Signal Separation Of Ultrasonic Lamb Waves Based On Wavelet-ridge

With the rapid development of materials science and industrial technology, plate material has been widely used in many fields of aerospace, information science and other industries. Compared with the traditional ultrasound scan point by point, lamb wave testing has the characters of far propagation distance, big one-time detection range, fast and efficient, etc. As the characteristics of frequency dispersion and multi-mode of lamb wave and the complexity of the testing mechanism, the application in industry is far from what it should reach. The main work of this paper are as follows:In this paper, first introduces the basic theory of lamb wave and several common time-frequency analysis methods. By collecting signals from the same source but transmitting to different distances, combinating of width and amplitude in time domain, verify that the Lamb wave has dispersion characteristics.Then researches the continuous wavelet transform and the the theory of wavelet ridge, and gives details of the crazy climber algorithm which can extract multi-ridge to some extent. Through the analysis and research on single-mode lamb wave with wavelet ridge method, show that lamb wave after transmission of a certain distance has the characteristics like asymptotic signal, and the ridge can reflect the dispersion characteristic, lamb wave also can be reconstructed with the ridge and the information on the ridge. Next, different situations that single-mode lamb wave mixed with different types of signals are discussed. The simulation results show that using wavelet ridge method, lamb wave can be separated from different mixed signals, while mixed with asymptotic signal, the ridge resolution should be taken into consideration.Finally, analyze multi-mode Lamb wave by adopting a variety of time-frequency analysis method, also, wavelet ridge method is used to separate signal. For signal instantaneous frequency ratio greater than two, according to the ridge curves that signal components correspond and the information on the ridge, directly separate signals. When the signal instantaneous frequency closed, public ridge is used to extract two or more components together. So that signals to be analyzed in pattern recognition and processing in the late take easy to some.