Residual Leakage Field Modeling

Abstract

Residual leakage fields are set up around defects in ferromagnetic materials after the active source of d. c. excitation has been removed [1]. Defect detection and characterization then occur by using any flux density sensitive transducer such as magnetic particles, magnetic tape, a moving coil or a Hall element [2]. Past analytical attempts at modeling these phenomena have largely been based on representing simple defect shapes by an equivalent dipole or magnetic charge distribution [3]. In order to examine the effects of realistic defect shapes and material B/H properties, finite element analysis techniques have been used [4,5] to model both active and residual leakage field effects. This paper discusses alternative B/H representations and their impact on the numerical modeling of defect residual leakage fields.