Contact fractures of glass plates and glass bulbs are experimentally studied under static loading. The fracture behavior of steel ball on glasses is divided into two classes; Hertzian fracture and bending fracture. The fracture load and the fracture stress obtained from the experiments of the Hertzian and bending fracture respectively are treated statistically using the Weibull distribution. In the case of the Hertzian fracture, the distribution of the fracture stress is significantly dependent on the thickness of the glass, while in the case of the bending fracture, the distribution of the fracture stress seems to be independent of the thickness.
Using FEM, the glass of 19mm thickness with the Hertzian crack is analyzed to obtain the value of J integral as the crack length increases, where the Hertzian crack is assumed to have the shape of the cone with the inclination of 22.5˚. As the crack length increases, the value of J integral decreases and the crack tip seems to close at the crack length of 18mm, which suggests the change of the shape of the crack from the Hertzian crack to the radial crack, leading to the abrupt fracture. This result is in agreement with the observed experimental result.
