Experimental study of sizing of surface cracks by using leakage magnetic field and Hall element probe

Experiments are performed for Hall element probe measurement of the distribution of the Hall voltage induced by the leakage magnetic field in the vicinity of a crack. The Hall voltages are measured along a line which is parallel to the direction of the applied field and is projected orthogonally at the centre of the crack The investigated cracks have different widths and depths and are cut mechanically in SS400 steel specimens. The width and the depth of the crack, as well as the surface density of magnetic charge at the crack walls are determined by using the measured Hall voltage data and an modified improved method for crack sizing. The computed results show that the employed mathematical model describes reasonably well the values of both the z-component of the intensity of the leakage magnetic field and the measured Hall voltage.