Research On The Fatigue Of Aircraft Structures.

Aircraft structure will be fatigue damaged under the alternating load,the article discuss the fatigue problem of aircraft structure. Fatigue lifeestimation is the basis of the fatigue analysis. By the investigation, wecan get fatigue analysis methods and choose the proper structurecrack-forming life assess method.Based on the aircraft structure fatigue theory, the article discussedthe theoretical basis of methods that are usually used for aircraftstructure fatigue crack-forming life estimation, i.e. the stress severityfactor approach (normal stress approach), the local stress & strainapproach, detail fatigue rating approach(DFR). Also the processes of lifeestimation of these approaches are studied in the article. Under theseapproaches, the 1if e of the lower flange connection region between a rib 6and rib 8 of the front bar of some aircraft are estimated and the fatiguelife of simulator of the connection region is experimentally tested and theestimation results and the experimental results are compared. In thesimulator test, the artic1e gives the method for superposition of twodifferent phrase and unrelated load spectrums and the method can be usedto solve the same question latter.From the work done above, we can get the following conclusion' Allthese life estimation approaches can be smoothly used to predict the lifeof aircraft, but they have their own limits. During the course of the lifeestimation, if the experimental parameters can be carefully chosen,aircraft structure life estimation has a positive effect on the structurefatigue des ign.