关于硬脆材料去除机理与加工损伤的理性思考

Rational Discussion on Material Removal Mechanisms and Machining Damage of Hard and Brittle Materials

硬脆材料是典型的难加工材料。长期以来,实现“延性域”磨削被认为是消除加工损伤的重要途径。从“临界切深模型”和“延性域磨削条件下的损伤”两个角度分析了“延性域”磨削理论存在的问题,从“尺寸效应”、“应变率效应”和“温度效应”三个方面讨论了影响硬脆材料磨削加工损伤的主要因素,并基于位错理论对磨削加工材料去除机理、变形和断裂机制、加工损伤等重要问题进行了理性思考。旨在澄清“延性域”磨削加工的概念,并证明了“延性域”磨削并不代表没有加工损伤。硬脆材料的塑性变形或脆性断裂是“尺寸效应”、“温度效应”与“应变率效应”三者相互竞争、综合作用的结果,超高速磨削在降低硬脆材料加工损伤、提高加工效率方面有巨大的工程应用潜力。

Hard and brittle materials are typical difficult-to-machine materials.For a long time,the realization of‘ductile-regime’grinding has been considered to be the main way towards obtaining high-quality parts.In this study,the problems associated with‘ductile-regime’grinding of hard and brittle materials are analyzed from two perspectives of‘critical depth model’and‘damage hidden underneath the ductile-regime’.The main factors resulting in grinding damage to hard and brittle materials are discussed from three factors of‘size effect’,‘strain rate effect’,and‘temperature effect’.Based on the dislocation theory,some important issues such as material deformation,fracture,and removal mechanisms,and machining damage are extensively discussed.This paper is intended to clarify‘ductile-regime’grinding,and further demonstrate that‘ductile-regime’grinding does not necessarily reflect grinding quality due to subsurface damage induced in a grinding process.Whether plastic deformation or brittle fracture should occur in grinding of hard and brittle materials is a result of the competition and comprehensive interactions among the‘size effect’,temperature effect’,and‘strain rate effect’.Ultra-high-speed grinding has a great potential in suppressing machining damage and improving machining efficiency for hard and brittle materials.