Scattering of Lamb Waves by a Cylindrical Mass Attached to the Surface of a Plate

Defect classification is the logical next step after localization in a Lamb wave based Guided Wave Structural Health Monitoring (GWSHM) defect detection scheme. Lamb waves are a preferred wave mode in GWSHM; therefore, classification can be facilitated via understanding of the Lamb wave scattering characteristics of defects. Many defects can be modeled either as (part-) through holes or accumulated masses on the surface. We consider and analytically solve the scenario of an attached mass on the surface of a plate. The mass is treated as an elastic isotropic homogeneous cylinder and the scattering response is obtained for incident fundamental symmetric and antisymmetric waves. Propagation is modeled via Mindlin plate theory, utilizing infinite series of Bessel functions as potential functions. Boundary and continuity conditions provide a linear system of equations for the expansion coefficients of the potential functions, which, solved numerically, produce the scattering response of the defect.