qbJL±g³qV~±j\Êjóªè D. Amutha RaniEãûCiE½öìãiERàKFE_èCO YAEZp¤ViW[}eA¤Z^[C4638687 ¼Ã®sçRaeºui¡P´22681 In this paper, surface stresses are estimated by means of sliding scratch and spherical indentation tests to understand the surface fracture of alumina specimens with respect to grain size. The critical load for materi al failure and the friction coecient determined from scratch test are used for the estimation of surface stresses by niteelement analysis. In spherical indentation test, the size

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... f the Hertz crack measured is proportional to the surface stress on cracking and hence the crack diameter can indicate the tensile stress on the surface of the specimen. Also, the radial tensile stress values are estimated using the critical load eval uated from the formation of circular ring crack. A similar trend of tensile stress degradation with increasing grain size is observed in both surface tests.