A finite element model for micro machining considering size effect of material behaviour and tool geometry

摘要

This paper presents a finite element model that is capable of describing the main characteristics in micro machining processes. By using strain gradient plasticity, a modified Johnson-Cook constitutive equation is formulated to model the size effect of material behaviour at micron level as well as the main features in macro machining processes. Based on the material model, a finite element model is developed, considering size effect, cutter edge radius and fracture behaviour. Size effect and chip formation are investigated in detail by FE simulations, applying the developed model. Two research findings can be drawn from the results: 1. size effect of micro machining can be well explained by modelling material behaviours at micron scale using strain gradient plasticity 2. from the chip formation studies, the minimum chip thickness is proposed to be 0.35 times of the cutter edge radius when the rake angle is 10 degrees and the radius is 2 μm.