| 講演要旨(和文) | | 渦電流探傷法は，金属表面の検査に利用されており、傷により誘導される起電力の差異を傷の検知に用いる．実験により，検知信号は傷の深さに影響を受けることが示されている．しかし、現在の検査手法では欠陥の有無は分かるが，欠陥の形状や大きさ，位置を評価する方法が未だ確立されていないため、より高い精度の検査を行うためには，定量的な評価手法が必要である．構造を2次元に，電磁場を3次元に想定してMaxwell方程式を解く，2.5次元の周波数領域有限差分法を用いて誘導磁場の計算を行った．計算モデルには海水と鉄板の2層構造を仮定し、欠陥による欠陥の深さと幅による誘導磁場への影響を調べた．また，得られた波数領域の磁場は高速フーリエ逆変換により空間領域と時間領域に変換した．これにより、磁場強度の空間分布から欠陥の大きさが，時間領域の磁場の位相・振幅情報から欠陥位置の特定できることが示唆された． |
|
|
| | 講演要旨(英文) | | The applicability and feasibility of eddy current detection method for the measurement of wall thinning and surface crack of steel structure have been practically confirmed by field and laboratory experiments. Recently, we could roughly understand whether or not there is a defect. However, it is difficult to estimate the exact position, size and shape of that. For more accurate inspections, there has been a growing demand to quantitatively evaluate the defects. Therefore, we have developed a numerical simulator to consider whether we could develop the high accuracy eddy-current method. Eddy current method uses the information of excitation and induced magnetic field of conducting material. In order to calculate the induced magnetic field by the defects, we used a 2.5 dimensional finite-difference frequency domain technique (2.5D-FDFD) to solve Maxwell's equations numerically. In this technique, we assumed the two-dimensional structure and the three-dimensional electromagnetic field. We used two-layer structure consisting of seawater and steel plate containing defects. To estimate characteristic of the induced magnetic field, we simulated for a variety of defects and compared what effect appear. As a result, we could confirm the effect of surface defects of steel plate on receiving magnetic field. |
|
|
|
| |
|