WOOD RESEARCH Volume 69, Number 4, 2024
CHUMIN CHEN, MING LI, SAIYIN FANG, and BO ZHANG

ANISOTROPIC VELOCITY MODEL AND ENERGY ATTENUATION CHARACTERISTICS OF ACOUSTIC EMISSION SIGNALS IN FINGER-JOINTED TIMBER AND SAWN TIMBER

Although anisotropic propagation behavior of acoustic emission (AE) in the sawn timber (ST) has been revealed, that in finger-jointed timber (FJT) is still less known.Therefore, a series of velocity and energy models of AE signalswere built as it propagates along different directions on the surface and inside of specimens (ST and FJT). At first, using polar coordinate system, velocity model in 36 directions was built in FJT, which was compared to ST.Furthermore, a continuous sine wave with a frequency of 165 kHz was selected as AE source to explore the energy attenuation law in FJT and ST respectively.The results showed that there are significant differences in velocity models between FJT and ST.The wavefront in STwas regular elliptical, while that in FJT has a clear depression in perpendicular to grain direction.This feature becomes more obvious with the increase of distance when AE signal propagates inside the FJT.Inside the FJT,energy magnitude in STwas 3.00-7.37 times of that in FJT

WOOD RESEARCH Volume 69, Number 3, 2024
CHUMIN CHEN, MING LI, SAIYIN FANG, JIALONG ZHAO, XIN ZHANG, FANGYONG LU, TINGTING DENG, and BO ZHANG

STUDY OF STRESS WAVE PROPAGATION PATH AND DEPTH IDENTIFICATION IN CRACKED WOOD BASED ON ACOUSTIC EMISSION AND COMSOLSIMULATION

The propagation velocity models were built using AE sensors to capture stress wave on pine specimen surface.On the different specimens, cracks were made in different numbers and the depth was gradually increased from 0 mm to 90 mm at 10 mm intervals. AE experiment was combined with COMSOL to investigate propagation path.The results show that R-squared is 0.996 when fitting tangent of angle to propagation velocity.At smaller crack depths, stress wave is diffracted around crack tip and then continues to propagate in to sensor along a straight line.However, as the crack depth increases, the reflected wave at the end face will arrive at the detection location faster with significantly weaker diffraction.The area with dimensions of20×10 mm was identified about the crack tip by crack identification method