Effect of Stress Concentration on the Bending Fracture Stress of Polycrystalline Alumina.

The effect of the stress concentration on the bending fracture stress has been investigated with circular notched round bar specimens under 4-point-bending loading. Polycrystalline alumina of a purity of 99. 5% Al//2O//3 varied in the ranges of grain size 1 to 65 mu m and porosity 2 to 33% has been applied. All investigations had been made at room temperature within normal environment. The results can be explained qualitatively by the rho -theory of Neuber and the statistical theory of Weibull. The rho -theory represents a useful approximation only for stress concentration within the range of large porosity and grain size.