Bending experimental study of structural steel beam on magnetic field gradient based on modified Jiles-Atherton model

摘要

Previous research of metal magnetic memory (MMM) primarily focused on uniaxial stress-magnetic field behaviors and the judgment criterion of stress concentration zone mainly depended on the tangential and normal component of MMM signals. Magnetic field gradient was only mentioned as an auxiliary condition. In this paper, the variation characteristic of magnetic field gradient under bending load was investigated. Four-point bending tests of Q235B I-steel beams were carried out. The results show that all magnetic field gradient curves are centrosymmetric about midpoint of measurement line. The position of concentrated load can be preliminarily predicted by the mutational point of magnetic field gradient slope on the flange and accurately judged by the zero-crossing position of magnetic field gradient on the web. Whether a specimen is under eccentric compression or not, can be determined by comparing average characteristic parameter values on both sides of specimen. The variation law of magnetic field gradient on both the flange and web can be well explained by the modified Jiles-Atherton model, which is constructed by replacing stress sigma with equivalent stress sigma(eq). The calculated results are in good agreement with measured data.