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Inconel718 is one kind of nickel-based superalloy strengthened by body centered tetragonal γ ″ and face centered cubic γ ′ precipitation, which has a high yield strength, high corrosion resistance and oxidation resistance at high temperature. Alloying elements exist in the form of high hardness compounds, such as TiC, NbC and other interphase hard point. These high hardness compounds result in the presence of high cutting temperature, large plastic deformation, especially the generation of residual stress in the machined surface. In this paper, the multi-scale finite element model of Inconel718 is established, and the cohesive element is added into the brittle phase particles to conduct the cutting simulation process. The accuracy of the established model is verified according to the chip morphology and the cutting force. The formation mechanism and distribution law of residual stress in the machined surface is studied deeply. The results show that the simulation results of the multi-scale finite element model which adds the brittle phase particles are closer to the experimental results. The larger the size of the brittle phase particles is, the smaller the residual stress of the workpiece is. Along the depth direction of workpiece, the influence of the brittle phase particles on the residual stress is getting smaller and smaller. This study provides a theoretical basis and reference for the further optimization of Inconel718 cutting performance and surface integrity.

Digital image correlation (DIC) is a digital-image-based whole-field deformation measuring technique. For use of the technique, the test surface of object has to be covered with random speckle pattern to ensure reliable and accurate matching. In practice, the quality of the speckle pattern has an important influence on the measurement accuracy of DIC. In this paper, an easy-to-compute parameter, called Shannon entropy which is from information theory, is employed for quality assessment of speckle patterns. Two sets of numerical translated tests are performed on three types of speckle patterns and five artificial speckle patterns with different Shannon entropies, respectively. Then, another test is performed on the computer-generated speckle patterns with nonuniform displacement field. All the results show that the measurement accuracy of DIC is related on the Shannon entropy of speckle pattern. Therefore, the speckle pattern with large Shannon entropy should be a so-called good quality speckle pattern.