Perturbed Magnetic Fields Induced By Mechanical Stress In An Infinite Plate With A Crack

Ferromagnetic materials are widely applied into large engineering equipments of the country and new technology areas in modern industry. As the unique early diagnostic nondestructive testing method for ferromagnetic components, the development of magnetism based non-destructive test (NDT) technologies calls for investigation of quantitative relation between deformation, stress, damage or fracture of structures and their induced magnetic quantities. Following the problem"the perturbed field of a half-plane magnetism structure caused by a point force"and"the perturbed magnetic fields of infinite plane with a circle hole", this article have a further study on the problem"the perturbed magnetic fields of plane crack". All these results and conclusions of the research provide NDT with mechanism basis.Based on the linearized magnetoelastic theory and the complex function theory, following the Fourier transform method, an infinite ferromagnetic elastic plate containing a central crack was considered under the case of the Earth's magnetic field, and the perturbed magnetic fields generated by structural deformation under an external magnetic field was analyzed. The results show that the perturbed magnetic field intensity component is proportional to the applied tensile stress. The perturbed magnetic field induced by mechanical stress is dominated by the displacement gradient on the boundary of the magnetoelastic solid. As for the magnetic intensity components of the perturbed magnetic field close to the crack, the tangent shows anti-symmetric distribution along the crack and inverses its direction sharply at the two faces of the crack, while the normal shows symmetric distribution along the crack and presents singular points at the crack tips. They both take on stronger local feature.