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A New Parametric Time-frequency Analysis Method for Instantaneous Frequency Estimation of Polynomial Phase Signal
FANG Yang;PENG Zhi-ke;MENG Guang;YANG Yang
   2012, 32 (3): 7-11.   DOI: 10.3969/j.issn.1006-1355.2012.03.002
Abstract （2001）            Save
Nonlinear chirplet transform, a new parametric method for time-frequency analysis was proposed by replacing the linear chirp kernel by a nonlinear polynomial kernel. By choosing the proper kernel characteristic parameters, the nonlinear chirplet transform can render a time frequency distribution of excellent concentration for signals whose instantaneous frequency trajectory is an arbitrary function of time. In this paper, the polynomial chirplet transform was applied to estimate the polynomial phase signals with arbitrary order. As the performance of the nonlinear chirplet transform highly depends on the kernel characteristic parameters, an algorithm to evaluate these parameters was developed in order to estimate the instantaneous frequency and the phase parameters of the polynomial phase signal. The effectiveness of the algorithm was validated by analyzing the signals from numerical simulation.
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Research on Shear Elastic Property of Viscous Liquid by Signal Processing Method
CAO Han-jie;NOIREZ Laurence;MENG Guang
   2012, 32 (2): 112-114.   DOI: 10.3969/j.issn.1006-1355-2012.02.027
Abstract （1266）            Save
By changing the connection condition in the interface between the substrates and viscous liquid in the experiments, the shear elastic property of the liquid with several-ten-micron thickness can be observed under the condition of low shear-strain rate. To confirm the property, the strain-stress signals in the experiments were collected and processed by the discrete Fourier transformation (DFT). From the viewpoint of phase difference of strain and stress in rheology theory, it was proved that liquid has shear elastic properties under some small-scale dimension conditions.
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Simulation and Experimental Study on Damage Detection in Welded Rectangular Tube Based on Guided Wave
LU Xi;;ZHOU Li-min;MENG Guang
   2012, 32 (1): 119-123.   DOI: 10.3969/j.issn.1006-1355-2012.01.028
Abstract （1654）            Save
Guided wave based detection methods have become a hot area of research in structural health monitoring (SHM), and have a great potential in engineering applications. A welded tubular component, which is a segment of train bogie frame, was investigated by using both finite element method (FEM) and experimental analysis for the purpose of damage detection. 3D FEM models were established to simulate the propagation characteristics of guided waves in the component. An active transducer network was employed to generate guided waves propagating in the structures and to collect response signals. Excitation frequency was carefully optimized to diminish the effect of the intrinsic multi-mode phenomenon of guided waves on the consequent signal interpretation. Continuous wavelet transform (CWT) and Hilbert transform (HT) were applied to all collected signals successively. Guided wave-based triangulation was developed and consequently utilized in damage location estimation. Effectiveness of the recommended approach was validated in experiments.
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Study on Propagation of Guided Waves in Thick Beam and the Selection of Excitation Frequency
SUN Xue-wei;LI Fu-cai;SUN Kai;MENG Guang;CHEN Xue-dong
   2011, 31 (6): 10-14.   DOI: 10.3969/j.issn.1006-1355-2011.06.003
Abstract （1680）            Save
Mechanism of guided wave propagation in the thick beam is investigated in this study. Professional software for calculating and drawing the dispersion curves of Lamb waves in isotropic structures is developed by using the Rayleigh-Lamb equation. A number of influencing factors, such as selecting the guided wave modes, reducing dispersion effects, increasing amplitude of the wave signal, improving resolution in time domain, and suppressing the effects of local symmetry, are considered for the selection of excitation frequency. The parameters of the excitation wave are therefore optimized, and a standard process of selecting center excitation frequency in guided-wave based structural health monitoring technique is proposed.
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Modeling of Vibration Drive by Electromagnetic Field for Rotary Permanent Magnet
LV Yang-ming;YANG Bin-tang;MENG Guang;XU Wen-bing;XIA Ming-lu;QIAN Wen-tao
   2011, 31 (5): 17-21.   DOI: 10.3969/j.issn.1006-1355-2011.05.005
Abstract （1766）            Save
A theoretical modeling method and the experimental verification for a proposed principle of rotary permanent magnet drive excited by electromagnetic field are presented in this paper. Electromagnetic torque of a permanent magnetic rotor under electromagnetic excitation is usually a nonlinear function of external electromagnetic field and its rotary angle. So, it is difficult to compute the electromagnetic torque directly by using common electromagnetic analysis methods. Based on surface magnetic charge, this study searches for a numerical method for calculating the drive torque with the electromagnetic field applied to the rotary permanent magnet. Meanwhile, the theoretical model for analyzing the relation of the torque of the combined magnetic field versus the excitation current and the rotary angle of the permanent magnet is established. This model may present a quasi-static and dynamic vibration drive process of the rotary permanent magnet under electromagnetic field excitation. The research finally validates the theoretical analysis and modeling method by experimental tests in terms of modeling accuracy and applicability of this theory in vibration drive.
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《Wave Propagation Analysis in a Beam Structure Using Spectral Element Method》
PENG Hai-kuo;MENG Guang
   2009, 29 (6): 62-66.   DOI: 10.3969/j.issn.1006-1355.2009.06.062
Abstract （2501）      PDF（pc） （1095KB）（1574）       Save

This paper presents result of application of spectral element method (SEM) for simulation of wave propagation in a beam structure and the crack is simulated by node separation method. Wave propagation characteristics in an aluminum beam structure are investigated. And the simulated results are compared with the analytical result from Lamb equation to validate the proposed model. The influence of cracks with different damage degrees to response signal are investigated and the damage detection method are studied. The conclusion can be useful for study of damage detection method based on Lamb wave.

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《An Approximated Method for Calculating Residual Mass Matrix and Residual Stiffness Matrix》
DONG Xing-Jian;MENG Guang
   2009, 29 (6): 11-14.   DOI: 10.3969/j.issn.1006-1355.2009.06.011
Abstract （2989）      PDF（pc） （898KB）（1912）       Save

A difficulty encountered when using theoretical component mode synthesis method with purely experimental data is that mass matrix and stiffness matrix are necessary in order to take the residual inertia relief attachment modes into account. Yet the mass matrix and stiffness matrix of a substructure are not always available from an experimental approach. To overcome this difficulty, the approximated expressions for the residual mass matrix and residual stiffness matrix are proposed in which the mass matrix and stiffness matrix are not needed. An improved CMS formulation is then developed for the case when taking the experimental data into account. It is based on the same formulation normally used when using analytical data. However, no need exists anymore to have the mass matrix and stiffness matrix of the substructures at the same time accounting for the residual inertia relief attachment modes. The accuracy and efficiency of the proposed CMS method are proved by a numerical example.
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《Survey and Outlook on the Research of the Unbalanced Magnetic Pull in the Motors》
BAI Hui-yu;JING Jian-ping;MENG Guang
   2009, 29 (6): 5-7.   DOI: 10.3969/j.issn.1006-1355.2009.06.005
Abstract （4622）      PDF（pc） （1121KB）（5008）       Save

A survey on the research of the unbalanced magnetic pull(UMP) in the motors is given in the paper. The mechanism of UMP is analyzed and summarized. The developing status of the research of UMP, especially the nonlinear UMP, is also introduced. The ways to preventing and reducing UMP are also summarized. Finally, the future research orientation of UMP is also discussed.

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《Dynamical Response Failure Mode Based Reliability Analysis of a Cantilever Rotor》
ZHANG Pengfei;JING Jianping;MENG Guang;WANG Yuhua;ZHANG Lixin
   2009, 29 (5): 58-61.   DOI: 10.3969/j.issn.1006-1355.2009.05.016
Abstract （2410）      PDF（pc） （1392KB）（1172）       Save

Cantilever rotor is the key component part of mechanical equipment. Based on the failure mode of dynamic response of the cantilever rotor, the ensitivity factors which affect structure reliability, such as load, size of structure, properties of materials, are analyzed. The utmost equations of the cantilever rotor in both static and dynamic states are built. Each equation is linearized at the average point by Taylor Expansion scheme. The reliability of structure is calculated by employing the theory of the primary second moment. The reliability results of considering and ignoring the inertial force respectively are compared mutually and analyzed. Then, an effective reliability analysis method for cantilever rotor is established.

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