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

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. © 2022 Editorial Office of Chinese Journal of Mechanical Engineering. All rights reserved.