A Physically Based Constitutive Model for Predicting the Surface Integrity in Orthogonal Machining of AISI 52100 Steel

The modification of surface characteristics, including microstructure, hardness variation and phase composition, is of great importance for the functional performance and reliability of machined components. Therefore, accurate, physically-based numerical models are needed to predict the material behavior by considering both thermal and mechanical effects. This study models metallurgical changes during dry orthogonal turning of AISI 52100 steel, varying tool tip geometry, initial material hardness, feed and cutting speed by a 2D finite element (FE) model that incorporates a physically-based constitutive law for material flow stress and a customized subroutine to predict grain size, material hardness and dislocation density evolution due to machining process. Furthermore, the model evaluates the transformation of martensite volume fraction in the affected layer of the workpiece, accounting for plastic deformation, cooling rate and austenitizing temperature. The proposed methodology was validated against experimental data predicting thermally and mechanically induced metallurgical phenomena and enabling the computation of grain size refinement, microhardness variation, machining-affected layers and phase transformation kinetics during the cooling phase.