| With high mechanical properties and good machinability, 2024 aluminum alloy is widely used in aerospace field. But because of the characteristic of sensitivity to environment, it is very easy to be corroded by environment and affected its comprehensive mechanical properties. Every year, disastrous accidents caused by corrosion emerge in endlessly. At present, the influences of environmental factors on the high strength aircraft aluminum alloy need further study, especially the coupling effects of them. The Safety assessment work for the workpiece needs to be strengthened in corrosion environment. The research on fracture behavior of the sample containing crack needs to be improved. Thus, it is significant to study the corrosion behavior of high strength aircraft aluminum alloy in the environment. In view of above three key problems, the following studies have been completed.The law of corrosion resistance for 2024 high strength aircraft aluminum alloy was inquired. Taking 2024 aluminum alloy as experimental material, the corrosion behaviors of high strength aluminum alloy in the atmospheric environment were simulated by controlling the experimental environment factors of relative humidity, concentration and temperature. The corrosion morphology of surface and transverse section were tested by OM and SEM. The depth of corrosion pits and corrosion losses were measured to analyze the corrosion degree of the samples. Range analysis and variance analysis are used to explore the influence degree of relative humidity, concentration and temperature. The results show that the influence degree of three factors on corrosion resistance of 2024 aluminum alloy is relative humidity>concentration>temperature. The coupling effect of relative humidity and concentration is the most serious, and the effect level is very significant in the coupling effects among three factors on the influence of corrosion resistance of 2024 alloy.The corrosion evaluation model for 2024 high strength aircraft aluminum alloy was constructed. The corrosion resistance of high strength aircraft aluminum alloy in the corrosion environment is divided into five grades. On the premise of analysis of the influence factors of corrosion resistance, the fuzzy comprehensive evaluation model is constructed, which is suitable for high strength aircraft aluminum alloy. AHP is used to calculate the weight vectors of the influence factors. The memberships of influence factors are determined by the trapezium distribution function. Fuzzy operation is implemented on weight vectors and membership matrix to obtain final assessment results. Samples of A37, A27 and A17 are evaluated by this model. Corrosion grades of three samples are I, I, III, respectively.The fracture behavior for 2024 high strength aircraft aluminum alloy with corrosion defect was simulated. The corrosion pit is been equivalent to a corrosion crack. 3D finite element model is established to study the influence of corrosion pit on mechanical properties under loading stress. Eequivalent stress and stress intensity factor along the crack front are calculated to analyze the fracture properties of samples containing equivalent crack. The result shows that there is obvious stress concentration along the crack front. The fracture starts from the equivalent crack. Cracks with different shapes have different unstable propagation forms. |
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