DEPTH MEASUREMENT OF SHORT CRACKS WITH AN ACOUSTIC MICROSCOPE

The depth of short cracks (70-200 mum surface length) has been measure d within an acoustic microscope by utilizing the nondestructive time-o f-flight diffraction technique (TOFD). The depth measurements were fir st carried out in the transparent polymer polystyrene, thus allowing a comparison between the acoustical values and direct optical measureme nts: the agreement in the results was better than 95%. The depth of a 70 mum long crack in an aluminium alloy was then measured, demonstrati ng the application of the technique to metals.