ANALYSIS OF GUIDED WAVE PROPAGATION THROUGH BENT WAVEGUIDES FOR FACILITATING NDE

Abstract

For almost two decades, guided waves have been employed as a non-destructive technique for thin plate testing. Bend shaped plates are the most frequently employed plate shapes in the mechanical, aerospace, and construction industries. These parts are prone to failure because of several issues like cyclic loading and high temperatures, and the severe operational conditions that exist in the bend area may lead to the emergence of cracks, notches. Lamb wave-based Non- Destructive Evaluation of structures has attracted consistent interest recently as a substitute for the expensive and time-consuming conventional methods owing to its distinct benefits, which include low cost, greater susceptibility to damage, and larger area scanning capability. These Lamb waves are multimodal, consequently it’s essential to comprehend which modes are susceptible to the defects. Currently, it is unclear how to effectively investigate the scattering behaviour of a Lamb wave through such bent plates when defects such as cracks and notches are present. Detecting such damage involves Lamb wave sensors and actuators placed on accessible straight portions of the plate, while the bent, damaged area is sandwiched between these segments. To analyze wave interactions through the bent section, the SAFE method models the straight portion, and the conventional FE method is used for the bent, damaged area. The hybrid SAFE-FE method facilitates this analysis, offering insights into how Lamb waves scatter through damage in the bent region. Despite extensive research on Lamb wave propagation through various defects in waveguides, a parametric investigation into the effects of notch characteristics and bent plate geometries on scattering ratios in bent plates has not been thoroughly explored. Such concerns established a new research approach of a hybrid SAFE-FE approach to address these gaps, aiding in the assessment of defect parameters for effective damage detection. Herein, This thesis rigorously investigates the intricate interactions between the fundamental Lamb wave mode and diverse configurations of bend waveguides, employing the hybrid (SAFEFEM) numerical framework. By coupling SAFE’s analytical strengths for simple geometries with FEM’s detailed analysis for complex regions, this hybrid approach allows for accurate simulation of Lamb waves across various domains, facilitating intensive study of wave interactions with structural defects. This combined methodology comprehensively analyzes Lamb wave behavior for damage detection and structural health monitoring, effectively bridging the gap between largescale wave propagation and localized defect analysis.