Study of acoustic emission propagation characteristics and energy attenuation of surface transverse wave and internal longitudinal wave of wood

To study the propagation characteristics and energy attenuation of different modal acoustic emission signals in wood, Zelkova schneideriana and Pinus sylvestris var.mongolica were used as test materials, and a test scheme was designed to separate surface transverse wave and internal longitudinal wave based on wave theory. The propagation characteristics of AE signal along the grain direction of wood was studied based on the discrete wavelet analysis, and then the energy attenuation model of AE signal was developed. The results show that when STW and ILW were propagated in wood, the energy of AE signal shows exponential decay with the propagation distance. STW has a more complex frequency domain distribution and more drastic time-frequency attenuation, and the propagation velocity of STW in Zelkova schneideriana and Pinus sylvestris var.mongolica was 1519.8 m.s−1 and 1118.8 m.s−1, respectively. The AE mode of ILW was relatively stable and always distributed in the low frequency band with fast propagation; the propagation velocity in Zelkova schneideriana and Pinus sylvestris var.mongolica was 6944.4 m.s−1 and 5168.4 m.s−1, respectively. Furthermore, the study shows that the propagation velocity of ILW is about 4.6 times that of STW in the same species of wood.