Research of non-destructive inspection methods for timber with ultrasonic propagation velocity and impedance measurement

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An ultrasonic propagation velocity measurement and an impedance measurement were applied to decayed timbers or timber attacked by termites to investigate possibilities of these measurements for diagnosis of those deterioration.The ultrasonic pulse velocity decreased suddenly at the point that internal deficiency was about 10% when it was measured by a direct transmission method. Contrary, measurement by a non-direct transmission method failed to detect internal deficiency. The result indicated that the ultrasonic propagation velocity measurement from one-side of the specimen is not insufficient to detect lacks of deterioration in timberIn the case of using the impedance measurement, specimens were artificially holed with various diameters and soaked in water for preparing the timber with different moisture content level. The specimens were subjected to the impedance measurement from only the one-side of specimens to investigate the possibility of the method to be applied for an inspection of deteriorated timber. The result indicated that the lacks inside of specimen affected the frequency dependence patterns of impedance at the frequency of 50Hz, especially.Effect of connecting metals on the impedance measurement was also investigated and found that in the case that there are metals nearby the electrode conductivity of the metals affects on the measurement.