of the simulated records and target show considerably good agreement with each other.
  • WANG Xinjie YUE Honghao Tzou H S DENG Zongquan
    . 2009, 28(9): 9-14.
    Abstract ( 2150 ) Download PDF ( 979 )   Knowledge map   Save
    Photostrictive materials, like ferroelectric lanthanum-modified lead zirconate titanate (PLZT) ceramics, can produce a photodeformation effect under irradiation of high-energy lights and thus can be employed in non-contact actuation and control of flexible structures. Based on couplings of opto-piezo-thermoelastic fields, mathematical modeling of the photostrictive actuator is presented. Governing equations of the cylindrical shell laminated photostrictive actuators are formulated. The control effectiveness of distributed actuators with two configurations is evaluated with the control actions. Based on the configuration of the actuators, the bending effect and membrane effect are analyzed while the curvature angels of the cylindrical shell are changing. Finally, the Lyapunov and proportional velocity feedback control algorithms are studied and the simulation results show that the distributed actuators are effective to controlling the low-frequency oscillations of thin cylindrical shells.
  • WU Jie SHANGGUAN Wenbin Jing Tang SONG ZhiShun Huzng ZhenLei
    . 2009, 28(9): 15-20.
    Abstract ( 1647 ) Download PDF ( 910 )   Knowledge map   Save
    A computer aided engineering (CAE) based design of experiment (DOE) is used to analyze the robustness for the decoupling layout of a powertrain mounting system (PMS). The PMS of a car is considered, and contributions of the mount stiffness parameters to variations of the frequencies and the decoupling ratios of the PMS are investigated, respectively. The analysis method discloses the key stiffness parameters for the robustness of the frequencies and the decoupling ratios of the PMS. Analysis results show that variations of the frequencies and the decoupling ratios are due to the variations of all the stiffness parameters. The variations of the stiffness parameters have more influence on the frequencies and the decoupling ratios in the three rotational directions than that in the three translational directions of the PMS. The presented robustness analysis method lays theoretical foundations for the robustness design of a generic PMS.
  • LIU Yu CHEN Jin PAN Yuna GUO Lei
    . 2009, 28(9): 21-24.
    Abstract ( 1662 ) Download PDF ( 1186 )   Knowledge map   Save
    To improve the accuracy of description of equipment performance degradation process, a novel method for performance degradation assessment is proposed, which bases on two techniques: Support Vector Data Description (SVDD) and Dempeter-Shafer theory. SVDD was used to assess the performance according to the data from single sensor, and the performance assessment results based on multi-sensor were sent to D-S theory as input to obtain the assessment result of the whole system. As shown in experience, SVDD can reflect the performance degradation of equipment parts, the results of the equipment given by D-S theory accord with the practical situation, and the algorithms can deal with the evidence conflict problem effectively, which have improved the accuracy and reliability of the assessment results.
  • CHEN Yi Jie MENG Qiang WANG Ya Jun NIE Chun Gui WEI Lai Sheng
    . 2009, 28(9): 25-29.
    Abstract ( 1680 ) Download PDF ( 933 )   Knowledge map   Save
    The vibration test was developed for the first time with regard to the self-improving semi-active hydro-pneumatic suspension of 8X8 wheel-type vehicle, and the diagram of the damping controlled hydro-pneumatic spring and the control principle of the semi-active suspension were given. After that, the coefficients of flow of electromagnetic valve in different current strength were got through experiment and curve fitting. In the situations of wave road and express highway, the vertical vibration accelerations at different points on the vehicle body were tested. This validates that the mean square root value of the acceleration of each test point has been restrained efficiently while damping real-time adjustment is realized, so that the vehicle ride performance has been improved significantly. The obtained test data can offer reference to the design of the semi-active suspension interiorly.
  • SONG Chunsheng ZHOU Zude HU Yefa
    . 2009, 28(9): 30-32 3.
    Abstract ( 2008 ) Download PDF ( 867 )   Knowledge map   Save
    In this paper, a unit of magnetic suspension supporting is designed and applied to floating raft vibration isolation system. A semi-active output feedback fuzzy controller is designed for floating raft isolation system with magnetic suspension isolator .Then, optimal stiffness of magnetic suspension isolator and the appropriate current could be obtained. Input force and output force response of floating raft isolation system, under complex-frequency exciting signal and impact exciting signal are simulated. The simulation results indicate the performance of magnetic suspension supporting floating raft isolation system with semi-active fuzzy control method is more effective in vibration isolation in comparison with the passive optimal system.
  • CAO Chongfeng YANG Shixi YANG Jiangxin
    . 2009, 28(9): 33-38.
    Abstract ( 2026 ) Download PDF ( 1558 )   Knowledge map   Save
    Focusing on the defects of different de-noising methods in processing non-stationary vibration signal, a method based on Gausses white noise assisted empirical mode decomposition (EMD) technique which adaptively eliminates noise involved rotating machine non- non-stationary vibration signal is presented. This method is an ensembled algorithm of EMD de-noising method, which applies dyadic scales decomposition characteristics of normal distribution white noise with EMD, could effectively suppress mode mixing that occurred in analyzing non-stationary vibration signal with EMD de-noising method and obtain higher signal-to-noise ratio(SNR). Simulation numerical signal and experimental signal of rotor running state are used to test and compare the performances of the method and EMD based de-noising method and wavelet de-noising method. The results show that the EEMD based noise cancellation method presented in the paper has more effective de-noising performance, not only eliminates random noise, but suppresses intensity noise and extracts vibration intrinsic modes that reflect real physical meaning of signal.
  • Yang Liu Zhongdong Duan
    . 2009, 28(9): 39-47.
    Abstract ( 2370 ) Download PDF ( 920 )   Knowledge map   Save
    In this paper, updating the finite element model of semi-rigid jointed structures is studied. Firstly, a hybrid finite element is proposed, composed of a beam element with two connections at both ends, in order to consider the semi-rigidity of joints of both rotation and shear effect. This hybrid finite element is suitable for model updating, and the stiffness matrix and mass matrix of the proposed element are described. Secondly, a parameterized scheme to update the boundary support parameters is presented. Finally, the proposed hybrid finite element and parameterized method are experimentally studied by updating the finite element of a 14-bay frame with test modal parameters. The results show that the proposed methods are suitable for model updating of semi-rigid jointed structures.
  • ZI Bin ZHU Zhencai DU Jingli
    . 2009, 28(9): 48-51.
    Abstract ( 2500 ) Download PDF ( 701 )   Knowledge map   Save
    Based on the characteristic of the cable-driven parallel manipulator (CPM), the control method is studied. Taking account of the model uncertainties and external disturbances for CPM, control strategy of the flexible system is discussed. In addition, considering the characteristics of nonlinearity, slow time-varying, and multivariable coupling of the system, a fuzzy control plus proportional-integral hybrid discrete-time control method combining PI control with fuzzy logic control(Fuzzy-PI), which can enhance the control performance for steady state errors, is developed for more effective and robust performance. The scheme with proportional-integral-tuning unit, which optimizes the control rules by adjusting factors, is utilized to carry out the trajectory tracking of the object. Numerical results show the tracking errors in X, Y, and Z directions with Fuzzy-PI, conventional fuzzy logic controller, and discrete-time nonlinear PID control arithmetic hold in the range of ±10cm, ±7cm, ±3cm, and ±15cm, ±8cm, ±5cm, and ±15cm, ±9cm, ±4cm, respectively, in the presence of external disturbances.
  • Lu Wei Teng Jun
    . 2009, 28(9): 52-55.
    Abstract ( 2168 ) Download PDF ( 952 )   Knowledge map   Save
    The optimal sensor placement is one of the most important contents of the study on structural health monitoring and is connected with the precision of the modal identification and the result of the model updating directly. In order to obtain the best information for the modal identification, the method of optimal sensor placement based on data fusion is proposed. In the method, the distance measure is used to be the fusion level; firstly, the synthesized support level of the proposed measured points is calculated through the calculation of distance measure matrix and the support level matrix; secondly, the optimal location of sensor is decided according to the size of the synthesized support level; thirdly, the method is proofed to be effective through an example of optimal sensor placement on space truss structure, in which the peak value method is used to identify the natural frequency and the identified frequencies of selected measured points and the unselected measured points are compared.
  • PENG haikuo MENG Guang LI Fucai
    . 2009, 28(9): 56-59.
    Abstract ( 2075 ) Download PDF ( 843 )   Knowledge map   Save
    Based on phased array, a method using a transmitter and a cross-shape piezoelectric (PZT) transducer array was proposed for the purpose of damage detection in plate structures. Lamb wave propagation in an aluminum plate with and without a crack was simulated using spectral finite element method. The response signals of the structure were taken in the location of the elements of the PZT array and the difference signals of those responses were calculated. The time shifting is carried out according to the scheme and the relative locations of elements in the PZT array and then the signals are summed to detect damages in structure. The damaged plate structure was investigated using a cross-shape array. The results demonstrate that the proposed method can effectively detect the damages in plate structures.
  • Liu Chun Zhou Yun Zhang Jichao Wang Dayang
    . 2009, 28(9): 60-64.
    Abstract ( 2206 ) Download PDF ( 628 )   Knowledge map   Save
    Based on Auto-Regressive method, fluctuating wind velocity series were simulated, and the wind-induced vibration response for the typical area of Guangdong Science Center in different wind pressure and in different wind directions was studied. Six kinds of wind-induced vibration control plans of adding non-linear viscous dampers are given and the control effects of different plans were analyzed in detail. The results show that the wind-induced vibration responses of the structure are reduced effectively by using the reducing vibration plans. The max vertex displacement and acceleration response can be respectively reduced by 18% and 84.9%. For the irregular long-span structures, it is suggested that the dampers are installed in the two sides of them to get the maximal reducing-vibration effect. For the structure with viscous dampers, the control effect of acceleration is better than that of displacement
  • Yang Hezhen Li Huajun
    . 2009, 28(9): 65-69 7.
    Abstract ( 1656 ) Download PDF ( 761 )   Knowledge map   Save
    The study is focused in the lateral response and parametric instability of the deep-sea risers due to the parametric excitation. As offshore hydrocarbon resources exploration and exploitation moving to much deeper waters, risers play more important roles than before, and face with many technological challenges. Especially, parametric resonance will appear, when riser system parameters lie within unstable region. The riser resonance can create serious damages which cause environment pollution and economical loss. Unquestionably, the risers for ultra-deep water have complex dynamic characteristics. Firstly, the governing motion equation of the marine riser is formulated. Then the stability behavior of the risers with and without nonlinear damping is investigated by employing the Floquet theory. The numerical simulations for the lateral response of the risers are validated for four typical cases. During the numerical solution of the governing equation, the coupling between the modes was considered. Finally, special attention has been paid to the effect of damping for the parametric unstable region changes. The results show that damping can effectively reduce unstable regions. Several useful suggestions are proposed for the design of deep-sea riser structures.
  • SHEN Lu ZHOU Xiaojun ZHANG Wenbin ZHANG Zhigang
    . 2009, 28(9): 70-73.
    Abstract ( 2343 ) Download PDF ( 1167 )   Knowledge map   Save
    Statistic bias occurs because same structure element was used in traditional morphological filter. Based on basic morphological transforms and their combination modes, a generalized morphological filter cascaded by different structure element was proposed to reduce noise of rotating machinery vibration signal. De-noising performance of generalized morphological filter on impulse noise and random noise were investigated. By comparing performance of generalized morphological filter and traditional morphological filter on simulation and practical signal, it is demonstrated that generalized morphology filter could reduce noise more effectively than traditional morphology filter. Generalized morphological filter algorithm includes addition, subtraction, maximum and minimum operations, and does not involve multiplication and division. Therefore, it has high calculation speed and better application value.
  • Zhang Guanghui;Liu Zhansheng;Zhang Zhengchuan
    . 2009, 28(9): 74-78.
    Abstract ( 2277 ) Download PDF ( )   Knowledge map   Save
    An experiment for the high speed hybrid gas bearing was presented in this paper to acquire the highest rotating speed of the system. The dynamic characteristics were analyzed by employing the three dimensions spectrum, response time diagram, bode diagram and axis center locus diagram. The results indicated that the low frequency whirl phenomenon of the rotor (weights: 15.19 kg) which supported by the hybrid gas bearings can be observed at the rotating speed of 42700rpm. This supplied the experimental supervision for the bearing support system design of rotating ramjet.
  • DU Bi-qiang;TANG Gui-ji;Shi Jun-jie
    . 2009, 28(9): 79-81.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Sampling real vibration signal with interferences was processed by morphological filtering, and the effect of noise reduction and primal feature reservation of morphological filtering is validated. The influences of the shape, width and amplitude of the structure element on the performance of morphological filters, and the influences of the vibration signals sampling rate on the size of structure element have been analyzed. Based on the analysis results, the general rule for shape, size of structure element on the design of morphological filter is elicited, which can be applied for de-noising and filtering of rotating machinery vibration signals.
  • Guofu Zhai;Yinghua Chen;Wanbin Ren
    . 2009, 28(9): 82-85.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Contact system of beam structure containing Hertzian contact is widely applied in hermetically sealed electromagnetic relay, the dynamic characteristics of which is considered to be the main cause of failure in mechanical environment. Combined with finite element method, Hertzian contact condition and Newmark β algorithm, the program for analyzing the nonlinear beam structure is complied. The impacts of Hertzian contact condition were investigated by the comparison of transient response between MSC.Patran/Nastran and the program. In order to validate the method, the shock experiment over the practical model was conducted, and the results show good consistency with the calculation.
  • LIN Yong;ZHOU Xiaojun;YANG Xianyong;ZHANG Wenbin
    . 2009, 28(9): 86-90.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This paper is devoted to exploring intelligent fault diagnosis methods which is based on pattern recognition of vibration spectrogram. Firstly, taking rolling bearing as an example, the GLCM extracted from SPWVD spectrogram and its characteristic statistic are described. Moreover a modified AIN algorithm is introduced and used in bearing fault diagnosis. Through the optimization of fault antigen sample,the memory antibodies sets are formed and classification is processed by the k-nearest neighbor method. A mass of fault sample are analyzed in the algorithm proposed and the results are compared with those obtained by BPNN. The comparison result indicates that the modified AIN algorithm has better classification ability as well as high diagnosis accuracy. As the intelligent fault diagnosis methods develop,methods based on spectrogram identification should be popularized,its practicability is proved through recognition of bearing fault in this paper.
  • WangHongli;GeGen;Xujia
    . 2009, 28(9): 91-94,1.
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    One stochastic dynamical model of a thin rectangular plate subject to in-plate stochastic parametrical excitation is proposed based on elastic theory and Galerkin’s approach. At first the model is simplified applying the stochastic average theory of quasi-integral Hamilton system. Secondly, the methods of Lyapunov exponent and boundary classification associated with diffusion process respectively is utilized to analyze the local and global stochastic stability of the trivial solution of system. Finally, it is explored that the stochastic Hopf bifurcation of the model according to the qualitative changes in stationary probability density of system response. It is concluded that the stochastic Hopf bifurcation occurs at two critical parametric values. And the results of numerical simulation support the theoretical analysis.
  • Duan Huming;Shi Feng;Xie Fei;Zhang Kaibin
    . 2009, 28(9): 95-101.
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    It’s reviewed that the research progresses of road roughness in the field of automobile engineering and transportation engineering in recent years. Based on the difference of viewport of investigation, three aspects are discussed. First of all is the research of basic theory including the definition of road roughness and the mathematical model of road roughness in power spectrum, the second is the analysis of experiments which include the development of instruments of measurement and the research progresses of test and simulation in road roughness, once more is the application of road roughness in engineering of automobile engineering and transportation engineering. The principle, characteristic and application in engineering of many kinds of road roughness in the field of automobile engineering and transportation engineering are discussed synthetically. In addition, the roughness of Chinese representative road are mentioned which is used to study and design automobile in China. In the end, the prospect of road roughness in the field of automobile engineering and transportation engineering is summarized.
  • YI Ting-hua;ZHANG Yong-heng;LI Hong-nan;GU Ming
    . 2009, 28(9): 102-108,.
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    The advanced GPS technology is becoming one of the most effective means for structural health monitoring (SHM), but the multipath effect has great influence on the monitor precision. In this paper, the concepts of SHM and common monitoring methods at present are introduced and the priorities of GPS in civil engineering are concluded. Then, based on the introduction to principles of GPS monitoring and its applications on some typical structures, the causes of multipath effect, the eliminating strategy and the research status home and abroad are mainly discussed. Finally, some key questions in view of the multipath effect for further study are proposed.
  • Liu Jintao;Liu Jie;Li Xiaohao;Dai li;Liu Hongyi
    . 2009, 28(9): 109-115.
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    For the problem of the amplitude instability of anti-resonant vibration machine, a kind of method choosing parameters which let the amplitude of driving-point anti-resonant vibration machine stable is put forword. The central idea of this method is to let the upper body’s amplitude smallest when anti-resonant vibration happens. Under this situation, when the excited frequency varies, the amplitudes of the machine’s upper body and lower body vary synchronologically. At the same time, the distance of the two resonant points should be large enough, then near the anti-resonant point the amplitude-frenquency response curve of the upper body and lower body will be flat. Therefore, the stability of the amplitude can achieve functional using requirements. For the occasions in need of high amplitude accuracy, small scale adjustment can bring out.
  • XU Bei-bei;JI Zhen-lin
    . 2009, 28(9): 112-115.
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    Three-dimensional finite element method is developed to predict and analyze the acoustic attenua-tion characteristics of perforated tube silencers. Comparisons of transmission loss predictions with experimental results for straight-through perforated tube silencers and three-pass perforated tube silencer illustrated that the finite element method can predict acoustic attenuation characteristics of perforated tube silencers accurately. The finite element method is then used to investigate the effects of geometrical parameters on the transmission loss of three-pass perforated tube silencer. The duct extensions into the chambers lead to lower resonant frequencies. To improve the low frequency acoustic attenuation of typical three-pass perforated tube silencer, end-resonator may be added on the right side of three-pass perforated tube silencer.
  • LIU Jingbo;LIU Yangbing;YANG Jianguo;JIA Quanlin
    . 2009, 28(9): 116-119.
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    The training base of emergency seismic rescue troops in China is built to satisfy the practical demands and offer a real training surrounding for seismic rescue troops. And the earthquake training ruin is one of main parts of the base. The process of blasting formation design for the earthquake ruin construction A (slab-column structure) is given in this paper. And the original structural design and the blasting scheme design of A are made. The 3D solid model of the construction A is build and the blasting formation process is simulated by use of ANSYS/LS-DYNA FEA software. By simulation analysis, not only the full process of blasting and collapsing of the structure is previewed, but also the structure collapsing formation is acquired. Furthermore the rationality and feasibility of the original structure design is verified, and some useful instructions for original structure design and blasting formation design are available by the research of blasting simulation.
  • He Zhixian;Gan Hong
    . 2009, 28(9): 120-124.
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    Dynamic performance of the mechanical system, which is composed of a shaft and two rolling bearings, is studied in this paper. First a rolling bearing 6310 with clearance is studied to obtain the formula between the applying load and the relevant displacement, and the problem is referred to as a static indeterminate problem and the Hertz theory is also used to solve it. Then the numerical solution is acquired. Two kinds of dynamical problems on variable loads are discussed for the system, one is to treat the shaft as rigid body and the other is to treat it as a flexible shaft. The special software ADAMS for dynamical simulation is used to solve the problems. The relation between amplitude and frequency, dynamic response of the system in resonance are obtained on variable load while the clearance of the roller bearing is stressed. Numerical results are shown that the flexibility of shaft and the clearance of the roller bearing obviously effect to the behavior of the system. The system is a nonlinear one and the greater the clearance is, the stronger the nonlinear property appears.
  • WU Ming Xiang;Chen Li;ZHANG Jian Wu
    . 2009, 28(9): 125-129.
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    To compensate image excursions casued by vibration displacements of vehicle bodies, the method of designing a new type of active suspension systems is proposed. A LQG control law for this new type of active suspensions is derived with theory of minimum principle. By utilizing numerical results generated by Matlab that compensation effects for image excursions which are achieved by a passive suspension, a LQG controller used in traditional active suspensions and a LQG controller used in this new type of active suspensions are analysed. The results show that the LQG controller used in this new type of active suspensions performs best in compensating image excursions and achieves higher imaging-stability precision than the electronic image stabilization method.
  • Yang Zhichun;Wang Wei;Gu Yingsong;Li bin
    . 2009, 28(9): 130-138,.
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    A new (pi) shape piezoelectric stack actuator (PISA) is designed and applied to the vibration control of a cantilevered beam. This new actuator consists of a piezoelectric stack and a shape metal pedestal. They are assembled together by a screw which provides the preload needed by the piezoelectric stack. The pedestal is designed to act as an external lever which will generate and transfer actuating moment to the structure. The pedestal makes PISA be a bending type actuator. Its bottom provides a flat bonding surface for PISA in vibration control applications. The actuation moment of PISA is derived and then it is used in a vibration control system for a cantilevered beam. Positive position feedback (PPF) control and neural network predictive (NNP) control strategies are adopted to control the first bending mode vibration of the beam. Simulation results demonstrate that, the amplitude of the first bending mode of the cantilever beam can be suppressed by 92% using NNP control strategy, while using PPF control strategy the amplitude can be reduced by about 57%. The results demonstrate that the proposed PISA can serve as a high efficiency piezoelectric actuator in structure vibration control applications.
  • Li Chunxiang; Li Weiwei
    . 2009, 28(9): 135-138,.
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    The main objective of the present paper is to analyze the wind-induced fatigue of inclined cables. Firstly, it is hypothesized that within the random stress cycle, the dispersion of between the maximum and minimum stress of the nodes contents with the Rayleigh distribution. Subsequently, the formula of fatigue reliability is formulated. Likewise, based on the fatigue objective reliability of bridge structures, the simple formulas for the estimation of fatigue life are then presented. Thirdly, on the basis of present researches, the influences of different wind attack angles are further assessed on both the fatigue reliability and fatigue life. Finally, taking the inclined cable in Songhuajiang Cable-stayed Bridge as an example, the time history stress and displacement of several positions in the cable at different wind attack angles, as well as the stress standard deviations, are calculated. With resorting to the stress and displacement under the most dangerous condition, the fatigue life is thus obtained so as to examine the wind-induced fatigue performance of the cable.
  • Li Rongfu Cheng Yuansheng Wang Yu Zeng Guangwu
    . 2009, 28(9): 139-142,.
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    The elastic-plastic dynamic buckling properties of saddle-shaped bulkhead under blast impact loading are studied using the finite element software ANSYS/LS-DYNA. The Budiansky-Roth buckling criterion is utilized to judge the dynamic buckling of saddle-shaped bulkhead, and the effect of initial imperfection amplitude on dynamic buckling of saddle-shaped bulkhead is analyzed and compared with the traditional domed bulkhead which has the same weight, and then the effects of main designing parameters on dynamic buckling of saddle-shaped bulkhead are discussed. The results indicate that the dynamic buckling load of saddle-shaped bulkhead is highly enhanced compared with the traditional domed bulkhead which has the same weight and is insensitive to initial imperfection. The optimal dynamic buckling property will be achieved if design parameters are properly selected.
  • Kun Zhang Siuseong Law Zhongdong Duan
    . 2009, 28(9): 143-148.
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    A new method is proposed to simultaneously identify structural physical parameters and input from several dynamic responses of a structure based on dynamic response sensitivity. The input forces on structures are represented by using orthogonal polynomial approximation, and the sensitivity of structural dynamic response with respect to the orthogonal coefficients of input forces and the physical parameters of structure is derived analytically. The identification equation is set up and is solved with the damped least-squares method to simultaneously identify input forces and structural parameters. A five-story plane frame and a nine-bay three-dimensional frame are taken as examples for validating the proposed method respectively. Numerical simulations with noisy measured accelerations and initial model errors show that the proposed method can accurately identify the input forces and detect the changes of structural physical parameters caused by structural local damages.
  • CAO Lei MA Yunyi HUANG Yuyin
    . 2009, 28(9): 149-154.
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    Based on the Riccati transfer matrix method and high precision intergration scheme combined with the extended homogeneous capacity technique, a new semi-analytical and semi-numerical method is presented for analyzing the vibro-acoustic interaction problems of ring-stiffened circular shells with finite length in underwater by solving a set of first order differential equations. This method is different from previous analytical method and FE-BE method. An analytical expression of the acoustic pressure is derived by linear combination of the basic functions which satisfies the Helmholtz equation. The vibro-acoustic interaction problem can be transferred into solving a linear algebraic equations in all acoustic pressure coefficients by matching points along the generating line of the shell by means of the continuity conditions of the normal velocity on the interface between the acoustic field and shell. The obtained numerical results show this method is efficient. It can also be extended to analyze the vibro-acoustic interaction problems of ring-stiffened conical shells and jointed conical-cylindrical shells with finite length.
  • YUAN Shengfa li xiu qiong
    . 2009, 28(9): 155-158.
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    Support vector machines is a general machine-learning tool that exhibits good generalization when fault samples are few. Since basic support vector machines is originally designed for two-class classification, a new multi-class classification algorithm named grid support vector machines is presented to solve the pattern recognition problems in fault diagnosis which is typical multi-class classification case. With this rid support vector machines, every class constructs two-class SVM classifiers with less than 4 other classes, and the total number of two-class SVM classifiers is less. The rid support vector machines is simpler and more extensible compared with other methods of multi-class support vector machines. The cracks in different positions of the shaft are regarded as different classes of fault, and are diagnosed by the grid support vector machines. The result shows the new methods distinctly improves the fault recognition accuracy and the diagnosis speed, and it is more suitable for practical application of multi-class fault diagnosis.
  • Zhao Yanqing Zhong Yang
    . 2009, 28(9): 159-162.
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    Asphalt mixtures are typical viscoelastic materials and pavements are subjected to dynamic loads under high-speed traffic. Thus, behavior of asphalt pavements can be more realistically described by conducting dynamic viscoelastic analysis. In this study, a three-dimensional dynamic viscoelastic model was developed for a typical asphalt pavement, and dynamic viscoelastic response of surface deflection and its influencing factors were evaluated. The results show that the deflection peak value and time of its occurrence were affected by the distance between the point of interest and applied load. Damping ratio has negligible influence on deflection peak value, while it has significant influence on the decaying rate of deflection vibration. The vibration decays more rapidly with an increasing damping ratio. Temperature has great effects on both the deflection peak value and decaying rate. Decaying rate increases with increasing temperature. Comparisons were made between the peak values of deflection obtained through dynamic and Quasi-static analyses. The results indicate that the peak values obtained from dynamic analysis were about 12% larger than those obtained from Quasi-static analysis, and the percentage of increase in the peak value varies with horizontal distance.
  • TIAN Haiyong LIU Weihua ZHAO Rixu
    . 2009, 28(9): 163-167.
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    A one-degree-of-freedom vibro-impact system with clearance is established. The analytic expression of Poincaré map of the system is derived, and the spectrum of Lyapunov exponents of the system is calculated numerically, the effects of the dynamical behavior of vibro-impact system with random disturbance is analyzed. At last, with the largest Lyapunov exponent, the stochastic bifurcation of random non-smooth system is studied. Numerical simulations show that period-doubling bifurcation also exists in the random non-smooth system, but is different from that in the deterministic system.
  • Dengfeng Xu Yu Zhu Songtao Jia
    . 2009, 28(9): 168-170.
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    Vibration isolator can insulate or weaken vibration from the ground or load and it helps to ensure the desired ultimate precision. Therefore, vibration isolator has been widely applied in lots of subsystems which are used in the field of ultra-precision machining, inspection and optics. Among most of vibration isolators, pneumatic vibration isolator is very popular due to its high cost-effective since its natural frequency doesn’t depend on the load. Based on C. Erin’s research, this paper introduce orifice number as parameter and improve the theoretical model of air bearing through derivation. Then, Structural parameters of chamber, orifice and piston are analyzed to assist structure optimum design. Meanwhile, it is concluded that if the length of orifice and the diameter is the same, the systems consist multiple smaller orifices perform better than those with single orifice. Finally, the theoretical analysis results are verified by the experiments. The research lays foundation for in-depth study of passive and active in the future.
  • Li Chunguang Zhang Zhitian Chen Zhengqing
    . 2009, 28(9): 171-174.
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    Aimed at the calculation for the equivalent rigidity of the truss stiffening girder in the aeroelastic model design of long-span suspension bridge with truss stiffening girder, in this paper, Aizhai bridge, which is a super-long –span suspension bridge across deep valley with single span, is taking as an example for investigation. In order to get the accurate equivalent rigidity characters of the truss-stiffening girder, finite element models of the truss-stiffening girder with different length were built, and then the theoretical formula for calculating the deformation of cantilever girder under concentrate force was adopted to evaluate the equivalent rigidity value of the truss girder. The analysis result indicted that the influence of local stress due to different load style disappeared at the section which is about two times section width distance from the load location, and the length of selected section model should be long enough to make the model have characters of single girder in both of vertical and cross directions. Furthermore, equivalent spring was designed to simulate the constraint effect of the tower and side main cable, based on the analysis of finite element model, equivalent aeroelastic model of single girder with rigid tower was built which dynamic characters showed good agreement with the prototype.
  • Li Cuncen Yang Ming Li Shiyang
    . 2009, 28(9): 175-179.
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    Ultrasonic motors employ the converse piezoelectric effect to excite the resonant mode of vibrator and utility the friction between vibrator and rotor to drive. The methods of exciting ultrasonic motors could be classified into three categories according to the number of vibration modes which used to superpose the periodic movement of point on contact surface; they are single vibration mode, superposition of two vibration modes with same frequency and superposition of multi-vibration-mode. Then the principles and characteristics of typical ones of each category are presented. At last the development of the exciting method of ultrasonic motors is addressed.
  • DING Qi MENG Guang LI Hongguang
    . 2009, 28(9): 180-183.
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    Presents a method of structural damage identification based on Spatial Hilbert-Huang Transform. Using beam as the research object, firstly, we analyzed the damage effect on the structural dynamic parameters theoretically, revealed the modal singularity caused by damage. Then we used EMD (Empirical Mode Decomposition) method to decompose the modal signal adaptively, got the characteristic frequency from Hilbert Transform, and identified the location and extent of damage effectively. The results of numerical experiment validated this method has high frequency resolution and good anti noise performance in damage identification.
  • Fu Weiqing Wang Tieying Ding Lin Chen Fei
    . 2009, 28(9): 184-187.
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    In the paper performance-based seismic design for smart isolation structure with magnetorheological damper were given. The design methed offered different performance level and performanc index for stucture Seismic responses under different earquake intensity. Complex design process also were presend. Design example proves the design process for smart isolation structure with magnetorheological damper met limited value of performanc index under different performance leves and design result reachs earquake-resistance design require. So the design method is feasible and effective.
  • Sun Dan Luo Songnan
    . 2009, 28(9): 188-191.
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    Considering finite deformation and cross Poisson effects, a new nonlinear wave equation in a functionally graded beam was derived by means of Hamilton principle. By using travelling wave reduced form method, the nonlinear partial differential equation of wave propagation in a functionally graded beam was transformed ordinary differential equation. The solitary wave solutions of displacement are obtained by using method of undetermined coefficient of displacement functions and solving the nonlinear differential equation of wave propagation. Two cases of functionally graded materials, elastic modulus and mass density along the depth varying with exponentially and parabolic type, were analyzed by examples. The curves of displacement are presented and the influence of parameters of the functionally graded materials and velocity of wave propagation on amplitude and width of solitary wave are analyzed.
  • Li ChunLai
    . 2009, 28(9): 192-194.
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    In this paper, we realize the chaos controlling and variant-stuctures synchronization of a continue chaotic system with a proportional and differential controller. And we analyse the conditions of the chaos controlling and synchronization in theory. Simulation result is presented to show the effectiveness、 simpleness and feasibility of the method.
  • He Wei Jiang Zhinong
    . 2009, 28(9): 195-199.
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    When a gear has a local fault, the vibration signal of the gearbox usually is amplitude-modulated (AM) and frequency-modulated (FM). The demodulation analysis has been extensively used for gear diagnosis. However, traditional demodulation methods are mainly applicable to amplitude demodulation, while frequency modulation is usually ignored. Although Hilbert transform can be used for frequency demodulation, it is liable to be affected by noise which often taints the gear vibration signal seriously. Due to the excellent anti-noise property of the delayed autocorrelation function, the delayed autocorrelation demodulation method has been applied to amplitude demodulation in low SNR by some researchers, but is rarely used for frequency demodulation. By derivation, it is found that the autocorrelation function of the FM signal is amplitude-modulated and that of the AM-FM signal is amplitude-modulated and frequency-modulated. Moreover, the modulation frequencies of both are unchanged. Therefore, the delayed autocorrelation demodulation method is applicable not only to amplitude demodulation but also to frequency demodulation. The simulation experiments and gear vibration signal analysis verify this conclusion and show that the delayed autocorrelation demodulation method is robust to noise.
  • Xie Xiangrong Yu Xiang Zhu Shijian
    . 2009, 28(9): 200-203.
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    The theory of flexible multibody dynamics is used in this paper to modeling the vibration isolation system for onboard machinery. The dynamical models of linear and nonlinear elastic elements are formulated. Combined these models with the motion equations of the single flexible bodies, the general model of the vibration isolation system for onboard machinery is deduced.
  • Liu Guohuan Li Hongnan Tian li
    . 2009, 28(9): 204-209.
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    The earthquake-induced ground motion is characteristized by complicated variation in space and time and may be different at dissimilar supports of structures. Relevant sdudies have shown that it is necessary for structures to consider the effects of multi-support excitations,especially for large span structures. The JIUJIANG Yangtze River highway bridge is a double-tower double-cable-side steel-box-beam cable stayed bridge, with 1432m full length and 768m main span length. In this paper, the presented spring impedance method for current displacement input model is firstly introduced. Spatially variable ground motion time histories are generated by the method of the reponse-spectrum-compatible artificial ground, then the responses of the highway bridge under uniform excitation and multiple support excitations are studied by adopting the time history analysis method. From the analysis results, it is founded that:considering multi-support can decrease the seismic response of the cable tower’s shear force、moment and displacement under longitudinal excitation, and the seismic design is favorable for cable stayed bridge; considering multi-support can increase, or decrease the seismic response of the cable tower’s shear force and moment under multi-dimensional excitation, the maximum of shear force may be increased about 10%;considering multi-support can increase the seismic response of the cable tower’s displacement under multi-dimensional excitation, the maximum of displacement may be increased about 100%; the response of considering multi-dimensional is larger than that considering longitudinal only. A conclusion is given that the multi-support and multi-dimensional earthquake excitations must be considered in the seismic analysis of the long-span cable stayed bridge.