Modeling Of The Catastrophe Of Chip Flow Angle In Transverse Turning Based On The Improved Unequal Shear Zone Model

During cutting process,the chip flow direction will change suddenly at a certain moment with the continuous change of cutting parameters,which is named the catastrophe of chip flow angle.It has been found experimentally that the cutting force can change up to 75% at the moment when the the catastrophe of chip flow angle occurs,for which its effect on cutting process and application potential in energy saving cannot be underestimated.Through theoretical analysis and experimental research,it is necessary and of great significance to explore the internal mechanism of the catastrophe of chip flow angle and to establish a mathematical model that can accurately predict the catastrophe of chip flow angle.Firstly,based on the analysis of the parameter sensitivity of the unequal shear zone model,an improvement scheme of this model is proposed.Two rounds of orthogonal cutting experiments of 6061-T6 aluminum alloy are designed and completed,and the unequal shear zone model is improved based on the experimental data.Compared with the data of two rounds of cutting experiments,the average absolute error of cutting force predicted by the improved unequal shear zone model is less than 10%.Secondly,according to the improved unequal shear zone model,the power of oblique cutting is derived by using the equivalent plane method,and the power of transverse turning when the tool nose radius is not zero is derived based on the power of oblique cutting.Thus,the potential function that can accurately describe the catastrophe of chip flow angle is obtained.Then,a method for establishing the mathematical model of catastrophe phenomenon based on the difference method is presented.In this method,the extreme value point of the potential function to the chip flow angle is obtained by difference method,and the equilibrium surface and the critical condition of the catastrophe of chip flow angle are obtained by the numerical method,and then a complete model of the catastrophe of chip flow angle in transverse turning is established.This built model is used to analyze the influence of the change of tool main declination angle,tool nose radius and rake angle on the catastrophe of chip flow angle.Finally,the verification experiment of the catastrophe of chip flow angle in transverse turning is completed,and a batch of experimental data of the critical condition of the catastrophe are obtained.It is experimentally found that the average absolute errors of the critical conditions predicted by the established model are 10.82% and 8.75% when turning concave and convex workpieces,which is a significant improvement over similar models established by the predecessor.In this paper,the mathematical model of the catastrophe of chip flow angle in transverse turning is established based on the improved unequal shear zone model.This model can reveal the inherent mechanism of the catastrophe of chip flow angle and accurately predict the critical conditions of the catastrophe,which further laid the foundation for the rational use of the catastrophe of chip flow angle.