Study On Numerical Simulation And Experiment Of Machining Process For Aerospace Monolithic Components

The machining distortion of monolithic components is one of the most striking problems that aviation manufacturing industry has to face. To effectively reduce or avoid distortion, it has important value to realize the prediction of machining distortion of monolithic components. Based on the metal cutting principles and some key technologies of simulation, a method combining theoretical analysis with finite element simulation and experiment is adopted in this dissertation to study the distortion prediction.The static and dynamic mechanical properties of 7050-T7451 aerospace aluminum alloy are studied based on the high temperature tensileness experiment and the high-speed compression experiment. Material's modulus of elasticity, tensile yield strength, and ultimate tensile strength are gained. The material constitutive equation of 7050-T7451 is established based on the experiments.Two finite element models including plain strain orthogonal cutting model and oblique cutting model with helical cutting edges are established firstly based on the established material constitutive model. The orthogonal and oblique cutting force experiments are carried out, and a good agreement between simulations and experimental results is achieved, which proves the established finite element models are correct. Then stress, strain, temperature, chip formation, and cutting force are simulated using the models in milling process of 7050-T7451. The cutting force needed by aerospace monolithic components simulation is provided by finite element model of oblique cutting with helical cutting edges.A modeling method called analysis step is presented to improve the efficiency of numerical calculation. The coupled thermo-mechanical procedure is embodied by application of cutting loads. The cutting force is gained by oblique cutting simulation, and applied to corresponding cutting positions with the cutter rotation. The heat source in milling is simplified to moving band heat source, and the cutting temperature field is obtained by heat conduction analysis of workpiece. A restart analysis system is developed to apply the boundary condition and cutting loads, remove the material, and map the data automatically.To verify the validity of modeling method of analysis step, the machining distortions of three small dimensional spars are studied firstly. Key factors influencing distortion such as initial residual stress, cutting loads, fixture, cutting sequence and path are synthetically considered. The processes are simulated automatically using the developed analysis restart system. The milling experiments are carried out, and the experimental results agree well with the simulations, which proves the presented method is correct. Based on the above studies, the machining distortion of a large aerospace monolithic components spar is studied. Due to the complexity of technics and structure of the part, its process and structure is simplified based on the modeling principle of finite element analysis of aerospace components. Then, its milling process is simulated using the presented modeling method, and the machining distortion is predicted successfully. The total...