Digital Image Correlation Based on Primary Shear Band Model for Reconstructing Displacement, Strain, and Stress Fields in Orthogonal Cutting

In metal cutting, a good understanding of both the elastic-plastic deformation and the mechanical behavior of the workpiece material in the primary shear band (PSB) is essential to optimize machining process and ensure product quality, particularly when machining hard-to-cut materials (such as Titanium alloys) with a low thermal conductivity that gives rise to thermal stress localization near the tool-chip interface. This article presents an extended digital image correlation (DIC) method to obtain the highly intensive and localized elastic-plastic strain and stress fields in the PSB during cutting, the reconstruction of which requires the deformation history of each material point and an appropriate material constitutive model. Unlike existing DIC methods that infer elastic strains from two sequential images, the extended DIC not only reconstructs the displacement field but more importantly also captures the elastoplastic evolution of the material during the dynamic orthogonal cutting process, from which the plastic strain/stress fields in the PSB are determined experimentally. The effectiveness of the extended DIC method was evaluated numerically and experimentally for orthogonal cutting of Ti-6Al-4V alloys.