RELATIONSHIP BETWEEN GRINDING MECHANISM E ND RESIDUAL CRACKS IN SINGLE-POINT GRINDING TEST OF ALUMINA CERAMICS WITH DIFFERENT GRAIN SIZES

In order to discuss the effect of grain size on material removal mecha nism and crack type beneath the groove, the single point grinding test s of alumina ceramics with three kinds of grain sizes were carried out by use of conical diamond. The specimens of dense alumina ceramics we re prepared by hot isostatic pressing (HIP) after presintering at vari ous temperatures. The state of grooves were observed by SEM, and grind ing force were measured by dynamometer. Main conclusions are obtained as follows: (1) Material removal mechanism changed from pseudo-plastic how type to brittle fracture type with increase in depth of cut. The depth of cut, which varied from pseudo-plastic dow type to brittle fra cture type, was increased with decrease in grain size. (2) The crack: type varied from lateral and median type to microcrack with increase i n grain size. (3) The normal grinding force was influenced by material removal mechanism of alumina ceramics.