Mechanics of Brittle Materials under Linear Temperature Increases

The results of work done to show the effects of surface roughness, residual stresses, strain rate, microstructure, alternating bending fatigue loading and a non-uniform stress field on the strength of small 2.-8.mm diameter alumina rods are given. The rods used in the work were characterized by determinations of grain size, porosity, hardness, surface roughness and damping factor. Static bend tests at room temperature are used to determine the Youngs modulus, the fracture stress, and the strain at fracture and to show the influence of specimen volume on the fracture stress. The effects of grain size and of porosity on these characteristics are shown. A new tensile test specimen is designed which achieves an almost uniform stress field in the test area. Some test results are given to show the validity of this procedure for brittle specimens.