Fracture Energy Evaluation Using J Integral in Orthogonal Microcutting

Abstract

Fracture in cutting of ductile as well as brittle materials can be characterized using parameters such as K, G, R, and Jintegral; of these, R has been widely used. To accurately evaluate the contribution of fracture energy in total cutting energy, Jintegral would provide a more comprehensive basis as it encompasses several fracture modes, material plasticity, and nonlinear behavior. Therefore, this work adopts Jintegral to evaluate the contribution of fracture energy to the size effect during microcutting of AISI 1215 steel. The work uses explicit integration method within ansys/lsdyna to simulate twodimensional (2D) orthogonal microcutting. Uand Vshaped cutting edges were used to represent a sharp cracktip and a blunt cracktip, respectively. Considering several alternative contours around cracktip, covering the plastic zone, Jintegral was calculated. Upon benchmarking Jintegral values with other simulations in the literature, the approach was adopted for microcutting simulations in this work. It is observed that Jintegral increases with uncut chip thickness, whereas it decreases with cutting speed, rake angle, and tool edge radius. The term (J/t0) defines contribution of fracture to the size effect in terms of Jintegral, which is in the range of 4–24% under various parametric conditions. The corresponding values of R were always found to lie above those of the Jintegral indicating that Jintegral is relatively more appropriate parameter to quantify the fracture energy during microcutting.