Ultrasonic technique for evaluation of bio-defects in wood: Part 1 – Influence of the position,extent and degree of internal artificial rots

Abstract

Artificial rots were created in Norway spruce beams 80×80×300, 120×120×300 and 150×150×300 mm by making notches of six various widths, and then by filling these notches with spruce sawdust, modelling two degrees of rot. The velocity of ultrasonic wave (UW) in the transverse direction was measured at three positions (first through notch, second through boundary of notch and non-attacked wood and third through undamaged wood), at a total of 15 locations for each beam. The UW propagation was significantly influenced by the position of transducers towards notches. In the first position, it decreased by 35–73% (on 450–1100 m s⁻¹), in the second position by 6–10% (approximately on 1650 m s⁻¹), while in the third position, it corresponded to original beams. In the most sensitive first position, UW velocities decreased more apparently at bigger notches. However, filling of notches with spruce sawdust had negligible effect for propagation of UW.