Cutting process modeling is still a significant challenge due to the severe plastic deformation of the workpiece and intense friction between the workpiece and tool. Nowadays, a novel experimental approach based on digital image correlation (DIC) technique has been utilized to study the severe deformation of the workpiece. However, the experimentally measured velocity field does not necessarily satisfy the equilibrium equation that is one of the fundamental governing equations in solid mechanics due to the measurement errors; hence, accurate stress fields could hardly be derived. In this paper, we propose a hybrid DIC-FEM approach to optimize the velocity field and generate a stress field that is in an equilibrium state. First, the analysis region for finite element modeling (FEM) is selected according to the captured image, and the DIC results are used to track the deformation history of the material points. Secondly, the deviatoric stresses of the analysis region are calculated by employing the plastic theory. Thirdly, the hydrostatic pressures are acquired through solving over-constrained equations derived through FEM. Finally, the velocity field is optimized to satisfy the equilibrium equation and the boundary conditions (BCs) with the DIC results serving as an initial value of the workpiece velocity field. To validate this approach, the deformations including the velocity and strain yielded by the hybrid method are compared with the DIC results. The stress fields are presented to demonstrate the satisfaction of the equilibrium equation and the BCs. Moreover, cutting forces calculated through the integration of the stress tensors are compared against the FEM simulations and the experimental measurement.

With the development of advanced image correlation and high-speed filming techniques, the kinematic field during the cutting process can be experimentally determined including the velocity and strain rate fields. As known, the setting parameters for the digital image correlation (DIC) as well as the optical parameters of the given camera and lighting system have a great influence on the spatial resolution and accuracy of the DIC results. In this study, the speckle pattern in terms of speckle size and intensity distribution are analyzed when using two different surface preparation methods. Moreover, the influences of the subset sizes for the image correlation on the strain rate are numerically studied. Interlaboratory measurements of the kinematic field during the orthogonal cutting of AISI 4140 were conducted with two different in-situ imaging setups. The material flow near the cutting tool edge determined from the velocity field is compared with the numerical simulation. The stagnation zone which is commonly found in the numerical simulation of the cutting process using a chamfered cubic boron nitride (CBN) tool was not observed in the experiments. Furthermore, slip-line fields were constructed from the experimentally determined strain rate components, from which the boundary conditions along the chip-free and chip-tool interface were derived.

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 experimental results.

Cutting edge radius is a crucial factor affecting surface integrity during metal machining, which determines product performance. However, the exact mechanism of how the cutting edge radius affects machined surface has not yet been understood, especially lacking in situ evidence during the material removal process. In this article, effects of cutting edge radius on surface roughness, subsurface deformation, and work hardening of nickel-based cast superalloy are studied through an in situ imaging approach. Based on continuous high-speed filming and digital imaging correlation (DIC) techniques, detailed chip formation and quantitative subsurface plastic deformation under various cutting edge radii are analyzed, and the formation of built-up edge (BUE) is observed when using a large edge radius. Furthermore, when the cutting edge radius is greater than the uncut chip thickness (h), the thickness of plastic deformation increases dramatically. On the other hand, the machined surface roughness can be improved when the cutting edge radius is between 30% and 60% of h. The sharp cutting tools or the cutting edge radius higher than 60% of h result in a poor surface quality on the machined surface during nickel-based cast superalloy machining. The effects of cutting edge radius on machined surface generation are systematically categorized as cutting with chipping, cutting with significant plowing, and cutting with plowing accompanied by BUE formation.

Metal mirrors will be widely used in the coming decades. Therefore, as one of the enabling technologies for metal optical freeform surface manufacturing, ultra-precision (UP) diamond turning error compensation has become a research hotspot. However, for the tool offset error and tool radius error, which are the main errors in UP diamond turning, no precise and efficient calculation method has been found in the literature. In this study, a more precise and efficient algorithm was developed and validated in three ways using on-machine measurement data and profilometer measurement data. After one compensation, the tool offset error can be reduced to below 0.1 μm, and the tool radius error can be reduced to below 1 micrometer, which will significantly improve the UP turning accuracy and efficiency of optical parts.

The use of ultrasonic surface rolling processing (USRP) in the machining of aeroengine blades remains in the exploratory stage, as the application of high contact pressure during USRP leads to substantial deformation, which has a detrimental impact on the aerodynamic performance of the blades. This study aims to address the deformation issue through two strategies for optimizing blades made from titanium alloy. Firstly, profiling pads are employed to effectively mitigate blade deformation during the machining process. Secondly, a comprehensive exploration of different USRP treatment parameters—such as pressure, indentation depth, spacing, and processing time—is conducted to investigate their effects on the surface morphology, hardness, and residual stress of aeroengine blades to ensure that they meet the specific deformation requirements for aeroengine components. The evolution of microstructure induced by USRP treatment of the blades is also examined. The experimental findings reveal significant improvements following USRP treatment, including a substantial reduction in surface roughness (from 2.6 to 0.2 μm), a significant enhancement in hardness (from 320 to 410 Hv), a refinement of surface grains, and the introduction of more favorable residual compressive stresses (about − 1000 MPa). These effects play an important role in improving the performance of aeroengine blades.