Highly Sensitive Detection of Defects in Piping Using Multireflecting Guided Wave Energy Trapping Method

A multireflecting guided wave energy trapping (MGET) method has been developed for the highly sensitive detection of defects in a pipe using a guided wave. The MGET method enhances the amplitude of a defect signal using two wave reflectors. In the MGET method, the two reflectors are set at both ends of a region of piping to be inspected, and a guided wave is generated, which propagates in the region of inspection. With this setup, multireflection can be observed between the two reflectors. If a defect exists in the region, the amplitude of the defect signal increases owing to the increase in the number of reflections at the reflectors because n combinations of multiple propagation paths having the same path length exist in the defect signal after n reflections. Details of the principle of the MGET method and its experimental verification are reported. The sensitivity of the MGET method is about 10 times higher than that of the conventional guided wave method. The efficiency of the method is quantitatively discussed by considering a simple mathematical model together with the experimental results.