| Monolithic components are being widely used in the field of aviation due to their lower height, higher structural efficiency and higher working reliability compared with traditional riveted parts. However, owing to the large dimension and complicated structure, monolithic components deformation during machining is almost inevitable. Material property and structure of monolithic components, initial stress, cutting force, cutting heat and clamping forces affect the deformation of monolithic components, Among these factors, clamping force is one of the main factors, especially for thin-walled components. Both theoretical and experimental analysis methods are used for the Researches of the mechanism of monolithic components deformation. A fixture layout optimization method based on genetic algorithm was proposed. It is possible to predict and control the deformation of monolithic component by using the theoretically optimized results.A finite element model of A17050-T7451 milling process was developed. Cutting forces, temperature distribution along tool-chip contact face, flow stress distribution in cutting zones and plastic strain were obtained during machining. The vary curves of milling force for single tooth milling process were predicted using the FEM model. It shows that milling force increases sharply at the beginning of the milling process, and then decreases slowly as the relative static milling process keeps up and at last goes down fast as the tooth leave the cutting area. The temperature on the chip, workpiece and milling cutter were predicated. It shows that the temperatures on the chip are much higher than that on the workpiece. The reason of this phenomenon is mainly because that the majority of cutting heat is carried off by the chip during high speed machining. The chip formation process was simulated. The simulated chip morphology is similar with that obtained from experiment by using the same parameters as FEM. The cutting forces of FEM model were well agreed with the experimental results. The predicted results were used as the initial conditions for the multi-stress coupled model.A workpiece deformation control model was developed. The system stiffness model of workpiece and fixtures was established. Fixture stiffness, workpiece stiffness and contact stiffness between workpiece and fixtures were considered. The constraint conditions were defined and the criteria of fixturing stability were carried out. The contact forces between workpiece and fixtures were predicted. The normal contact forces predicted were well agreed with the experimental results. The workpiece deformation and contact forces between workpiece and fixtures under different system stiffness were predicted. And the workpiece deformation and contact forces between workpiece and fixtures under different cutting forces and clamping forces were predicted. It is proved that controlling of cutting forces is the basic factor that can reduce the clamping forces and clamping deformation for a given clamping scheme. So, the optimization of cutting parameters must be analyzed based on cutting forces. Selecting higher cutting velocity, smaller axial depth of cut, large radial depth of cut, can reduce workpiece deformation on the premise of cutting efficiency.The modal analysis model for frame-shaped thin-walled monolithic components was developed. Through study on the vibration modes during the milling process, it is indicated that the vibration direction of thin-walled monolithic components is mainly along wall thickness direction. It is can be concluded that the wall thickness direction is the weakest direction of monolithic components that can cause the deformation during milling process. As the wall thickness of monolithic components decreases, every rank of natural frequency decreases. The first ten natural frequency and modes were predicated for different clamping types. It shows that when the top surface is clamped every natural frequency and amplitude decrease comparing with no top clamping. To validate the simulated results, modal experiment was designed and the simulated results of the first six natural frequencies were compared with experimental results. The error between simulation and FEM is within 6%. For thin-walled monolithic components, to avoid resonance, the natural frequency of monolithic components should be predicated and the cutting parameters or clamping types should be adjusted. Multi-stress coupled model including monolithic components initial stress, cutting mechanical stress and clamping stress was developed. Monolithic components material properties, initial stress, clamping forces were added on the multi-stress coupled model as initial conditions. Transient milling forces and heat getting from the 3D FEM milling process were added on the multi-stress coupled model as dynamic loads. The moving track of dynamic loads is the same as the real tool-path in experiment for milling the workpiece. The monolithic components deformation and stress, strain distribution were examined during cutting process. The releasing process of fixture was simulated and the final deformation and distribution of stress and strain of monolithic components were achieved. To validate the multi-stress coupled model, the experimental test of frame monolithic components was designed. The predicted deformation of monolithic components by FEM was well agreed with the experimental results.A determination method of optimal clamping position and clamping amount for frame monolithic components was established. The objective function is to minimize the deformation of monolithic components during milling process. A genetic algorithm method combined with finite element method was proposed. A recurrent optimal model was established to optimize clamping position and clamping amount of frame monolithic components. Two study cases were carried out. Through comparing the deformation of monolithic components during machining using optimal fixture layout and the layout derived by experience, the effectiveness of fixture layout optimization method is verified.
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