Abstract: In order to study the chip formation mechanism of PTFE materials in cutting processes, single factor orthogonal cutting experiments and quasi-static mechanics experiments were designed. Firstly, cutting speed and cutting thickness were taken as variables, the continuous chip and chip edge forming mechanism of PTFE materials were proposed based on the shear plane theory and fracture theory. Secondly, by analyzing the height and spacing of the edges, the influences of cutting parameters on the edge morphology were explored. Finally, the fractal theory was used to analyze the cutting force stability, revealing the relationship among the number of burrs, frequency and cutting force stability. The results show that the PTFE continuous chips are generated because the true compressive strain of the materials does not exceed the fracture yield strain in the cutting processes. The burrs are produced because of the nucleation and propagation of cracks at the lamellar structure of the chip edges. In addition, cutting parameters will affect the generation of burrs, when the cutting speed is as 100 mm/min and the cutting thickness is as 0.3 mm, the number of chip edges is the least, the frequency is the smallest and the cutting force is the most stable. The research results may provide reference for the edge suppression and surface processing quality optimization of PTFE materials in cutting processes. 

Key words: polytetrafluoroethylene(PTFE), mechanism of chip formation, chip edge, shear plane theory, fracture theory, fractal theory

摘要： 为了研究PTFE材料在切削过程中的成屑机理，设计了单因素正交切削实验以及准静态力学实验。首先，基于剪切平面理论和断裂理论，以切削速度、切削厚度为变量，提出了PTFE材料的连续切屑及切屑毛边成形机理;然后通过分析毛边高度和间距，探究切削参数对毛边形态的影响规律;最后，利用分形理论对切削力稳定性进行分析，揭示了毛边数量、出现频率与切削力稳定性的关系。结果表明，PTFE连续切屑的产生是因为切削过程中材料真实压缩应变未超过断裂屈服应变，毛边的产生则是因为切屑边缘片层状结构处裂纹的形核与扩展。此外，切削参数会影响毛边生成，在切削速度100 mm/min、切削厚度0.3 mm工况下，切屑毛边数量最少、出现频率最小，切削力最稳定。研究结果可为PTFE材料切削过程毛边抑制和表面加工质量优化提供参考。

关键词: 聚四氟乙烯(PTFE), 成屑形成机理, 切屑毛边, 剪切面理论, 断裂理论, 分形理论