Fatigue crack initiation and growth in riveted specimens: an optical and acoustic microscopic study

摘要

While optical microscopy on riveted specimens reveals only surface cracks, the acoustic C-scan images reveal subsurface and buried cracks emerging to the surface. This is of particular interest for fatigue cracks that initiate below the outer surface such as with chamfered riveted panels. Fatigue crack initiation and growth in riveted panels of Alclad 2024-T3 were characterized using optical microscopy and scanning acoustic microscopy to obtain C-scan images. The C-scan images were obtained using a focused transducer with a center frequency of ca 50 MHz, and the peak value of the back surface echo of the plate with countersunk rivet holes was recorded in the C-scan images. Data on the initiation and development of fatigue cracks at rivets in riveted Alclad 2024-T3 are given.