Acoustic emission for tracing fracture intensity in lime wood due to climatic variations

Acoustic emission (AE) monitoring was used to trace directly the fracture intensity in cylinders of lime wood subjected to variations in temperature and relative humidity (RH) in their environment. High-frequency components produced by mechanical fracturing were extracted from the raw AE signals using the wavelet transforms. The accumulated energy of these components depended on the magnitude and rate of the RH variations. The AE activity correlated well with predictions of the numerical modeling carried out as the first part of the present investigations. In particular, the AE activity became negligible below the allowable magnitude for the rapid RH variation predicted by the simulation, or when the time interval allowed for the RH variation was long enough. Furthermore, AE proved capable of tracing the progressive evolution of damage at the microlevel, which preceded failure of wood discernible from the macroscopic perspective.