Determination of stepped plate thickness distribution using guided waves and compressed sensing approach

Abstract

Guided waves recently have attracted significant interest as a very promising research area. The signals registered by a specially designed sensor network are processed to assess the state of the tested structure. Despite the constant development of novel damage detection algorithms employing guided waves, the phenomenon of wave propagation still needs detailed recognizing and understanding for the further progress of non-destructive wave-based methods. Special attention is paid to guided waves in plate-like structures, but the majority of considered cases concern plates with constant thickness. However, in the real world, we often deal with specimens with variable thickness. The thickness variability of the specimen is often forced to fulfill the construction requirements and optimize stress distribution or is the result of degradation i.e. corrosion. Thus, the development of NDT methods forces the need of considering specimens with complex geometry and the problem of wave propagation in waveguides with variable thickness is crucial for improving novel as well as so far proposed algorithms.The article presents the results of the analytical, numerical and experimental analysis of wave propagation in plates with variable thickness. The analysis concerns the influence of thickness distribution of plate structure on wave velocity, the time course wave packet and amplitude. Moreover, the novel approach based on constrained convex optimization for determining the plate thickness distribution has been proposed and verified during numerical and experimental campaigns.