A Simple Magnetostatic Sensing Method for Assessing the Local Hysteresis Properties in Ferromagnetic Sheet Materials

Global hysteretic properties of electrical steels can be measured using ring or strip samples, while the assessment of the local hysteretic properties is a much more difficult task since the measurement method needs to be very sensitive. This paper presents a new method wherein the intensity and spatial distribution of the magnetic field, arising from large gradients in the local magnetization, are measured. These large gradients are induced by the passage of a test sample through the steep gradient field of a small, proximate permanent magnet. Magnetic field measurements during both directions of motion provide information indicative of the hysteresis properties. We theoretically analyze these measurements and show experimentally that the measurements correlate well with all the significant aspects of conventional hysteresis loops. The results given in this paper are qualitative, and the method is both by its simplicity and its sensitivity to important hysteresis features a powerful means of magnetic nondestructive evaluation. [Read More]