15 November 2014, Volume 33 Issue 21
    

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  • Jungao Wang Shixiao Fu* Yuwang Xu Leijian Song
    . 2014, 33(21): 1-7.
    Abstract ( 392 ) Download PDF ( 679 )   Knowledge map   Save
    Under the top vessel motions, dynamic responses of the catenary risers would generate relatively oscillatory flow around themselves. Such oscillatory flow would easily trigger the ‘intermittent VIV’ at sag-bend part of the riser. This paper mainly focuses on the experimental investigations on the behaviors of a flexible cylinder in oscillatory flow with different combinations of both maximum reduced velocity and number. Fiber Brag Grating (FBG) strain sensors were used to measure the VIV response of the model cylinder. Then, modal analysis and wavelet analysis were adopted to deal with the experimental data, and VIV response featured of “time sharing” including “amplitude modulation” and “mode transition” was observed which is distinguished from that in steady flow. Finally, the effects on “time sharing” of VIV in oscillatory flow from both reduced velocity and number were discussed and summarized.
  • ZHANG Yi-fang;YAN Xiao-qiang LING Qi-hui
    . 2014, 33(21): 8-12.
    Abstract ( 300 ) Download PDF ( 183 )   Knowledge map   Save

    Large modern hot strip mill is a complex electromechanical system.Vibration of rolling mill is a serious problem which effect the stability of production. By using torque telemetry system to test the torsional vibration of mechanical drive system,it is found that two typical characteristics of the strong or weak vibration exist in the waveform and spectrum of torsional vibration,meanwhile, there are harmonics in motor current and rolling force during rolling mill production, and when harmonic frequency is close to the natural frequencies of main drive system, rolling mill present a heavier torsional vibration on mill main drive system. For the study of its mechanism ,using computer simulation , the correlation of main drive torsional vibration and harmonic excitation by motor current and rolling force is solved. Research shows that with the harmonics excitation change, torsional vibration presents polymorphic variation strong or weakly on main drive system,which lay a theoretical foundation for vibration suppression.

  • Wang Wei;Wang Mingxing
    . 2014, 33(21): 13-20.
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    Application and research status of cast steel is introduced in steel structure, especially in steel frames. A cast modular joint and its design approaches are proposed, appropriate for rectangle or square tubular column to H-beam connections. The cast modular joint is conceived base on the concept of utilizing stable plastic dissipation of panel zone. Nonlinear finite element analysis is conducted to simulate monotonic loading and cyclic loading of the cast modular joint and traditional welded connections. Rupture Index is introduced to evaluate the propensity for ductile fracture initiation of different joints under large plastic deformation. Energy dissipation features are analyzed and demonstrated from multiple aspects, including stiffness, load carrying capacity, ductility, energy dissipation capacity, energy dissipation mechanism and plastic deformation modes. Research shows that the proposed cast modular joint exhibits better seismic performance than traditional welded connections, with sufficient developed dissipation capacity of seismic structure system on the premise of no ductility loss.


  • Yang Qing-chao He Qi-wei Sun Fang-xu
    . 2014, 33(21): 21-25.
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    Line spectra are the most visible signs of marine vessel radiate noise spectra, which can be detected, tracked and identified by passive sonar. Since the feature of line spectra could not be changed by traditional isolation system, and hence it is harmful to the acoustic stealth of marine vessels. According to the principle of line spectra chaotification method and the characteristics of the vibration isolation system, a new method of generalized chaos synchronization based on parameter perturbing is introduced. The numerical simulation results show that this method can make the system change into chaotic state with tiny energy, furthermore, the intensity is weakened and the line spectra structure is changed.
  • ZHU Shi-yao LEI Yong-jun XIE Yan LI Jia-wen
    . 2014, 33(21): 26-30.
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    With the aim to investigate and mitigate the disturbance induced by sun-track drive of solar array, the main factor inducing this disturbance was analyzed based on the mechanotronics model of solar array with drive assembly, and, starting with steady-state moment equilibrium equation, disturbance-mitigation drive methods for close-loop compensation and open-loop compensation by updating input signal to compensate speed fluctuation of the drive assembly were presented. The results indicate that harmonic electromagnetic torque can be approximate to the proportional control for rotation angle, and cogging effect is an important factor which causes this disturbance in drive process. Both disturbance-mitigation drive strategies are clearly capable of improving the speed stability and the disturbing torque stability without degrading the pointing accuracy of solar array, but the disturbance-mitigation effects are gradually muted as the error of cogging torque amplitude increases. Taking various factors combined into consideration, the disturbance-mitigation drive method for open-loop drive control is preferable, which could achieve the speed stability and the disturbing torque stability under 1% and 1.15%, respectively, while the error of cogging torque amplitude is below upper limit of 11%.
  • DU Xiao-qing;Fei Chen-jie;Kuan Zhong-hua;Zhao Yan
    . 2014, 33(21): 31-37.
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    Aerodynamic characteristics of an inclined circular cylinder in a span-wise shear flow were investigated using Large Eddy Simulation (LES). The effects of the shear flow on the pressure distributions, Strouhal number, time history and power spectral density (PSD) of aerodynamic forces, and span-wise correlation of wind forces of the inclined cylinder were discussed. Furthermore, the possible mechanism of the influence of the shear flow on the cylinder was proposed. Under the condition of a uniform incoming flow, present computations confirmed the existence of the axial flow behind the inclined cylinder as well as a decreased Karman vortex shedding caused by the axial flow. However, when the incoming flow involved span-wise linear non-uniformity, it was found that the intensity of the axial flow decreased and even suppressed if the intensity of the shear flow was high enough. Furthermore, the shear flow caused the recovery of the intense Karman vortex behind the inclined cylinder and had substantial effects on the aerodynamic characteristics of the cylinder.
  • SHEN Guo-hui;XIANG Guo-tong;XING Yue-long;GUO Yong;SUN Bing-nan
    . 2014, 33(21): 38-43.
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    In order to identify the damping characteristics of transmission towers, Empirical Mode Decomposition (EMD) and Ensemble Empirical Mode Decomposition (EEMD) were employed to obtain Intrinsic Mode Functions (IMFs) of time histories of accelerations obtained from aero-elastic wind tunnel tests of transmission tower. The frequency and damping of the tower under various wind velocities and wind azimuths were identified using EEMD, improved Random Decrement Technique (RDT) and Hilbert transformer. The distribution characteristics of damping along with wind velocities in the along-line direction and in the cross-line direction were also investigated. Results show that the vibrating modes of IMFs obtained from EEMD are much clearer than those obtained from EMD. Furthermore, the mode mixing problem is still existed to some extend in the IMFs obtained from EMD. Totally speaking, the natural vibrating frequency of the tower in the along-line direction decreases with the increase of the wind velocity, whereas the natural vibrating frequency in the cross-line direction increases with the increase of the velocity. However, the trend of damping in the cross-line direction with respect to wind velocity is not obvious.

  • GUO Yuan-jing WEI Yan-ding ZHOU Xiao-jun TANG Fang
    . 2014, 33(21): 44-50.
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    Extracting the impact feature from rotating machinery fault vibration signal, is significant to some faults dignosis. Based on the fact that S tansform is suitable for processing the signal with impact feature, an effective impact feature extracting method with the use of threshold denoising for S transform spectrum is proposed. Firstly, the time-frequency spectrum of a time-domain signal is obtained by S transform. As the spectrum coefficients are complex numbers, the spectrum threshold denoising method is carried out according to the modulus magnitude of coefficients. During denoising both the hard and the soft threshold functions are used, respectively. Most importantly, the optimal threshold estimation is available between zero to the maximum modulus of the coefficients by step iterative algorithm, evaluated with the introduced modified risk function. Finally, inverse S transform is used on the denoised time-frequency spectrum to reconstruct the time-domain impact feature. The processing results of simulated signal and rolling bearing fault vibration signal have shown that using the acquired optimal threshold, S transform spectrum threshold denoising method can successfully extract the impact feature from noise mixed signal, so as to realize related fault dignosis.

  • WANG Xiu-li;YUAN Shou-qi;ZHU Rong-sheng;FU Qiang;WANG Jiang-guo
    . 2014, 33(21): 51-59.
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    To study the effect of the number of blades and guide vanes to the reactor coolant pump radial force under variable flow transition conditions, applying computational fluid dynamics software CFX to the numerical simulation and test of the blades and guide vanes radial force variation, when changing the number of blades or guide vanes. Compared the numerical simulation results with the experimental results, the experimental data error within the control of the numerical simulation data. The results showed that: with the number of blades varying and the flow rate increasing, the radial force of the reactor coolant pump impeller increasing with the number of blades, and reaching the maximum in the number of 7, the periodicity of the impeller to withstand the radial force tends regularity, radial force balance tends to the optimum working condition. With the flow rate decreasing, the position of the impeller radial force offsets and rotates regularity in the spin cycle, and the variation gradient of the offset and rotation is different. The variation gradient of the impeller radial force offset and rotation is significantly greater than the variation gradient corresponding to the large flow increasing. Seen from the comprehensive comparison: when the number of blades is five and the guide vanes is 11,the radial force on the impeller is the minimum.

  • LAN Xiang-jun;FENG Zhi-hua;ZHU Xiao-dong
    . 2014, 33(21): 60-66.
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    Based on the classical laminated plate theory and von Kármán-type equations, the nonlinear governing equations of motion for the composite laminated plates under axial loading, in which, the boundary damping is taken into consideration, are derived. Galerkin approach is employed to transform the governing partial differential equations to ordinary differential equations. Using the method of multiple scales, the approximate solution of the plates by deterministic parametric resonance excitation are obtained and analyzed. Results show that the unstable interval bandwidth for the trivial solution is only related with linear damping, whereas the boundary nonlinear damping can weaken the resonance amplitude of the non-trivial solution and reduce the corresponding resonance range effectively. On the basis of nonlinear dynamic model, the resulted Foker-Planck-Kolmogorov equation is analyzed by using the narrow-band random excitation combined with finite difference method. The stochastic bifurcation and jump phenomenon of the response for the amplitude stationary joint probability density caused by the boundary nonlinear damping are sequentially investigated. Results show that a very small increment of the damping will induce a sharp jumping of the stationary motion from the non-trivial solution to the trivial one.

  • BAO Xing-xian
    . 2014, 33(21): 67-72.
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    responses, and then the Structured Low Rank Approximation (SLRA) method wasimplemented to achieve the filtered data. Finally the modal parameters are estimated by using complex exponentialmethod (Prony’s method) from the noise reduction signals. The effectiveness of the proposed method was verified byusing numerical and experimental studies.

  • FANG Xin-yu;XU Jin-yu;LIU Shi;Chen Teng-fei;Wang Peng
    . 2014, 33(21): 73-79.
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    Three used most commonly specimens:Normal Brazilian disc,flattened Brazilian disc and holed Brazilian disc were simulated by the finite element analysis software LS-DYNA, based on which we adopted flattened Brazilian disc to carry on dynamic splitting tests with granite specimens. By comparing the simulation and test results, we gain the relation of strain rates and tensile strengths of rocks and discuss the optimal specimen size of rock dynamic splitting tests. The results show: Fattened Brazilian disc fits the condition of broking from center well so that the test results will be more credible; For the rock mode used in the paper, we suggest the central angle of flattened Brazil disk to be 20°~24°; If holed Brazilian disc is used in the dynamic splitting tests, the suggested aperture ratio is about 0.4~0.5; Otherwise, the dynamic splitting strengths of rocks are increasing with the increase of strain rate, of which the increase rate decreases while this growing trend is affected by the specimen size observably.


  • Wang Yuansheng;Ren Xingmin;Deng Wangqun;Yang Yongfeng
    . 2014, 33(21): 80-84.
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    Combining the features of Frequency Slice Wavelet Transform (FSWT) and denoising source separation (DSS), we propose an underdetermined DSS method based on FSWT. This method is used to deal with the blind source separation (BSS) problem of rotating machinery in the case of the number of observed mixtures being less than that of contributing sources. New mixed signals can be reconstructed through the FSWT method, which is effectively way to solve the problem of the dimension insufficient in underdetermined blind source separation. As the same time, the method can solve the problem of time-frequency analysis in FSWT. Applying FSWT-DSS method to the rotor fault detection, we have diagnosed the sudden unbalance phenomenon through the measured fault signals of the rotor. The simulation and experimental results, and their analysis show preliminarily that the FSWT-DSS method is indeed efficient in analyzing the fault diagnosis and it has an important engineering significance for fault detection of rotating machines.


  • Liu Tao;CHEN Jin;Dong Guang-ming
    . 2014, 33(21): 85-89.
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    The fusion of multi-channels bearing monitoring information can obtain more accurate result in bearing fault diagnosis. Therefore, a rolling element bearing fault diagnosis scheme based on KPCA and coupled hidden Markov model (CHMM) is presented. At first, the features are extracted from bearing vibration signal from multi-channels respectively. Then, the KPCA is utilized to reduce the feature dimension. At last, the new KPCA feature is input into CHMM to train and diagnose the bearing fault. The data acquired from bearing at normal condition, inner race fault, outer race fault and rolling body fault are analyzed. And the results demonstrate the effectiveness and validity of the proposed method.
  • LI Xiao-peng;ZHAO Guang-hui;LIANG Ya-min;WEN Bang-chun
    . 2014, 33(21): 90-95.
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    In order to realize continuous sinking pile, the model of five-way rotary valve is designed based on the cycle vibration excitation law, and then the experiment system of hydraulic vibratory piling machine is designed. The pore size and rotating frequency of rotary valve are changed to analyze their influence on the system dynamic characteristics and get the best parameters. Simulation results show that the system working characteristics is the best and the sinking efficiency is the highest when the value of pore size is 10mm and rotating frequency is 20Hz. Finally, experiment is conducted and the acceleration curves of hydraulic piston-rod are got by the B&K data acquisition and analysis system. The results demonstrate that the theoretical analysis of five-way rotary valve is correct and the experiment system of hydraulic vibratory piling machine is feasibility. The research provides evidence for selecting reasonable parameters and improving work efficiency in practical construction system.
  • SHEN Xing;NI Xiao-bo;YE Ai-jun
    . 2014, 33(21): 96-101.
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    Based on seismic performance demand of bridge in transverse direction and current research work on metallic damper, a new type of metallic damper which can be used in transverse direction of bridge is now proposed firstly. Then, mechanic performance is explained and an optimized design method for metallic damper is introduced. Finally, a quasi-static test is carried out on two samples of designed metallic dampers. The results depict that this new type of metallic damper possesses a good property of hysteretic energy dissipation. And hysteretic model can adopt equivalent bilinear model. Moreover, the metallic damper presents large displacement capacity (drift ratio is larger than 50%) and can adapt to the complex contact condition during the ground motion fairly. In addition, different triangular steel plates exhibit perfect synchronism substantially.
  • WANG Xiao-qing;JIN Xian-long;
    . 2014, 33(21): 102-107.
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    For the bottleneck of time and memory in serial large-scale mesh generation, this study presents a method for large-scale parallel unstructured mesh generation. Firstly, the initial mesh is generated on the geometry and the initial mesh amount is controlled by the relative volume ratio and the optimal decomposition. Then, the initial mesh is decomposed by the graph partition method of graph theory. At last the parallel mesh generation is processed by split method. The proposed boundary judgement method based on the shared element solved the matching problem of the partition boundary nodes. Examples which illustrate the efficiency and applicability of this framework are presented and the examples show that this parallel mesh generation method can get high parallel efficiency and high quality tetrahedral mesh.
  • XU Sheng;LIU Jinyang
    . 2014, 33(21): 108-113.
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    In this paper, geometric nonlinear dynamic model of spatial slender beam with large deformation is established, and then a dynamic experiment is carried out to verify the correctness of the dynamic model. Firstly, the position and the attitude of the cross-section of the beam is described by 3 absolute position coordinates and 3 rotational angles, and then based on the assumption of the coincidence of the tangent of the neutral axis and the normal vector of the cross-section, the number of the generalized coordinates of each node is reduced. Variational dynamic equations of the spatial slender beam are derived based on virtual work principle. Comparison of the simulation time of the geometric nonlinear model and LS-DYNA software verifies the efficiency of the formulation. By leading into kinematics constraint equations, dynamic equations of the hub-beam multibody system are obtained. In case of large deformation, experiment of the rigid-flexible coupling system composed of an air-bearing test bed and a spatial beam is carried out to verify the correctness of the geometric nonlinear model of spatial beam.
  • LIU Zhi-dong;PANG Baojun;LIU Gang
    . 2014, 33(21): 114-118.
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    To response the impacting threats from orbital debris, an onboard monitoring system based on acoustic emission (AE) technique is presented to manned pressurized cabin for detecting the impact events by capture the hypervelocity AE signals propagate in the module wall. Usually the module wall is made by welding from integral stiffened shell structures, AE signals will cross stiffeners during the propagation leads to reflection, transmission and mode conversion. In this paper, numerical simulation is adopted to study the mode conversion characteristic of AE signal. The results indicated that: after passing through a stiffener, a portion of S0, A0, S2 mode converts to A0, S0, A1; A1 mode will partially convert to S0.
  • Zuo Chunyuan;Feng Xin;Zhou Jing
    . 2014, 33(21): 119-124.
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    A three-dimensional effective electromechanical impedance model for embedded PZT transducer is proposed by considering the coupled vibration effect between the piezoelectric ceramic (PZT) patch and the host structure. The coupled electromechanical admittance equation is derived by adopting the concept of effective mechanical impedance for the piezoelectric materials. The equation contains the contributions not only from PZT but also from the host structure. The theoretical electromechanical admittance of PZT in the free-free condition can be obtained by the equation, which is then utilized to extract the effective mechanical impedance of the structure.
  • Zuo Chunyuan;Feng Xin;Zhou Jing
    . 2014, 33(21): 125-130.
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    Based on the proposed three-dimensional model of the effective electromechanical impedance,the electromechanical admittance equation was derived in part Ⅰ of the companion papers. By using the theory of the effective electromechanical impedance, a novel methodology for monitoring structural inherent properties is proposed in this paper. The effective mechanical admittance of the host structure is extracted from the measurement of the coupled electromechanical admittance, and then structural mechanical admittance is used to monitor the structural inherent properties. To investigate the feasibility of the proposed approach,a lab-scale concrete beam was utilized to monitor the strength gain during the curing age with the variations in the measurements of the effective electromechanical impedance. The results demonstrate the efficiency and feasibility of the proposed method.
  • DUAN Chengyin;DENG Hongzhou
    . 2014, 33(21): 131-136.
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    A wind tunnel test is conducted to investigate the aerodynamic behaviour of transmission tower subjected to ambient excitation and the eigensystem realization algorithm is employed in the procedure of modal parameter identification. The concept of modal participation factor (MPF) is introduced, which represents the impulse response amplitude of each mode therefore is an indicator to discriminate system modes from noise. Then the modal energy contribution (MEC) of each mode is evaluated on the basis of MPF as well as corresponding eigenvalue. With the aid of MPF and MEC an auto identification scheme is applied to minimize the subjective influence in modal parameter identification. The experimental results are examined in a variety of wind speeds and wind attack angles and theoretical values derived from quasi-steady assumption are compared as well. The study reveals that the aerodynamic damping ratios of transmission tower are generally positive. The longitudinal aerodynamic damping tends to intensify as the wind speed increases, while in lateral direction no clear trend is observed. There is a nonlinear dependency of aerodynamic damping ratio on mean wind speed therefore the quasi-steady assumption is adjusted by introducing higher-order terms of wind speed.


  • SHEN-Yongkang.;FANG-Hanmei;ZHAO-Chunlong;LIU-Quanhong;WANG-Zhengzhong
    . 2014, 33(21): 137-141.
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    Flow-induced vibration and these influences factors to great trash-racks were investigated for hydraulic trash-racks of power intake at Pakistan Jinnah Hydropower Project. The numerical analysis model was presented, the fluid-structure interaction effect were investigated by element touch between fluid and structure, these influences factors on dynamic character of great trash-racks were studied according to racks, fluid-structure interaction, brace constraint and boundary condition, the judgment conditions on vortex-resonance occurrence of great trash-racks were improved. The results showed that gird bar and fluid-structure interaction were important to influence the dynamic characters of great trash-rack, structure reinforce were maybe reduced the dynamic safety for great trash-racks, yet brace constraint and boundary condition were small effect on the trash-racks vibration. The study provided a new basis for evaluating the flow-induced sympathetic vibration for this model trash-rack and some references for revising these related technical standards.
  • LIANG Bin;LI Rong;LIU Xiaowan;NODA Nao-Aki;XU Hongyu
    . 2014, 33(21): 142-147.
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    Based on the Flügge’s shell theory, coupled vibration characteristic of submerged ring-stiffened cylindrical shell under hydrostatic pressure is examined. By means of conversion switch on axial wave number, the coupled frequency of submerged FG cylindrical shell with various boundary conditions is obtained, using wave propagation method and Newton method. Results are compared to known solutions, where these solutions exist. The natural frequency of ring-stiffened cylindrical shell is studied. The effects of hydrostatic pressure, size and number of rib and boundary condition on the natural frequencies of submerged ring-stiffened cylindrical shell are illustrated by examples.
  • Guan Wenbo;Yang Huiwei;Hu Jianxing;Han Zhijun;Lu Guoyun
    . 2014, 33(21): 148-154.
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    In this paper, numerical simulations are carried out to study the dynamic response of the single-layer empty thin-wall spherical shell, single-layer liquid-filled thin-wall spherical shell and double -layer liquid-filled thin-wall spherical shell under impact loading. These are subjected to impact loading under a drop hammer then the modes and features of deformation are obtained in all the cases. Numerical simulation is carried out by ANSYS and LS-DYNA then deformation and energy absorption of three kinds of spherical shell are obtained. Numerical results show that inward dimpling region of single empty spherical shell is according with mirror reflection under impact loading; Due to effect of the internal liquid, for liquid-filled spherical shell the edge of its inward dimpling region appears larger transition zone and the inward dimpling of liquid-filled spherical shell is according with mirror reflection. If the impact energy is sufficient, the edge of inward dimpling will be ironed by the hammer. Although single-layer empty thin-wall spherical shell has better capability of energy absorption, the vertex displacement of it is larger, so that the effective protection space decreases in it. Double-layer liquid-filled thin-wall spherical shell can absorb most of impact energy with smaller vertex displacement, due to this it can provide satisfying protection in it. Energy absorption and deformation of single-layer thin-wall spherical shell is similar with double-layer liquid-filled thin spherical shell.
  • LIANG Zhe;PENG Su-ping;ZHENG Jing
    . 2014, 33(21): 155-160.
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    The method of Empirical Mode Decomposition(EMD) can filter and denoise the nonstationary microseismeic signal.But there exists serious end effect in its application which could affect the decomposition results. For improving the end effect, the wave extension of microseismic data endpoint based on LMS adaptive filter was proposed to the low frequency characteristics of microseismic signal.Trained by the internal data, LMS adaptive filter extend the wave from the endpoint to the left and right sides.The minimum and maximum that were in coincidence with internal signal trend were obtained in extension process and the extension length was determined adaptively by extension algorithm.The wave was decomposed by EMD method and mode components were acquired.For correcting the error brought by the interpolation algorithm, he residual signals were extended again.According to characteristics of the signal frequency, the mode components were reconstructed selectively in order to denoise.The adaptive LMS fiter extension method is verified by the simulation data and the microseismic monitoring data from coal mine, the results show that the method can obviously reduce the end effect of empirical mode decomposition, and have great effect especially to microseismic signals of low frequency.

  • Wang Wen Xu Li;Fu Weiping Kong Xiangjian Ma Yushan
    . 2014, 33(21): 161-165.
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    Aiming at the fluid-structure interaction of the control valve-pipeline-fluid system, a system simulation model is built with consideration of a valve positioner. The predictor-corrector method and the fluid-structure interaction finite element method are given respectively for solving response of the valve core-stem system and the valve-pipeline-fluid system. The vibration response of the system is analyzed by ANSYS software under the conditions of fixed and varying opening as well as flow-opening and flow-shutting. The results show that the pipeline and flow direction have great influence on the displacement of the valve core-stem system and the fluid unbalanced force on the valve core.
  • Ma Chicheng Zhang Xinong Liu Zhengyong Hu Dike
    . 2014, 33(21): 166-171.
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    In this paper, dynamic responses and time frequency feature analysis for a fluid-structure coupling system with variable mass in a tank are performed. A finite element model is established by using virtual mass method, including the influence of the change of the mass. The responses of the time varying mass tank are calculated by using Newmark direct integration method. The effect of time varying mass on the dynamic response of the tank system is mainly investigated. The time frequency features of the fluid-structure coupling system are obtained by using smoothed pseudo-Wigner-Ville transformation (SPWVD). Results show that the decrease of the mass induces the increase of the vibration frequencies of the system, and generates an additional negative damping. The additional damping is proportional to rate of change of the mass. Based on the dynamic responses and the time frequency analysis for different conditions, the frequency range can be determined by the range of the mass of the system. The additional negative damping causes the vibration decay slowly, and the additional damping can cause the system vibrate with increasing amplitudes while the mass changes rapidly. Smoothed pseudo-Wigner-Ville distribution is an efficient tool to decompose nonstationary signal.
  • LIU Xiang-jian;CHEN Ren-wen
    . 2014, 33(21): 172-176.
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    For improving rainbow shape piezoelectric transducer generating capacity under given dimension, aiming at external force and displacement incentive environment, relations between generating capacity and structural parameters and material properties of rainbow shape piezoelectric transducer were analyzed by simulation. The results show that on external force incentive environment, the output voltages of the rainbow transducer decrease as the width and initial curvature radius increase, the output voltages of the transducer increase as the length and elastic modulus ratio increase, the output voltages of the transducer have a maximum as the thickness ratio increases; on external displacement incentive environment, the output voltages of the transducer decrease as the thickness ratio and length and elastic modulus increase, the output voltages of the transducer increase as the initial curvature radius increases. Moreover, the output voltages of the inside piezoelectric film are larger than the outside piezoelectric film.

  • SHEN Ting-ao;TU Ya-qing;LI Ming and ZHANG Hai-tao
    . 2014, 33(21): 177-182.
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    In order to improve precision and dynamic response speed of the correlation method for phase difference measurement under the asynchronous sampling circumstance, an improved method for phase difference measurement based on correlation theory is proposed. Firstly, two reference signals which have 90 phase shifted are introduced by using two original signals with the same frequency, then, via digital filter with zero phase, correlation function of the original signals and reference signals are directly computed, some properties about correlation and sine function are adopted to obtain the computational formula for phase difference. Theory analyses and experiment results show that it is not necessary for the proposed algorithm to know the signal frequency in advance, and the measuring accuracy for this method is not affected by whether synchronous sampling or not, it can also measure the dynamic phase difference. Compared with the traditional methods, it is superior to accuracy, robustness and universality.

  • ZHU Jian-qu;JIN Wei-dong;ZHENG Gao;ZHU Bin;
    . 2014, 33(21): 183-188.
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    To solve the problem that it is difficult to identify the fault of high-speed train running gear caused by multiple detection points and large amounts of data, a running gear fault recognition method with multi-feature and multi-source information fusion is proposed based on the fuzzy evidence theory. Firstly, the information fusion degrees of sensors are obtained by calculating the difference of membership degrees which can reflect a certain feature of different sensors belonging to different fault modes. The fusion degrees are used to determine the weights of different sensors during fusion, thus the membership degrees between different sensors with similar characteristics can be obtained after information fusion. Then, the basic probability assignment functions are converted from the fused membership degrees. Finally, the information of different characteristics is fused on the basis of evidence theory. Experimental results show that four cases, including the normal, loss air of air spring, without anti-yaw shock absorber and without transverse shock absorber, can be identified effectively, and the satisfactory fault identification rates are obtained at different speeds, all these verify the validity of new method.
  • YANG Yang;XU FeiKou Jian-feng TANGZhong-bin
    . 2014, 33(21): 189-192.
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    Impact resistanceof Thermal ProtectiveSystem is an important determinant for the safe serviceof Space Airplane in orbit.Firstly, based on the impact experiments, the debris cloud structure model of plain-woven C/SiC composite under impact load wasproposed and analysedqualitatively, in which the special axial columnar high energy zoneof C/SiC debris cloudwas emphasized.Secondly, based on the Autodyn orthotropic composite model,the material parameters were derived,whoserationality was verifiedby the comparison of numerical results with the experimental results.Finally, the residual velocity of projectile, the axial average velocity and the distributed angle of debris cloud were selected as the main characteristic parameters based on the debris cloud characteristics of C/SiC composite. Taken Al spherical projectile impact model as the object, the impact resistanceof C/SiCwas analysed and assessed for various conditions.
  • Yang Zhen-dong;Gu Zhen-qi;Dong Gong-ping;Yang Xiao-tao;Shen Hong-li
    . 2014, 33(21): 193-201.
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    The transient exterior flow field of a car was computed by LES, and then sunroof buffeting noise characteristic was predicted using FW-H acoustic model based on Lighthil-Curle acoustic analogy theory. Based on the study of the vehicle’s sunroof buffeting noise character, this paper introduces modern optimization algorithm to the sunroof deflector’s design. The main objective of this study is to minimize the weight sound pressure level (SPL) value of driver’s left ear and passenger’s right ear. The deflector’s installation angle、groove width and depth were taken as design variables. Based on twenty sampling points by the method of the Design of Experiment (DOE), the Kriging model was constructed. Then, the Genetic Algorithms were used to optimize the shape of the deflector, and a set of optimal parameters was obtained. Simulation results show that the monitor’s SPL of buffeting noise after the optimization of deflector reduces by up to 21.6% compared with that of the original deflector.

  • HE Lei;SHANG Xing-chao;ZHOU Ke-dong;JIANG Yuan-qing;ZHANG Zuo-you;SUN Quan-ling
    . 2014, 33(21): 202-206.
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    The pneumatic weapon has broad application prospects with the advantages of simple structure of ammunition and controllable energy. The working principle of a kind of compressed air driving weapon was proposed in this paper. Based on the theories of gas dynamics and Hertz contact, the model of the variable mass thermodynamics process and friction force was established, and the dynamic model of the launching process was established thereby. By MATLAB/Simulink, the numerical simulation solutions of the state parameters of inner gun-barrel gas and the motion parameters of the projectile were obtained under the condition of a constant pressure of the air supply. Based on the above work,the effects on the launching process caused by the changes of compressed air pressure and the structure parameters were analyzed. The results have great theoretical significances to guide the research and design work of the compressed air driving weapon.
  • LI Bin;XIA Hong
    . 2014, 33(21): 207-212.
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    Touching upon that the crack fault of the rotor may occur after the RCP has operated a long time, the fault feature can be identified effectively by the method of the wavelet analysis. Based on the simulation signal of the vibration model of the RCP cracked rotor and the method of CWT, the cross-correlation coefficients between the fault signal and the different wavelet basis which are selected from the wavelet basis library can be computed. After confirming the maximum of the cross-correlation coefficients, the optimal wavelet basis applied to the fault signal of the cracked rotor will be found. And the three-dimensional diagram which covers the power spectrum, the scale of transform and the frequency will be described, once the signal analysis of the fault is completed by use of the optimal wavelet basis. The results of simulation illustrate that the wavelet basis selected by the maximum cross-correlation coefficients can become the optimal wavelet basis, and the fault feature of the cracked rotor can be recognized effectively.


  • Li zhijun;WU Xiaochao;Xu xiuli;Li xuehong
    . 2014, 33(21): 213-217.
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    To study the ride comfort of the long span bridge, five tests of vibration for vehicle passing the bridge in different condition were conducted. The effect of the dynamic characters of the vehicle and the bridge, the roughness of the deck and the vehicle speed on the vibration inside vehicle was investigated by analyzing measured vibration data. A time frequency domain method based on wavelet transform was used to extract the energy distribution of vibration inside the vehicle The results show that the dynamic characters of the vehicle have more influence on vertical vibration inside the vehicle. However the dynamic characters of the bridge deck have more influence on lateral vibration inside the vehicle. The vibration amplitude is mainly determined by the roughness and the expansion joint and increase with the vehicle speed. The lateral vibration of the vehicle passing the Cross Sea Bridge has a rapid increase as the vehicle speed exceed 80km/h. The research results have important reference value in evaluating ride vibration comfort of long-span Bridge.