Stress Field Analysis in Orthogonal Cutting Process Using Digital Image Correlation Technique

Cutting stress field in machining process plays a significant role in the understanding of cutting mechanics and prediction of surface integrity, tool wear, and failure. It is in great need to get accurate and reliable cutting stresses in the chip formation zone. In this paper, a new methodology to obtain the cutting stress field is proposed. The deformation field containing elastic as well as plastic parts can be obtained via digital image correlation (DIC) technique. The orthogonal cutting stress field can be obtained with the experimental determined deformation field and material constitutive model as inputs. However, the challenge is to handle the inaccuracy of infinitesimal elastic deformation involved in the total deformation due to the inaccuracy of the obtained images. We develop a method to modify the hydrostatic pressure field based on mechanical equilibrium equations to compensate the inaccuracy of elastic deformation part. Besides, Eulerian logarithmic strain based on a least square plane fit on a subset of displacement data is adopted to reduce the image noise. The stress distribution along the shear plane and tool-chip interface can be extracted and integrated to calculate cutting forces. A feasibility study is performed by comparing the cutting forces predicted based on this new method against the experimental measurements. The comparison of cutting parameters obtained through DIC technique with finite element method (FEM) predictions is also made.