Stress analysis of the crack propagation on glass in laser thermal cleavage with high speed photography

• Main Authors: Heng-JuiChang, 張恒瑞
• Other Authors: Jehn-Ming Lin
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/21080754888526304403

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 100 === Abstract The crack of the soda-lime glass in laser thermal cleavage was investigated in this thesis numerically and experimentally. In the laser cleavage of glass and other brittle materials, the laser is mostly treated as a heat source to generate the thermal stress to cleave the substrates. In the numerical simulation, the thermal stress was computed by the finite element method to analyze the temperature and stress distributions induced by the laser heat source. In the experiment, the crack propagation was visualized by a high-speed camera and the micro-crack was examined by an optical microscope. With various cleavage paths and boundary conditions, the numerical and experimental results were compared and verified. The results show that the crack propagation varies with boundary conditions and cleavage paths. In the laser cleavage of brittle materials, the crack growth does not completely follow the cleavage path; on the cleavage path with various rotational angles, the crack will generate in different fracture modes at the turning point. For different cleavage conditions such as starting points inside and outside the glass surface, the laser-induced thermal stress states are significantly different; a tension stress state may transform to shear stress state and change the fracture mode from opening to sliding. Therefore the micro-cracks may occur and affect the cleavage quality mainly at the starting point, end point, and the turning point in the laser cleavage of glass.