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

为探讨用超声波传播速度和阻抗测量方法对腐朽木材和白蚁蛀坏木材进行诊断的可能性，采用直接透射法测量木材的超声波传播速度，发现在木材内部缺陷约10%处，超声波传播速度突然下降。相反，通过非直接传输方法的测量未能检测到内部缺陷。结果表明，从木材的一侧测量超声波传播速度并不足以检测木材的劣化缺陷。在使用阻抗测量的情况下，人工钻孔不同直径的试样，并在水中浸泡，以制备不同含水率水平的木材。为了探讨该方法应用于劣化木材检测的可能性，仅对试件的一侧进行了阻抗测量。结果表明，试样内部的缺陷对阻抗的频率特性有较大影响，特别是在50Hz处，同时还研究了金属连接对阻抗测量的影响，发现金属电极附近存在金属时，金属电极的电导率对阻抗测量有影响。

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.