Comparison of plain piezoceramics and interdigital transducers for crack detection in plates

Abstract

Lamb waves have attracted great attention in non-destructive evaluation (NDE) due to its efficiency in interrogating a reasonably extensive distance along the plate. Such waves can be efficiently excited using piezoceramic transducers with good control on the pulse charactertistics to assess the health of structural components, such as the presence of cracks. Through selective generation of Lamb waves within a frequency range, linear cracks can be detected via time-of-flight analysis of the wave, by using plain piezoceramics transducers with strategic positioning. Alternatively, using a well-designed inter-digital transducer (IDT), a single Lamb mode can be generated. It is shown that using IDT enhances detection accuracy and robustness in view of its controllability on the duration and direction of the generated wave. It is thus able to locate curved crack accurately as well as trace its geometry. The performance of both actuators are compared experimentally using both plain piezoceramics and IDT to detect different cracks, namely, linear crack, curved crack and multiple cracks, on aluminum plates. Plain piezoceramics provide accurate detection for linear and multiple cracks, and are able to estimate the geometry of a curved crack reasonably well. However, IDT is more efficient and provides accurate results for these three cases.