Theoretical Model of Self-Magnetic Flux Leakage and Its Application in Estimating the Depth Direction of a Fatigue Crack

In this study, theoretical models were proposed to explain the changes in self-magnetic flux density (SMFD) due fatigue cracks presence and absence of external magnetic fields. Three proposed: rotation domain model (RDM), concentration (CDM), vertical (VDM), considering deformation non-deformation possibilities. To prove model, with different depth angles fabricated through testing EDM processing on CT specimens. addition, tunnel magnetoresistance (TMR) sensors used evaluate 3-axis distribution SMFD. Comparing simulation experimental results, similar tendencies occurrence angle their effect SMFD observed. According RDM, occurs direction crack length (y-direction), while CDM explains that does not occur if is a perpendicular surface. VDM shows SMFDs (x-direction) specimen surface (z-direction). Interestingly, these trends agree which confirms validity thus can be estimate crack.