氮化硅陶瓷加热辅助铣削过程中边缘碎裂实验与仿真

Experiment and Simulation Analysis of Edge Chipping in Laser Assisted Milling of Silicon Nitride

边缘碎裂现象是陶瓷加工过程中常见的一种现象,是影响加工质量的主要因素之一。激光加热辅助切削技术通过提高切削区温度,改善局部材料的性能,可以降低切削力,减轻铣削加工过程中的边缘碎裂。采用理论与实验分析及仿真模拟的手段研究了激光加热辅助铣削氮化硅陶瓷过程中的边缘碎裂现象,出口边缘碎裂由于刀具离开工件时缺乏支撑,是主要的碎裂形式。仿真模拟扩展采用扩展有限元方法,模拟了材料出口边缘裂纹形成、扩展及碎裂的过程。理论分析、试验结果与仿真结果表明切削区温度是影响边缘碎裂的主要因素。当切削区温度超过氮化硅陶瓷的软化温度后,工件的加载应力与边缘韧性都随温度升高而发生变化,导致边缘碎裂随温度升高而降低。

Edge chipping of ceramics usually happens in ceramics machining and affects the quality of products. Laser assisted machining can decrease cutting force and reduce edge chipping by increasing the heating assisted cutting zone temperature to improve the local properties of the material. The mechanisms of edge chipping in laser assisted milling is investigated by theoretical analysis,simulation and experimental study. Exit edge chipping is the main chipping due to the sudden release of the stress and the loss of material support when the tool is leaving the workpiece. An extended finite element model has been developed to simulate the chip formation,crack propagation and chipping process. The simulation and experimental results show that the cutting zone temperature is the main factor affecting the edge chipping. When temperature is above the softening temperature of silicon nitride ceramic,the two major factors,loading stress and edge toughness,will affect the edge chipping changes with increasing temperature leading to the decrease of the width of edge chipping.