コンクリート中の鉄筋の渦流試験に関する基礎的研究

抄録

A eddy current method is effectively applied to detect surface opening cracks on metal materials and reinforcing steel bars buried in concrete structures. The measurement of the covering depth and diameter of bars using the instrument was already been reported. To the best of the authors knowledge, amplitude, phase and pattern on Lissajous' patterns obtained from the shapes of bars, adjacent bars and inclined bars have not been reported.
An attempt has therefore been made in this paper to find the correlation between rienforcing bars and Lissajous' patterns using eddy current testing. A probe coil was used, and bars were measured at 8kHz. The results obtained were as follow:
Lissajous' patterns were influenced by the bar materials, diameter and covering depth of the reinforcing bars. In detection of the deformed bars, Lissajous' patterns were shown as a loop. Even when the specimen made of the same material, the pattern in Lissajous' pattern changes depending upon the shape of specimen. In other words, while the pattern from a round bar presents a linear figure, the pattern from a flat bar does a curved figure. The smallest limit of distance between two bars recognizable was almost 80mm. This is nearly equal to coil diameter.