Evolution of residual stress when turning a fillet radius in stainless steel

Most studies have been carried out to investigate the surface integrity induced by metal cutting process. However, the previous studies are limited to a longitudinal turning or orthogonal cutting operations and the residual stresses generated in a fillet radius have been ignored. This study uses a combination of experiments and numerical simulations to study the evolution of cutting forces, temperature, chip morphology, and residual stress distributions while turning a fillet radius in AISI 304. Finite Element (FE) models were developed with a Coupled Eulerian and Lagrangian (CEL) method, where the geometric model of the workpiece was established taking into account the previous machined surface profile at the four specific cutting faces. The model was validated by experimental cutting forces, chip morphology, and residual stress profiles. The changing trend of shape and area of uncut chip cross-section during fillet turning were analyzed to explain the evolution of cutting forces and temperatures. The results show that the cutting force components in cutting speed and tangential directions increase during the early stage of the fillet turning process and decrease after that, while the force in the radial direction shows an increasing trend during this process. The maximum temperature at the machined surface is increased along the tool path. In addition, magnitude and depth of residual stress are slightly changed during the fillet radius turning process, but a reduction of the residual stress profile can still be noticed.