Investigation On The Fatifue Strength To Different Lug Structures Of XXX Aircraft

The lugs is an important connection structure in the aviation aircraft,but due to the unique structural characteristics of the lugs,fatigue cracks generate easily during the service of the aircraft.According to the estimation of relevant departments,the hole edge cracks account for about one-third of the total number of fatigue cracks in the aircraft,so it has a great significance to study the fatigue strength of aircraft lugs.In this paper,based on the typical lugs of XXX aircraft,the influence of parameter variation on the failure load,fatigue life and fatigue crack growth life of lugs under three different structures is investigated by using the combination of finite element and test.The ABAQUS software is used to establish the tensile mechanical model of lugs.The failure load and failure mode of each parameter lug is calculated.Compared with the test results,the damage load of each type lug is increased with the increase of the extruded projection area.However,the change of the outer edge angle and the bottom chamfer don't affect the damage load of the lug,and the failure form of each parameter lug mainly depends on the extruded projection area.Based on the tensile model of the lug,the stress model of the hole edge under peak load is established,and the stress concentration coefficient of the different extruded projection area type ear pieces are solved.The comprehensive test results and numerical calculation results show that the Lug fatigue life of the lugs increases with the increase of the extruded projection area and the outer edge angle,and the influence of the extruded projection area on Lug fatigue life of the lug is greater than that of the outer edge angle.The median life of the fatigue of the ear does not change with the change of the bottom chamfer,and the crack always extends along the net section of each parameter ear.Based on the tensile model of the lug,a model for calculating the fatigue stress intensity factor of each type of lug is established.The accuracy of the finite element method is verified from the analytical method and the experimental structure,and the cracks in each type of lug are fitted.The stress intensity factor as a function of crack length.Fracture mechanics method is used to calculate the fatigue crack growth life of each type of lug.The results show that the fatigue crack growth life increases rapidly with the increase of outer edge angle,and the extruded projection area and the bottom chamfer have little effect on it.