25 September 2011, Volume 30 Issue 9
    

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  • Duan Chen-dong;GAO Qiang
    . 2011, 30(9): 1-5.
    Abstract ( 985 ) Download PDF ( 734 )   Knowledge map   Save
    In order to extract fault features from vibration signal, a noval fault diagnosis approach using time-fquency slice analysis was proposed in this paper. Firstly, vibration signal was decomposed by applying frequency slice wavelet transform (FSWT). Thereafter, on the basis of time-frequency energy distribution of the decomposed components, zoom analysis was adopted over those interested time-frequency slice intervals which were selected for feature extraction. By making time-frequency segmentation and signal reconstruction, features in time and frequency domain were revealed over the seleced slice intervals. As a result, the fault features were successfully separated from the vibration signal. The proposed approach can efficiently extract accurate fault characteristic information for condition monitoring and fault diagnosis, it has been appeared a satisfactory effect in diagnosis for rub fault of a gear-box in a refinery.
  • LI Yong;ZUO Shu-guang;YANG Xian-wu;WU Xu-dong
    . 2011, 30(9): 6-9.
    Abstract ( 1623 ) Download PDF ( 951 )   Knowledge map   Save
    Considering the nonlinear characteristic of tire’s grounding friction and using the calculation formula of lateral stiffness obtained by energy method, a dynamic model of the polygonal wear of tire was established based on the lateral vibration of tire tread. Utilizing this model, the generation mechanism of polygonal wear was discussed, and the effects of speed, toe-in angle and vertical load for tire wear were analyzed through numerical simulation. The results show that: the polygonal wear is the circumferential uneven wear which is the overlay of even wear and disturbance wear caused by the tread’s lateral self-excited vibration, which is a typical nonlinear self-excitation vibration phenomenon; based on Lyapunov stability theory, the self-excited vibration of tire is proved to be a kind of stable periodic vibration caused by Hopf bifurcation of system; high speed, large toe-in angle and overload are the possible reasons which lead to polygonal wear of tire.
  • WANG Yan-qing;LIANG Li;*GUO Xing-hui;LOU Ling-na
    . 2011, 30(9): 10-14.
    Abstract ( 1488 ) Download PDF ( 458 )   Knowledge map   Save
    A cantilever thin laminated circular cylindrical shell is investigated in this paper. Based on Donnell’s nonlinear shallow shell theory, nonlinear wave equation of the system is derived, in which the effect of dynamic Young’s modulus, damping and geometric large-amplitude are considered. Galerkin method is used to disperse the wave equation. Applying averaging method, we solve the nonlinear response of the system with two neighboring axial modes participation, and the results obtained are compared with that gained by numerical method. The effects of different parameters on the complex dynamic response are also investigated in this study. Results show that, 1) due to the frequencies of the two modes selected are very near, it exist 1:1 internal resonance in the system; 2) the complex vibration response of the system is affected by exciting force or nonlinear terms evidently, but it is not very sensitive to damping.
  • JIN Yang;HAO Zhi-yong;ZHENG Xu;JING Guo-xi
    . 2011, 30(9): 15-20.
    Abstract ( 1230 ) Download PDF ( 922 )   Knowledge map   Save
    The relationship between the Gaussian window’s time standard deviation in the continuous time domain and the ability of the STFT amplitude spectrum with Gaussian window to separate order components is established quantitatively according to numerical experiments. The problem with taking the order slices of the STFT amplitude spectrum as the instantaneous amplitude estimates is pointed out. The premises for successful Gabor order waveform reconstruction are examined. An improved flowchart for Gabor order waveform reconstruction, which abandons the try-and-error mode in choosing the analysis parameters, is formulated based on the established relationship between the Gaussian window’s time standard deviation and the ability of the STFT amplitude spectrum to separate order components. Simulation shows that the envelope obtained from the Hilbert transform of the reconstructed order waveform obtained by employing the improved flowchart can be used as a valid instantaneous amplitude estimate.
  • Liu Jing-bo;Guo Dong;Wang Zong-gang;Fei Bi-gang;Wang Qian-yuan
    . 2011, 30(9): 21-25.
    Abstract ( 1322 ) Download PDF ( 429 )   Knowledge map   Save
    This paper presents a new method to combine the finite element analysis and limited vibration signals measured in the spot.The dynamic response of structures (antennae of China Mobile) under practical wind loads can be acquired by it. Firstly, the limited vibration signals of structures are measured under impulsive wind loads, such as acceleration time history and frequency spectrum. Secondly, the time history of impulsive wind loads is simulated by equation of structure motion and then it is applied to the model of finite element. By this finite element analysis, the correction factor k between simulated wind loads and practical wind loads is obtained. Finally, the correction wind loads is applied to this model again. The internal forces of structure are gained under practical impulsive wind loads. It shows that the finite element analysis gets the results in accordance with that of experiment, which provides a easy method for total process analysis of structures under impulsive wind loads.
  • ZHANG Wen-bin;WANG Hong-jun;TENG Rui-jing;LI Jun-sheng
    . 2011, 30(9): 26-29.
    Abstract ( 1598 ) Download PDF ( 595 )   Knowledge map   Save
    Due to practical data were easily interrupted and useful information was covered by noises, a novel de-noising approach was proposed based on the adaptive structure element for generalized morphological filtering (ASEGMF). Firstly, the sine structure element was selected according to the feature of vibration signal, and the length scale and the height scale were defined. Secondly, the peak distance and the peak height were defined by signal’s local characteristic, and the length scale and the height scale of sine structure element were gotten by adaptive method. Finally, the interrupted vibration signal was de-noised by the generalized morphological filter cascaded by one small and one big adaptive structure elements. This method conquers the selective random of current morphological filter, the structure element are gotten adaptively by signal’s local characteristic without artificial interference. Practical and simulation results show that this method has better de-nosing effectiveness. It’s suitable for on-line monitoring and diagnosis of rotating machinery.
  • Cheng Jun-sheng;Li Bao-qing;Yang Yu
    . 2011, 30(9): 30-34.
    Abstract ( 1144 ) Download PDF ( 1013 )   Knowledge map   Save
    Targeting the frequency demodulation characteristics of the gear fault vibration signal in the tart-stop process, the order spectrum method based on the generalized demodulation time-frequency analysis and the instantaneous frequency calculation is proposed and applied to the processing of the gear transient signal in this paper. The generalized demodulation time-frequency analysis approach which is a new signal processing method can decompose a multi-component signal into some single-component signals whose instantaneous frequency posse physics sense. Each single-component signal can be amplitude and frequency modulated signal. Therefore, the generalized demodulation time-frequency analysis approach is very suitable to process the multi-component amplitude and frequency modulated signals. When fault occurs in gear, the gear vibration signal in the start-stop process shows the multi-component amplitude and frequency modulated characteristics. In the order spectrum method based on the generalized demodulation time-frequency analysis and the instantaneous frequency calculation, firstly the multi-component signal is decomposed into some single-component signals by using the generalized demodulation time-frequency analysis method; secondly the instantaneous frequency of each single-component signal is calculated; thirdly each instantaneous frequency is resampled in angle-domain; finally the spectrum analysis is applied to each resampled signal and the order spectrum can be obtained. Hence, the fault characteristics of the gear vibration signal can be obtained and the gear work state can be identified according to the order spectrum. The analysis results form the simulated and experimental signals show the effectiveness of the proposed method.
  • Yuan Xing;Zhu Yong-sheng;Hong Jun;Zhan You-yun
    . 2011, 30(9): 35-39.
    Abstract ( 1420 ) Download PDF ( 386 )   Knowledge map   Save
    In the previous bearing models, vibration characteristics have a larger error compared with the practical project because of neglecting the impact of pedestal and rolling element. A novel prediction model has been developed to obtain the vibration response due to localized defect of bearing system in order to solve the problem. In the analytical formulation, the contacts between the rolling elements and the races are considered as non-linear springs. The contact force is calculated using the Hertzian contact deformation theory and the bearing system is modeled as multi-degrees-of-freedom system. The implicit type numerical integration technique Runge–Kutta method is used to solve the non-linear differential equations iteratively. A computer program is developed to simulate surface defects of the components. Then grey incidence degree (GRD) is employed to investigate the Condition assessment based on hybrid features obtained from the novel model. The new technique is experimentally evaluated using vibration signals measured on rolling bearings system that contain localized defects, and good results were obtained that verified the validity and effectiveness of this paper.
  • HU Zi-dong;LI Li;Nie Su-fei;
    . 2011, 30(9): 40-45.
    Abstract ( 1056 ) Download PDF ( 685 )   Knowledge map   Save
    The temperature properties of LRB used for isolated bridges are studied. The seismic response of isolated bridges including temperature effect are purposed. The range of temperature tests from -40℃ to 50℃, the characteristics of LRB under different temperature environmental conditions are measured by quasi-static testing. Base on experimental results, using regression analysis, the function of LRB correlated with temperature is derived. An numerical implementation of isolated bridges under seismic excitation which considered the effect of LRB is presented. The result of the lateral force-deformation of LRB is compared. From the comparative analysis of the result of pier shear、deck drift and deck acceleration, it is indicated that if temperature effect is unconsidered, pier shear and deck acceleration will have higher error and there is less influence of deck drift.
  • Wang Ai-lun;Chen Jin-bo;
    . 2011, 30(9): 46-49.
    Abstract ( 1345 ) Download PDF ( 410 )   Knowledge map   Save
    The finite element model of two-stage bladed disks in gas turbine rotor was established. The modal characteristics of multistage and single bladed disk were compared. The effect of interstage contact coupling on frequency veering characteristic of bladed disk was focused on. The results show that new modes of stage-coupled vibration appear due to interstage contact coupling. The frequency veering characteristic is modified that modes near frequency veering region are less dense, such modification leads to a low sensitivity to mistuning for bladed disk. The modal characteristic of mistuned two-stage bladed disks was analyzed. It is verified that mode localization degree of mistuned bladed disk is reduced greatly.
  • Wang She-liang;Tian Xiu-ting;Dai Jian-bo;Zhao Xiang
    . 2011, 30(9): 50-54.
    Abstract ( 970 ) Download PDF ( 422 )   Knowledge map   Save
    According to the magnetic control characteristics of giant magnetostrictive material (GMM), a smart actuator was designed, which can permit an active vibration control of the structure. In this study, the working principle and design method of this actuator were analyzed, and its output performance was tested. Based on the dynamic modeling of the actuators, the actuating control equation was derived for the whole cylindrical reticulated shells. Meanwhile, on the basis of actuating efficiency, the position optimizing criterion independent of control method was presented. In overall considering the coefficient of control effect, hardware cost, system complexity and other factors, the numbers of actuators were determined preliminarily,and then the placements of actuators were optimized using genetic algorithms. Finally, by the use of LQR active control algorithm, the active vibration control was performed on a cylindrical reticulated shell. The analytical results show that the optimal placements of the actuator can efficiently reduce the dynamic response of the structure, and can desirably realize an active vibration control. Additionally, the simulated results of the active control demonstrate the superiority and reliability of application of the genetic algorithm to such problems.
  • WANG Guo-bo;XIE Wei-ping;YU Yan-li
    . 2011, 30(9): 55-58.
    Abstract ( 1392 ) Download PDF ( 927 )   Knowledge map   Save
    Steel structure, especially welded steel structure, is very sensitive to dynamic load. The new structure form, which called the unification of bridge and building, is adopted in Wuhan railway station in the passenger special line from Wuhan to Guangzhou. Much attention must be paid to the fatigue life of large-span steel structure because of the long-term dynamic load. Refined finite element calculation model of ten tubes welded cast steel joint, which includes welding seam, is built and its fatigue life is analyzed based on hot spot stress method and Miner linear cumulative damage theory. The results show that the dynamic stress caused by train load has little influence on the fatigue life of cast steel joint, and the large-steel structure can meet the demand of service life of 100 years. The analysis method in the paper can provide reference to fatigue life evaluation of similar structures in future in China.
  • GUO Ying-qing;XU Zhao-dong;FEI Shu-min;CHEN Yong
    . 2011, 30(9): 59-63.
    Abstract ( 1291 ) Download PDF ( 789 )   Knowledge map   Save
    In the course of the vibration mitigation control of structures with magnetorheological (MR) dampers, the displacement and the acceleration responses are two important control targets. That is, the vibration mitigation control of structures with MR dampers is a multi-objective optimization control. Therefore, in this paper the particle swarm optimization (PSO) algorithm is used to control the displacement and the acceleration responses simultaneously. Numerical analysis for a five-floor structure with one MR damper installed on each floor is carried out under the PSO algorithm, the ON control algorithm and the OFF control algorithm respectively. It can be concluded that the PSO algorithm can reduce the displacement responses of the structure obviously, at the same time, it can reduce the acceleration responses of the structure to a certain extent.
  • Ren Yong-sheng;Du Xiang-hong;Yang Shu-lian
    . 2011, 30(9): 64-69.
    Abstract ( 1076 ) Download PDF ( 614 )   Knowledge map   Save
    Wind turbine blades are flexible structures that can often be modeled as anisotropic composite thin-walled beams, exhibiting bending-twist coupling. The equations of motion for a single wind turbine blade are derived using Hamilton’s principle and a variational-asymptotical method(VAM). The structural model includes anisotropy, warping function, centrifugal loads, precone and pretwist angle. The aerodynamic loads are determined based on blade element momentum (BEM) theory and quasi-steady airfoil aerodynamics. The Galerkin’s method is employed in order to solve the coupled differential equations. Aeroelastic stability is investigated through eigenvalue analysis. Numerical results are obtained for the blades with Circumferentially Antisymmetric Stiffness (CAS) configuration, the effects of the fiber orientation, pretwist angle and inflow on blade aeroelastic stability are investigated.
  • GAO Xuan-neng;LIU Ying;WANG Shu-peng
    . 2011, 30(9): 70-75.
    Abstract ( 1588 ) Download PDF ( 1566 )   Knowledge map   Save
    By employing algorithm ANSYS/LS-DYNA and based on the proof of correctness and reliability of the model and parameters selection, an appropriate model for calculating the shock wave pressure distribution of the large-space cylindrical reticulated shell under explosive loading was established. Using the Proper Orthogonal Decomposition (POD) method, the problems of spatiotemporal asynchrony of shock waveforms and pressure distributions on the large-space structure surface were solved and the calculation for dynamic response of large-space structure was greatly reduced and simplified. The numerical simulation and analysis of shock wave pressure field of the large-space cylindrical reticulated shell under explosion was carried out. And the influence of span and ratio of rise to span on the pressure distribution of the structure was researched. The results showed that the calculation model is suitable for the dynamic response analysis of the large-space cylindrical reticulated shell under explosion.
  • LI Qing-lu;LI Shi-rong
    . 2011, 30(9): 76-78.
    Abstract ( 1019 ) Download PDF ( 469 )   Knowledge map   Save
    Based on geometrically non-linear theory for axially extensible beams ,an exact mathematical model of post-buckling transverse free vibration of FGM beams made of metal and ceramic subjected to axial force were derived. By using shooting method , pre-buckling and post-buckling free vibrations of one simply supported another fixed Euler FGM beam were solved and characteristics curves of the lower non-dimensional frequencies versus load parameter of FGM beams under the different graded index were plotted. The numerical results show that all the frequencies of unbuckled beams decrease continuously with the increment of the load. However, when the beams are in post-buckled state, the effect of axial force on all ordets of natural frequencies are different.
  • Xu wan-hai;Wu ying-xiang;Zhong xing-fu;He yang;Liu pei-lin;Feng xian-hong
    . 2011, 30(9): 79-83.
    Abstract ( 926 ) Download PDF ( 414 )   Knowledge map   Save
    this paper was analyzing the parametric excitation instability regions of slender flexible cylindrical structures in the offshore engineering, using L-P, modified L-P and harmonic balance method, comparing the three different methods, and drawing the first three instability chart, helping build up design guidance for TLP tethers and risers.
  • Zhang Kang;Cheng Jun-sheng;Yang Yu
    . 2011, 30(9): 84-88.
    Abstract ( 1553 ) Download PDF ( 548 )   Knowledge map   Save
    To determine the product function (PF) criterion in local mean decomposition(LMD) method, the orthogonality criterion (OC) is introduced into LMD method according to the orthogonality of the PFs. The iteration’s end point of the PFs can be defined by comparing the value of OC in each iteration with the fixed threshold. By analyzing the simulated and actual signals, it is validated that the PFs defined by the orthogonality criterion satisfy the orthogonality condition and reflect the internal physics information of the analyzed signals. Thus, the signal’s correct decomposition is achieved.
  • Wu Xu-dong;Zuo Shu-guang;Lei lei;Yang Xian-wu;Li Yong
    . 2011, 30(9): 89-93.
    Abstract ( 1239 ) Download PDF ( 337 )   Knowledge map   Save
    Based on the tread-road single degree-of-freedom vibration model, the research studies the physical characteristics of suspension, tire and tread simultaneously, and establishes suspension-tire-tread four degree-of-freedom ADAMS vibration model by means of multibody dynamics theory method. Simulation results show that the energy of vibration will be transferred to suspension and tire when the tread vibrating violently, and the toe-in angle, the camber angle and the vertical beating of tire will also start vibrating with the same frequency, but in various degrees. That verify the reasonableness of simplification of theoretical model, and the correctness of the theoretical model is proven. At last, the numerical simulation of bifurcation is applied to the four degree-of-freedom system, and the vehicle speed range which can generate self-excited vibration of tire tread is found. The dynamic differential equations in the theoretical model can be used to further not only theoretical but also experiment research.
  • Liu Shu-lian;Zheng Shui-ying
    . 2011, 30(9): 94-97.
    Abstract ( 1270 ) Download PDF ( 309 )   Knowledge map   Save
    To simply and reliably improve the rotor-bearing system stability and eliminate the oil whip online, one method of using an improved passive electromagnetic damper to increase the damp is proposed. Its configuration is similar to that of electromagnetic bearing, but no sensors and no closed loop control are needed. When rotor rotates, the electromagnetic damp is formed because of the eddy currents inside the surface layer of rotor to decrease the vibration. Increasing direct current can enhance damp, but the stiffness of system will be decreased and bring resistance torque and heat of damper. In order to improve the characteristics of damper and avoid decreasing the stiffness, one new method of increasing damp by adding extra circuit is present, based on not changing the configution and static current. By choosing the appropriate parameters of extra circuit devices, the damping coefficient of the improved damper is more evident than that of the original damper. When the improved damper is applied to the rotor bearing system, the experiment shows that the effect of decreasing the vibration and eliminating the oil whip is better with the improved damper.
  • Zhang Qing-xia;; Duan Zhong-dong; &#;ukasz Jankowski
    . 2011, 30(9): 98-102.
    Abstract ( 1208 ) Download PDF ( 442 )   Knowledge map   Save
    A dynamic load identification method was introduced and complemented, in which the force was approximated using the shape functions from the finite element theory. The computational work is deduced a lot by calculating the weights of shape functions instead of indentifying the discrete load time history. It improves the performance of the deconvolution method in a long sampling time or high sampling frequency. Moreover, it improves the ill-conditioning of the inverse problem, and increases the robustness to noise. A numerical continuous beam compares and verifies that the load can be identified precisely by this method with 5% Gaussian noise pollution. In a cantilever beam experiment, via the measured structural responses, this method enables the online load identification which is performed repeatedly in a moving time window.
  • TAO Wei-jun;HUAN Shi;ZHU Shi-jian;LI Xiao-yong
    . 2011, 30(9): 103-106.
    Abstract ( 989 ) Download PDF ( 366 )   Knowledge map   Save
    Continuous linear vibration isolation system has been designed, it can produce highly nonlinear, and the linear part and nonlinear part are corresponding with the model geometry. Both are completely separate and easy to adjust in the experiment. So this greatly increases the device prospects in engineering application. And for specific parameters of the vibration isolation system under harmonic driving forces, the use of numerical methods analysis the dynamics of this system. The results show that the system can generate chaotic motion, and has a good ability in line spectrum reduction.
  • Wang Y G;Liu M
    . 2011, 30(9): 107-110.
    Abstract ( 909 ) Download PDF ( 422 )   Knowledge map   Save
    The Virtual Turning Damper (VTD) stemming from Turning Mass Damper (TMD) is introduced. The mathematical model of VTD is deduced from TMD firstly. The parameters of VTD are designed by the placement of poles and zeros and explained with an example. The influence of non-pure modal measurement on VTDk and modal control spillover are analyzed. The method about optimal placement of a VTDk is presented. The multi-VTD is studied. VTD can be designed by use of the commercial control software. The realization of VTD is more softness than MTD. It is easy to control the wide-band vibration with multi-VTD.
  • WANG Tian-yu;WANG Feng-xiang;Cheng Fang
    . 2011, 30(9): 111-115.
    Abstract ( 1622 ) Download PDF ( 564 )   Knowledge map   Save
    The high speed machine, due to its small size, high power density and high efficiency, meeting the economy development needs of low-carbon and energy saving, is one of the great concerns in electrical engineering. Vibration is the bottleneck of stable operation for high-speed machine. Therefore, it is necessary to study vibration for the reliable operation of high-speed machine. Rotor vibration sources include mainly the centrifugal force generated by eccentricity and unbalanced magnetic pull. The combined FEA and Newmark method is used to calculate the non-linear unbalance response due to the unbalanced force. The simulation results of different vibration frequencies are verified by tests. Studies have shown that the vibration frequencies of machine are mainly the fundamental frequency composition caused by eccentricity and 10 frequency-doubled due to unbalanced magnetic pull caused by dynamic eccentricity. Vibration amplitude of 2 frequency-doubled is more significant. The corresponding measures to reduce vibration are proposed according to vibration analysis.
  • Shan Ying-chun;Liu Yao-guang; Liu Xian-dong; He Tian
    . 2011, 30(9): 116-119.
    Abstract ( 910 ) Download PDF ( 285 )   Knowledge map   Save
    A method for near-field coherent sound source identification is proposed by combining interpolated array technique with two-dimensional spatial smoothing. First, actual received signals are converted to far-field signals by interpolated array technique. Second, spatially smoothed covariance matrix is calculated through two-dimensional spatial smoothing. Then, the signal power in a giver vector can be obtained, and the location of sound sources can be obtained. Simulation results have show that this method is much more accurate than conventional beamforming on identification of sound source.
  • YANG Qiong-liang;LIU Jing-hua;CHEN Jian;TANG Guo-an
    . 2011, 30(9): 120-123.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The mathematical model of the constrained damping pipe with the function of supporting and vibration reduction is established. The analytical expressions of displacement, dynamic stiffness and loss factor of the damping pipe about the geometric and physical parameters are obtained. The result shows that the length of the damping layer has significant effect on loss factor and there is an optimal length which makes loss factor a max value when the other parameters are given. It provides a quick and convenient optimization method to design a damping pipe.
  • Tang Shi-zhen;Huang Wei-ping;LIU Jian-jun;DENG Yue
    . 2011, 30(9): 124-128.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The variation of response amplitude and fatigue damage of riser with two-degrees-of- freedom is proposed, considering four kinds of different frequency ratios (drag force frequency/lift force frequency). The results show that under a low frequency ratio and low reduced velocity, the in-line vibration will restrain the cross-flow vibration. And also with the 6.3< reduced velocity <8.0, the cross-flow amplitude will increase clearly considering the in-line vibration. With the increase of frequency ratio, the effect will be weakened. The cross-flow vibration influences the in-line vibration severely in all the cases. The in-line amplitude will increase evidently. The fatigue damage with two degrees is great lager than that with one degree with low frequency ratio. The fatigue in in-line direction is inclined to be influenced by the cross-flow vibration with a high frequency ratio.
  • Lei Ya-guo;He Zheng-jia
    . 2011, 30(9): 129-135.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to perform condition monitoring and fault diagnosis for large-scale and complex and key mechanical equipment effectively, hybrid intelligent fault diagnosis and prognosis technique by synthesizing and utilizing multiple artificial intelligent techniques and advanced signal processing methods, has been given high regard and studied widely by inland and overseas researchers. Based on investigating a good deal of relevant literature, the extensive concept of the hybrid intelligent fault diagnosis and prognosis technique is introduced, the inland and overseas state-of-the art is reviewed in this paper, and the problems existing in present studies are also analyzed and pointed out. Finally, aiming at the state-of-the art and existing problems, the development trends of the hybrid intelligent fault diagnosis and prognosis technique are discussed in the end of the paper.
  • Jiang Shuang-yan;Chen Huai-hai;He Xudong;Cui Xu-li
    . 2011, 30(9): 136-144.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    H∞ loop-shaping control method is proposed in the paper for the MEMA(Multi Exciter/Multi Axis) random vibration test. In practice, the response spectrums of the control points are always difficult to meet the reference ones at the frequencies where the frequency response function matrices are ill-conditioned. An H∞ pre- compensator is decomposed and designd for the controller. The conditions of the frequecy response fucntion matrices are improved and the controlled plant is decoupled by an algorithm. The Fourier spectrum of the drive signal is shaped by the compensator in the control loop to replace the original one. The experiment shows that with the present method in this paper, the drive singal is mended, the response spectrums of the control points are improved because the poor conditions of the frequency response function at specified frequencies are rejected.
  • LIU Hao-ran;ZHU Zhan-Long;SHI Pei-Ming;HOU Dong-Xiao
    . 2011, 30(9): 140-144.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Considering the nonlinear stiffness of a torsional vibration system with three degree of freedom, the nonlinear equation of a torsional vibration which contains coupled terms is established. With time-delays control, the method of multiple scales is employed to obtain the analytical solutions of time-delays dynamic system when primary resonance and 1:1 internal resonance occur simultaneously. The necessary and sufficient condition of the stability of system is deduced by using the Routh-Hurwitz criterion. Moreover, the stability of the coupled system is well-controlled by choosing appropriate time-delays parameters, and the numerical results are presented that confirm the analytical predictions.
  • Zhou Hong-tao;Yang Shao-pu;Zhu Hong-xia
    . 2011, 30(9): 145-149.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Regarding to the lateral semi-active suspension system of high-speed locomotive based on the Magnetorheological damper, parameter adaptive fuzzy control strategy on the basis of the quantization factor, scaling factor of the general fuzzy control were brought forward based on the analysis of the modified BOUC_WEN mechanical model. Then the lateral semi-active suspension system based on the strategy of parameter adaptive fuzzy control was established and analyzed in SIMULINK. The results showed that compared with the strategy of passive control and general fuzzy control, parameter adaptive fuzzy control strategy could reduce the lateral vibration acceleration obviously and made the vehicle stability and comfort of passengers improved.
  • Liu Y;Wang F S;Yue Z F
    . 2011, 30(9): 150-154.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A finite element model of hailstone impacting composite structural has been established according to considering the fluent character of the hailstone adequately. The material models, damage criterions of the hailstone and laminate composite plate have been given in this paper, the critical velocity of the hailstone and damage model to composite plate are investigated by explicit finite element method using LS-DYNA. The analysis and simulation results indicate that: the damage criterions of the hailstone and composite plate given in this paper could present the impacting procedure properly; the primary failure model of the composite plate(AS4/8552) is matrix cracking in the process of hailstone impacting, when the hailstone velocity reaches 125m/s, the fiber breakage will appear on the top face of the composite plate, but the compressive failure never occur in the whole process.
  • WU Xiao
    . 2011, 30(9): 155-156.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on nonlinear vibration theory, analyzed the Trilinear Pendulum’s natural vibration of nonlinear tortuosity with perturbation and fourier series method. And the formula of natural vibration frequency was derived using undetermined coefficient method. The precision of this formula was proved effective by calculating on practice examples. Such formula provides a theoretical basis for measuring trilinear pendulum’s moment of inertia.
  • SHI Gang; GAO Guang Yun
    . 2011, 30(9): 157-162.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This paper presents a study on the problem of the ground vibration isolation efficiency by open trench as passive barriers in homogeneous saturated ground. The investigation is accomplished with the aid of the semi-analytical boundary element method (BEM) in cooperation with the basic solution of the thin layered method (TLM). Consequently, a two-dimensional (2D) semi-analytical BEM model is put forward, where the TLM basic solution is employed, to use open trench as passive vibration isolation taking into account the dynamical interaction of soil-structure. Effect of the model parameters on effectiveness of vibration isolation by open trench is investigated and discussed in detail. The results show that open trenches are efficient to isolate the ground vibrations due to the incident Rayleigh wave. When the depth of the open trench is less than a Rayleigh wavelength, increasing the depth results in an increase in the screening effectiveness, and that the width has less effect on vibration isolation efficiency. Furthermore, the parameters of saturated soil, as well as the drainage boundary conditions of half-space, have less effect on the screening effectiveness.
  • YAN Qi;LI Jie;
    . 2011, 30(9): 163-168.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on rational analysis, an evolutionary -phase-spectrum model which can be used in fluctuating wind speed simulation is proposed. According to the characteristic speed of eddies with different frequencies in turbulence, the concept of phase-evolving speed is put forward. Afterwards, it is illustrated that real wind speed history could be regarded as the evolutionary results of eddies with initial phases of zero after a evolutionary time . The probability distribution of is presented through statistics of the identified value from measured fluctuating wind speed histories. Then, it is easy to get samples of evolutionary -phase-spectrum. Combined with Fourier amplitude spectrum, fluctuating wind speed could be obtained through inverse Fourier transform. The evolutionary -phase-spectrum model is a rational description of Fourier phase spectrum and is recommended to be used in wind load simulation in wind-resistance calculation and reliability analysis of structures.
  • Ye Xian-hui;Cai Feng-chun;Zang Feng-gang;Zhang Yi-xiong
    . 2011, 30(9): 169-173.
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    Based on the extended Lagrange equations for systems containing non-material volumes, the equations of motion for the cracked cantilevered pipe conveying fluid are set up by using the mode functions which satisfy the boundary conditions and geometrical discontinuity conditions obtained by adding polynomial functions to the modal functions of the uncracked beam. The numerical example is utilized to analyze the dynamical performance and flutter characteristic. The calculated results show the critical flow velocity of pipe conveying fluid is descended when the crack is emerged near the clamed end and it is reduced more with the increase the depth of crack. But when crack position is far from the clamed end for certain distance, the critical flow velocity is ascended with the appearance of crack. In addition, the flutter modes of system are changed when the crack is appeared.
  • Song Pan;Dong Xing-jian;Meng Guang
    . 2011, 30(9): 174-177.
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    The residual dynamic flexibility, a new definition of the inertia relief attachment mode is proposed. The free-interface component mode synthesis method based on the residual dynamic flexibility can compensate for high-order truncate modes and it’s easy for experimental measurements. The approximated representations of residual mass and residual stiffness are deduced by partly ignoring the dynamic effects of the truncated modes. This method is used to set up the dynamic model of the full structure by coupling experimental model of component A and finite element model of component B. The problem of spatial incompleteness is solved by estimating the rotation mode shapes using a numerical differentiation method. Finally, numerical examples have demonstrated the validity and efficiency of proposed method.
  • GU Cheng-zhong; WU Xin-yue; ZHANG Wen-qun
    . 2011, 30(9): 178-183.
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    A three-dimensional nonlinear dynamic model for gear transmission system is developed considering the time-varying meshing stiffness, tooth surface friction and backlash. Based on the contact point place, we deduced the expression of time-varying meshing stiffness and tooth surface friction coefficient about time, considering the dynamic distribution of load. It is difficult to solve the strongly non-linear variant differential equation, so a method is proposed which change the variant differential equation to ordinary differential equation using increase the dimension of differential equations. And the numerical solution of differential equations is obtained using 4 to 5 order adaptive variable steps Runge-Kutta method. The effects of teeth surface friction and web damping and stiffness on the nonlinear dynamic of gear is analysis systematically, and it provides a theoretical basis and directions of research for in-depth study of the gear transmission system.
  • Li Chun-xiang;Xu Shuang-zheng;Qin Ji-biao
    . 2011, 30(9): 184-190.
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    Employing a case of Ningxia TV Tower (NXTVT) as the background, the three-dimensional (3D) finite element model of NXTVT is established by resorting to SAP2000 software. The shape of NXTVT resembles a small bottom, large top, and slender-waist-middle vase. Likewise, its floors are arranged discontinuously, thus leading to the uneven distribution of the structural mass and stiffness. Hence, there is a need of a high demand of seismic performance in the design of this structure. At the outset, the dynamic characteristics of the structure are analyzed and investigated. Based on this, the multi-dimensional seismic responses of the structure under the operating base earthquake (OBE) with a return period of 50 years are analyzed by use of both the response spectrum method and FNA time history method. Then, the time history analysis of NXTVT with the nonlinear fluid viscous dampers (NFVDs) is carried out to evaluate the seismic response mitigation performance of NFVDs to this structure under the multi-dimensional earthquakes. Through extensive numerical analysis and comparisons, the conclusions obtained herein will be much useful for the design of the NVFDs for NXTVT or similar projects under earthquakes.
  • Xiong Zhong-ming;Wang Chao;Lin Tao
    . 2011, 30(9): 191-196.
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    Large-span steel structure has been widely used in large-scale public buildings such as stadiums in recent years. But the location of defects has not been solved well which will affect the safety in the using process. In the background of the large span steel structure of a college stadium, a simulating study on the location of the defect based on neural network was put forward, the modal parameter before and after the structural damage was obtained from ANSYS model analysis of the large span steel structure, and which is taken as input parameter of the neural network. In order to improve the convergent speed and the diagnostic accuracy of the network model for the structural defects, when locating the structural damage, on one hand, the structure subdivided into a large amount of sub-structure and narrow the damage scope; on the other hand, input high frequency into different experimental samples of the neural network to conduct experiments to detect the influence of the damage location and damage degree caused by it. The results showed that the technology of neural network for the defects location of large complex structure was feasible, and the identification accuracy was greatly enhanced by improving the method, it will provide a meaningful reference for network improvements and improving the accuracy, interference immunity and generalization ability of neural network
  • Yan Zhi-xin;;Ye Zhen-hui;;Liu Pei-lin;;Cao Xiao-hong;
    . 2011, 30(9): 197-201.
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    Both the height and the difficulty of chimney blasting demolition are increasing gradually. This paper establishes stress models of the supported segment of the remaining based on dynamic principle, and analyzes the regulation and the determining factor of the variation of cut neutral axis. The punching factor is used to consider with influence of sudden load. We adopt the node-split reinforced concrete model, and make the numerical simulation study of the reinforced concrete chimney collapse process by means of ANSYS/LS-DYNA. Through the analysis of the stress-time curve of reinforced concrete element, it is indicated that a node split model can reflect the difference of the mechanical properties between materials of steel and concrete.
  • Chen Zhi-min;Zhu Hai-chao;Kuang Gong-xian
    . 2011, 30(9): 202-206.
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    The conventional near-field acoustic holography technology can not mirror exactly modulation characteristics of cyclostationary sound field through the reconstructed results. So the demodulation ability of the cyclic autocorrelation function was used to extract the feature cyclic frequency, the cyclic spectrum density (CSD) was obtained through the cyclic Wiener-Khinchin relation, and the CSD was adopted as reconstructed physical quantity in planar near-field acoustic holography instead of the spectrum of pressure. The experiment research show that the feature frequence of cyclostationary sound field can be extracted exactly and its essential characteristics can be observed directly from the reconstructed results.
  • Feng Hao;Jin Shi-jiu;Zeng Zhou-mo;An Yang;Zhang xi-mo
    . 2011, 30(9): 207-210.
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    Aiming at the problem that direct cross-correlation method for time delay estimation in the pipeline abnormal vibration events passive positioning is easily affected by the noise, a new method based on third-order cumulant and adaptive filter delay estimation for locating the pipeline vibration is put forward. The abnormal vibration signals are processed using third-order self-and cross-cumulant estimation, so the related Gaussian noise and symmetrical distribution noise can be suppressed. The adaptive filter is adopted to estimate the time delay of third-order Self-Cumulation and Cross-Cumulation, which can suppress the non-Gaussian correlated noise even without the prior knowledge. The field test proved that, this method can accurately locate the pipeline abnormal vibration events, suppress the noise commendably, and improve the performance of time delay estimation. Compared with the direct cross-correlation time delay estimation method, the relative positioning error reduces from 2.7% to 0.6%, positioning consistency increases three times, and the average positioning accuracy is up to 14m.
  • ZHONG Wei-hui;HAO Ji-ping;LEI Lei
    . 2011, 30(9): 211-215.
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    The impact load acting on actual structure is often very complex, which has greatly influence on dynamic buckling of structure. The dynamic buckling of elastic compression bar under two-parameters impact load is studied, by simplifying the load with equivalent rectangular pulse. The impact buckling of ideal elastic compression bar and with initial imperfection are analyzed and calculated. Based on the examples of axial compression bars with both ends simple supported and fixed, the influence law of impact loading form on dynamic buckling of axial compression bar is initially revealed, and some valuable conclusions are drawn.
  • Ji Hong-wei;Wang Hui-wen
    . 2011, 30(9): 216-220.
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    It is very important to characterize the cushioning properties of cushioning material for optimizing pack design, and it is a very effective method to characterize the cushioning properties of materials by using dynamic cushioning coefficient. In this paper, we investigate experimentally the dynamic cushioning coefficient for expandable polyethylene material. Based on dynamic compression experiments, the stress-strain curve of the cushioning material was determined by using high-speed image measurement technology, resulting in the deformation energy per unit volume and dynamic cushioning coefficient of the material can be deduced. Thereby, the dynamic cushioning property of the cushioning material has been characterized directly by the dynamic cushioning coefficient, and this research result provides an important theoretical basis for the cushioning packaging design.
  • Xie Zui-wei;He Shao-hua;Wu Xin-yue
    . 2011, 30(9): 221-226.
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    To investigate dynamic response behaviors of rotating machinery subjected to seismic or non-contact underwater explosion shock, we always start from the study of rotor-bearing systems representing those machines under base motion. Due to the gyroscopic effect and the interaction between rotor and bearing, system matrixes are nonsymmetric, so, conventional mode-superposition method cannot be applied to solve the system motion equations. Numerical direct time-integration methods are now used commonly obtaining a transient response of rotor-bearing systems, but compared to linear superposition method, they require more computing resources. For the above reason, a superposition method in complex domain was proposed. With no need to decouple equations, linear superposition computation of responses can still be performed just like that in the conventional mode-superposition method. Firstly, shock excitation and response were both expanded into a complex form of Fourier series, including forward and backward rotating items. Characteristic equations were obtained by the fact that coefficient matrixs of same rotating frequency are equal. Characteristic equations were then rewritten into simple pencil of matrix’ latent value equations. Inverse matrix of which elements are called “ Frequency Response Coefficient” of the pencil of matrix was calculated out by using its right and left latent vectors which were normalized. Responses in each frequency were obtained by the product of the inverse matrix and shock excitation, and then synthesized into overall responses of the system. An engineering example is to compare the proposed method and the results of numerical integration methods, comparative analysis shows that the proposed method to meet the engineering requirements, and can be used as a universal method of shock response and transient response computation of rotor systems.
  • SUN Kai;MENG Guang;YE Lin;LI Fu-cai
    . 2011, 30(9): 227-231.
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    This paper discusses the possibility for damage size identification in relatively thick structures with PZT transducers using guided wave approach. Based on optimized excitation wave parameters and PZT transducers layout, the finite element simulation was carried out with commercial FE analysis software Abaqus. The FE modal was then validated by experiment, and good agreement is found between the experimental measurements and numerical simulation. Simulation results show that the arrival time and amplitude of damage-reflected wave packet as well as transmitted wave packet change regularly with the increasing of damage depth or thickness, based on which the features can be extracted for the purpose of damage size judging.
  • Zhao Yue-jing;Qin Zhi-ying;Peng Wei
    . 2011, 30(9): 232-236.
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    The model of vibrating cone crusher is simplified as the model of locomotory cone motion in horizontal plane. The materials layers between the locomotory cone and immovable cone will affect the motion of locomotory cone. The dynamics equations are built with the materials layers as piecewise line contract force model. Then the dynamics equations are analyzed. The result indicates the materials layers is the main source of the nonlinear system. The materials layers make the system having complex motion instead of harmonic motion with single frequency. These affect fragmentation of the vibrating cone crusher.
  • Cheng Tao; Xiang Yu; Li Jian;Yu Ling
    . 2011, 30(9): 237-242.
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    The behaviours of foamed aluminum-filled prisms were studied under quasi-static loading conditions by LS-DYNA. Column shell ratio (R) is the base to compare foamed aluminum-filled prisms with different cross sections. Energy absorption quantitative analysis and comparison of foamed aluminum-filled prisms was carried out by specific energy absorption, specific force and energy absorption rate. Specific energy absorption of foamed aluminum-filled square prism was highest. Energy absorption rate of foamed aluminum-filled octagonal prism was highest (78%). The share of square pipe in total energy absorption of foamed aluminum-filled square prism is least (57%). Different shape and structure have great influence on foamed aluminum-filled prisms. Meanwhile, the deformation pattern and inherent mechanism of foamed aluminum-filled prisms are analysed.
  • Jia Hu;Shen Zhao-wu
    . 2011, 30(9): 243-247.
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    With a view to obtaining the characteristics of the underwater detonation acoustic signals of fiber-based detonating cord, the analysis of its sound pressure level is carried out in this paper based on the results of underwater explosion pressure tests. Then the paper discusses the energy distribution status of underwater detonation signals at different frequency ranges by analyzing the time frequency characteristics of those underwater explosion signals by adopting the wavelet transform method. The research results show that the underwater explosion of fiber-based detonating cord boasts a high level of acoustic power and that the energy of the underwater detonation signals of fiber-based detonation cord is mainly concentrated in the area of less than 40KHz, of which the highest level of energy is below the frequency of 5KHz. Therefore, if used as a source of sound interference, the fiber-based detonating cord is fully capable of covering all the working frequencies of various types of underwater acoustic equipment, as a result of which it may serve an important purpose in underwater warfare. By using wavelet analysis, reasonable researches can be made regarding the characteristics of the underwater acoustic signals of fire-based detonating cord so as to precisely and accurately analyze the characteristics of those signals.
  • Chen Di-yi;Shen Tao;Ma Xiao-yi
    . 2011, 30(9): 248-252.
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    In order to eliminate lateral oscillations of spinning disks and dispel their adverse effect on the system performance or the working conditions of the system, the chaotic complex dynamic characteristics of the four-dimensional nonlinear equations in lateral oscillations of spinning disks were analyzed, including the space trajectory, the Lyapunov exponent and the Poincare map. And the chaotic orbits of the spinning disks were stabilized to fixed points and periodic orbits by means of proportional integral sliding mode control (PISMC) method, and MATLAB Simulations were presented to confirm the validity of the controller. Furthermore, it is discussed that the value of gain coefficient impact on system performance including buffeting, the time and peak in the transition process of controlled system and controller and so on. The results provide a theoretical basis for the application of PISMC and the chaos control of mechanical systems.
  • Ge Gen;Wang Hong-li;Xu jia
    . 2011, 30(9): 253-258.
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    One stochastic two dimensional dynamical model of a simple supported thin rectangular plate subject to in-plate stochastic parametrical excitation is proposed based on elastic theory and Galerkin’s approach. At first the model is simplified applying the stochastic average theory of quasi-integral Hamilton system. Secondly, the methods of Lyapunov exponent and boundary classification associated with diffusion process respectively is utilized to analyze the local and global stochastic stability of the trivial solution of system. Finally, it is explored that the stochastic Hopf bifurcation of the model according to the qualitative changes in stationary probability density of system response. It is concluded that the stochastic Hopf bifurcation occurs at two critical parametric values. And the results of numerical simulation support the theoretical analysis.
  • WANG Bin-hua; LU Peng-min
    . 2011, 30(9): 259-259.
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    In order to analyze the vibration problem of arm system on concrete pump truck from the perspective of fluid-solid interaction theory, its dynamic equation is established based on cantilever conveying pipe theory. Fluctuating velocity of concrete flow and vibration boundary conditions of arm system are experimentally measured. The vibration responses of arm system with two speeds of fluctuating and constant velocity are achieved by the method of simulation calculation. Simulation results show that displacement responses are in agreement with each other. Therefore, the velocity fluctuation has little influence on stress history of arm system. When the swivel table of concrete pump truck is under stationary state, the vibration responses of arm system with two speeds are achieved by the method of simulation calculation. Simulation results show that car-body vibration as a result of cylinder impact action has great influence on arm system vibration. Therefore, it is proposed that the vibration of swivel table should be mainly considered.