Morphology of Cleaved Surface and Observation of In Situ Crack Propagation During Cleaving
Soshi Iwatsuki*, Hirofumi Hidai*,**,, Souta Matsusaka*, Akira Chiba*, and Noboru Morita*
*Department of Mechanical Engineering, Chiba University
1-33 Yayohi-cho, Inage-ku, Chiba 263-8522, Japan
**Molecular Chirality Research Center, Chiba University, Chiba, Japan
In laser cleaving, the thermal stress caused by laser heating and water-jet cooling propagates previously induced cracks in the workpiece material. The laser-cleaving conditions affect the quality of the fracture surface, and therefore, elucidating the relationship between the cleaved surface, cleaving conditions, and crack propagation is essential. Against this backdrop, in this study, we investigated the morphology of the cleaved surface and visualized the crack propagation and stress in situ using a high-speed polarization camera. The distance between the glass edge and cleaved surface was varied. When the laser-cleavage line was close to the glass edge, twist hackles were formed on the cleaved surface. The area in which the twist hackles formed on the cleaved surface coincided with the lagging section of the crack front. Furthermore, the twist hackle reached the specimen surface, and the edge of the surface exhibited a sawtooth shape. Observations with the high-speed polarization camera revealed that the internal stress was asymmetric with respect to the crack when the twist hackles were formed.
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