| Summary: | 碩士 === 國立屏東科技大學 === 車輛工程系所 === 95 === In the process of laser drilling, the laser with high power density impinging on the work piece will increase the temperature on it and induce the thermal stresses that usually cause the residual stress in a structure. In this paper a finite element model with the moving heat source and mesh remove technique in software package ABAQUS is used to simulate the process of percussion drilling with ultrashort laser. The temperature profile and residual stress distributions around the laser-formed hole can be calculated by a sequentially coupled thermal-stress analysis. The materials for numerical model include 304 stainless steel and aluminum ceramic. The effects of parameters such as the power density, the preheated temperature in the workpiece, and pulse frequency on the drilling results will be investigated. The results showed that the laser with high pulse frequency will lead to a high temperature around the drilling hole. Moreover, on the condition of the same pulse frequency, the drilling speed will be increased due to the raise of the power density, which leading to a temperature decrease around the drilling hole. Finally, the thermal stresses can be also effectively depressed when the workpiece with a higher initial temperature.
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