Finite element method and experimental investigation for hairline crack detection and characterization

Abstract

This paper reports on a quantitative technique based on the Magnetic Flux Leakage (MFL) method, for the detection and interpretation of the MFL signals caused by rectangular hairline cracks in pipeline structures. This was achieved through visualization and 3D imaging of the leakage field. This research is aimed at detecting hairline cracks caused by granular bond separation, which occurs during manufacturing, leaving pipelines and steel structures with miniature cracks. The investigation compared finite element numerical simulation with experimental data. The response of the MFL probe scanned above a hairline crack was first predicted using an optimized 3D finite element model. The MFL signals associated with both the surface and far-surface cracks were compared. The results show that the depth, width and length of the various hairline cracks can be estimated by using the distribution pattern and strength of the (Bx), (By) and (Bz) components of the MFL signals.