Modelling and experimental investigation of magnetic flux leakage distribution for hairline crack detection and characterization

The Magnetic Flux Leakage (MFL) method is a well-established branch of electromagnetic Non-Destructive Evaluation (NDE) extensively used to assess the physical condition of ferromagnetic structures. The main research objective of this research work presented in this thesis is the detection and characterization of the MFL distribution caused by rectangular surface and far-surface hairline cracks. It looks at the use of the direct current and pulsed current techniques to investigate the presence of hairline cracks in ferromagnetic steel pipelines, by comparing the Finite Element Modelling (FEM) technique with practical experiments. First, the expected response of an MFL probe scanned across the area of a hairline crack was predicted using the 3D FEM numerical simulation technique. The axial magnetization technique is employed and the characteristics of the surface and far-surface leakage field profile