Influence of Friction Models on Finite Element Simulations of Machining

In the analysis of orthogonal cutting process using FE simulations, predictions are greatly influenced by two major factors; a) flow stress characteristics of work material at cutting regimes and b) friction characteristics mainly at the chip-tool interface. The influence of work material flow stress upon FE simulations may be less or even none when there is a constitutive model for work material that is obtained empirically from high-strain rate and temperature deformation tests. However, the difficulty arises when one needs to implement accurate friction models for cutting simulations using a particular FE formulation. In this study, a thermo-mechanical updated Lagrangian finite element formulation is used to simulate continuous chip formation process in orthogonal cutting of low carbon free-cutting steel. The effects of using various chip-tool interface friction models on the simulations are investigated. Experimentally measured stress distributions on the tool rake face are utilized in conjunction with metal cutting theory to develop several friction models and the evaluation of the results for the friction models is carried out. The results depict that the use of various chip-tool interface friction models has at most influence in predicting chip geometry, forces, stresses on the tool and temperature at the chip-tool interface and the predicts are best when using variable shear friction model at the chip-tool interface. Predictions presented in this work also justify that the FE simulation technique used for orthogonal cutting process is an accurate and viable analysis as long as flow stress behavior of the work material obtained realistically and friction at the chip-tool interface is modeled correctly.