Study the effects of ferrous materials inside wood on the propagation characteristics of acoustic emission signals

Abstract

ABSTRACT This study compares the propagation characteristics of acoustic emission signals for wood containing ferrous material by implanting ferrous nails into wood specimens to investigate the acoustic emission (AE) detection method of foreign metal objects inside the wood. It obtains specimens for the comparative test by drilling holes and implanting ferrous nails into identical Zelkova schneideriana and Pinus sylvestris var. mongholica specimens. Initially, the AE source is generated by conducting pencil-lead break (PLB) tests on the specimen surfaces according to ASTM standards, and the AE signals are then collected at the specimen surface with a 1 MHz sampling frequency. The effects of ferrous materials on the propagation characteristics of AE signals are examined using FFT and EWT methods for the time–frequency analysis of the original AE signals. Finally, the signal generator produces the 150 kHz pulse train at the PLB location. The AE signal energy is calculated based on the alternating current principle to establish the corresponding AE energy attenuation function. The results showed that the proportion of AE signals in the frequency ranges of (30–60 kHz) and (150–180 kHz) increases significantly when ferrous nails are present in the specimens.