Fracture behavior of fused quartz with laser-induced internal flaws

Abstract

Pulsed-laser light was used to generate internal flaws in fused quartz. The size of the flaw produced was proportional to the amount of laser pulse energy above a threshold value of 2.5 mJ. Specimens of different flaw sizes were tested at room temperature under four-point bending. The bending strength decreased as the flaw size increased, and a Griffith relationship was established between the lateral flaw size and the critical stress at the flaw tip. Characteristic demarcation lines were observed on the fracture surfaces of specimens with a flaw size greater than 0.25 mm. It is suggested that the formation of the demarcation line is caused by a discontinuous change of stress intensity in the dynamic process of the crack propagation.