Optical method for fatigue crack detection

Abstract

A 1-D optical Fourier spectrum analyzer system is used to detect fatigue cracks as small as 0.5 microm in titanium test samples. Signatures obtained from scans of reflected laser light diffraction patterns show features linked to the presence of surface cracks. Signature characteristics are preserved without a need for critical focusing or optics-to-sample positioning. Analytic modeling of a crack surface profile is used to explain the primary cause of the observed signature properties.