Leakage Magnetic Field And Its Applications, Non-destructive Testing Flaw Detection

In the light of the status that there are caustic faults in the oil well tubing and there are not effective inspections, in this paper the plane roundness fault model of the is studied, and the magnetic leakage flux distributing model at the direction of the normal of the roundness fault is proposed. Based on the analysis about the test requirements and the saturated magnetization of the armor plate, the excitation magnetic circuit satisfying the testing condition and a validation system are designed. Because the geometric, of the magnetic leakage at the direction of the normal of the roundness fault has the feature of two peaks: a positive and a negative, using the linear regression and the software Matlab, two regression equation are proposed: one is about the peak value of the magnetic leakage and the diameter and depth of the roundness fault; the other is the distance between the two peaks and the diameter of the roundness fault. The result of the validation system proves that the two equations are valid, and an applied method using for quantificationally inspecting the roundness faults is proposed according to the two equations.