Guided Wave-based Damage Localization in Isotropic Structures with Smoothly Varying Thickness
Abstract »Modern technical structures, e.g. in the aviation and maritime industry, aim at an increased material efficiency and optimized weight. Therefore, the structural thickness changes locally according to the particular load case. At the same time the varying thickness represents a challenge for active and passive structural inspection by means of guided elastic waves, because the phase and group velocity of each wave mode changes with the thickness of the structure. As a result, conventional beamforming techniques for damage and acoustic source localization are inherently affected by errors, because the average group velocity and not the actual group velocity is used in the localization procedures.
In this paper, a generalized delay-and-sum beamforming approach for damage localization in isotropic structures with smoothly varying cross section will be presented. This formalism takes the spatially varying group velocity of the adiabatic wave motion into account. Damage localization results based on the fundamental symmetric wave mode in a structure with a linear and quadratic thickness profile will be presented and discussed.