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

Abstract

Carbon steels are commonly used in railroad, shipment, building, and bridge construction. They provide excellent ductility and toughness when exposed to external stresses. They are able to resist stresses and strains effectively, and guarantee safe operation of the devices through nondestructive testing (NDT). The magnetic metal memory (MMM) can be used as an NDT method to measure the residual stress. The ability of carbon steel to produce a magnetic memory effect under stress is explored here, and enables the magnetic flux density to be analyzed. The relationship between stress and magnetic flux density has not been fully presented until now. The purpose of this paper is to assess the relationship between stress distribution and the magnetic flux density measured by the experiment. For this, an experimental method for examining a carbon steel plate (SA 106), based on the four-point loading test, was used. The effect of stresses resulting from the applied loads on the response of the experimented SA 106 specimen was examined. A three directional tunnel magnetoresistance (TMR) measurement system was used to collect the triaxial magnetic flux density distribution in the SA 106 specimen. In addition, finite element method (FEM) analyses were performed, and provided information on the direction and distribution of the stress over the studied SA 106 specimen. Indeed, a correlation was derived by comparing the stress analysis by FEM and the measured triaxial magnetic flux density.

Using Metal Magnetic Memory to Evaluate the Effect of Welding Method and Weld Temperature on Magnetic Field Strength in Structural Steel

“…Previous studies have indicated that residual stresses and stress concentrations can have an impact on mechanical properties, erosion resistance, dimensional precision, fatigue damage resistance, and structural life [8,10]. In papers [11,12], it was proven that residual stress affects the magnetic properties of ferromagnetic materials.…”

Theoretical Model of Self-Magnetic Flux Leakage and Its Application in Estimating the Depth Direction of a Fatigue Crack

“…However, it is difficult to apply it to very narrow cracks, such as fatigue cracks. In addition, the change in the magnetic flux density (MFD) with the change in stress remains unclear, where conventional studies on MMM states that the magnetic flux density changes when stress changes or fatigue cracks occur, even when no external magnetic field is applied [32][33][34][35][36]. Therefore, it is uncoherent to use a magnetic dipole that assumes that an external magnetic field is applied which make the specimen in a magnetized state.…”

“…This is because of the magnetic field distribution in the stress region, which is related to the magnetic field distribution generated in the sample after the stress is released, and the pattern was confirmed experimentally. On the other hand, Berkache et al [33] compared the stress analysis using the finite element method (FEM), measured the 3-axial magnetic flux density distribution, and examined the correlation. The stress distribution, which uses the parameter of the 3-axial magnetic flux density, was set as a qualitative relationship in the third polynomial formula.…”