Evaluation of chip formation simulation models for material separation in the presence of damage models

This paper appraises two major chip formation techniques in finite element (FE) simulation of machining. The first one considers chip formation as a wedge indentation process, while the second one considers chip separation due to ductile fracture. The first technique has been implemented in an Arbitrary Lagrangian-Eulerian (ALE) simulation of machining and the chip formation is assumed to be due to plastic flow. Therefore, the chip is formed by continuous remeshing of the workpiece. In the updated Lagrangian (UL) simulation as an implementation of the second technique, the Johnson-Cook (J-C) damage criterion is used where elements in the sacrificial layer are deleted, as the accumulated damage in such elements exceeds the predefined critical value. The experimental data of the Assessment of Machining Models (AMM) effort for orthogonal cutting is used as a source to verify the models. It is found that predictions of the first technique for strains and temperatures within the deformation zones are not satisfactory and the predicted resistance of workpiece material to cutting is unrealistically high. Instead, the results obtained by second technique are shown to be more reasonable with less computational cost and less possibility of software crash. However, in the case of calculating the field variables the major differences are located in the material separation affected zones; the two thin boundary layers on the cut surface and underside of the chip.