Wave velocity analysis and repeatability of artificial acoustic emission in homogeneous materials: steel and aluminium plates

Abstract

In this study, wave velocity calculations and the repeatability of the Pencil Lead Break (PLB) test were examined through two use-cases involving homogeneous materials: a 5mm aluminium plate and a 2mm steel plate. The PLB test is a widely used and straightforward method for generating artificial acoustic emissions. Ensuring its repeatability is essential for reliable signal processing in acoustic emission (AE)-based analysis. PLB tests were repeated under controlled conditions, and the resulting AE waveforms were analysed using Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT). Time-of-arrival (TOA) values were extracted to calculate wave velocities using known distances between the source and sensors. The measured velocities—approximately 5100m/s for aluminium and 5700m/s for steel—were consistent with expected Lamb wave mode behaviour. The research emphasises the importance of applying consistent PLB force to produce clear waveform characteristics and valid TOA-based velocity estimates. These findings support the validity of TOAbased wave velocity measurement methods for thin homogeneous plates and establish a foundation for extending similar methodologies to more complex materials and acoustic emission scenarios.