Effect of moisture content on propagation characteristics of acoustic emission signal of Pinus massoniana Lamb

The propagation velocity and energy of acoustic emission (AE) signals at different moisture contents (MC) of wood are studied, providing a theoretical basis for studying the law of wood stress and strain with the change in MC. The AE source was simulated by lead core fracture on the surface of Pinus massoniana Lamb. Signal de-noising was performed by discrete wavelet decomposition method. On this basis, the propagation velocity and energy of AE signals at different MCs were studied according to the signal cross-correlation analysis and time difference localization method, and the law of velocity and energy change with MC was further determined by fitting. The fitting results show that the propagation velocity of AE signals decreased exponentially with the increase in MC. Moreover, the propagation velocity decreased rapidly when the MC was below fiber saturation point (FSP), and decreased relatively gently when the MC was above FSP. In addition, the energy attenuation of the AE signal was obvious during the propagation process, and the energy attenuation rate of the AE signal presented a linear relationship with the increase in MC. The change in MC has a significant effect on the propagation velocity and energy of AE signals of wood.