A novel methodology for condition assessment of wood poles using ultrasonic testing

This paper presents a new methodology based on theoretical, numerical, and experimental studies for condition assessment of wood poles using ultrasonic tests. Conventional ultrasonic testing of wood poles is based only on wave velocity measurements. Whereas in the new methodology, the condition assessment of a wood pole is represented by statistical quantities called dissimilarity indices; which are computed from ultrasonic measurements. These measurements include compressional wave velocities, transmission factors, and elastic moduli in the radial and tangential directions. The dissimilarity index is computed by comparing the measured parameters in a given pole section with the corresponding expected values and standard deviations for a sound pole. Four ultrasonic transmitters, with nominal frequency of 50 kHz, are evenly spaced around the circumference of the cross-section of the pole. For each transmitter location, an array of five receivers at different angles from the transmitter is used to measure the response of the wood pole to the ultrasonic excitation. Thus, a total of 14 independent raypaths across the section are defined for each test. Laboratory results show that for an area of decay of 30% of the cross-section, the wave velocity and the transmission factor decrease by 51% and 96%, respectively. Whereas the average elastic moduli in the radial and tangential directions are 80% and 43% smaller than the expected values for a sound pole. The observed deterioration pattern in a blind test is in perfect agreement with the predicted condition using the new methodology. (C) 2012 Elsevier Ltd. All rights reserved.