Development of a NDI system using the megneto-optical method (preliminary report-development of the magneto-optical inspection system)

摘要

Combined use of a magneto-optical sensor (MO sensor) and leakage magnetic flux (LMF) to test a material has many advantages like non-contact and real time inspection, elimination of electrical noise, and high spatial resolution. A crack can bevisualized from the high contrast bright and dark areas of the MO sensor as two kinds of large magnetic domains appear around the crack when the analyzer is fixed. If the light spot is larger than these domains, we can obtain information of the LMF on the area of the light spot from the reflected light intensity. This intensity is related to the strength of the external magnetic field.This paper describes a novel NDI system using the principles of the MO sensor and LMF. The main characteristic of the system is that image data and LMF information can be obtained at the same time. It is possible to carry out rapid and accurate inspection of cracks from the intensity of the reflected light, and to estimate the crack size more effectively than by the existing methods with their diverse data. The advantages of this NDI system are demonstrated using two specimens.