Modeling The Perturbation Flux Density Of Current Flowing Around A Small Surface Crack As Detected By A Gmr Probe

Modeling was used to assist with the design of eddy current GMR probes for detecting small cracks. The approach was to (1) compute the eddy current flow generated by a planar coil and (2) then compute the perturbation flux density B' as the current flows around a surface crack. In Step 1, the Dodd and Deeds analytic solution was adapted to the geometry of an N-turn horizontal coil. The maximum induced current density from Step 1 was then used to compute B' for a crack with half-penny cross-section and oblate spheroidal 3D shape.