Glass fracture in the region of its contact with steel balls

Results of experiments on indentation of steel balls of various diameters into glass samples shaped as rectangular parallelepipeds are reported. The limiting load of formation of a ring-shaped crack near the contact region and the radius of this crack are experimentally determined. The field of the contact stresses in the fracture region is found by using the Huber solution of the Hertz problem of pressing a ball into an elastic half-space. Modeling fracture caused by contact interaction is based on using the local criterion of the maximum stresses and several non-local criteria: criterion of mean stresses, Nuizmer criterion, and gradient criterion. For calculating the parameter that has the length dimension and is included into the nonlocal fracture criteria, the limiting tensile stress and the critical stress intensity factor of glass are experimentally determined for beams without and with a notch. It is demonstrated that the experimental data on the ring-shaped crack radius are most adequately predicted by the gradient criterion among all criteria considered in the study. However, this criterion overpredicts the limiting tensile stress in the course of beam bending, which is caused by the scale factor.