25 August 2009, Volume 28 Issue 8
    

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  • ZHAO Ling;LIU Ping;LU Yuan-yuan
    . 2009, 28(8): 1-5.
    Abstract ( 2364 ) Download PDF ( 1937 )   Knowledge map   Save
    Abstract: For three hollow columns of non-obstructive particle damping, the influences of factors such as particle filling ratio, mass ratio, structural configuration of cavity and particle material type etc on the damping characteristics of columns are investigated by free vibration experiments, using iron powders, lead powders and sand grains as filling particles respectively. The reasonable structural configuration of cavity is explored. Test results indicate that the particle filling ratio and the mass ratio are principal influencing factors for the damping of columns and that maximum effect of damping improvement for columns may be obtained by rational choice of mass ratio or filling ratio in designing non-obstructive particle damping columns. In addition, the application of multicavity configuration and multicavity particle filling scheme, and the adoption of suitable material type of particles are beneficial to the damping enhancement of columns. No matter metal or nonmetal particles are adopted, the mass ratio should be controlled at a range of 0.3 to 0.5. If only small amount of particles is filled, higher structural damping can be acquired by using metal particles such as lead powders and iron powders than by using nonmetal particles. The experimental results may provide the basis for the rational design of non-obstructive particle damping columns.
  • WU Hui-min TANG Zhi-ping
    . 2009, 28(8): 6-10.
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    Abstract: The dynamic response of the TiNi alloy clipped beam under large mass low-speed impact loading and the phase transformation evolutional character were investigated by employing numerical method. The purpose of this study is to explore the effect of phase transformation on the dynamic behavior of the structure. It is shown that the response consists of five periods, i.e. elastic flexural wave propagation; localization phase transformation which leads to structural instability; stationary phase transformation hinge forming; expanding of the phase transformation hinge and traveling of the phase transformation hinge; hinged bar structure. The phase transformation hinge is a general hinge which is formed under the bending moment and axial force. The phase transformation hinge has different characters compared with plastic hinge.
  • Zheng Mingjun;Lin Yi;Wang Haihua;Bu Jian-qing
    . 2009, 28(8): 11-15.
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    Abstract: Based on the study of the mechanics features of air spring including the nonlinearities in material, geometry, contact, the nonlinear finite element analysis was applied to study nonlinearity characteristic of air spring. The three-dimensional finite element model of a cystiform air spring was established with the method of nonlinear finite element analysis. The analytical results were confirmed by the experiment with the use of an air spring test bench. The different contributions to the nonlinear stiffness characteristic of the multiplayer cystiform air spring were studied, which related to the inflation pressure, capsule parameters and additional chamber volume. The results show that the inflation pressure, capsule cord angle and additional chamber volume of the air spring have distinct influence to the stiffness character; whereas, the number of capsule card layer, interval of capsule card layer and interval of capsule card grid, capsule card material have little impact.
  • LI Li;YE Zhi-xiong;JIANG Yi-cheng;FANG Qin-han;
    . 2009, 28(8): 16-19.
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    Abstract: Wire damper (bretelles) is an ideal device to protect overhead conductors from damage by aeolian vibration, which is widely used on long span transmission lines in China. After the theoretical mechanical model of wire damper is built, the complex static deformation of wire damper is solved and established, energy dissipation calculation formulae are derived, so the vibration energy dissipated by β wire dampers can be considered in energy balance method. Then the computer program based on energy balance method is developed by applying Matlab, and Ultra high Voltage (UHV) Yangtze River large crossing ground wires are analyzed. One β wire dampers plus stockbridge dampers combination anti-vibration measure is designed to suppress its aeolian vibration. The calculation results show that this damping device can satisfy with UHV long span transmission lines vibration prevention requirement. So this method can provide reference for the research and construction of UHV engineering projects.
  • YAO Xiong-liang;Ji Fang;QIAN De-jin;PANG Fu-zhen
    . 2009, 28(8): 20-24.
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    Abstract:Based on wave analysis method, the characteristics of vibration wave propagation from typical hull structure are analyzed according to wave conversion and impedance characteristic in non-homogeneous structure, and the formula of sound transmission loss incident by plane bending wave is deduced. On this basis, the influence of impedance mismatch ship foundation on isolation performance is discussed. The results show that 十structure greatly impedes the bending wave propagation, and the redistribution of bending wave in mutated-section is mainly determined by natural impedance of the two plates. The resistance at the connection of ┻┳ structure increased and its isolation performance is better than十structure. The isolation performance of structure obviously increased with the increment of the impedance mismatch level of the mutated-section, therefore more sound transmission loss can be get by bringing in a number of mutation of cross-section. The impedance mismatch base aggravated wave conversion, scattering and reflection of vibration wave in the hull plates, so that the total isolation performance improved significantly. This article aims to provide reference for acoustic design of typical hull structure.
  • TENG Jun;ZHU Yan-huang;ZHOU Feng;LI Hui;OU Jin-ping; FU Xue-yi;GU Lei
    . 2009, 28(8): 25-29.
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    Abstract: The identification technology of frequency and damping ration based on complex Morlet wavelet transform is introduced, the principle of modal shape identification based on wavelet coefficients is deduced. In order to improve the identification precision of closely spaced modals, a method is developed to adaptive select the band wide and center frequent of mother wavelet based on minimum standard deviation. The natural frequency of large-span spatial structures are very low and closely, and it’s very difficult to excite the structures by exciter, in order to identify the modal parameter of large-span spatial structures, a combination method of NExT and wavelet is proposed. The results of numerical simulation and the analysis of data from the field test of Olympic venue NAC (National Aquatics Center) show that, it is effective to identify the low and closely spaced modal by complex Morlet wavelet.
  • JIANG Hua;WANG Jun-jie
    . 2009, 28(8): 30-34.
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    Abstract: The compression, tensile and damage characteristics of HJC concrete was demonstrated by single brick element compression and tensile simulation, the model was applied to simulate Hanchak perforation experiment,by setting maximal principal strain, equivalent plastic strain and maximal tensile hydrostatic pressure failure index in the simulation, residual velocity and slab failure phenomenon was compared with those from experiment results, both maximal principal strain failure index and maximal tensile hydrostatic pressure failure index obtain good agreement with projectile residual velocity in the experiment than equivalent plastic strain failure index. In addition, equivalent plastic strain failure index show less reasonable spall phenonmon on the surface of slab.
  • CHEN Xiao-qiang;ZHU Hong-ping;WANG Dan-sheng;GE Dong-dong;
    . 2009, 28(8): 35-41.
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    Abstract: A new time-domain structural damage identification strategy, improved kinetic energy density-based method, is developed using the measured acceleration signals. The kinetic energy density index is deduced theoretically and an existing method based on this index is introduced. Several faults of this existing method are pointed out and the corresponding reasons are analysed. According to these, an improvement utilized the wavelet packet transform and the correction of datum line techniques is made then. Afterwards, this improved kinetic energy density-based strategy is applied to structural damage detection of a numerical two-span continuous beam model and an experimental three-storey steel frame model. The results verify the effectiveness and performance of this new strategy, show its immunity of the interference of excitation force and noise and demonstrate its adaptability of various structures without complete modal information. Consequently, it is obvious that this new strategy possesses a certain practical engineering value.
  • ZHANG JIABIN;CHEN GUOPING
    . 2009, 28(8): 42-45.
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    Abstract: Based on the stochastic subspace method, using the property of matrix space, the projection from future data row space to past data row space is modified to an update mode for subspace tracking though QR decomposition. The left singular vector of the projection has been tracked by subspace tracking algorithm. Then the modal parameter is obtained by least square method. online modal parameter identification is Realized by output-data only. At last though an experiment, the efficiency and stability of the method has been proved by tracking the changing of the modal space and the modal parameter.
  • YANG Xin-wen;ZHAI Wan-ming
    . 2009, 28(8): 46-49.
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    Abstract: In order to predict and control wheel/rail impact noise due to wheel flats in fast speed and semi-high speed railway, a model which could simulate wheel/rail impact noise is set up based on the vehicle-track coupled dynamics theory and the sound radiation theory. The acoustics performances of wheel/rail impact noise due to railway wheel flats had been studied with wheel/rail noise simulation software TTINSIM. The results demonstrated that railway wheel flats which cause wheel/rail impact noise are important sources. Wheel/rail impact noise due to wheel flats are focused mainly in frequency domains upon 250Hz. Impact noises due to wheel flats is related to length and quantity of wheel flats and the train speed. The differences of impact noises due to new flats and old flats are 2~3dB(A).
  • YUAN Yong YU Hai-tao CHEN Zhi-yi
    . 2009, 28(8): 50-56.
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    Abstract: So far, Equivalent Static Method has been mainly used in the seismic design of underground structures in China; however, Free-filed Deformation Method and Response Displacement Method have been mainly used in foreign countries. The seismic design discrepancy of Equivalent Static Method, Free-field Deformation Method and Response Displacement Method was analyzed and evaluated in this paper. In analysis, the benchmark model was set for underground structure in soft soils, and the seismic response of underground structure was acquired by using dynamic time-history analyses. Assuming the same stratum and buried depth, based on the discrepancy comparison analysis of deformation and internal force along with different structural stiffness, evaluation of applicability was made for the three pseudo-static seismic design methods. The result shows: Equivalent Static Method could be applied well under the condition of large stiffness of shallow-buried frame structures in soft soils, in other cases it will lead to large deformation and internal force of structure; Free-field Deformation Method could be applied in the condition that the stiffness of structure is relatively small or approached to the surrounding soil, and the Pseudo-Triangular Pressure Distribution Model would prior to the Pseudo-Concentrated Force Model; Response Displacement Method could be suitable to the seismic design for shallow-buried frame structures with different stiffness.
  • ZANG Yuping; ZHANG Dejiang WANG Weizheng
    . 2009, 28(8): 57-60.
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    Abstract:The de-nosing principle using wavelet was discussed and the de-nosing property was compared using general threshold strategy. Following them a per-level de-nosing method based on the analysis to the autocorrelation of the wavelet detailed coefficients is proposed. The maximum wavelet decomposing level is determined according to the minimum interest frequency. The step of the per-level de-nosing method is then given and its experiment research to vibration model is processed. The results proved that the method is better for de-nosing, which is more suitable to recover the interest weak signal from intense background noise. Last, its application in the engine vibration is processed and the results proved that it can inhibit the background noise effectively and recover the interest information. It provides a practical strategy for engine vibration pre-processing.
  • Tao Xin-min;Xu jing;Fu Qiang;Liu Xing-Li
    . 2009, 28(8): 61-64.
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    ABSTRACT: To solve the problem that traditional Kernel Fuzzy C-Means Algorithm (KFCM) is very sensitive to outliers and noises in the training set, a novel Kernel fuzzy C-Means Algorithm based on distribution density around samples and maximum variance between clusters method is proposed in this paper. In the proposed method, the value of distribution density around samples is used as weight values according to the feature of sample distributing to overcome the shortcomings of KFCM’s sensitivity to noises and outliers. The maximum variance between clusters methods is applied to segment the sample’s distribution density vector, whose segmentation results are used to as the initial centers of the proposed KFCM algorithm, which overcomes the problems of KFCM sensitivity to initial values. The proposed method can not only solve the problems of traditional KFCM’s sensitivity to noises and outliers and sensitivity to initial values, but also can be applied to analyze samples’ contribution to clustering performance. The experimental results with various real data sets illustrate the effectiveness of the proposed algorithm. The proposed method is applied to fault diagnosis field which outperforms traditional cluster methods.
  • Li Chunxiang;Liu Chenzhe
    . 2009, 28(8): 65-69.
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    Abstract: The numerical simulations of wind loads are critical in the design of structures. Harmony superposition method is most widely used among all the simulation methods for tall buildings. Likewise, the time expense of harmony superposition method can be significantly shortened by resorting to the FFT technique and various kinds of interpolation techniques without a significant loss of the accuracy. Square polynomial interpolation technique, cubic polynomial interpolation technique, and two kinds of spine interpolation techniques with different end conditions are adopted in the paper to simulate the wind velocity time series at 10 points in a 100-metre building. Two indices, designated as the root mean square error ( ) and error factor ( ), are introduced to measure the accuracy of these four interpolation techniques with respect to the traditional harmony superposition method (without introducing the interpolation technique) and likewise their time expense is recorded. Finally, the best interpolation technique is picked out through comprehensively taking into account both accuracy and time expense.
  • YUAN Sheng-fa;CHU Fu-lei
    . 2009, 28(8): 70-73.
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    Abstract: Rub-impact is the ordinary failure of rotating machinery, and its position detection is a problem pending deeply study. Sphere support vector machines, a kind of multi-class support vector machines, is improved after the influence of the size of sphere on the classification is taken into account and a effective and simple rule of classification is derived from rational analysis and simulation experiment. The rub-impacts in different parts of shaft are regarded as different faults, and their position detection becomes a large-scale multi-class fault diagnosis and can be solved by the improved sphere support vector machines. The experiment of rub-impact position detection of simulation shaft shows that the improved sphere support vector machines distinctly improves the fault recognition accuracy, the diagnosis speed and the data processing capability, and is more suitable for practical application of large-scale multi-class fault diagnosis.
  • Zhang Wenbin;Zhou Xiaojun;Yang Xianyong;Lin Yong
    . 2009, 28(8): 74-77.
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    Axis trace is an important content for vibration signal analysis in time domain of rotating machinery; different axis trace expresses different operating condition or basic fault information for rotor. On the base of deep research box-like spectrum feature of harmonic wavelet, a new method that need not decomposition to purify the axis trace was proposed by using the harmonic window method. With this method, the signal could be decomposed into any frequency band, and then the interested frequency band could be abstracted and reconstructed in time domain, so the purification of axis trace was completed. The effectiveness of this method has been proved by the successful purification of axis trace coming from the test-bed. This method has simple algorithm and easy on-site application; it provides a new method for signal analysis of rotor fault.
  • Li Xingguo Jin Xin He Yulin
    . 2009, 28(8): 78-83.
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    Because the usual method cannot take the coupling relation between the rotor structure and aerodynamic load, in which the correctness will be influenced. Aiming that problem,the combine simulation is used in this paper, which can take the coupling into consideration. 600KW wind turbine is researched on rotor structural dynamics, which results are compared to the test results. The comparison shows that the modified theory can be used to the structural analysis of wind turbine. But the simulation will cost much time, the ANN is used to predict the structural dynamics of wind turbines after calculating sample using combine technology. The result shows that ANN combined with simulation can reduce the time and ensure the correctness.
  • GAO Hao-peng;HUANG Ying-yun;WANG Xue-shan
    . 2009, 28(8): 84-87.
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    In the foundation of traditional analysis of diesel dynamics, the transmission of power system of TBD234 V6 diesel engine was molded by the software of 3D solid mold and the mold was transferred to the software of dynamic analysis of mechanical systems, then dynamical simulation of the transmission of power system was done at the case of taking vibration absorber, not taking vibration absorber and shocking. Results analysis indicated that the model can accurately simulates the force of the transmission of power system. This analytical process provided a kind of simple, credible and feasible method, which can use to design the structure of the transmission of power system and deal with the malfunction.
  • XIA Kaiquan; QIAN Zhendong; LIU Yun
    . 2009, 28(8): 88-90,9.
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    In order to study the dynamic response of high voltage transmission lines with self-supporting double-loop steel tower under mechanical fault, the non-linear dynamic finite element model of a domestic 500kV high voltage transmission line system was established. The reliability of coupling system model was verified by static calculation results. Transient dynamic analysis method was proposed to analyze the variation law of dynamic response under cable rupture. The results show that upper crossarm cable rupture has no effect on cable tension at adjacent suspension points, but it has significant influence on tension in the insulator and tower component of upper crossarm next to the broken span. The research results can provide the theoretical base for the design of transmission line.
  • ZHANG Zhan-yi LIU Jie YING Huai-qiao LI Yun-gong YAO Zhao
    . 2009, 28(8): 91-93.
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    According to properties of the rotor local run-impact fault and characteristics of the vibro-acoustic signals, a method is adopted to diagnose the minor local rub-impact fault of sliding bearings based on the Empirical Mode Decomposition (EMD) of vibro-acoustic signals. The rub-impact fault characteristics can be separated from rotating excitation signals automatically in that the EMD needs no fixed basic functions and adaptively adjusts with the signal properties. A rub-impact experiment of sliding bearings without lubrication was setup, vibration hologram measurements taken, and the time domain properties of the vibro-acoustic signal Intrinsic Mode Function (IMF) compared to the rotor radial displacements and bearing abutment accelerations. The rub-impact component is determined by comparing the IMF marginal spectrum to the frequency spectrum of the bearing abutment acceleration. It is proved that the method based on EMD of vibro-acoustic signals is effective to diagnose the rub-impact fault.
  • LIU Xiao-bing;LIU Zhi-wen;CHEN Zheng-qing
    . 2009, 28(8): 94-98.
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    Compared with common single deck bridge, the cross section aerodynamic optimization of twin deck bridge girder is stricter because the aerodynamic performance of both forward girder and leeward girder should be good at the same time. Based on a twin deck bridge which is under construction, a serial of wind tunnel tests of the sectional models were performed to get the best girder cross section through aerodynamic optimization of basic shape of girder cross section, position and height of repair-vehicle rail. This start a preliminary study on cross section aerodynamic optimization of twin deck bridge girder.
  • Tang Baoping;Chen Jianbo;Zhang Guowen
    . 2009, 28(8): 99-102.
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    A new method of holospectrum based on correction of phase difference is put forward against to the lower precision of traditional holospectrum in noisy interference. First it takes windowed FFT transformation of signal in time domain and then the frequency,amplitude and phase are corrected by correction of phase difference.At the last, the holospectrum is synthesized.Through the simulation and the analysis of flexible rotor’s vibration signal,The result shows that it has higher precision in practice and can diagnose the rotation machinery fault more accurately and more effectively.
  • Ran Chengsong;Xu Zhaodong
    . 2009, 28(8): 103-105.
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    The usual semi-active control algorithms are determining the optimal control force based on structure feedbacks of displacement and velocity responses. But in actually, these strategies lead to negative affect to controlling effect, because of difficulties of measurement of displacement and velocity responses, data transmission and line layment. This paper puts forward a new discrete control algorithm based on inter-storey displacement and inter-storey velocity responses. The inter-storey displacement could be measured precisely by displacement meter attached to magnetorheological damper, while the inter-storey velocity could be obtained by differential inter-storey displacement, then the control force of the damper in this storey could be determined independently. The results of the numerical analysis illustrate that the proposed control algorithm have good damping effects in the earthquake.
  • Ran Chengsong;Xu Zhaodong
    . 2009, 28(8): 103-105.
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    The usual semi-active control algorithms are determining the optimal control force based on structure feedbacks of displacement and velocity responses. But in actually, these strategies lead to negative affect to controlling effect, because of difficulties of measurement of displacement and velocity responses, data transmission and line layment. This paper puts forward a new discrete control algorithm based on inter-storey displacement and inter-storey velocity responses. The inter-storey displacement could be measured precisely by displacement meter attached to magnetorheological damper, while the inter-storey velocity could be obtained by differential inter-storey displacement, then the control force of the damper in this storey could be determined independently. The results of the numerical analysis illustrate that the proposed control algorithm have good damping effects in the earthquake.
  • Huanglei Jiang Weikang Yan Weihua Ma Jianping
    . 2009, 28(8): 106-108.
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    On controlling the jet noise, the most effective way is to reduce the noise aiming at the acoustic sound source. Based on the principle of the producing of jet noise, this paper theoretically analyzes the influence of the nozzle’s shape on the noise. Properly changing the shape of the nozzle can reduce the velocity of flow along the jet’s axis direction on the vertical grads, and thus weaken the intensity of the turbulence which results in the reduction of the jet noise. Numerical computation indicates that the improved nozzle could obviously reduce the velocity of the flow field. The experiment verifies that the jet noise can be effectively inhibited by changing the flow field, and the sound level can be reduced by 3~4 dB (A).
  • YUAN Guoqing;JIANG Zhe
    . 2009, 28(8): 109-112.
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    The sound power sensitivity analysis reveals the relationship between the radiation power caused by the structure vibration with the design variables of the structure. A new method for solution of sound power sensitivity is presented by using acoustic radiation modal model to deal with radiation part and using finite element vibration model to deal with vibration of the structure part. In the plate model with the infinite baffled panel, this method is verified by a common method of using Rayleigh integral model to deal with radiation part. In conclusion, it is proved that this method is feasibility.
  • HUANG hai-yan;WANG De-yu
    . 2009, 28(8): 113-116,.
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    This paper presents a collaborative optimization (CO) strategy on reducing vibration of engineering structure. Different objective functions in various subsystem-level optimization models are used. In system-level optimization model, a new objective function is advised to minimize relative deviation value between the collaborative objective function and single disciplinary objective function. And it eliminates the effect of different dimensions and the order of magnitudes among objectives. The proposed CO architecture enables multi-objectives of the system and subsystem-level’s to be considered at both levels during optimization. A bi-level optimization strategy is advised. The proposed optimization and strategy are demonstrated with two examples. One of them is a reducer optimization problem, and another is a mixed structure which is made up of pillar, beam and plate. The results of examples show that the proposed CO model is feasible and reliable, and can not only effectively decrease the dynamic responses of engineering structure, but also the final structure has better global properties.
  • YUAN Yongxin;DAI Hua
    . 2009, 28(8): 117-120.
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    An efficient numerical method for updating the damping and stiffness matrices simultaneously using a few of complex measured modal data is developed. By applying the singular value decomposition, the optimal corrected damping and stiffness matrices that satisfy the equation of motion are found in a weighted Frobenius norm. This model updating method is direct and the updating process is very simple. Numerical results show that the presented method can be used to update the finite element model to get better agreement between analytical and experimental modal parameters.
  • HU Jia-guang;ZHANG Jin;JING Shou-yong
    . 2009, 28(8): 121-123.
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    The plane wave expansion method was employed to calculate the elastic wave band gaps of new nesting complex triangular lattice phononic crystal composed of steel columns embedded in air matrix, and each single column basis is replaced by two tangency-columns.Numerical results show that, compared with the simple triangular lattice phononic crystal, the wider band gaps appear at lesser filling-fraction and lower frequency area are easy to be obtained, at the same filling-fraction, the widest first band gap for the nesting complex triangular lattice is 4.4 times wider than that of the first band gap width of simple triangular lattice, and its mid-gap frequency is only half of the first mid-gap frequency of simple triangular lattice.
  • LI Chao-feng;WANG De-gang;LIU Jie;WEN Bang-chun
    . 2009, 28(8): 124-127.
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    The finite element method was employed to establish a nonlinear dynamical model of the existing bearing-rotor experimental system. In order to save the computing time, the fixed interface mode synthesis method was adopted to reduce the original system to 12-degree-freedom from 56-degree-freedom. Based on the satisfaction result of the comparison between the reduced one and the original, the Newmark-β method was employed to solve the reduced model numerically. And the three-dimensional spectrogram, bifurcation diagram, three-dimensional amplitude diagram, chart of axes track, etc were used to analyze the nonlinear character of the dynamical system comparing with these results of the experimental system. Results show that the numerical dynamic model more truly reflects the characteristics of the nonlinear experimental system. So that, there are very important actual meanings for applying the FEM and dimension reduction theory into the research of the local nonlinear rotor systems, which can provide more accurate verification and reference for the advanced nonlinear dynamic design of the complex rotor system.
  • Shen Chaoyong; Zhou Fulin; Huang Xiangyun; Chen Jianqiu; Jin Jianmin;
    . 2009, 28(8): 128-133.
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    There are little literatures about vertical dynamic characteristic and seismic performance on high-rise building with stagger transfer stories, in this paper, one coming from practical project will be studied with SAP2000V9 program. The effect of number of vertical modes on the internal force of the upper, lower transfer beam and the axis-force of main vertical components are studied. Vertical acceleration, vertical drift and vertical dynamic strain are computed, the dynamic response at the end point, column point on the upper, lower transfer beams with different stories are researched and compared when earthquake waves and spectrum are input. The axis-force of the columns on the upper, lower transfer beams, supporting shear wall, shear wall supported by frames, columns supporting shear walls are calculated when earthquake waves and spectrum are input, and compared to the value under the representative gravity load. The result shows the basic vertical modal plays a very important role in effect on the internal force of transfer beams and the axis-force of main vertical components, the modals above the 5th modal have little effect on them; the displacement and acceleration at the column point on the transfer beam are greater than those at the end points of the upper, lower beams; the vertical strain of the vertical component at the end point of the upper, lower transfer beams have sudden change at the stories which are just above the two transfer stories respectively, simultaneously the vertical strain of the vertical components at the stories between two stagger transfer structures increase partially; the higher the location of the vertcial component is, the greater the versus between the internal force of it under the spectrum load and that under the representative gravity load; under the vertical earthquake, the axis force of supporting shear wall at the top story and that of shear wall supported by frames at the three bottom stories will occurs sharply change.
  • SU Yongzhen YUAN Shenfang
    . 2009, 28(8): 134-137.
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    Acoustic emission (AE) signal is used for localization and characterization of acoustic emission source. When there are multiple impact sources, it is a difficult problem that locating impact sources because AE signals are mixtures of multiple statistically independent signals and the mode of mixing is unknown. Fortunately, blind source separation (BSS) by independent component analysis (ICA) can solve the problem in recent years. In the paper, the feed-back neural network based on information maximization (informax) principle is used to separate the signal mixed by two independent continuous AE signals induced by two simultaneously impact events on an aluminum beam. Meanwhile, time delay between two PZT sensors for each source is obtained. Then two sources position are determined based on two-point localization formula. Time delay estimation by ICA based on informax principle is verified by simulation experiment. Furthermore, experiment on aluminum beam indicates that multiple impact sources locating can be solved by ICA.
  • Tang Jinyuan Peng Fangjin Huang Yunfei
    . 2009, 28(8): 138-143.
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    Established precise three-dimension model of spur gear based on hob-shaving process with virtual manufacturing approach. Carried out dynamic simulation analysis based on corner contact. Obtained the dynamic stress variation law of the gear under impact loads. The simulation results shows that the position of the maximum dynamic stress of the root of tooth under different condition appears in the both sides symmetrically, that the dynamic stress was bigger than the ISO Standard theoretic static strength under impact loads, and that the position of the maximum dynamic stress is on the high side of the dangerous section determined by ISO Standard, that the dynamic stress caused by the engaging-in impact was the maximum under different condition, and that the shorter the impact time is, the larger the dynamic stress is.
  • WANG Yingze ZHANG Xiaobing YUAN Yanxiong
    . 2009, 28(8): 144-147.
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    The vibration response about the rarefaction wave gun in the action of various loading is researched. Based on the actual loads act on the barrel in the launch process, the vibration response equation which considering the elastic effect of the barrel is established with the interior ballistic equations. By Rayleigh-Ritz modal method the vibration equation is dispersed to the second-order time-variant equations. After numerical calculation the vibration response and relation between vibration response and interior ballistic property in the different parameters are attained, and then the theoretical references about the optimization of firing precision and the reasonable choice of interior ballistic parameters are also attained.
  • Xiao Xiang Ren Wei-xin
    . 2009, 28(8): 148-153.
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    Based on the data-driven stochastic subspace identification (SSI) algorithm, an improved on-line SSI procedure is presented to automatically extract the operational modal parameters of structures. The Hankel matrix’s dimension parameters i and j are determined by experiential approach and the Mode Transfer Norm (MTN) is used to improve the stabilization diagrams. A singular entropy-based approach is implemented to determine the system so that the identification procedure becomes more automatic. To reduce the calculation work, the Choleshy factorization technique is used to handle the lower tri-matrix R. As a result, the calculation efficiency is much improved when the data are overlapped for two different time windows. The applicability and efficiency of proposed method are validated via both simulated 3-span continuous beam and full-size bridge that was tested on field under operational conditions. It is demonstrated that the approach has an advantage of calculation time and precision. The proposed method can be used to perform online operation modal parameter identification of large-scale structures.
  • CHEN Xinrui HAO Zhiyong YANG Chen wang yuxing
    . 2009, 28(8): 154-157.
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    Magnesium alloy is light, and has large specific stiffness, great damping and excellent shock absorption. It had been made into automotive dash successfully. In order to avoid severe requirements of theoretical model and experiment condition limits, sound insulation performance of dash could be obtained by structure-sound interaction method. This approach was validated by comparing the numerical solutions with experimental results. Sound transmission loss of automotive dash in diffuse field was computed. The results indicated that in low frequency band, comparing with steel based dash, sound insulation performance of magnesium alloy based dash is much better. Replacing steel by magnesium alloy, original structure of dash needs to be improved, and its eigenfrequency should be beyond the peaks of noise source, avoiding deterioration of acoustic characteristic in certain frequency bands. Applying magnesium alloy to vehicle could lose weight as well as improve cab’s acoustic environment.
  • hen Bin Liu Ge
    . 2009, 28(8): 158-162.
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    Used the characteristics method to be solved the water hammer coupled transient response law owing to valve open-shut moves, study to active control to the chemical piping system; using of nonlinear programming algorithm, the optimal curve law coupling water hammer calculation of valve were derived, in order to realize on the project, applied the optimization of a ANFIS approach to substitute for the optimal curve, the pressure amplitude of the largest margin is 8 kPa; The use of ANFIS valve open-shut law, experiment shows the end of the piping pressure dropped by as much as 13.04 percent, the valve optimal curve law could be effectively reduced the amplitude of water hammer pressure, proved the control measures is effectiveness.
  • ZHANG Jiawei ZHOU Shijun
    . 2009, 28(8): 163-167.
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    The corresponding nonlinear differential equation with the effect of dead loads taken into account is formulated from Hamilton principle. Based on the equation, the effect of key physical factors, including the magnitude of dead loads, the height and span of the arch beam, the moment of inertia and the radius of inertia, etc, on natural frequencies of the arch beam, are discussed by using Galerkin method. It is shown that the existence of dead loads raised the natural frequencies of arch beams, and the differential equations can be applied to both arch and straight beams. The varying deterrent effect of dead loads relates to the magnitude of dead loads and the stiffness of structures. The effect is more apparent for flexible structures and at lower natural frequencies.
  • SHEN Lu ZHOU Xiaojun ZHANG Zhigang ZHANG Wenbin
    . 2009, 28(8): 168-171.
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    Serious end effect will be produced while the upper and lower envelope is constructed in the process of EMD. Similar extrema extension method was proposed to overcome the problem. Abscissa difference of adjacent extrema at both ends of data was considered as the shape characteristic, then the shape characteristic and average of extrema were used to extend signal. Both trend of extrema variation near boundary and rest of extrema were considered in similar extrema extension, while only the extrema near boundary was used to extend signal in current
  • su Yongsheng Wang Yongsheng Duan Xiangyang Zhang Yongxiang
    . 2009, 28(8): 172-174.
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    It is difficult to pick up weak signal at the domain of fault diagnosis. A new weak signal feature extraction method based on Fourier Transform is presented. Firstly,time serial was switch to frequency domain;Secondly,the value of frequency was transformed into time complex number field; Moreover, the breadth of complex number was calculated. The arithmetic gives prominence to the part character information of signal by simulation. The weak impulsion in mixed-signal is given preferable reappearance and is also picked-up in powerful background noise. Lastly, the gear fault diagnosis experiment indicates that this algorithm is able to extract the weak fault feature signal.
  • Yu Aimin Yang Changjin Hao Ying
    . 2009, 28(8): 175-179.
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    Coupled vibrational behavior for spatial curved beams with general cross-sectional shapes, based on naturally curved and twisted beam theory, is theoretically investigated. In the governing equations of motion of the beams, all displacement functions and the generalized warping coordinate are defined at the centroid axis and also the effects of rotary inertia, transverse shear deformations and torsion-related warping are included in the present formulations. The explicit analytical expressions which give the vibrating mode shapes of the beams are derived by rigorous application of the computing package MATHEMATICA and a process of searching is used to determine the exact natural frequencies. In order to demonstrate the validity of the present theory, the natural frequencies and vibration modes of a curved beam of elliptic cross section with clamped-clamped boundary condition are evaluated and compared with the FE-results using PATRAN’s beam elements.
  • XU Qiang CHEN Jianyun Li Jing
    . 2009, 28(8): 180-183.
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    The aim of this page is as follow: based on wavelet function, to solve the questions, which is that the trigonometric series method can not account for the local defect of seismic wave when using it to generate artificial seismic wave. The research methods of this page are as follow: Firstly, this page explains the process of generating artificial seismic wave based on trigonometric series method. The aim is to show the defect of this method. Secondly, this page explains how to use wavelet function to transform target power spectrum into wavelet base. Then high frequency wavelet base multiplied by cosine function with random phase to gen rate artificial seismic wave. And this page explains how to calculate the target power spectrum accurately. Thirdly, An example is gave to explain the better properties of this method as trigonometric series method to generate artificial seismic wave. And this page compare with the effect of different wavelet base to generate artificial seismic wave. The conclusion is that Daubechies wavelet transform (db4) is better than Daubechies wavelet transform (db1) to generate artificial seismic wave. And it can not improve precision to increase the layer of wavelet function.
  • Tang Guoning Peng Meng
    . 2009, 28(8): 184-187.
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    Aimed at the two different reorganizations of vibration mill research and explore, according as the basically dynamics formulation of disperse milling medium group, vibration mill movement characters have been educed on two extremely conditions which just considered either frontal impacting or lateral cutting .Based on this , numeric calculation have been accomplished on the condition of given parameters by using software MATLAB. The conclusion is of important instructional value for design and application of vibration mills .
  • Gao pinxian Su yanchen Wu Chuanhui
    . 2009, 28(8): 188-190,.
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    In equipments running condition monitoring, the vibration analysis is the most used method, the analysis parameters of which include the amplitude characteristic and power spectrum. Different from the conventional regulation method, taking advantage of the phase characteristic of vibration signal, this paper deals with the equipments condition monitoring by the lag characteristic arising when the signal passing system. Here we carried on on-line monitoring to the condition of the vehicle hang system, and made a deep discussion on this issue from both theory and method sides. Compared with the analytical method based on the amplitude characteristic, the phase characteristic method is more effective. This new approach not only enriches the analytical contents of the vibration monitoring, but also broadens the analytical path of the vibration monitoring.
  • Shen Hualong Wu Yunxin GuoJunkang
    . 2009, 28(8): 191-194.
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    The deformation and instability caused by residual stress of high intensity aluminum alloy material is a problem, which is always puzzled in engineering .Vibratory stress relief (VSR) technology is a method for reducing residual stress and improving the size stability of member, and the mastery of vibratory stress relief technics is vitally important. This paper introduces the basic principle of vibratory stress relief technics ,then uses high intensity aluminum alloy thick plates to do VSR experiment by suspending simplistic vibration platform, which reveals the specific technics process of VSR and reachs to ideal aging results. The vibratory stress relief technics of aluminum alloy thick plates directly influence the aging results.