25 October 2011, Volume 30 Issue 10
    

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  • GU Ming;ZHANG ZhengWei;QUAN Yong;XIONG Yong
    . 2011, 30(10): 1-5.
    Abstract ( 1115 ) Download PDF ( 620 )   Knowledge map   Save
    71 rigid models of typical square and rectangular tall buildings are tested with high frequency force balance (HFFB) technique in four different simulated wind fields; and their base torsional moment coefficients are obtained accordingly. Effects of parameters such as wind field, models’ aspect ratio and side ratio on the RMS values of the torsional moment coefficient at the base of the structure are then studied. The test results indicate that the effect on the torsional fluctuating forces is changed with the side ratio, and the side ratio has a strong effect on the across-wind fluctuating forces. The influence of models’ aspect ratio is negligible because the aspect ratio only induces the microvariation of the distribution of the aerodynamic force in the top of the model, and the influence of wind fields is varied with different side ratios. New formulas for the standard deviation of the base moment coefficient of torsional wind loads on the tall buildings are formulated by using the nonlinear least - squares method, and the errors of the empirical formula are analyzed, which provides technical support for the revisions and supplements of load codes. And by comparison with the results from the present wind tunnel test results and data in literatures, the precision and applicability of the present formulas are finally verified.
  • SUN Xin-hui;HAO Mu-ming;WANG Huai-wei
    . 2011, 30(10): 6-8,18.
    Abstract ( 1689 ) Download PDF ( 889 )   Knowledge map   Save
    PolyMAX is a broadband modal identification algorithm developed in recent years. It has many advantages in handling high noisy data, closely coupled modes and high damping structure. A fast implementation of PolyMAX is achieved by avoiding matrix inversion and multiplication in calculating reduced normal equations. A simulation case of seven DOF system and an application case of gas turbine disk are employed to validate the fast implementation. The results show that fast implementation can speed up modal identification significantly with little accuracy loss.
  • ZHOU Zhi-hui;ZHANG Jun;QIN Wen-xiao;ZENG Qing-yuan
    . 2011, 30(10): 9-13.
    Abstract ( 1416 ) Download PDF ( 398 )   Knowledge map   Save
    The running performance of train on Wuyijiang bridge is analyzed with energy random analysis theory for derailment. The calculated result shows that though the lateral amplitude exceeds the limit value of traffic safety given by code, the running safety , smoothness and comfort of train on Wuyijiang bridge can be guaranteed with the existing operation condition, and the measurement of rate-limiting or reinforcement is not needed to be taken for this bridge. By comparison between the lateral amplitude of the bridge and the limit value of traffic safety, it can be seen that the existing limit value of traffic safety of the lateral amplitude is too conservative. A method for establishing index of traffic safety for railway bridge is proposed on the basis of the analysis theory for train derailment, and the detailed contents are as follows. The lateral amplitude on the middle of beam is determined as index for traffic safety for the system of beam and pier. The critical system of beam and pier with which the running safety, smoothness and comfort of train can be guaranteed is determined. The lateral amplitude of critical system of beam and pier is calculated and determined as limit value for traffic safety. The limit value of lateral amplitude for traffic safety for Wuyijiang bridge is determined as L/6200, and the research findings have been applied by Jinwen railway corporation.
  • Qian Zheng-wen;Cheng Li;Chen Wei;Li Ying-hong
    . 2011, 30(10): 14-18.
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    The initial iterative value is difficult to choose when there are multiple periodic solutions in solving the nonlinear vibration equations. Moreover, the simple iterative solution process of conventional approaches is inefficient to track the periodic solution with different outer excitation. In the view of these two problems, the homotopy method is employed so that the initial iterative value can be chosed easily. The solution curve variated with outer excitation is tracked by the predict-correct method. Both the stable and unstable periodic solutions can be calculated by using this method. The feasibility of the method is verified by calculating the Duffing oscillator equation. It is show that the simulation results using this method agrees well with the theoretic approximate results and the results using the Rung-Kuta method.
  • YI Ting-hua;ZHANG Yong-heng;LI Hong-nan;GU Ming
    . 2011, 30(10): 19-24,4.
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    In order to study the influence of common construction materials on the GPS monitoring signals, the experimental study on multipath effect was carried on. A set of simulating and monitoring system for GPS multipath signals was established, and the continuously two-day-long GPS monitoring data of different materials were obtained by means of placing board, PVC sheet and ceramic tiles with different dielectric constants at different heights and distances from the receiver antenna. The improved particle filtering algorithm is being used in the GPS data post-processing. By comparison, it’s shown that the experimental results coincide with the simulation results of GPS multipath signals very well. The multipath errors caused by the same reflecting material decrease with the distances increase and under the condition of increasing the same distance, the extent of decrease is more and more small. While the multipath errors caused by the reflecting materials with different dielectric constants at same distance increase with the dielectric constants increase.
  • ZHENG Ling;ZHOU Zhong-yong
    . 2011, 30(10): 25-29.
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    An magneto-rheological (MR) damper is nonlinear typically. The nonlinear relationship between the input and the output of the MR damper should be characterized accurately in order to improve the accuracy of vibration control system with MR dampers and maintain its control stability. The challenge of the conventional parametric modeling is computational complexity and the identification of a large number of parameters. A non-parametric modeling of MR damper based on the adaptive neuro-fuzzy systems theory is presented to overcome the drawback of conventional parametric modeling in this paper. The experimental results from MR damper ( RD-1005 , Lord Company ) are used as reference data to follow. It includes two adaptive neural fuzzy subsystems which describe the relation between the MR damper input and output for specific voltage and voltage change respectively. The results shows that the non-parametric MR damper modeling based on adaptive neuro-fuzzy theory can accurately approach to the experimental model of the MR damper and describe the nonlinear characteristics of the MR damper. This method provides a key technical support for precise control and goal realization of vibration control system with MR dampers due to short calculation process.
  • MA Lin;HAN Wan-shui;LIU Jian-Xin;lI Jia-wu
    . 2011, 30(10): 30-34,4.
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    The critical wind velocity and driving velocity are studied for three kind of typical vehicles driving on the deck of cable-stayed bridge within strong side wind environment. The effect on vehicles’ side deviation relative to the bridge deck of bridge’s side buffeting and the character of following coordinate for vehicles’ moving equation are analyzed, the calculation formulas of relative side slipping and its velocity are attained. Based on the previous research, the wind-vehicle-bridge coupling vibration system including vehicles’ side moving degrees and pilot’s behavior is studied, and corresponding program code is written and tested. With a cable-stayed bridge engineering background, critical wind velocity are attained of three kind of typical automobiles driving on the bridge deck. Results show that the critical wind velocity will not be significantly influenced by controlling objective of driver behavior. The accident types of the different vehicles are possibly different. For box-type truck, critical wind velocity of side slipping is always lower than that of overturning. But for cars like Santana and Jia-bao, overturning accident will play a controlling role when driving velocity is high, while side slipping accident will do when driving velocity is low.
  • Li Zhi-nong;Tang Gao-song;Xiao Yao-xian;Wu Guan-hua
    . 2011, 30(10): 35-38.
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    A Volterra series identification method based on Adapt Ant Colony Optimization (AACO) algorithm is proposed. In the proposed method, the Volterra kernel is identified by ant colony optimization algorithm. the parameters of the ant colony algorithm can be adaptively adjusted as the incre.ase of evolution number. At the same time, the proposed method are compared with the Volterra kernel identification method based on basic ant colony optimization (ACO). The simulation result shows that the proposed method and ACO identification method have good identification accuracy, convergence stability and robust anti-noise performance whether in the noise-free or noise environment. However in the convergence speed, the proposed method is supirior to the ACO identification method.
  • SHANGGUAN Wen-Bin;XIE Xinxing;DING Wei;HUANG Xing;XU Chi
    . 2011, 30(10): 39-44.
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    A method for determining frequency response function and road spectrum iteration steps of road simulation experiment were given and discussed in this study. Taking one Hydraulic Engine Mount (HEM) in a car as study example, and the road spectrum exerted on the HEM was acquisied in a proving ground. The road spectrum was reconstructed with remote parameter control technology, and the results show that the reconstructed load agrees well with the original one. Also, the method for determining the load block sequence was given and discussed. The durability experiment for an HEM was carried out with MTS 831 test rig using the methods presented in this paper. It’s shown that the methods are effective in doing durability experiment for a mount.
  • TANG Xian-guang;GUO Yu;DING Yan-chun
    . 2011, 30(10): 45-49.
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    Vibration generated by incipient faults of rolling element bearing is usually with low energy and dispersed frequency distribution, then, it is easy merged in strong disturbances from other vibration sources. Performing the Hilbert Huang Transition (HHT) directly may fail to remove the noise from the observed modulated signals by separating the Intrinsic Mode Function (IMF) accurately since the vibrations are lower at the signal-to-noise ratio and more frequency modulation. In this paper, a new fault-diagnosis approach is proposed based on the ICA and the HHT. In the approach, the vibration signals are decomposed by the Empirical Mode Decomposition (EMD) to get stable IMF components at first. Then, the IMFs which contain the fault information of the rolling element bearing mostly are selected and the corresponding envelopes are extracted by band-pass filter and the Hilbert transform. Subsequently, the independent component analysis (ICA) is employed to separate the envelopes to independent components (ICs) according to the independent of vibration sources. Finally, the envelope spectrums of the ICs are calculated respectively and compared with the fault characteristics of the rolling element bearing to realize the accurate faults diagnosis of rolling element bearings. Simulations and tests verified the feasibility of the method.
  • WANG Lin;HU Xiu-zhang;HUANG Yan-long;LI Yong-chi
    . 2011, 30(10): 50-53,8.
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    Based on the assumptions of linear elastic and one-dimension stress wave, spalling experimental study of steel fiber reinforced concrete bar with fiber volume ratio of 0, 0.75% and 1.50%, respectively, is carried on by using Φ75mmSHPB, and the dynamic tensile strength is obtained by calculating the stress signal recorded by the strain gauge pasted on the specimen considering the shape dispersion and attenuation of stress waves traveling through concrete material. The results show that the dynamic tensile strength is affected by the strain rate and the fiber volume ratio. This paper presents an effective method for testing the dynamic tensile strength of brittle material. The reinforced mechanism of steel fiber is analyzed based on the micro scanning technique.
  • HE Xu-hui;CHEN Zheng-qing;LI Chun-guang;FANG Jun
    . 2011, 30(10): 54-60.
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    The time-varying mean values of measured wind speed, wind direction signals of wind-rain induced vibration are extracted, and the nonstationary wind speed model based on wavelet analysis is proposed. By using the field measured wind speed data of wind-rain induced vibration on the Dongting Lake Bridge on April, 2003, the wind characteristics of turbulence intensity, integral scale, wind spectra and probability distributions are calculated. The calculated results are compared with those obtained by the nonstationary wind speed model based on empirical mode decomposition (EMD) and traditional stationary wind speed model. The compared results indicate that the wavelet-based nonstationary wind speed model is more reasonable in nonstationarity analysis of wind-rain induced vibration. At the same time, the correlation between the tower and deck longitudinal fluctuating wind speed component based on the Davenport correlation function is also discussed.
  • LI Chun-xiang; WANG Ying-jun;ZHONG Qiu-yun;QIN Ji-biao
    . 2011, 30(10): 61-72,1.
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    The structural height and antenna mast height of Ningxia TV tower (NXTVT) is 216m and 104m, respectively. The shape of NXTVT resembles a small-bottom, large-top,and slender-waist-middle vase, which consists of three storey segments with 28 floors in total. The discontinuous arrangement of floors leads to the uneven distribution of mass and lateral stiffness of the structure. Thus, this structure with complex geometry requires a high demand of seismic performance. Firstly, ANSYS code is employed to analyze the dynamic characteristics of NXTVT. Simultaneously, for the purpose of comparison, the results of the structural natural frequencies using SAP2000 code are also taken into consideration. The numerical results indicate that the third and eight modes of the structure are torsional ones, and furthermore the torsional effect is considerably significant. The ratio of the first torsional period to the first translational period meets Chinese code, but close to the limiting value. Then, the responses of this building under frequent earthquakes are analyzed using both the mode superposition response spectrum and time-history method, respectively. The whiplash effect can be brought out clearly through the time-history analysis. Accordingly, the seismic performance should be evaluated based on the simultaneous considerations of the results of the aforementioned two methods. Under the multi-dimensional earthquakes, the structural deformation meets the requirements of code for seismic design of buildings. Finally, the responses of the structure under the 8 degree (0.2g), 8 degree (0.3g), and 9 degree rare earthquakes are analyzed using the dynamic elasto-plastic time-history method, in order to check both the deformation indices and development of the plastic zone of the structure. The numerical results demonstrate that the inelastic deformation meet the requirements of code for seismic design of buildings. Likewise the middle story segments is the weaker part, which is right the slender-waist of the structure. Therefore, the Ningxia TV tower can meet the requirement of no damage under frequent earthquake, repairable damages under basic earthquake, and no collapse under rare earthquakes. Through extensive numerical analysis and comparisons, the conclusions obtained herein will be much useful for the earthquake-resistant design of NXTVT or similar projects under earthquakes. Additionally, the analysis approach has reference values in the calculation of the structures with complex geometry utilizing commercial finite element program.
  • WANG Yong;YAO Tai-ke;CHEN Guang
    . 2011, 30(10): 73-76,9.
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    The vibration control of space flexible structures is difficult due to that they are with close models and that the structures parameters can be easily influenced by the complex space environment. That is valuable to study the adaptive inverse control. Multi-variable adaptive inverse control is successfully applied to a 2-D flexible plate test system with close modes, and good experiment results are obtained. Persistent disturbances are suppressed effectively. When the structure parameters change, the procedure of online identification and controller adaptation starts and effective vibration suppression is realized again.
  • WU Cong-xiao;ZHOU Yun;WU Congyong;DENG xue-song
    . 2011, 30(10): 77-81.
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    A processing method of shear wall core with high-level story isolation technology(PMIT)is proposed, which the principle, configuration, characteristics are illustrated. The problem in the isolation story that the core shear wall need break could be overcome to use the new method. With the use of ETABS software, the PMIT models of setup the viscous damper or elastic spring, no damper and elastic spring in the pre-fixed gap between the core shear wall and the around upper structure , the model of suspension method and frame-support shear wall structure model are built, nonlinear time history analysis under frequently occurred earthquake are conducted. The results show that: (1) comparing with frame-support shear wall structure, the story drift of substructure of isolation story is reduced with PMIT, however, it increased by 150% with suspension method. The structural seismic performance with PMIT is not influenced. (2)comparing with the structure with suspension method, the tension force of the lateral isolator in isolation story decreased by 50% only during the horizontal earthquake action to add the viscous damper in the pre-fixed gap, the overturning resistance performance could be obviously improved.
  • CHANG Jun
    . 2011, 30(10): 87-90,1.
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    The health status of the in-service bridge structure, related to the safety of people’s lives and property, therefore, it is extremely important to understand their damage status. At present, the damage identification usually has to suspend the operation of the in-service bridge, causing a huge economic impact. In order to solve this problem, the paper presents a in-service bridge damage location identification method without interrupting the operation of in-service bridge. Curvature mode method is an ideal method to identify the structural local damage, with d advantage of easy to operate and sensitive to damage location, while the frequency is easy to test with high precision. An improved structural damage identification method is presented, based the change rate of structural curvature and frequency. In order to solve the problem that inspecting works always interrupt the operation of the in-service bridge, the stochastic subspace identification method is introduced in the method. Finally, the combination method presented herein is verified by a simple support steel beam tested in the laboratory. The test results show that the improved combination index method can effectively identify the bridge damage location without interrupting the in-service bridge operation.
  • Chen Liang;Li jian-zhong
    . 2011, 30(10): 91-97.
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    Intensity measures (IM) should be reasonably selected on the basis of earthquake engineering and earthquake resistance of structures for seismic design and analysis of long-span bridges. The nonlinear dynamic time-history analysis was conducted for a long-span highway cable-stayed bridge with two towers. It is concluded that the influence of frequency content in the range of period with predominant cumulative modal mass participation on structural seismic demands is significant because of obvious higher mode effects in different directions of long-span bridges. The effects of spectra in the high-frequency domain on structural seismic demands are more than in the low-frequency domain. In general, PGA and short-period spectra accelerations are applicable to be as IMs to conduct dynamic time-history analysis.
  • LIU Xiao-ping;ZHENG Hai-qi;ZHU Tian-yu
    . 2011, 30(10): 98-101.
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    Feature selection can eliminate the redundant features in the original features set, find an optimal subset of features and enhance the classification accuracy and efficiency in machine fault diagnosis. A feature selection method based on evolutionary Monte Carlo is proposed. Support vector machine (SVM) is applied as the fault classifier, the evaluation criterion is the Wrapper model, and the evolutionary Monte Carlo is implemented for optimal feature subset selection. This method is applied on the feature selection of the rolling bearing fault diagnosis based on vibration signal. Experimental results indicate the proposed method is effective for feature selection in fault diagnosis.

  • LI Yan;JIA Gui-xi;YUAN Qi-long;CUI Feng-kui
    . 2011, 30(10): 102-103,.
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    Using closed-field unbalanced magnetron sputtering technique, CrC composite coating was prepared on the steel ball substrate of bearing 6204. The vibration performances of ball bearing coated with CrC composite coating on the steel ball and uncoating general ball bearing were tested and been comparatived analysis. Results indicate that, Compared to the uncoating steel ball bearing, CrC coating steel ball bearing significantly reduces the value of bearing vibration, especially under the high-speed or high loads conditions damping effect is particularly significant. The smooth performance of bearing vibration is obviously enhance.
  • Li Bing;Zhang Pei-lin;Mi Shuan-shan;Liu Dong-sheng;Ren Guo-quan
    . 2011, 30(10): 104-108.
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    Impulsive modulated type signal is the characteristic response of a defected roller bearing. How to extract the impulsive signal from the noised vibration signal becomes the key step for fault diagnosis of bearing. A novel method named Adaptive Multi-scale Morphological Gradient (AMMG) based on the mathematical morphology is proposed for feature extraction of roller bearing fault signal in this study. The AMMG technique has the advantage to depressing the noise as well as keeping the detail components of the signal. Comparing study is done with the most used envelope demodulation and the morphological close method. Results of application to the simulated signal and the real bearing fault signal demonstrated that the proposed AMMG technique can extracts the impulse signal more effectively from the original signal disturbed with strong background noise. Moreover, the computation of AMMG is relatively simple and it has provided one an effective and fast way to feature extraction for fault diagnosis of roller bearing.
  • ZHOU Jing;FANG Xiao-dan
    . 2011, 30(10): 109-115.
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    Most unfavorable shear behavior of concrete frame columns subjected to velocity pulse-like excitations is studied. First floor columns of reinforced concrete frame structures is used to investigate the effects of vertical and horizontal velocity pulse-like acceleration on shear behavior of concrete columns. Three equivalent velocity pulse sine excitations are employed to execute nonlinear dynamic time history analysis. Combined effects of vertical-to-horizontal peak acceleration ratio, arrival time interval of peak acceleration between vertical and horizontal excitations, shear span ratio, as well as fundamental period on shear-resistant demand and shear-resistant capacity is concerned with the assessment of the effect of velocity pulse action. The results demonstrate that shear-resistant demand of concrete columns increase with increasing intensity of velocity pulse, and shear-resistant capacity decrease with increasing vertical-to-horizontal peak acceleration ratio. Arrival time interval between vertical and horizontal excitations has an important influence on the most unfavorable shear behavior of concrete frame columns. At higher values of shear span ratio, the influence of velocity pulse excitations is significant. Nonlinear regression analysis of analytical data of the present study is carried out, and empirical approach considering different effect of these factors is proposed.
  • LI Shu-xun;ZHAO Zi-qin;ZHANG Yun-long
    . 2011, 30(10): 116-121.
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    Strong vibration and high noise were generated in high temperature and pressure superheat steam trap of domestic company. Numerical simulation with finite element method was used to analyze the unstationary characteristic of inner 2D field for the steam trap. Based on the two methods of time-average flow analysis and large eddy simulation(LES),it was found the main factors of vibration and noise in steam trap. According to the characteristic of the frequency spectrum of the noise signal, mechanism with the high acoustic level and principle of throttle step-down ,throttle injection muffler of low vibration and noise steam trap was designed, and the spec-trum analysis was implemented. The results of numerical analysis match with the theoretical analysis ,which pro-vides the reliable basis for the noise elimination vibration damping and capability choiceness.
  • WEI Jun-feng;YANG Yi;WEN Zhou-bin;FENG Hai-hong;
    . 2011, 30(10): 122-128.
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    A method which can be used for detecting Rub and Buzz defects in time domain is presented. Empirical Mode Decomposition of sound response signal is performed and aliasing parts in Intrinsic Mode Functions (IMFs) are removed by referencing the difference between stimulus and IMFs. Vibration modes, which are caused by Rub and Buzz defects, are extracted and be used for fault detection. The validation was composed of simulation and measurement of defective samples. In the simulation, constructed sound responses representing quality and fault products were analyzed. Simulated symptoms from rubbing, buzzing and loose particles problems were detected. In the measurement validation, IMFs and high-order harmonic distortions (HOD) of sound responses from 20 samples were measured and analyzed. The results show that the frequencies and amplitude characteristics of defects are concordant with the results by HOD method. Furthermore, according to the type of defects, different time-domain features can be found in local features of IMFs.
  • WANG Jian-hong;WANG Dao-bo
    . 2011, 30(10): 129-135.
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    A novel subspace predictive control algorithm based on subspace identification is discussec to solve the actuator saturation limitations in a range of active vibration and noise control problems. This algorithm not only combines the system identification and control design, but also gives the future predictive values directly based in the input-output datas. This combination enables antomatically tuning the parameters and avoids the systen identification procedure in tradictional model predictive control. Meanwhile the subspace predictive permits limitations on allowable actuator saturation. When considered the constrain condictions caused by saturation, we convert the constrain optimization problem to un constrain optimization problem using the linear matrix inequality technology. Then an ellipsoid optimization algorithm is proposed to generate a sequence of ellipsoids with decreasing volume. An upper bound on the maximum number of possible iteration steps is derived. This upper bound can not be obtained in all the intelligent algorithms. Finally as an example of hellicopter flutter in hover mode, we design the closed loop feedback controller using the subspace predictive control and elliposid optimization algorithm which are proposd in this paper. From the simulation, we can see that the output responses of the close system can track the desired output values well. Then this method’s efficiency is proved.
  • CHEN Guo;SHAN Bo;XIAO Yan;
    . 2011, 30(10): 136-142.
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    To study seismic behavior of lightweight bamboo frame residential house, shake table tests were conducted using a full-scale model, which simulated a first floor room unit of a typical two storey house, 2.44m by 3.66m in plan and 2.6m in height. Earthquake lateral resistance was provided by glubam shear walls around the perimeter of the model. The test results indicate that the model performed elastically and had essentially no visual damage for 0.3g PGA. The tested glubam house can withstand applications of three different seismic ground motions in the order of 0.5g PGA without collapse. The observed damage remained noncritical for 0.5g PGA. Inter-story drift in the first story was generally below most code required values. After subjecting shakings of 0.5g PGA, the model was retested under a pushover loading condition and showed sufficient deformability. The tests reveal that glubam house can meet the requirements for the seismic intensity of 8 as described in the China Seismic Design Code.
  • CUI Tao; ZHANG Wei-hua
    . 2011, 30(10): 143-146,.
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    In order to treat the time-consuming problem of synchronous simulation of aero-dynamics and dynamics of train system, a new simulation method is proposed based on the Arbitrary Lagrangian Eulerian(ALE). First, the models for side-wind computational fluid dynamics and train multibody system dynamics are built up respectively. Then, the combined simulation is performed through parameters passing, solution control and dynamic grid, where the track excitations are not considered, the final equilibrium state of train in side-wind is acquired state by state, and the steady attitude and the corresponding aerodynamic loads caused by the side-wind are computed more efficiently. Finally, the aerodynamic loads and track excitations are applied on the train multibody system, the dynamical performance and safety index is analyzed.
  • YUE Qiang;SI Rong-Jun
    . 2011, 30(10): 147-152.
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    The new protective crust with compound structure was presented in order to reduce the distortion of the mining life-saving system under gas impact load and improve the anti-blasting ability. The dynamic response of the new protective crust to the shock wave of gas explosion was analyzed with numerical analysis method of the finite element analysis. The analysis focused on the deformation, the stress and the strain of the new protective crust under shock wave. The analysis results were compared with the dynamic response results of the single-layer protective crust. The results show that the new composite structure with flexible material layer can delay the shock effect of the gas explosion load to the mining life-saving system, and can protect the internal module of the mining life-saving system not to destroy seriously. Its fabrication technology is simple, and cost is low. The simulation experimental environment can be established and reference data can be provided for the design of the mining life-saving system by using numerical analysis method.
  • FENG Wu-wei;MENG Qing-feng
    . 2011, 30(10): 153-159.
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    The wire bond shear strength is one of important index of bond quality. The paper using the electrical signal from the ultrasonic generator supply as the information carrier, the feature extraction method of ultrasonic electrical signals in bond shear strength identification is investigated. A new feature extraction method based on the subband envelope segmentation is proposed for characterizing the transient ultrasonic electrical signal. The filtered subband envelopes of ultrasonic electrical signal is separated into three phases individually, namely envelope rising phase, stable and damping phase. The waveform features are extracted from each phase of the envelope for further bond shear strength identification. To remove the irrelevant information and reduce the dimension of original feature variables, the principal component analysis is carried out for the feature selection. Using the selected features as inputs, an artificial neural network (ANN) is constructed to identify the complex bond fault pattern. By analyzing experimental data with the proposed feature extraction method and neural network, the results demonstrate the advantages of the proposed feature extraction method and the constructed artificial neural network in identifying bond shear strength.
  • WANG Xin; LOU Wen-juan;SHEN Guo-hui
    . 2011, 30(10): 160-164.
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    Aeroelastic model of single D section iced conductor and bundled crescent section iced conductors were made, The dynamic characteristics of vertical and rotational movemoment of the conductor model are simulated by springs and additional weight. By varying ratio of vertical and rotational self-vibration frequency of the conductor model, vetical galloping and vertical-torsional coupled galloping of D section iced conductor, vertical-torsional coupled galloping of bundled crescent section iced conductor were excited and recorded respectively in the wind tunnel under appropriate wind speed and attack angles. Vertical and torsional aerodynamic damping in galloping were identified by Hilbert transform, impacts of wind speed, attack angle, ratio of vertical and rotational self-vibration frequency, iced profile and number of sub conductors on aerodynamic damping are discussed. aerodynamic damping identified from vetical galloping of D section iced conductor is compared with theoretical Den Hartog aerodynamic damping. It indicate that the aeroelastic model have a negetive aerodynamic damping in vaule, and its magnitude increase with test wind speed; the identified aerodynamic damping of single D section iced conductor in vertical galloping have slightly lower magnitude than the theoretical Den Hartog aerodynamic damping. Number of sub conductors influences aerodynamic damping of bundled conductors with the same iced profile. Torsional response has a complicated impact on aerodynamic damping.
  • WANG Hong-qiang;SHANG Chun-yang;GAO Rui-peng;LI Zi-nan
    . 2011, 30(10): 165-168.
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    It is crucial to obtain an accurate threshold to distinguish the original signal from the noisy signal in wavelet shrinkage de-noising, an important de-noising algorithm. This paper proposes a new improvement method to the previous wavelet shrinkage schemes, that is, to transform the coefficients to enlarge the area where the original signal and the noise is close. The results of the simulation illustrate it brings improvement in the index of SNR, SME and visual effects. The experiments also demonstrate it could improve the effect of de-noising while reserve the details of the original signal.
  • XUYong-gang; MAHai-long; FENG Ming-shi; CUI Ling-li
    . 2011, 30(10): 169-172.
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    The relationship between the size of differential resonator phase diagram and amplitude of the signal to be detected was verified through simulation experiment methods. The larger differential resonator phase diagram, the larger amplitude of signal on condition that all the parameter are set to the same value. The relative size of the signal amplitude was obtained from the differential resonator phase diagram. According to characteristics of differential resonator phase diagram, a new method was proposed to identify the differential resonator phase diagram. At last, equipment failure and its expansion process was discovered through analysis the data measured from factory. Its differential resonator phase diagram is identified and achieved the desired results.
  • ZHANG Ye-wei; FANG Bo; LI Song;TANG Ye; WANG Long
    . 2011, 30(10): 173-176.
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    Starting from the physical mechanism, the nonlinear equivalent dynamic models of discrete isolation system was set up by the deformation of the cubic polynomial function and fractional derivative operator, and the vibration transmissibility from the bottom of the isolator to the satellite was obtained by harmonic-balance method, also the phenomenon of vibration isolation platform affected by excitation magnitude was explained from the physical mechanism by numerical solutions, providing references for the design and practical application of discrete whole-satellite vibration isolation platform.
  • HUO Shi-hui; WANG Fu-sheng; YUE Zhu-feng
    . 2011, 30(10): 177-182.
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    Spring Analogy Method (SAM) was improved through introducing the control of mesh quality in the present study. Then its results were compared with these obtained through the traditional SAM. It can be seen from the numerical simulation that mesh quality declined with the increase of rotation angle in the unstructured dynamic meshes based on SAM. The quality of mesh which is generated through improved SAM is better than that generated through the traditional SAM for the same rotation angle. Mesh deformation capability in improved SAM is larger than that in the traditional SAM. It is about 13°in the traditional SAM and 27°in the improved SAM. Finally, numerical simulations on two-dimensional airfoils using LESM were carried out. It is found that the results of improved SAM show a better agreement with experiment results. The improved SAM can be used in the numerical simulation well.
  • YAO ling-yun;YU de-jie; ZANG xian-guo
    . 2011, 30(10): 188-192.
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    It is well known that the standard finite element method (FEM) is unreliable to compute approximate solutions of the Helmholtz equation for high wave numbers due to the numerical dispersion. The cell-based smoothed radial point interpolation method (CS-RPIM) is extended to solve the 2D acoustic problem and the formulation of CS-RPIM is presented for the two-dimensional acoustic problem. In present method, the acoustic domain is discretized using triangular background cells, and each cell is further divided into several smoothing cells, the acoustic gradient smoothing technique is implemented to each smoothing cell. The system equations are derived using the smoothed Galerkin weak form, and the essential boundary conditions are imposed directly as in the finite element method (FEM). The CS-RPIM will greatly reduce the numerical dispersion error and obtain accurate results for acoustic problems because of the properly softened stiffness. Numerical examples have been studied, including a tube and a 2D problem of a car acoustic problem and the results show that the CS-RPIM achieves more accurate results and higher convergence rates as compared with the corresponding finite elements, especially for high wave number.
  • LIU Li-yuan;JI Zhen-lin
    . 2011, 30(10): 193-196.
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    According to the characteristics of turbocharged engine intake noise, two kinds of intake silencers are designed, and the finite element models for the intake silencers were created. By using the corrected expres-sion of the acoustic impedance of perforation in contact with fibrous material and the acoustic characteristic pa-rameters of aluminum silicate, transmission loss of the silencers is predicted, and the FEM predictions agree rea-sonably well with experimental results. Finally, the effects of combined structure on the acoustic attenuation per-formance of intake silencers are analyzed.
  • ZHANG Meng; LI Ai-jun; LIU Shi-min
    . 2011, 30(10): 197-202.
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    Generally, we design the flexible aircraft’s controller based on reduced-order model but there is reduction error because of model reduction, so it is need to design the controller with strong robustness. In order to resolve the problem, mixed optimal PID controller parameters optimization is studied based on the reduced-order model of a flexible aircraft with 12-order. Firstly, balanced truncation reduction method is employed to get the reduced-order model with 6-order. Secondly, the suitable robust weighting functions are selected based on the model reduction error in frequency domain. And then in order to compute the performance index, a simplified computation method of norm of system error is proposed. At last, differential evolution algorithm is employed to optimize the parameters of the mixed optimal PID controller. Simulation results indicate that the order of the mixed optimal PID controller can stable the parameter and non-parameter uncertainties simultaneously. The stabilization of elastic structure deformation and the control requirement of the rigid modal are also accomplished effectively.
  • Liu Shu-kui;Wu Zi-yan; Zhang Yu-bing
    . 2011, 30(10): 203-207.
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    At first, the linear structural identification model is obtained based on a series of conversions of the dynamic characteristic equation, then the posterior distribution of the model is achieved by using the Bayesian updating theory. Utilize the structural modal parameters, and take their randomness into consideration, the samples of the parameters from the conditional posterior distribution of the linear structural identification model is achieved. During the process, the Gibbs sampling based on the Markov Chain Monte Carlo method is taken. The numerical examples show that the Gibbs sampling can not just identify the damage degree and locations in different ways with little error, but can make a probability measure of the identified values.
  • LI Bing;ZHANG Pei-lin;REN Guo-quan;MI Shuan-shan;LIU Dong-sheng
    . 2011, 30(10): 208-211,.
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    The vibration signals generated by engine can be regarded as a typical nonlinear signal. The fractal geometrical theory has provided an efficient tool to characterize the nonlinearity of such a signal. Multifractal contains more information compared to the single fractal dimension and can characterize the geometrical feature and local scale feature more appropriately. In order to overcome the deficiency of the traditional calculation method of the generalized fractal dimensions, a mathematical morphology based generalized fractal estimation technique is proposed in this study. Signals acquired from different types of engine condition, i.e. normal condition, misfire fault and intake valve clearance fault were employed to evaluate this new method. Results have revealed that the generalized fractal dimensions calculated by mathematical morphology were very stable and have a superior capacity to distinguish the different engine operating states. Otherwise, mathematical morphology operation contains only the simple addition,subtraction, maximum and minimum operations which can dramatically reduce the computational complexity compared to other techniques. Thus the proposed method has demonstrated a more fast and effective technique for accurate fault diagnosis of engine.
  • LV Xiang-Feng; PAN Yi-Shan; LI Zhong-Hua; DAI Shu-Hong
    . 2011, 30(10): 212-215,.
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    Using explosive loading, adopting equivalent material simulation test methods, having the aid of digital speckle correlation method(DSCM), the failure law of rock burst roadway is studied under the condition of the different positions of blast holes and explosive loads. Test results show that impact stress wave is mainly in roadway direction and crack, broken or collapsing area are taken place nearby the roof after the explosion. As the explosive loads increasing, the destructive power also amplified, especially for upper rock mass. So the impact energy is the main factors of roadway destruction. It also show that the failure process of rock burst roadway can be divided into three stages of tenso-shear crack, repeat tenso-shear breakage and damage. Among them, when the distance between blast hole and roadway is 450mm, explosive charge is 6.0g, cracks are taken place nearby the roof of roadway, it belongs to the stage of tenso-shear crack. As the distance is 300mm, explosive charge is 6.0g, the crack at tunnel roof is developing, and also partial separation slumping at the top of roadway, this is the stage of repeat tenso-shear breakage. For the distance is 200mm, explosive charge is 8.0g, the roadway is destroyed after the explosion, it is clearly the stage of damage. The simulation test results provide a powerful prediction and prevention for the safety of rock burst roadway.
  • LI Ying-hua; YANG Li-ming;TANG Li-qun;LIU Yu-ping;WEI Zhi-qiang
    . 2011, 30(10): 216-220.
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    Concrete materials used in structures generally work in state of complex stress and may bear dynamic load. So, Instron Servo-hyduaulic testing system and SHPB with confining pressure device are used in this article to investigate into the dynamic mechanical behavior of concrete material-mortar under multi-axial stress state in a wide range of strain rate; according to equivalent strength model, the strain rate coefficient and related material constants of mortar are determined experimentally; the damage evolution law of mortar under SHPB impact with confining pressure is suggested and the damage evolution parameters are determined by experiments. The experimental data are in good agreement with the theoretical values.
  • SU Yan-Cai; GE Pei-qi; YAN Ke;HU Rui-rong
    . 2011, 30(10): 221-223.
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    Heat transfer characteristic of a vibrating cylinder in two-dimensional fluid flow was numerically investigated by the dynamic meshing and UDF programming technology via Fluent CFD software. The influence of flow velocity and the vibrating direction of cylinder on heat transfer were discussed. The numerical results show that, comparing with the still cylinder heat transfer, when the flow velocity is well below the maximum cylinder vibrating speed, the cylinder vibration has a significant influence on heat transfer enhancement, and the influence was reduced with the increase of the flow velocity, when the flow velocity is 4 times as the max cylinder vibrating speed, increase of the average Nu was only 1.2%. Study on Vibrating heat transfer characteristic of cylinder vibrating along different directions at the same flow velocity shows that the vibrating direction has little influence on heat transfer enhancement.
  • GUO Ji-feng; REN Wan-bin; ZHAI Guo-fu;ZHAO Hong-wei
    . 2011, 30(10): 224-227.
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    The piecewise linear vibration model of electromagnetic horn which including movable iron core and diaphragm with the time-variable electromagnetic force excitation were built. Then the vibration responses of horn were obtained by using numerical integral method. According to the calculated steady vibration displacement amplitude and frequency, the acoustic characteristics of electromagnetic horn were analyzed by the simulation software. Therefore, the relationship between the vibration displacement amplitude, frequency and sound pressure level variation principle between initial pressure of contacts and gap parameters were also investigated comprehensively. The conclusions which were drawn are valuable in optimizing the electroacoustic device such as electromagnetic horn.
  • Sun Qi-guo
    . 2011, 30(10): 228-230,.
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    Based on the 3D mechanical model for a large gap annular flow developed by authors, the zero-order perturbation equations of 3D non-linear partial differential equations of the motion of an eccentric rotor in a finite-length large gap annular flow are derived in this paper. The zero-order perturbation equations are also 3D non-linear partial differential equations, and it is a little difficult to get their solutions. Therefore, a simplified numerical method, which is based on the analysis results of a finite-length concentric large gap annular flow done by authors before, is put forward in order to analyze the dynamic coefficients of the eccentric rotor in the finite-length large gap annular flow. Comparing with existing numerical results and testing results, this method is sufficient and accurate. Numerical results show that the dynamic coefficients of the eccentric rotor in the finite-length large gap annular flow have still not the features: the main terms are equal, the couple terms are equal and opposite, comparing with that of the concentric rotor in the finite-length large gap annular flow. All main terms of dynamic coefficients increase exponentially in different degrees with the increase of eccentricity ratio, this shows that the dynamic coefficients of an eccentric rotor in a finite-length large gap annular flow will increase greatly in a large eccentricity.
  • WANG Bo;SUN Wei; TAI Xing-yu; WEN Bang-chuan
    . 2011, 30(10): 231-235.
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    Spindle-bearing,spindle-holder and holder-tool interfaces exist in the NC spindle system, and the characteristic of these interface has the significant influence on the spindle system dynamics. It is important to obtain the influence law for the dynamic design and modification of the spindle system. The paper takes a spindle system of vertical machining center as its object and builds the dynamic model with the finite element method, based on which, the contrastive analysis researches the inherent characteristic of interfaces and the law of influence of tool point FRF. The conclusion can be described as follow: the characteristic of spindle-bearing interface strongly controls the rigid modal of spindle system and tool point frequency response function (FRF) of low frequencies, however, the characteristic of spindle-holder and holder-tool interface directly influences the elastic modal and tool point FRF of high frequencies. Besides, the paper also could provide reference for the dynamics characteristic and stability forecast of spindle system.
  • WEI Qi-ke; LI Zheng-liang
    . 2011, 30(10): 236-240.
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    Because of the high tower and long-span of the ultra-high voltage long-span transmission tower-cable system that is not enough only considering seismic responses of the system under the uniform excitation. Based on the established precise 3D finite element model of the ultra-high voltage long-span transmission tower-cable system, the longitudinal seismic responses characteristics of the system are researched under traveling wave excitation and compared with those under uniform excitation, through the geometric nonlinearity dynamic time history integration method. The results show that the traveling wave excitation can increase, or decrease the seismic responses of the transmission tower, which are mainly related to the phase difference; the effect of the traveling wave on the line’s displacement responses is obviously in the vertical direction, but is not significant on the line’s axial force.
  • JIANG Jian;ZHANG Wen-ming;Duan Guang-hong; XIANG Dong
    . 2011, 30(10): 241-244.
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    By applying the explicit dynamic finite element method the dynamic response of dropping hammer in collision experiments for the extra-large engineering vehicle FOPS was simulated. A 170 tons electric wheel mining dump truck was taken as an example to illustrate the methods for establishing finite element model and applying boundary conditions and loads. The rule of energy conversion of whole process, the impulse force form and the rule of impact deformation were analyzed. The rule of impact deformation for change thickness of roof panel and mass of drop hammer was analyzed when impact energy was constant. The results indicated that the FOPS has been the stage of plasticity mechanism deformation and absorbed 10343J energy at the first impact, 88.6% of the total energy. The FOPS structural component had not invaded DLV during being impacted; the FOPS met the standard of the international requirement. The influence of the deformation of the impact center on thickness of roof panel was great and on mass of drop hammer was less. The impact deformation became smaller with the increase of thickness and the FOPS was unqualified when the roof panel less than 2.4mm.
  • WU Xiao;LUO You-xin
    . 2011, 30(10): 245-248.
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    The dynamic response of the beam with functionally graded materials was studied by Timoshenko beam corrective theory. The neutral plane site of the beam with functionally graded materials was determined by the static equilibrium equations, and the vibration equations of the beam with functionally graded materials were also established by Timoshenko beam corrective theory, the expression for the natural frequency of the beam with functionally graded materials and the analytical solution for forced vibration of the beam with functionally graded materials under the action of harmonic load were obtained. The effect of neutral plane site, gradient index to dynamic responses of the beam with functionally graded materials were discussed, and Timoshenko beam corrective theory was verified by finite element method. Analysis of examples indicates that the neutral plane site had more greatly influence on dynamic responses of the beam with functionally graded materials.
  • Jiang xin-hua;Zhang ping-jun;;Pen jin-min
    . 2011, 30(10): 249-253.
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    A resonant frequency and resonant amplitude model presents based on the loader analyses of the resonant part of Resonant Cement Pavement Breaking Vehicle (RCPBV). The mathematical model of the frequency control based on proportional pump-controlled-motor system is established with regard to the nonlinear and parameter uncertainties of Electro-hydraulic system of the machine firstly, the backstepping sliding mode control algorithm is designed, the adaptive controlling law for parameters uncertainties is given to ensure the asymptotic convergence of resonant frequency tracking based on the Lyapunov function. Simulation and experimental on vehicle results show that the method meets the controlling requirements of cement pavement breaker with better Frequency tracking performance.
  • LIU Hong-biao; GUO Xun; LI Guo-dong
    . 2011, 30(10): 254-259.
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    In order to find out a handy and effective method in structural damage detection, plate, steel shell and five stories steel frame structure model tests are carried out. Based on experiment results and Ohm’s auditory law, Musical Tone Law Method (MTLM) in structural damage detection is proposed. This method is effective for symmetrical structure in structural damage detection, such as framed structure, cable structure, shell structure, and so on. It is clear that Fourier spectrum of symmetrical structure is similar to musical tone’s according to the model tests. That is just the fundament theory of MTLM. Model tests prove that MTLM is effective in detecting damage of China disk and radial damage of steel shell. However, it is invalid for circular damage of steel shell, and the dominating causation is that circular damage makes stiffness of steel shell decrease little. In the damage detection test of five stories steel frame structure, it is first time to use the frequency ratio as diagnostic parameter in structural damage detection filed, and damage was detected successfully.
  • ZHANG Peng; JIA Zhong-yin
    . 2011, 30(10): 260-264.
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    The paper investigated the bifurcation, chaotic dynamics and active control of simply supported piezoelectric sandwich beams with axial loading. Based on the piezoelectric materials constitutive relations and von Karman type geometrically nonlinear strain-displacement relations, considering a proportional and derivative potential feedback laws coupling the direct and inverse piezoelectric coefficients, the nonlinear partial differential equation of motion of the beams is derived by Hamilton’s principle and then discretize it using Galerkin approach. Numerical simulation is carried out to investigate the dynamic bifurcation of the beams. The results show that the oscillation of the piezoelectric sandwich beams can be controlled with the gain proportional and derivative potentials of the considered feedback control.
  • HE Qing-bo; LIU Yong-bin; WU Qiang; LI Peng; HU Fei;KONG Fan-rang
    . 2011, 30(10): 265-269.
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    Machine condition diagnosis is studied by combining the principal component analysis (PCA) and the subspace methods. In the principal component subspace-based method, two subspace structures, called information compression subspace and class-specific subspace, are presented to represent and classify machine condition pattern. The proposed methods can extract effective and stable low-dimensional features of machine condition by the PCA, and effectively identify machine condition with low computational complexity based on the subspace methods. Experimental analysis with fatigue condition diagnosis of an automobile transmission gearbox shows that two principal component subspace-based methods have achieved excellent results with respective merit, and can be effectively applied to machine condition monitoring and diagnosis.
  • LIU Zhi-jun; RUI Xiao-ting; YANG Fu-feng; YU Hai-long; JIANG Shi-ping
    . 2011, 30(10): 270-273.
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    The relation between cable tension and natural vibration frequencies needs to be defined accurately for measurement of cable tension by vibration method. Transfer matrix method of multibody system was used to compute natural vibration frequencies of cable on the base of cable-vibration discrete model. The relation between cable tension and natural vibration frequencies was described by solving eigenvalue problem. The computing value of cable tension was amended until the difference between the theoretical calculation results and the measurement results reached the minimum. The final computing value of cable tension is regarded as the actual cable tension. The field measurement results are analyzed and it is indicated that the proposed method has high computational efficiency because of low order of system matrix and can effectively satisfy the requirements for measurement precision of cable tension.