VIBRATION TECHNIQUE FOR ROT DETECTION IN WOOD POLES AND TREES

摘要

1393857 Sonic detection of decay in wood FANNER MFG CO PTY Ltd and A D SHAW 22 March 1973 [11 April 1972] 13768/73 Heading H4D A wooden object such as a pole is tested for internal decay by applying a vibrational force to the object at a selected point, measuring the strength of emergent energy from the object at several points spaced along the length of the object and comparing the measurements to determine the pattern of energy strength variation with distance along the object. In the embodiment described the vibrational force is applied by a transducer driven with a square-wave signal whose frequency is adjusted for resonance within the pole. A piezoelectric pick-up is fixed in turn to spikes driven into the pole at measurement points spaced along a line diametrically opposite the vibrating transducer, or respective pick-ups may be fixed to the spikes. The pick-up signal feeds a meter calibrated in RMS velocity. A sound pole is stated to result in a general decrease in measured energy with increasing distance from the point of application of the force, whereas for a decayed pole the measurements at points removed from the point of application may be some 50% greater than a measurement adjacent the point of application.