Experiment investigations of Lamb waves in an aluminum plate

Lamb waves have dispersive and multi-modal characteristics during its propagation.In actual applications,the multi-modal signals overlap and the useful modes can not be identified if relevant parameters are not properly selected.The dispersion,wave structure and incident angle curves of Lamb waves in an aluminum plate are drawn with dichotomy based on the characteristics that the Lamb wave dispersion curve is the distribution of real solutions of a Lamb wave dispersion equation.S0 mode Lamb wave is selected to detect the flaws with different types in 1mm thick aluminum plate based on the dispersion curve.The results show that S0 mode Lamb wave is very sensitive to cracks and through defects; however,the amplitude of S0 mode don't change linearly with the defect size.Meanwhile,the sound field directivity of S0 mode Lamb wave is very concentrated,and the defects deviated from the beam axis can not be detected.