RESEARCH ON THE EFFECT OF WOOD SURFACE CRACKS ON PROPAGATION CHARACTERISTICS AND ENERGY ATTENUATION OF LONGITUDINAL ACOUSTIC EMISSION

Abstract

To investigate the effect of Zelkova schneideriana surface cracks on the longitudinal wave propagation characteristics of acoustic emission (AE). Different sizes and numbers of cracks were made on the surface of the specimen, the propagation characteristics of AE longitudinal waves along wood texture direction were studied. Firstly, five regular cracks with the same length, different width, depth and equidistant distribution were fabricated on the surface of thespecimen. Theburst and continuous AE sources were generated by lead core breakage and signal generator, and the AE signals were acquired by 5 sensors with sampling frequency was set to 500 kHz. Then, the propagation speedof AE longitudinal wave was calculated by Time Difference of Arrival (TDOA) based on lead core breakage. Finally, the 150 kHz pulse signals of different voltage levels generated by the signal generator were used as AE sources to study theinfluence of cracks on the attenuation of AE longitudinal wave energy. The results showed that the AE longitudinal wave propagation speedunder the crack-free specimen was 4838.7m.s-1. However, after the regular crack was artificially made, the longitudinal wave speedreduced to a certain extent, and the relative error of the change was not more than 9%. Compared with the energy decay rate of 1.29 in the crack-free specimen, the decay rate gradually increased to 2.08 with the increase of the crack cross-sectional area.