Grinding-induced residual stress estimation by indentation-fracture methodin ground silicon nitrides

An estimating procedure for grinding-induced residual stress based on the i ndentation-fracture (IF) method was proposed by considering a nonuniform di stribution of residual stress in the specimen depth. The proposed procedure was applied to gas pressure sintered and pressureless sintered silicon nit ride ceramics, which were ground under different grinding conditions. The e stimated residual stress was found to be compressive for both materials. Th e residual stress was dominantly affected by the grit size of the grinding wheel rather than the cutting depth. Although the dependency of the estimat ed residual stress on the grit size was different between the two materials , it was revealed that the estimated residual stress in both materials qual itatively corresponded with the stress measured by the x-ray diffraction me thod. In both materials, the bending strength was reasonably correlated wit h the estimated residual stress. It was elucidated that the proposed proced ure was applicable to a relative evaluation of the grinding-induced residua l stress in machined silicon nitride ceramics.