Three-dimensional thermal analysis for Laser assisted machining of ceramics using FEA

摘要

Laser-assisted machining (LAM) is an effective method machining difficult-to-machine materials such as ceramics which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. To understand the thermal process of laser heating and predict the operation parameters for experiment system, a transient, three-dimensional heat transfer model for LAM of silicon nitride is developed using Finite Element Method. The model is based on temperature-dependent thermophysical properties and considering convective heat transfer and radiation exchange. A method of locally refining mesh according to machining sequence is used to reduce calculating time. The effects of the operating parameters, such as laser power, laser beam diameter, laser preheat time, cutting depth, feed rate and rotational speed on the average temperature of cutting region and the temperature of laser incidence are investigated. The thermal stresses induced from the high temperature gradient are also investigated. The maximum normal thermal stress failure criterion is used to predict the possibility of cracking on silicon nitride material owing to thermal stress. The method of selecting optimizing operation parameters is presented.