DETECTING SMALL FATIGUE CRACKS BY ACOUSTIC MICROSCOPY

The acoustic microscope has shown great potential for use in fatigue e xperiments. A comparison between acoustic and optical images of fatigu ed Aluminium Lithium alloy specimens shows that the acoustic microscop e has the ability to monitor very small cracks. Since it is easy (a) t o find cracks and to locate their tips, (b) to detect damage ahead of a crack tip, (c) to distinguish cracks from slip bands and (d) to moni tor the coalescence of cracks, the acoustic microscope can now be used with increasing confidence for obtaining data and understanding the m echanisms involved in metal fatigue.