Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama 700-8530, Japan.
Department of Civil, Environmental and Applied System Engineering, Faculty of Environmental and Urban Engineering, Kansai University, 3-3-35 Yamate, Suita 564-8680, Japan.
Sensors (Basel). 2022 Dec 29;23(1):380. doi: 10.3390/s23010380.
Infrastructure facilities that were built approximately half a century ago have rapidly aged. Steel sheet piles, the inspection object in this study, are severely corroded, resulting in cave-in damages at wharfs. To solve such a problem, non-destructive inspection techniques are required. We previously demonstrated plate thickness measurement using extremely low-frequency eddy current testing. However, when the steel sheet piles are located in water, shellfish adhere to their surface, causing a lift-off of several tens of millimeters. Therefore, this large lift-off hinders the thickness measurement owing to fluctuations of magnetic signals. In this study, sensor probes with different coil diameters were prototyped and the optimum size for measuring steel sheet piles at high lift-off was investigated. Using the probes, the magnetic field was applied with a lift-off range from 0 to 80 mm, and the intensity and phase of the detected magnetic field were analyzed. Subsequently, by increasing the probe diameter, a good sensitivity was obtained for the thickness estimation with a lift-off of up to 60 mm. Moreover, these probes were used to measure the thickness of actual steel sheet piles, and measurements were successfully obtained at a high lift-off.
大约半个世纪前建造的基础设施迅速老化。本研究的检测对象钢板桩严重腐蚀，导致码头发生塌方损坏。为了解决这个问题，需要采用非破坏性检测技术。我们之前已经展示了使用极低频涡流检测进行板厚测量。然而，当钢板桩位于水中时，贝类会附着在其表面，导致几十毫米的提离。因此，由于磁信号的波动，这种大的提离会阻碍厚度测量。在本研究中，我们制作了具有不同线圈直径的传感器探头，并研究了测量高提离钢板桩的最佳尺寸。使用这些探头，在 0 到 80 毫米的提离范围内施加磁场，并分析检测到的磁场的强度和相位。随后，通过增加探头直径，在高达 60 毫米的提离下，厚度估计获得了良好的灵敏度。此外，这些探头还用于测量实际钢板桩的厚度，并在高提离下成功获得了测量结果。
