Enhancement of Lamb wave–based in situ structural health monitoring through guided local geometry changes

Abstract

The incorporation of in situ structural health monitoring is currently an afterthought used to address critical areas identified in testing or service. This article investigates the use of local geometry changes to improve detectability of damage in the form of a line crack at a given fatigue critical location. A methodology encompassing especially developed Lamb wave tools is presented, which may allow the implementation of in situ structural health monitoring at the design stage of critical structures. A systematic redesign will be presented based on Lamb wave technology, which has been enabled by high-speed ray-trace modelling. By modelling propagation of wavefronts as rays, the high cost of iterating designs in finite element or experimental methods can be overcome. Implementing the ray-trace modelling, optimized design changes lead to improved damage sensitivity. Damage sensitivity has been quantified through well-used scatter/difference techniques. This was followed by analysing the strength and stiffness of the redesigned structures to reveal any consequential changes. To demonstrate the efficacy of this proposed methodology, a case study is presented where the fatigue critical location of structure representing the lower wing skin of an aircraft structure is analysed.