Finite element modelling of orthogonal machining of hard to machine materials

This paper presents a detailed finite element model to predict deformation and other machining characteristics involved in high-speed orthogonal machining (cutting speed > 54 m/min) of hard-to-deform materials like Ti6Al4V. The influence of various cutting parameters like feed rate, spindle speed, and rake angle, on the output parameters like cutting force and surface finish, was analysed. The paper tries to relate the degree of surface finish with the variance of the effective plastic strain. The Johnson-Cook material model is used to describe the material constitutive behaviour, and the Johnson-Cook damage model is used to establish the damage criteria. Due to the high machining costs associated with the titanium alloy, the model is first validated using aluminium alloy (Al2024-T351), and the same model is then extended to predict the results for titanium alloy. The matrix for the design of experiments (DOE) considers a full factorial approach, with about 48 simulations, for a proper understanding on the influence of the major machining parameters. A dynamic, explicit integration scheme is used along with the arbitrary Lagrangian-Eulerian (ALE) technique to accurately predict material flow. This paper also presents a unique method to tackle the commonly encountered numerical issues involved in modelling self-contact.