Theoretical modeling of Zirconia (ZrO2) ceramics cutting force and turning removal mechanism under considering impact loading

In order to improve the machining efficiency of Zirconia (ZrO₂) ceramics, the material is removed by brittle fracturing during turning ceramics, creating a discontinuous cutting process. Impact loading occurs when the rake face of the tool makes contact with the workpiece, and excessive impact loading force affects machined surface quality and tool wear. However, considering the continuous cutting process, it might not be appropriate enough to reflect the realistic situation. Considering the effect of impact loading phenomenon (ILP) on the removal and cutting force of ZrO₂ ceramics, the impact loading stage and static cutting stage have been proposed by brittle solid fracture mechanics and crack propagation for the first time in this paper to solve the problem. The rake face static resultant force of the tool has been theoretical modeled in the static cutting stage by using the theory of maximum tensile stress of mixed crack fracture with the consideration of crack path, cutting parameters and tool geometry angle. The dynamic coefficient was calculated by energy transfer theory in the impact loading stage, and the rake face impact loading resultant force of the tool was modeled by considering dynamic coefficient. Finally, the theoretical model of total cutting force was modeled based on the influence of elastic recovery of workpiece’s machined surface on the flank face of the tool. The experimental validation results indicate that the maximum relative error for the total tangential force is 12.76%, and the maximum relative error for the total radial force is 12.83%. When the cutting speed exceeds 48.36 m/s, the impact phenomenon becomes significant. The comparison between the analytical predictions and the experimental results presents a good agreement. This study has also proved that, as expected, the initial crack is formed during the impact loading stage. Once the initial crack propagation stabilizes, the static cutting stage deflects the initial crack. Moreover, the variations in the direction of initial crack propagation during the impact loading stage under different cutting parameters are also discussed. The proposed relationship between ZrO₂ ceramics material removal and cutting force, considering the ILP, suggests that by reducing the cutting speed and appropriately increasing the cutting depth and feed rate, the influence of impact loading can be mitigated and the initial crack path altered. This approach not only improves the machining efficiency but also enhances the surface quality of ZrO₂ ceramic workpieces and reduces tool wear. This work provokes more in-depth thoughts about ILP in the cutting ceramics process and provides the guiding significance for industrial ZrO₂ ceramics machining.