Nondestructive evaluations of iron-based material by magnetic diagnosis tools

Abstract

Magnetic properties have been investigated for a diagnosis tool of iron-based material of A533B, SUS304 in an applied stress range up to 640 MPa, by using a leakage magnetic flux sensor of GaAs Hall element, a magnetic noise pickup coil and by observing X-ray diffraction. The magnetic Barkhausen jumps were observed at an optimum field sweeping condition of 140kA/ms at which 2-D fractal dimension was found at 1.6\pm 0.3 . In this condition, averaged magnetic fields for discontinuous magnetizations were evaluated as a monotonic increasing parameter with increasing residual stresses, insensitively to the geometrical configuration between the sensing pick-up coil and the yoke in a wide residual stress range between 0.1 and 8%. stresses in the L\"uders band were found tilted around 35 degrees. The surface leakage flux and the magnetic noise observations in this study were found detectable for the material surface less than about 50 \mu m.