A Numerical Study on Baseline-Free Damage Detection Using Frequency Steerable Acoustic Transducers

In structural health monitoring (SHM) a considerable amount of damage detection algorithms based on guided waves (GW) have been developed. Most of them rely on extensive transducer networks, besides preliminary reference measurements of the structures. This originated a growing demand for hardware simplification and cost reduction of the wave-based SHM methods, driving the conception of new solutions enabling both: the reduction in the amount of sensors required for doing measurements, as well as a diminution of quantity of signals needed for the algorithms to work. The simplification in damage detection procedures can be achieved by using a novel type of special shaped frequency steerable acoustic transducers (FSATs). The spiral shape of these FSATs allows focusing wave energy in a certain direction, which is associated with their excitation frequency. Thanks to this property, presence of damage can be established by identifying signal reflections, while its localization can be determined based on time of flight and the relationship between direction of propagation and its spectral content. This article presents the concept of baseline-free damage detection using FSATs over an aluminium plate with point damage through Finite Element (FE) analysis. Numerical simulations were performed for several cases, varying excitation frequency and damage position.