Lamb Wave Modes Decomposition for the Application to Structural Health Monitoring

초록

Due to the dispersive and multi-mode nature of the Lamb waves, it is a challenging task to decompose each Lamb wave modes into the symmetric and anti-symmetric modes for the application to structural health monitoring. Thus, this paper proposes a Lamb wave mode decomposition method based on two fundamental rules: the mode group velocity ratio rule and the mode amplitude ratio rule. The mode group velocity ratio rule means that the ratio of the group velocities of A0 and S0 modes is constant, while the mode amplitude ratio rule means that the ratio of the magnitudes of A0 and S0 modes in a measured response signal must be always larger than unit once the center frequency of the input signal is so determined that the magnitude of A0 mode in the excited signal is larger than that of S0 mode, and vice versa. The proposed method is verified through the experiments conducted for an aluminum plate specimen.