Abstract

During chip formation there is a substantial increase in the specific energy as chip size is reduced during machining. It is believed this is due to the fact that all metals contain defects such as grain boundaries, missing and impurity atoms, and when the size of the material removed decreases the probability of encountering a stress-reducing defect decreases. Since the shear stress and strain in metal cutting is unusually high, discontinuous microcracks usually form on the primary shear plane. If the material is very brittle, or the compressive stress on the shear plane is relatively low, microcracks will grow into larger cracks giving rise to discontinuous chip formation. When discontinuous microcracks form on the shear plane they will weld and reform as strain proceeds, thus joining the transport of dislocations in accounting for the total slip of the shear plane. This chapter focuses on machining at the micro- and nanoscale and attempts to explain the dominant features of machining as the size effect becomes significant. © Springer International Publishing Switzerland 2009, 2015. All rights are reserved.