Three-dimensional turning force prediction based on hybrid finite element and predictive machining theory considering edge radius and nose radius

Cutting force provides a basis for predicting tool wear and fracture, surface quality of component, as well as vibration and power demand of machine tools during the process of turning. Based on the finite element and mechanical analysis model, a three-dimensional (3-D) cutting force prediction model with consideration given to the edge radius and the nose radius of cutting tool is proposed in this paper. Firstly, combined with cutting force experiment, 3-D cutting simulation is performed in Deform to determine the appropriate Johnson-Cook (J-C) material constitutive model, and the two-dimensional (2-D) orthogonal cutting model is simulated by applying the determined J-C model. By observing the strain rate distribution in the shear zone, the shear angle is obtained, while the nonlinear regression model of shear angle, cutting speed and cutting thickness is conducted. Then, taking into account the impact of nose radius on the cutting process, 3-D oblique cutting is converted into equivalent orthogonal cutting using the chip flow angle and the equivalent cutting edge. The method used to determine the strain rate coefficient of the second deformation zone is redefined in the modified Oxley model, and the chip forming force is calculated. Based on the Waldorf slip line field model, the plowing force generated by the edge radius is predicted. Finally, the cutting force of 3-D oblique turning is obtained by means of coordinate transformation. The proposed model is validated by the excellent consistency between the theoretical predictions and the results obtained after referencing literature data and performing experiment of cutting 304 stainless steel and Inconel 718.