Tomographie ultrasonore pour les arbres sur pied

Abstract

Ultrasonic tomography was used for the detection of degradation of transversal section of a beech, attacked by white decay. The image reconstruction of the transversal section of the tree in 2D was obtained with a software, which used the values of ultrasonic velocities measured at different heights from the ground. The attacked wood is characterised by low velocities. The measurements were performed with special transducers of 1 MHz, without damaging the bark of the tree. To improve the readings of the signals, a frequency analysis was performed. The ultrasonic tomographies were compared with the corresponding photographic images and with data obtained with a "Resistograph". A good agreement between ultrasonic tomographies and photographs was observed. The image resolution is between 4 and 5 cm. Presently, this is the best resolution ever obtained with an acoustic nondestructive method on a standing tree.