Consideration of Magnetizer for Magnetic Particle Testing of Omnidirectional Crack in 3D Shape Test Object

Abstract

Mechanical parts, plants and cross-linkages inspected with MT are typically complex 3D shapes. In the complex 3D shape portion, because a magnetizer often cannot be configured to the inspection portion and the test object cannot be appropriately magnetized, there is a possibility of overlooking a crack in such an instance. Thus, MT system development that was successfully able to detect omnidirectional cracks in 3D shape portions was considered in this study's trials. Two magnetizers were hence arranged face-to-face, and the magnetization of omnidirectional scenarios for all surfaces of 3D shape test object (arranged in between both magnetizers) was evaluated.

Consideration of multi‐coil type magnetization system for magnetic particle testing of omnidirectional crack in all surfaces of 3D shape test object

“…Furthermore, we considered a magnetization system with two three-pole coil type magnetizers arranged opposite to each other so as to generate rotating field in 3D space. 9 As a result, we confirmed that the whole surface of a test object can be omnidirectionally magnetized by rotating one of the opposing magnetizers. At the same time, it became clear that some problems arise unless a magnetizer is rotated during testing by means of a mechanical drive; specifically, rotating field is not obtained, or X, Y, Z components of rotating field are nonuniform.…”

“…Furthermore, we considered a magnetization system with two three‐pole coil type magnetizers arranged opposite to each other so as to generate rotating field in 3D space . As a result, we confirmed that the whole surface of a test object can be omnidirectionally magnetized by rotating one of the opposing magnetizers.…”

“…Magnetic pole arrangement of two opposing magnetizers as seen from the midpoint is illustrated in Figures and . With the previously developed three‐pole coil type magnetizer shown in Figure , one of the opposing magnetizers is mechanically rotated so as to shift relative positions of respective poles; as a result, rotating magnetic field is generated in 3D space . In so doing, however, a mechanism is required to rapidly rotate the magnetizer while iron powder is applied in MT; as a result, the magnetization system becomes complicated, while testing safety becomes problematic.…”

“…With the previously developed three-pole coil type magnetizer shown in Figure 3, one of the opposing magnetizers is mechanically rotated so as to shift relative positions of respective poles; as a result, rotating magnetic field is generated in 3D space. 9 In so doing, however, a mechanism is required to rapidly rotate the magnetizer while iron powder is applied in MT; as a result, the magnetization system becomes complicated, while testing safety becomes problematic. In addition, with three magnetic poles, distribution of rotating flux density was confirmed to be nonuniform for some locations of test object and directions of magnetization.…”

“…In this study, we examined generation of uniform rotating magnetic field in 3D space using multi-coil type magnetizers in order to implement efficient and highly reliable MT for 3D shape test objects. 10 We conducted numerical analysis by finite element method to evaluate magnetic flux density distribution in each surface of a 3D test object placed between two magnetizers, and to confirm effectiveness of the magnetization method. In addition, we evaluated optimal size relationship between magnetizers and test object, and examined magnetization conditions; thus obtained results are reported below.…”