MAGNETIC LEAKAGE FIELD DUE TO SUBSURFACE DEFECTS IN FERROMAGNETIC SPECIMENS

This paper describes analytical expressions for the magnetic leakage f ield of two types of internal defects: two dimensional rectangular and elliptical defects as functions of the applied magnetic field strengt h, the defect size and the distance below the surface. In this study, the magnetic image effects from the spatial boundary and the defect bo undary are taken into consideration. That is, the leakage field of rec tangular-like defects or elliptically shaped defects 'below the surfac e' are derived by using the modified dipole model and image theory. Th e profiles and strengths of leakage fields calculated from the propose d analytical forms are presented under various conditions and compared with experimentally measured ones.