Physics-Based Milling Process Simulation And Applications In Machining Distortion Prediction Of Aeronautical Monolithic Components

The distortion of monolithic components due to CNC machining is one of the most striking problems that aeronautical manufacturing technology has to face up to, and hinders the development of the aeronautical industry seriously. So, it has greatly academic and engineering value to predict and manipulate machining distortion of aeronautical monolithic components. Aim to predict machining distortion, key techniques of physical modeling and simulation in the milling process of aeronautical monolithic components are studied on deeply by using theoretic analysis, mechanics modeling, finite element simulation and experiments verification.In chapter 1, the background and significance of this dissertation are introduced firstly. Then, the state of the art in the research of physical simulation in cutting process and machining distortion of the aeronautical monolithic components at home and abroad is summarized. Finally, the research target, contents and overall frame structure of this dissertation are shown.In chapter 2, based on theoretic analysis of milling mechanism, complex milling process can be equivalently simplified as combination of fundamental orthogonal/oblique cutting process. Furthermore, through orthogonal straight-tooth milling experiments, empirical equations are established between fundamental cutting variables and cutting parameters when cutting is processed between carbide cutting tool and aeronautical aluminum ally 7050-T7451. The empirical equation is used as basic input variables in the following milling force model and milling temperature model.In chapter 3, by cutting edge discretization, mechanistic approach and unified mechanics of cutting approach are used to set up milling force model separately. Then, by milling force experiment, the prediction precision and relative merits of these two models are analyzed, and the validity of empirical equations established in chapter 2 is verified.In chapter 4, through the simplicity of heat transfer model, investigation of key techniques, such as analytical calculation of heat flux, thermal load discretization and dynamic enforcement etc. are carried out respectively for straight- and helical-tooth milling process. With given heat flux, a three dimensional finite element model is proposed to simulate the distribution of temperature field in the workpiece.In chapter 5, a prototype of physical simulation system is developed to simulate the whole NC milling process of aeronautical monolithic component. The key problems concerned with the finite element modeling and automation of simulating process, such as tool-path file discretization, material removal, dynamic load enforcement, adaptive mesh generation and dynamic mesh data management, restart analysis etc. are studied deeply.In chapter 6, with the help of the physical simulation system, two finite element models of milling process, corresponding to the whole- and local machining distortion prediction of typical aerospace components, are proposed respectively, and the distortion is predicted. By experiment verification, it can be concluded that the finite element modeling strategy of whole milling process proposed in this dissertation is correct and valid.In chapter 7, systematical summary for the whole work in this dissertation is given, and the future work is discussed.