Simulations of Wood Viscoelastic Acoustic Emission Propagation Behavior and Wave Velocity Estimation Based on COMSOL Software

In order to study the influence of wood viscoelasticity characteristics on the propagation behavior of acoustic emission (AE) signals, a finite element simulation model of wood specimens was established by setting the viscosity coefficients of wood in COMSOL software. The effectiveness of the simulation model was verified by combining the results of wood AE experiments. Firstly, a Hanning window modulated sine pulse signal was generated by a signal generator at a distance of 100 mm from the left end face on the surface of the fir specimen. Two AE sensors were placed at a distance of 200 mm from the left end face at a distance of 300 mm on the surface of the specimen to collect the AE signals. Then, a filter was used to denoise the AE signals collected by the sensors. Secondly, finite element simulations were conducted on the fir specimen to obtain the displacement cloud map of elastic wave propagation in the specimen and the propagation law in viscoelastic materials. Finally, the time difference of arrival (TDOA) method was used to compare the transverse and longitudinal wave velocities and time-domain waveforms obtained from the simulations and experimental measurements. The results showed that the simulated transverse and longitudinal wave velocities were 1 118 m/s and 5 245 m/s, and the experimental transverse and longitudinal wave velocities were 1 290 m/s and 5 209 m/s, respectively. The amplitude attenuation and the time-domain waveforms were in good agreement when comparing the simulated and measured waveforms with the experimental waveforms. Therefore, the effects of viscoelasticity on Chinese fir specimens and the validity of the simulation model were confirmed.