Flutter Stability Analysis Of Cutting System Considering Nonlinear Cutting Force

Regeneration flutter during machining is a major factor affecting part machining quality,tool life and production efficiency.The control of flutter and stability prediction is one of the important challenges in the field of machining.The cutting system is essentially a complex nonlinear system.The study of flutter starts with the stability of linear system analysis.This analysis method is relatively simple and cannot explain many phenomena occurring in milling flutter.Therefore,the research of nonlinear cutting system it has become more common at first,and the consideration of nonlinear factors is the key to the research of nonlinear cutting systems.Nonlinear cutting force is a very important reason for the nonlinearity of cutting systems.Therefore,the thesis focuses on the prediction of milling flutter stability of nonlinear cuttfing forces.The main research contents include:(1)Firstly,the dynamic model of a single-degree-of-freedom flutter system considering nonlinear cutting force(cubic polynomial cutting force)is studied.Then the multi-scale method is used to solve the nonlinear dynamic system,and the stability leaflet is obtained.After that,the emphasis on nonlinear cutting force parameters is studied.The stability of the system is affected by the nonlinear cutting force parameters.As the nonlinear cutting force parameters increase,the stable region of the system decreases and the unstable region expands.Furthermore,the influence of external force amplitude on vibration amplification and its stability.In addition,the frequency of the external excitation and the change in spindle speed affect the slope of the amplitude curve and whether the system has a stable solution.(2)For the model of the two-degree-of-freedom milling system,the full-discrete method is used to analyze the flutter stability of the dynamic model,and then the general cubic polynomial cutting force is considered,and the multi-scale method is used to solve the problem.The influence of the nonlinearity of the structure and cutting force on the stability of the milling system.As the nonlinear cutting force coefficient increases,the unstable region expands,the nonlinear stiffness coefficient increases,the stable region of the lobes expands,and the unstable region decreases..The linear cutting force model and the general polynomial cutting force model are compared.(3)The exponential instantaneous cutting force and exponential average cutting force model are studied respectively,and the dynamic model is solved by single frequency method and multi-frequency method respectively.The simulation results of the two methods are in good agreement.Then,with the increase of nonlinear cutting force coefficient,cutting thickness index,radial immersion ratio and other parameters,the stability of the stable lobes is reduced.As the structural damping coefficient increases,the stability lobes the stable area is expanding.For the comparison of the four cutting force models,the four types of cutting force models,the largest area of the stability lobes are the linear cutting force model,followed by the exponential instantaneous cutting force model and the exponential average cutting force model.The stability of the force model is very close to the leaflet,and finally the general polynomial cutting force model.