Boundary Element Analysis of Crack Propagation in Laser Scribing of Glass

Laser scribing generates a shallow median crack on a glass surface as a pre-processing for division without physical contact. It utilizes thermal stress caused by heating with the laser beam and by cooling with the water jet. In laser scribing, different crack propagation phenomena are observed between the areas near and far from the glass edge. In this research, we examined experimentally how the crack propagates from the glass edge to the glass center. The crack propagation mechanism was considered through a crack propagation analysis where FEM and BEM are combined. The obtained conclusions are as follows: The initial crack propagates to become a through crack due to the tensile stress generated inside the glass during the period when the glass edge is heated. In the subsequent cooling period, large tensile stress is generated in the vicinity of the glass surface. The crack propagates quasi-steadily only in this region to become a surface crack of constant depth. The depth of the shallow crack can be estimated by the crack propagation analysis by setting a suitable threshold of the stress intensity factor.