Interaction between the fundamental lamb modes and the front edge of a crack in a metallic plate

Numerical simulations followed by experimental validations were carried out to study the interaction of the fundamental Lamb modes when incident at the front edge of a horizontal crack in a metallic plate. During the interaction, the incident fundamental Lamb mode underwent mode conversion and started propagating in the main and sub-waveguides along with the mode-converted Lamb mode. The amplitude of the mode-converted Lamb mode propagating in the main waveguide was negligible compared with that of the incident wave group. It was found that the amplitude of the transmitted Lamb modes from the main waveguide to the sub-waveguides is nearly the same as the incident wave group's amplitude; wave groups propagating in the thicker sub-waveguides are found to be carrying higher power than their counterparts in the thinner sub-waveguides. Furthermore, it was observed that variation in power coefficients and amplitude-based factors with respect to frequency of excitation were not very significant. Moreover, it was also shown that amplitude of the reflected wave groups in the main waveguide depends on phase velocities of Lamb modes in the main waveguide and sub-waveguides for a given thickness ratio.