1991 Volume 40 Issue 454 Pages 818-824
Most of engineering ceramics are finished by grinding. Residual stresses and defects introduced into ceramics during grinding are two main factors which influence the strength of ground ceramics.
In the present study, the specimens of pressureless sintered silicon nitride were ground by a diamond wheel of #170/200 grain size number in the longitudinal direction, and the bending strength perpendicular to the grinding direction was determined by four point bending. The residual stress measured by the X-ray method was compression on the ground surface and the compression zone extended about 20μm. The bending strength of ground specimen was lower than that of buffed standard specimens. The size of grinding flaws was estimated from the bending strength and the residual stress distribution by using the effective crack length model. The estimated flaw depth of 45μm agreed with the crack measured on the edge surface of the specimen.
The bending strength of ground specimens was recovered by removing the surface layer by about 40μm. This recovery agreed with the model prediction based on the flaw depth estimated above.