In-situ DIC measurement to investigate initial generation mechanism of residual stress during the machining process

Residual stresses induced during the cutting process have either beneficial or detrimental effects on the corrosion resistance and fatigue performance of the manufactured parts. To effectively control or restrain residual stresses, it is crucial to gain a deep understanding of the mechanism behind their generation during the cutting process. However, the understanding of the mechanism of residual stress generation during the cutting process remains limited. This work aims to investigate the initial mechanism of residual stress generation through the subsurface deformation information within the machined and unmachined subsurface zones using the in-situ digital image correlation (DIC) technique. A high-speed in-situ measurement system was developed to obtain high-resolution microscopic images within the cutting zones. Meanwhile, a new Drop Hammer based Orthogonal Cutting (DHOC) testing machine was designed to achieve orthogonal cutting with continuous cutting speed change. Displacement and shear strain fields were obtained to identify the material flow characteristics within the subsurface zones. The effect of subsurface deformation caused by serrated chip formation on the generation of residual stress was revealed. The initiation of residual stress development was determined based on the subsurface deformation state during the cutting process. This work provides a new viewpoint to understand the generation mechanism of residual stress and develops a measurement methodology for investigating the generation process of residual stress during the cutting process.