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

An estimating procedure for grinding-induced residual stress based on the indentation-fracture (IF) method was proposed by considering a nonuniform distribution of residual stress in the specimen depth. The proposed procedure was applied to gas pressure sintered and pressureless sintered silicon nitride ceramics, which were ground under different grinding conditions. The estimated residual stress was found to be compressive for both materials. The residual stress was dominantly affected by the grit size of the grinding wheel rather than the cutting depth. Although the dependency of the estimated residual stress on the grit size was different between the two materials, it was revealed that the estimated residual stress in both materials qualitatively corresponded with the stress measured by the x-ray diffraction method. In both materials, the bending strength was reasonably correlated with the estimated residual stress. It was elucidated that the proposed procedure was applicable to a relative evaluation of the grinding-induced residual stress in machined silicon nitride ceramics.