A Study on the Characteristics of Lamb Wave Based on the Finite Element Method

Abstract — Electromagnetic ultrasonic Lamb wave, with the advantage of quickly detecting the defect, is widely used in nondestructive testing of thin plate. However, it is related to the characteristics of Lamb waves that selecting mode of guided waves and estimating the detecting range. Therefore, this paper studies the propagation characteristics of Lamb waves, including directivity of sound field, multi-mode and dispersion. This paper mainly studied on the Lamb wave characteristics of the 1mm-thick aluminum plate based on the finite element method. Results show that: A0 and S0 modes, which are only detected in the plate, have a strong directivity of sound field when the excitation frequency is in the range of 0.08MHz to 1MHz. There is only A0 mode in aluminum plate when the excitation frequency is lesser than 0.188MHz. When the excitation frequency is in the range of 0.45MHz to 0.64MHz, the displacement amplitude of the S0 mode is gradually increasing. The displacement amplitude of the A0 mode is minimum, while it is larger in the S0 mode when the excitation frequency is 0.64MHz. The results of this paper provide a basis for selecting the best excitation frequency and mode of guided waves, which have the promising application prospect in quickly and accurately nondestructive testing. Keywords-nondestructive testing;EMAT; Lamb; dispersion; finite elemen