A scattering solution based on modal decomposition method is proposed to study Lamb wave scattering near a rectangular notch on a plate. The resonant characteristics of the reflection coefficients of the first symmetric and antisymmetric Lamb mode are investigated at low frequency. It's found that the resonances are subjected to a coupled modulation of the traveling Lamb modes in the remnant thinner plate. The decoupled modulation functions respecting to a varying notch width are subjected to the half-wavelength of a particular Lamb mode, while the original phases in the functions are mainly affected by the notch depth, which regarding to a0 mode at different notch depth are illustrated. The relations between scattering coefficients at outside of the notch region and the resonant characteristics in the open-end plate region are confirmed by our research and the feasibility of the proposed solution is also proved.

rectangular notch; Lamb wave; scattering; resonance