透波性Si3N4陶瓷铣削过程刀具-工件摩擦特性

摘要

透波性Si3N4陶瓷是制造天线窗的主要材料之一,铣削过程中刀具-工件摩擦特性与加工表面形貌紧密相关.本文以透波性Si3N4陶瓷铣削加工为研究对象,通过分析加工过程中刀具-工件接触关系得到摩擦接触区域主要集中于切削刃后刀面与工件表面;探究了不同加工机理下接触区域摩擦机理,塑性域加工摩擦机理为粘着摩擦、刀具表面粗糙度波峰犁沟摩擦和陶瓷粉末滚动摩擦,脆性域加工还包含碎裂型陶瓷颗粒犁沟摩擦;在此基础上应用已有的微观表面形态与表面接触的摩擦力及摩擦系数理论给出了Si3N4陶瓷与铣刀材料的摩擦系数计算公式;通过实验对分析结果进行了验证.结果表明:透波性Si3 N4陶瓷加工机理转变的临界切深值大于0.3 mm且小于0.4 mm;摩擦系数计算公式最大误差率为20.46%,能在一定程度上反映加工过程中摩擦特性演化规律;加工机理初始转变阶段,摩擦系数值降低,且摩擦系数对表面粗糙度影响呈现三阶多项式分布规律.该研究为提高透波性Si3N4陶瓷铣削加工表面质量提供了参考.%Wave-transmitting Si3N4ceramics is one of the main materials for making the antenna window. The tool-workpiece friction characteristics in milling are closely related to the machined surface morphology. Through the tool-workpiece contact relationship analysis, the friction contact area is mainly focused on the cutting edge flank surface and the workpiece surface. The friction mechanism of the contact area under different processing mechanisms has been analyzed. It comes to conclusions that the friction mechanism is adhesive friction, plough friction of tool surface roughness crest and rolling friction of powder for the plastic domain processing,while it also includes the plough friction of the broken ceramics particles for the brittle domain processing.The friction coefficient calculation formula has been proposed with the existing friction theory and the analysis results have been verified with the experimental data. It shows that the critical cutting depth of the transition mechanism for the wave-transmitting Si3N4ceramics is in the range of 0.3 to 0.4 mm. The maximum error rate of the friction coefficient formula is 20.46%, which can reflect the evolution of the friction characteristic to some extent. In the initial machining mechanism transition stage,the friction coefficient decreases,and the influence of friction coefficient on surface roughness follows the third order polynomial distribution. This study provides the reference for improving the surface quality of wave-transmitting Si3N4ceramics milling.