Numerical Simulation Of Distortions Resulted From Residual Stresses In Aircraft Aluminum Parts

7000 series and 2000 series high strength aluminum alloys have been widely used as the key materials of aircraft structures due to their high strength-to-weight ratio, excellent corrosion resistance, and high fracture resistance. These precipitation -hardened aluminum alloys gain their high strengths through heat treatment involving a severe quenching operation, which introduces a very high level of residual stresses. Residual stresses not only result in unexpected machining distortion, but also increases the possibility of unpredicted fatigue failures and stress corrosion cracks (SCC). Therefore, it is of interest to investigate residual stresses in aircraft aluminum parts. In this dissertation, the main work done and the main results obtained are as follows.First, the research background of this dissertation is set forth, and summarized with the overview of the history and the current development of residual stress research, based on reading a lot of literatures, and summarized with the general situations of aircraft aluminum alloys quenching and numerical simulation, those are pointed out objective, significance, methods of this research.Second, on the numerical arithmetic of the quench-induced residual stresses ground, the quenching process of 7075T73 aluminum plate is simulated, the effect of material characteristics along with the plate temperature varying in quenching is considered, and on conditions of the different water temperature and different plate thickness, the quenching processes are compared. More, residual stresses of the plate relieved by stretching distortion are simulated. Otherwise it is compared between the simulating results and the experimental results of the literatures, they are good agreed.Third, forecast model, which is used to compute machining distortion due tooriginal residual stress existed in the aluminum alloy plate, is established. The total plate thickness is divided in some layers, single direction and bi-directional machining, as well as before and after residual stress relieving, are simulated, the distortions by original residual stress in the plate arising are received, making the experimental plate(250×55×45mm), and the plate is machined, get its distortion, the simulating results are validated by distortion value of the experimental plate, there is odds between them, but their distortion trend are coincident.Fourth, according to the actual aircraft frame part, the scale component is machined, and the quenching process of the scale component is simulated, which obtain temperature field and residual stress field in the frame scale component. Farther, applying the simulating method of the experimental plate validated by experiment, according to the processing of underside machining, top surface machining, and different machining sequences of the different trough on the scale component, the different machining processes of the scale component are simulated, its different distortion values caused by residual stress are get.The research is supported by National Natural Science Foundation of China (50175102) and Natural Science Foundation of Zhejiang Province (M503034).