Surface Defects and Strength of Sheet Glass Under Cyclic and Long-Term Static Loading

Abstract

Specific surface defects in sheet glass, which occurr in the float-line production process, significantly affect the strength and fracture of structural glass elements under mechanical loading. The major defects that are usually detected in the fracture focus of glass elements tested are surface microcracks of the depth down to 100 μm. Using laminated specimens and a special cassette method of their testing, the strength and fracture of sheet glass were investigated under long-term cyclic and static loading. Cassettes with several specimens of the same thicknesses are tested in such a way that each specimen is subjected to pure bending loading at the same level of tensile stresses on the surface to be tested. An assessment of special features of fracture, geometrical parameters and the size of the fracture source at the critical stage of specimen loading is made by using the microfractographic analysis. For cyclic tests, a tendency is revealed towards increasing the critical value of the stress intensity factor KIc as compared to that under long-term static loading.