Magnetic Recording Method (MRM) for Nondestructive Evaluation of Ferromagnetic Materials

Abstract

This paper proposes and experimentally investigates a novel nondestructive testing method for ferromagnetic elements monitoring, the Magnetic Recording Method (MRM). In this method, the inspected element must be magnetized in a strictly defined manner before operation. This can be achieved using an array of permanent magnets arranged to produce a quasi-sinusoidal magnetization path. The magnetic field caused by the original residual magnetization of the element is measured and stored for future reference. After the operation or loading, the magnetic field measurement is repeated. Analysis of relative changes in the magnetic field (for selected components) allows identifying applied stress. The proposed research methodology aims to provide information on the steel structure condition unambiguously and accurately. An interpretation of the results without referring to the original magnetization is also possible but could be less accurate. The method can be used as a standard technique for NDT (Non-Destructive Testing) or in structural health monitoring (SHM) systems.

Nondestructive Evaluation of Tensile Stress-loaded GFRPs Using the Magnetic Recording Method

“… The quasi-sinusoidal magnetization patterns recorded on the strip sensors vary their characteristic parameters with the successively strained samples. In contrast with the study results for the metal samples [ 20 , 21 ], only amplitude is utilizable for the unequivocal condition assessment of the GFRPs. The changes in the frequency are barely visible and thus cannot be used as a criterion.…”

“…This issue will be investigated in the future works. To sum up, the difference is that in the case of ferromagnetic structures [ 20 , 21 ], no additional tape is necessary because the material itself can be used as a sensor element. Concerning non-ferromagnetic structures, it is necessary to connect the sensor with a tape made of ferromagnetic material to the tested structure.…”

“…In the experiments presented below, we demonstrate that the MRM method (Magnetic Recording Method) described elsewhere [ 20 , 21 ] can be employed for the periodic monitoring of maximum deformations in structures made from nonmagnetic composite materials. The approach presented here, elaborated upon in subsequent paragraphs, combines the concept of a thin sensor (placed on the surface of the deforming element)—that is derived from resistive tensiometry—with the utilization of deformation-dependent permanent changes in the magnetization state of the sensor, which constitutes the essence of the MRM.…”

Micro Non-Destructive Testing and Evaluation

“…At the same time, optical methods are being perfected to tackle challenging problems at the micro and macro scales [ 9 , 10 ]. Moreover, magnetic methods are still very powerful for detecting defects in several materials and components [ 11 , 12 , 13 , 14 ], especially when talking about large components. Indeed, such methods are being further developed and extended to new materials such as concrete [ 15 ] and to applications such as residual stress determination [ 16 ].…”

Distribution of Magnetic Flux Density under Stress and Its Application in Nondestructive Testing

“…[22,23]. Moreover, the MMM method offers distinctive features; among which, the simplicity of the operating principle, the low cost of the measuring equipment, the need for no external sources of the magnetic field, and no treatment of the surface of the structures nor the premagnetization or demagnetization of the target specimens [5,[24][25][26].…”