The crack shape evolution in unstable, flexural fractures for soda-lime glass beams by phase-field analysis

Abstract

In this work, phase-field simulations were used to investigate the unstable crack propagation in brittle plates fractured in bending. The evolution of crack front shapes was studied considering over 20 scenarios and accounted for both the effects of the Poisson’s ratio and the plate’s width. The crack front in unstable cracks was found to be nearly elliptical only when the cracks were relatively short, with depths less than half the plate’s thickness. In general, unstable cracks resulted in intersection angles of 88°±6° between the crack front and the free surface. Higher Poisson’s ratios led to more oblong cracks but had no obvious effects on the intersection angles. It was found that the evolution of the crack shape was unaffected by the plate’s finite width up to crack lengths equal to 80% of the plate’s width. A cursory literature review on flexural fatigue cracks in steel and on subcritical crack growth in glasses suggested that the description of the crack front proposed in this work could also accurately describe the crack shapes for these types of fractures. However, differences in the behavior among these cases became more evident for crack depths larger than 60% of the plate’s thickness.