2001 年 37 巻 6 号 p. 484-492
The non-destrutive inspection of cracks in concrete structures has been attempted using electromagnetic wave, infrared ray, sound wave and so on. Inspection using electromagnetic wave sometimes did not detect cracks, since concrete structures contain iron bars. The infrared ray was hard to use in tunnels, because difference in temperature was hardly observed before and behind the cracks. It was also difficult to detect cracks using an ultrasonic wave because of the reflected waves strictly superposing on each other.
This paper proposes two non-destructive inspection methods using ultrasonic wave which detect the cracks in concrete structures. One is based on a multi-reflected-wave model, the other a stationary wave model. The methods enable not only detection of the cracks but also an accurate measurement of their positions. These methods should be selected depending on the sensor to be used and the object to which the inspection is applied.