Modeling of Characteristics of Magneto-Optical Sensor Using FEM and Dipole Model for Nondestructive Evaluation

Abstract

The magneto-optical nondestructive inspection system (hereafter refer to as RMO system) using magneto-optical sensor (hereafter refer to as MO sensor) offers the benefits of providing image data and LMF information at the same time. Therefore this system makes it possible to carry out remote and high speed inspection of cracks from the intensity of the reflected light and to estimate the shape of a crack more effectively than by already existing methods. In other words, the shape of crack could be evaluated using image data, and crack depth can be determined by calculating the intensity of reflected light. The purposes of this study were to confirm the vertical components of leakage magnetic flux from a crack using RMO system and to verify the effects of MO sensor using the finite element method and dipole model calculation. The effectiveness of these analysis methods was compared with experiments using a RMO system and several types and sizes of the crack on plate specimens. The volume of a crack could be estimated using the optical intensity regardless of the shape of cracks.

Hall sensor array based validation of estimation of crack size in metals using magnetic dipole models

“…The Hall element sensors were arrayed in a 2-D plane with high spatial resolution that can detect cracks at high speed. Several theoretical analyses have also been conducted over the years such as finite element method (FEM) [12][13][14][15], analytical modeling of PEC based on time-harmonic problems [16,17], and extended truncated region eigenfunction expansion (ETREE) [18]. These methods produce results that are in have good agreement with the experimental results.…”

A Study of Magnetic Charge per Unit Area of Dipole Model for the NDE

“…The specimen was magnetized by using a yoke type magnetizer, which had a 250mm of poles interval and 4,000 turns of coil at 0.34A input current. Also, the differential magnetic field to the magnetization direction, ∂H Z /∂x, was used in the experiment and analysis results because the ∂H Z /∂x data can eliminate the bad influence of the magnetic field from the poles of the magnetizer and the leaked magnetic field from the crack can be extracted efficiently by using ∂H Z /∂x [7][8][9].…”

Development of Signal Processing Circuit of a Magnetic Camera for the NDT of a Paramagnetic Material

“…Also, the quantitative distribution of the electromagnetic field is important in the evaluation of the position, shape and size of a crack in the NDT applying an electromagnetic method. Conversely, an NDT technique using Faraday effects was introduced to inspect cracks on paramagnetic materials such as aluminum alloy and stainless steel, which are commonly used in airplanes and atomic power generation plants [1][2][3][4][5]. The Faraday effect is a magneto-optical effect, in which the plane of the polarized light beam is rotated when light passes through a ferromagnetic material such as a bismuth doped iron garnet film.…”