Abilasha Ramadhas

Abstract: Inspection of practical plate assemblies is challenging due to the presence of complex features such as bends and corners. The objective is to investigate the influence of bends or curvature in the transverse direction on the propagation of guided waves in plates. A 3D finite element (FE) simulation shows that bends in plates can concentrate and guide ultrasonic energy along the direction of wave propagation. An interesting feature-guided mode that is surprisingly similar to the A0 (fundamental antisymmetric) Lamb mode in normal plates was identified when the bent plate is subjected to 'in-plane' excitation as the generation of this type of mode for a thicknesswise symmetric excitation is unexpected. These results are validated with experiments and discussed using Semi Analytical Finite Element (SAFE) models.

Abstract: Recent research by the authors shows that bends in plates can act as features that can concentrate and guide ultrasonic energy along their axis. At low frequencies, two feature-guided modes are identified when the bent plate is subjected to ‘in-plane’ or axial excitation applied uniformly along a through-thickness line bisecting the bent edge. Of these, the slower mode has properties similar to the A0 (fundamental antisymmetric) Lamb mode in flat plates. This paper focuses on the faster bend-guided mode that is similar to the S0 (fundamental symmetric) Lamb mode in flat plates. Using 3D finite element (FE) simulation validated with experiments, this mode is shown to be more strongly generated in smaller angle bends. Features of the mode including velocity, attenuation and modal structure are considered in detailed studies. Results are discussed in light of simple modal studies using the Semi Analytical Finite Element (SAFE) method, suggesting a relationship of bend-guided waves to modes of curved bars.