Detection of a Rectangular Crack in Martensitic Stainless Steel Using a Magnetoreactance Sensing System

A magnetic flux leakage testing system based on the magnetoreactance effect was used to detect a rectangular crack in martensitic stainless steel. Detection of the transverse rectangular crack was achieved by probing the magnetic leakage fields from the crack using a magnetoreactance sensing system. The system was able to detect a small crack with a width of 1 mm and a depth of 1.5 mm even at a low frequency of 100 kHz. The influences of exciting-current intensity, sensing direction, and testing distance on the detection sensitivity were measured. As expected, the magnetic leakage signal strength increased with increasing exciting-current intensity. The magnetoreactance sensor was more sensitive to the magnetic leakage fields when it was perpendicular to the crack.