Evaluations of Grinding Surface in Ceramics :1st Report, Flaw Characterization using Ultrasonic Detector

Abstract

Nondestructive inspections of surface flaws of zirconia in grinding were investigated by using the available method submerged Rayleigh Wave detection. Shockwave transducers with two different characteristics of resonance frequency (15 MHz, 25 MHz) and focusing diameter (1 mm, 0.4 mm) were selected. Flaw calibrations of the system have been carried out for artificial flaws instead of real grinding flaws. The results obtained are itemized as follows. ( 1 ) The depth of the flaw represented by a scratch could be estimated quantitatively, and the detectable limited depth would be 2.5μm. ( 2 ) For small defects inspected by means of Vickers indentation, smaller focusing diameter of the transducer made for higher inspection sensitivity, still inspectability was explicitly decreased in comparison to the case of the scratch. ( 3 ) Compressive residual stresses remaining on the surface made for lower estimations of length. ( 4 )Real surface flaws caused by heavy grindings, as a factor of strength degradation, could easily be detected.