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This study proposes a comprehensive experiment-based method to determine stress field and slip lines in metal cutting process. The chip geometry and workpiece's strain and strain rate fields are determined using an in-situ imaging technique. The two-dimensional (2D) heat transfer problem for the steady-state cutting process is solved to derive the cutting temperature, and the flow stresses of work material in the main deformation zone are calculated based on the plasticity theory. Furthermore, the stress field is comprehensively determined to satisfy the stress equilibrium, friction law along the tool-chip interface, and traction-free boundary condition along the uncut chip surface. In addition, slip lines in the main deformation zone are derived according to the direction of maximum shear stress without the assumption of perfect rigid-plastic material. The proposed method is validated by comparing the cutting forces calculated based on the obtained stress field with the experimentally measurements.

Imaging techniques have been widely implemented to study the dynamics of chip formation. They can offer a direct method and a full field measurement of the cutting process, providing kinematic information of the chip formation process. In this article, the state of the art of the imaging techniques reported in the literature has been summarized and analyzed. The imaging techniques have been applied to study the chip formation mechanism, friction behavior, strain/strain rate, and stress fields. Furthermore, the study of surface integrity has been advanced by deriving the thermo‐mechanical loading, subsurface deformation, and material constitutive model from the imaging technique. Finally, achievements in the area of imaging techniques have been summarized, followed by future directions for their application in the study of surface integrity.

White layer (WL) formation in metal cutting is generally found to have negative effects on the corrosion and fatigue life of machined components. Nowadays, the mechanism of the WL formation has not been understood very well, especially about the contribution of the thermal and mechanical loadings generated by the cutting process on WL formation. The relationship between subsurface plastic strain caused by mechanical loadings and the formation of WLs is of our concern. To address this issue, WL formation in hard turning of AISI 52100 under dry and cryogenic cooling conditions is investigated by subsurface plastic strain measurement using the micro-grid technique, observed by scanning electron microscope (SEM). Due to the considerable low temperature, WL is mainly generated by the mechanical effect rather than the thermal one, and this hypothesis is supported by physically based finite element method (FEM) simulations. From the investigations, we discover the existing plastic strain threshold, which governs the occurrence of WL in hard turning of AISI 52100 steel under cryogenic cooling conditions.

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