ABSTRACT
As defined by Liptai et al. (1972), Nichols (1976), Lord (1983); Lynnworth (1989); Stephens and Levinthall (1974), and Williams (1980), acoustic emission is a transient elastic wave generated by the rapid release of energy within a material. The aim of acoustic emission analysis is to obtain information about the source of this phenomenon from the detected ultrasonic signal. Acoustic emission in solid wood or in wood-based composites can be generated by stress level—(high or low rate) plastic deformation, crack propagation, drastic variation of temperature and moisture content, drying, sap cavitation in vessels, freezing, phase transformation, anisotropy and nonhomogeneity of the anatomic structure in adverse environmental conditions, rapid collective motion of a group of anatomic elements, modification of the orientation of crystallites in microfibrils, dislocations in cellulosic chains, etc.
