EVALUATION OF MATERIAL DEGRADATIONS BY MAGNETIC SENSORS

摘要

Degradations of iron based materials of A533B and SUS304 have been investigated on magnetic properties in a stress range up to 670 MPa, by using a magnetic flux sensor of GaAs Hall element, a pickup coil for magnetic noise detections and by observing X-ray diffraction. Magnetic Leakage flux was observed to detect the remanence changes with locally different residual stresses. Magnetic Barkhausen noises were also observed at an optimum field sweeping condition of 140kA/ms at which 2-D fractal dimension was found at 1.6+-0.3. In this condition, average magnetic fields for discontinuous magnetizations were evaluated as a function of the residual strains up to 8 %. In this study, we found that the residual stresses estimated by the leakage fluxes and by the magnetic noises were limited less than 100μm from the surface.