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Extraction of Transmission Bearing Fault Characters Based on EMD Fractal Technology

XIA Jun-zhong;LIU Yuan-hong; DAN Jia-bi;YANG Gang;XIAO Yun-kui

2012, 32 (2): 119-122. DOI: 103969/j.issn.1006-1355-2012.02.29

Abstract （1206）

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Since the vibration signal of faulty bearing has fractal characteristics, the fault modes of a transmission bearing can be effectively identified by using fractal dimensions. However, the noise in the signal has a serious influence on the fractal dimension calculation, so empirical mode decomposition (EMD) method is necessary for solving the problem. In this article, the vibration signal of the transmission bearing was decomposed into intrinsic mode function (IMF) components by EMD, and then the fractal dimensions of these components were calculated to extract the fault characters of the transmission bearing in different conditions. The results show that EMD method is able to separate signals in different frequency bands effectively, and the fractal dimensions of specific IMF components are able to reflect the working state of the transmission bearing sensitively, which can be selected as the characteristic parameters to diagnose the transmission bearing’s fault. The combination of EMD and fractal dimension is an effective method of transmission bearing’s fault character extraction.

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Ultrasonic Detection of Lamb Wave Stimulation and Modal Analysis of Thin Steel Plate Structure

AI Chun-an;WANG Xue-yong;LIU Yu

2012, 32 (1): 137-140. DOI: 10.3969/j.issn.1006-1355-2012.01.032

Abstract （1406）

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This paper studies a common method and its procedure of ultrasonic detection of Lamb wave stimulation in thin steel plate structure. The signal was stimulated by ultrasonic oblique incident Lamb wave and the modes of the signal were analyzed. According to the experiment, it is found that with a proper combination of frequency and incident angle, selection and control of the modes of the Lamb wave can be realized. Thus, the best stimulating strategy of the detection can be obtained. This study is of important significance for the Lamb wave testing in engineering application.

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Numerical Research on Stochastic Resonance Effect in Bistable System

XIA Jun-zhong;LIU Yuan-hong;MEI Jian-min;LEN Yong-gang;ZHANG Wei-feng

2011, 31 (4): 21-25. DOI: 10.3969/j.issn.1006-1355-2011.04.005

Abstract （2052）

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The model of stochastic resonance in bistable system is analyzed based on adiabatic approximate theory. Ingredients of stochastic resonance, including system parameters, noise intensity, signal amplitude and frequency, are studied. It is concluded that there is an optimal noise intensity for the stochastic resonance system, and augmentation of the signal amplitude is favorable to the occurrence of stochastic resonance. However, the increase of signal frequency will cause the peak of signal in output power spectrum to leave the low-frequency area that noise energy concentrates on. It makes the peak of signal decrease rapidly and the stochastic resonance phenomena disappear gradually. For the fact that signal amplitude, frequency, noise intensity often exceed the requirements of small parameters in the adiabatic approximation theory and turn into large parameters, the re-scaling method for realization of stochastic resonance of large parameter signals is discussed.