Simulation of the chip morphology together with its evolution in machining of Inconel 718 by considering widely spread cutting speed

This article establishes a finite element method (FEM) model to characterize and classify the chip morphologies of Inconel 718, which tends to form shear localized chips. Orthogonal cutting simulations in a wide range of speeds with three uncut chip thicknesses are carried out to model the plastic deformation of Inconel 718 and thus the formation of the serrated chips by utilizing the Johnson-Cook (JC) constitutive law with the criterion of the accumulated plastic strain. Evolution trends of the chip deformation results are of the main interest and focus is placed on the chip segmentation. Simulation results show that Inconel 718 exhibits a chip pattern transition from the continuously smooth form to the regularly serrated form with the increase of cutting speed. However, the disappearance of chip serration is also observed at still higher cutting speeds. The primary shear angle and the segment inclination finally reach the same asymptotic value of 45^∘. The shear band spacing drops significantly before the two plateau regions are achieved. Apart from these, the scatter plot of specific cutting force tends to be a concave shape, while the scatter plot of chip segmentation degree tends to be a convex shape. Meanwhile, the chip thickness ratio approaches an asymptotic value, and the average velocity of chip sliding on the tool rake face almost equals the cutting speed. At the same time, the simulation results are compared to the results by experiments or simulations in the published literatures. Moreover, the FEM model is validated by comparing the chip morphologies from the experiments and the simulations, respectively. The proposed work is fundamental for not only increasing understandings of the metal cutting process of Inconel 718, but also hypothetically providing a framework of the chip generation under the cutting speed from low to high range.