Magnetic leakage field due to sub-surface defects in ferromagnetic specimens

Non-destructive Evaluation Method for Far-side Corrosion Type Flaws in Oil Storage Tank Bottom Floors Using the Magnetic Flux Leakage Technique

“…8 in the case of other lift-off values. Essentially, the flaw signal strength of ∆By is more sensitive to the thickness 7) . Thus, similar experiments for the specimen with a different thickness of 22 mm were performed.…”

“…The practical and usable analytical model for magnetic leakage field arising from a far-side flaw deals with the equivalent double current model 7) with the basic geometry shown in Fig. 9.…”

“…In this model, the influence of the boundary surface between the mediums I and II is taken into consideration by the mirror image method 10) . The magnetic leakage field at a point(x, y), H(Hx, Hy) arising from the far-side slot in the medium II uniformly magnetized can be described as the following forms 7) , (1) (2) where the equivalent current moment I2 is given by (3) (H0: Applied magnetic field strength, µ: Relative permeability of the specimen) and the mirror image factor m2 due to the presence of boundary between the mediums I and II is given by (4) The other geometrical parameters in the above equations are denoted in Fig. 9.…”

An Analytical Model for Prediction of Magnetic Flux Leakage from Surface Defects in Ferromagnetic Tubes

“…Förster [6] derived analytical expression for the induced surface charge density of surface defects with rectangular cross-sections by accounting the magnetic properties of the material and the applied magnetizing field strength. Zhang et al [7] proposed an analytical expression for two kinds of sub-surface defects, such as rectangular defects and elliptical defects, while considering the magnetic image effects from the spatial boundary and the defect boundary. Mandache and Clapham developed an analytical model based on dipolar magnetic charge to determine the larger length of surface breaking defects in ferromagnetic steel plate.…”

Model based defect detection for free stator of ultrasonic motor

“…Traditional non-destructive testing and evaluation (NDT and NDE) techniques include ultrasonic technology [1], acoustic emission [2], magnetic field analysis [3], penetrate testing [4], eddy current techniques [5], X-ray analysis [6], impact-echo testing [7], global structural response analysis [8] and imaging and usage of wavelet [9]. These methods propose many different algorithms for identifying and localizing the damage.…”