Time-Reversal Lamb Wave Used In Defect Detection Of Aluminum-Alloyed Plates

Ultrasonic nondestructive testing is used widely in industry because it has the advantages of low cost, high efficiency in the detection and having no hurt to the operator and so on. And, the method of lamb wave used for detecting is more suitable for the thin and broad plates detecting. However, because of Lamb complex theory, the method can not be widely applied.In this article, firstly, lamb dispersion curve is solved. Then, the property of lamb wave is well elaborated. And, the principle of lamb wave testing in the thin aluminum alloy plates is illustrated. And, the way of lamb wave excitation is selected. In comparison of analysis methods of lamb modes, STET is selected in this article, and an experiment is used for explaining this method.Secondly, time-reversal is used to focus signal energy to reduce lamb dispersion. In the inhomogeneous media, Time reversal can be used to achieve acoustic self-adapted focusing, which is better than the other method such as time delay focusing, because it immunes to the influence of types of sound source and media. Then, time reversal method is discussed. And, the time reversal lamb wave detection system is set up.At last, the artificial defects are made. Time reversal lamb wave is used for detecting some types of plates with different defects. By analyzing focusing signals, the location and property of defects can be defined.