Study On Theory And Application Method Of The Nondestructive Magnetism Testing For Steel Structures

With the booming development of the technology and society, the study and the use of large-span space structures and bridges turns out to be more and more prevalent in recent years. Whereas the large-span structure is complicated in stress state and constitution, and often affected by various factors in service such as, design load, construction, surroundings and human resources, the quality of the structural material changes, and damages occur, which all contributing to its deterioration. The internal force and distortion of the worse ones will probably beyond the permission, thus endangers normal use and safety of the overall structure. The study on the real time non-damage inspection of the large-span steel structure carries great weight both on theory and application.Based on a new point of view, this paper has studied the fundamental theory and engineering application technology. The summary is listed below:Magnetic domain structure of ferromagnetic is systemically analyzed basing on the theory of iron-magnetic. And we analyze the microcosmic mechanism of magnetic domain structure. According to the minimum principle in energy, we analyze the microcosmic mechanism of magnetic domain construction and the main factor that affect the shape, size and connecting of the magnetic domain etc. From the microcosmic mechanism of ferromagnetic, we analyze how stress influence the magnetic domain and magnetic domain wall, and discover the increase of stress energy and magnetism elasticity energy which destroy the balance of system energy make up the influence of magnetic domain structure, and set up basic disciplinarian between stress and characteristic of magnetism.With the use of the ANSYS program, the study compared the magnetic hysteretic curves of the stressed steel bars and those of the stress-free ones, evaluated the effect of the stress on the bars when they are saturated magnetized, and got the qualitative connections between the bar stresses and the parameters of magnetic characteristicThrough the researches above and the magnetization theory combined, this paper set up the fundamental relationship between the stress and magnetism conductance primarily. It also analyses the ferromagnetic materials using ANSYS program, educed the variation laws of the magnetic characteristic of ferromagnetic materials under the stress, which founded the theory bases for engineering application...