Crack penetration layer in a single point diamond grinding of sintered silicon nitride

The purpose of this paper is to get fundamental informations for estimating depth of crack layer under ground surface of sintered silicon nitride which is one of typical engineering ceramics. This paper proposes a estimation method of the depth of crack layer generated in a transitional cutting process, which is a fundamental phenomenon in grinding process, with a single point diamond, as a function of normal cutting force, generated groove depth, Poisson's ratio, fracture toughness and a characteristic parameter of affected structure zone based on linear fracture mechanics. And the rule of the characteristic parameter, which is decided by interference type of cutting edge, is experimentally found out. The characteristic parameter decreases with increasing groove depth in conformity with the exponential function determined by indentation characteristic and nose radius of cutting edge in spherical interference region, and it turns to constant at critical interference depth according to vertical angle of cutting edge. By applying the method in each cutting phenomenon of a cutting edge in grinding of silicon nitride, the depth of remained crack layer in a grinding process can be estimated and grinding conditions or stock removal in successive grinding process can reasonably be determined.