On the selection of an empirical material constitutive model for the finite element modeling of Ti6Al4V orthogonal cutting, including the segmented chip formation

Finite element modeling of machining aims for guidance in the choice of the cutting parameters and for the comprehension of the involved phenomena. The modeling of the behavior of the machined material is a key parameter to develop a realistic model. It is nowadays still extremely difficult to acquire experimental data on the material flow stress due to the extreme conditions encountered during machining. Many constitutive models are found in the literature and there is a lack of objective information to choose the best suited for a given application. Four empirical constitutive models are used in this paper to represent the Ti6Al4V titanium alloy during an orthogonal cutting operation. All of them are based on the well-known Johnson-Cook model. The results of this study show that the influence of the constitutive model on the chip morphology and on the cutting force is high and that the strain softening phenomenon should be taken into account to produce a segmented (or saw-toothed) chip as it is experimentally observed. For the cutting conditions adopted, adding damage properties in the chip is moreover required to obtain a morphology close to the experimental reference. All these elements allow to get a reliable numerical model able to reproduce cutting forces and chip morphology (either continuous or segmented) for various cutting conditions.