Effect of Rake Angle on Strain Field During Orthogonal Cutting of Hardened Steel with c-BN Tools

In the case of hard machining of steels, negative rake tools generate compressive deformation and high temperature under the cutting edge, leading to phase transformation or “white layers”. The resulting surface integrity can be predicted by numerical simulations which may be validated by comparing simulated and measured strain fields. Recent high speed imaging devices have facilitated strain field measurement by Digital Image Correlation (DIC), even at high strain rates. However, the analyse is generally restricted to the primary shear zone and not to the workpiece under the machined surface. For this study, a double-frame camera and a pulsed Nd:YAG laser, generally used in the field of fluid mechanics, have been employed to record images during an orthogonal cutting operation of a hardened steel. The effect of the rake angle and the edge preparation of c-BN tools on the subsurface displacement field, which has been experimentally investigated by using DIC, are presented in this paper together with an analysis on the origins of the strains. The results of these measurements will be used to validate cutting numerical simulations or to improve hybrid modelling of surface integrity.