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�������պ����ѧѧ�� 2008, Vol. 34 Issue (7) :833-837    DOI:
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ʱƵ�����ڳ��������źŷ����е�Ӧ��
������, ��ռӢ, �����, ���X*
�������պ����ѧ ��е���̼��Զ���ѧԺ, ���� 100191
Application of time-frequency analysis to ultrasonic-guided-wave signal interpretation
Zhou Zhenggan, Feng Zhanying, Gao Yifei, Zhu Xuan*
School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing 100191, China

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ժҪ ���������ź���һ�ַ�ƽ���ź�,����Ƶɢ����,���ô�ͳ��ʱ���Ƶ������������ܽ�ʾ��Ƶ����ʱ��仯���ص�.Ϊ�˽����һ����,�о��˵����źŵķ�ƽ������,�����˶�ʱ����Ҷ�任(STFT,Short-Time Fourier Transform)ʱƵ����ԭ��,�ֱ�����������ͷ��Ѱ������ڴ����ĵ����źŽ�����STFT��ʱƵ�׷���,�ó��������ڵ����ź��и�Ƶ�ʳɷ���ʱ��ı仯���,�����������źŵ�ģʽת������,�ȽϾ�ȷ�ؼ����˵�����Ⱥ�ٶ�;���ڷ��Ѱ��ڵĵ����ź�,��������й¶�Ƚ�����,������Ƶ��Ϊ1.5��MHzʱ,A0ģʽֻ�ܽ����봫��,���ʹ�ò���STFT���ܺܺõؽ���ģʽʶ��.�о��������,���������������Զʱ,����STFT���Զ����źŽ��ж�̬��Ƶ�׷�����ģʽʶ��,���ɶ�ʵ�ʵ�Ⱥ�ٶȽ��нϾ�ȷ�IJ���.
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Abstract�� Ultrasonic guided wave is a kind of non-stationary signal and characterized by disperse. Its frequency spectrum variation can not be traced with traditional methods in time domain and frequency domain respectively. To solve the problem, the non-stationary characteristics of guided waves were studied, the theory of STFT(short-time Fourier transform) was introduced, the STFT and time-frequency spectrum analysis were applied to the signal interpretation of guided waves propagating in an aluminum plate and a honeycomb core structure plate. The frequencies variation of the signal propagated in aluminum plate can be analyzed as well as mode conversion and precise group velocity. Due to energy leakage, A0 mode propagates just in short distance in honeycomb core structure plate when the excitation center frequency is 1.5��MHz, which results in that mode conversion can not be done well. The results show that in further distance can the STFT method be applied to not only the frequency spectrum analysis and mode identification of guided waves but also an accurate measurement of their group velocity.
Keywords�� ultrasonic testing   guided waves   dispersion   time-frequency analysis   STFT(short-time Frourier transform)   aluminum plate   honeycomb core structure plate     
Received 2007-06-12;
Fund:

������Ȼ��ѧ����������Ŀ(50475006)

About author: ������(1967-),��,������̶��,����,zzhenggan@buaa.edu.cn.
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������, ��ռӢ, �����, ���X.ʱƵ�����ڳ��������źŷ����е�Ӧ��[J]  �������պ����ѧѧ��, 2008,V34(7): 833-837
Zhou Zhenggan, Feng Zhanying, Gao Yifei, Zhu Xuan.Application of time-frequency analysis to ultrasonic-guided-wave signal interpretation[J]  JOURNAL OF BEIJING UNIVERSITY OF AERONAUTICS AND A, 2008,V34(7): 833-837
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