Small ferromagnetic resonators have been shown to provide effective electromagnetic detectors for surface flaws in magnetic and nonmagnetic metals. As such a resonator is moved along \u27the surface of a test piece it experiences a frequency shift when it passes over a flaw. lwo detection mechanisms are present: (1) an eddy current effect (2) a perturbation of the dc magnetic bias field used to tune the resonator. Results are given for experiments performed on machined slots in aluminum, titanium and steel and on tightly closed fatigue cracks in titanium. Results are also presented for some measurements on titanium aircraft fasteners
