Ball bearing inspection with an acoustic microscope

The authors have developed an amplitude- and phase-measuring acoustic microscope to detect surface defects a few micrometers deep in ceramic ball bearings. The system is capable of measuring phase variation on the order of 1°. The phase detection capability is necessary to detect shallow surface depressions when no crack is present at the bottom of the depression, and the detection of the defect, through V(z) variation, requires operating the system in the gigahertz frequency range. A C-scan system is operational and allows the detection of fissures and gouges, even when shallow. A novel B-scan system has been designed in order to detect smaller cracks and to get full coverage of the bearings