MAGNETIC FLUX LEAKAGE TESTING MECHANISM AND ITS APPLICATION
Magnetic flux leakage (MFL) testing is a nondestructive testing technique, which can be widely used in industries for in-service inspection of ferromagnetic materials, such as steel structure components, oil pipes etc. In this paper, at first the theoretical background of MFL is investigated, the distribution of the leakage magnetic flux is given by the figure and the tangential (Hx) and normal (Hy)components of the leakage field at a point (x, y) are also given by the equations. Then according to this, the fundamental principle of MFL testing is that, the permanent excitation circuit can be adopted to magnetize the axial excitation of the oil pipe; when the pipe passed through by the magnetizing field. Then the leakage field (caused by the local damage) can occur at the local region of the pipes surface once the local damage and the wall thickness damage exist in the oil pipe; or the change of MFL in the air gap (caused by the wall thickness damage) will take place between two poles of probe units; the adoption of Hall sensor arranged between two poles can test the variation of MFL, that is, the information concerning the damage of the pipe can be acquired. Four variation characteristics of testing signals corresponding to four different kinds of damages are presented, which are the oil pipe without damages, with the local damages, the wall thickness damages and both damages respectively. At last, an example of the oil pipe with the local damages and wall thickness damage is illustrated to verify the effectiveness of MFL.
magnetic fluz leakage nondestructive testing damage principle wall thickness Hall sensor
Er-Gang Xiong She-Liang Wang Jun-Feng Zhang Bo Li
College of Civil Engineering, Changan University, Xian 710061, P.R. China School of Civil Engineering, Xian University of Architecture & Technology, Xian 710055, P.R.China School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, P.R.China
国际会议
广州
英文
154-158
2009-11-28（万方平台首次上网日期，不代表论文的发表时间）