New crack generation phenomena by crack collision in 10 mm thick tempered glass

High speed photography by Caustics method using Cranz–Schardin camera was used to study crack propagation and divergence in thermally tempered glass. Tempered 10 mm thick glass plates were used as a specimen. New crack generation by two crack collision was observed. Regarding the presence/absence of new cracks, the dependence of the two cracks on the collision angle was confirmed. Considering that it is based on the synthesis of stress 𝜎CR generated at the crack tip, tensile stress necessary for the generation of new cracks could be created.

Crack propagation and divergence phenomena observed by Caustics method in tempered glass

High speed photography by Caustics method using Cranz-Schardin camera was studied for crack propagation and divergence in thermally tempered glass. Tempered 10 mm thick glass plates were used as a specimen. Two types of bifurcation and branching as the crack divergence could be observed and clarified even in 10 mm thick tempered glass. The difference of the shadow spot sizes between bifurcation type and branching type could be confirmed.

Experimental Study on the Dynamic Behavior of Running Crack Affected by Defect Shape and Filling Material

Using the caustics method and the experimental system of digital laser dynamic caustics, the model experiment of drop hammer impact loading was carried out, and the effect of the defect shape (circular and rectangular) and the filling material (air, epoxy, and silicone rubber) on the propagation behavior of the running crack was investigated. The experimental results show that, under the impact loading, the running crack initiates at the end of precrack and propagates toward the defect. After the running crack connects to the defect, it accumulates energy within a certain period before initiating again at the upper edge of the defect. Subsequently, only one running crack is formed at the upper edge of the circular defect, but two running cracks are formed at the upper edge of the rectangular defect. The defect shape and the filling material have a significant effect not only on the energy accumulation time of the running crack at the defect but also on the stress intensity factor when initiating at the defect. The effect degree of the defect shape on the running crack propagation behavior is in the following order: circular defect > rectangular defect, whereas the effect degree of the filling material on the running crack propagation behavior follows this order: air > silicone rubber > epoxy.