抄録
Uniaxial and equibiaxial strengths of soda-lime glass specimens having a controlled surface flaw introduced by Vickers microhardness indentation were determined in both four-point bend and concentric-ring loaded-disk tests. The tests were conducted at three or five stressing rates in both air and pure water environments. Tensile strength increased with the stress rate for each loading condition, and the data could be represented by a straight line on a logarithmic plot of fracture stress as a function of the stress rate. The tensile strength and the gradient of the increase in the strength were greater for the biaxial tension mode of stressing than for the uniaxial mode in the water environment, though there was no significant difference between biaxial and uniaxial stressing in air. The stress state effect in a water environment could be explained by assuming that the rounding of the initial crack tip was caused by the reaction of water with the glass at the crack tip.
