FE modelling techniques for the simulation of guided waves in plates with variable thickness

Structural health monitoring based on ultrasonic guided waves is widely spreading attention in diagnosis and prognosis of engineered parts. Plate-like structures, such as those used in the aerospace sector, are often characterised by a variety of geometric features, either stiffeners or cross-sectional variations, which can affect the guided wave propagation mechanisms, complicating the measurements analysis. An in-depth knowledge of the phenomena involved in the interaction between guided waves and discontinuities is required to extract the key damage-related features from the collected signals. In this paper, the effects of a variable thickness on guided wave propagation are numerically investigated. Different finite element modelling techniques are proposed and compared to efficiently reproduce the geometric discontinuity. The 0-order fundamental modes excited and sensed by an array of piezoelectric transducers are considered; the group velocities are thus calculated and compared to prove the effectiveness of the approaches.