| Summary: | 碩士 === 華梵大學 === 機電工程研究所 === 92 === Two new laser cutting techniques of pre-scribing controlled fracture method and unstable fracture method were proposed in this paper. The feasibility of laser cutting with closed cutting path was also discussed. It was found that the unstable failure will occur in cutting a closed straight-line or a closed circle. In the pre-scribing controlled fracture method, a diamond wheel is used to scribe a micro-groove along the cutting path in an alumina substrate. The substrate is then separated by applying a defocused laser beam throughout the scribed line for driving the micro-crack through the substrate thickness. The cutting speed of the pre-scribed substrate is larger than that of the un-scribed substrate by four times. The alternative laser cutting technique with unstable fracture method was developed successfully. Applying a defocused laser along the scribed line within a short length about ten millimeters, a great thermal stress will be induced at the scribed groove and make the substrate breaking unstably along the scribed line. The breaking speed is very high and the quality of breaking surface is very good. But the cutting will fail, if cutting geometry is asymmetrical.
The finite element software ANSYS was used to analyze the temperature field and stress field. The SEM photographs of the breaking surface and the acoustic emission data were obtained to analyze the micro-mechanism of the laser cutting process. Finally, the relationships between laser power, scribing depth, and specimen size were also investigated.
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