Effect of Grinding Residual Stress on Bending Strength of Ceramics

Abstract

The X-ray diffraction method was used to measure the residual stress on and beneath the surfaces of sintered alumina and silicon nitride ground with diamond wheels of #200 and #80 grain-size numbers. The residual stress measured on the ground surface was the largest compression on the surface of silicon nitride ground with a #80 diamond wheel. The depth of the compression zone from the surface was between 20 and 30μm.
The compressive residual stress due to grinding with a #200 diamond wheel improved the bending strength of ceramics. On the other hand, gringing with #80 diamond wheel often introduced flaws into ceramics, reducing the benefitical effect of the compressive residual stress. The effect of gringing residual stress on the relation between the bending strength and the defect size was discussed on the basis of fracture mechanics. A model was proposed to assess the effects of the residual stress and the material defect on the bending strength of ceramics.