Numerical Simulation Of Amphibious Aircraft Body And Connection Strength Based On Friction Stir Welding Technology

In recent years,domestic large aircraft have been unveiled,in which AG600 as the world’s largest amphibious aircraft has attracted much attention.The biggest feature of amphibious aircraft is that it can take off and land on the water surface,and its hull structure bears the huge pressure generated by hitting the water surface.Therefore,in the process of aircraft development,it is necessary to undergo strict strength analysis to test whether the aircraft meets the strength requirements and ensure its flight safety.In this paper,the amphibious aircraft fuselage with friction stir welding is taken as the research object.Through the numerical simulation method,the finite element numerical simulation is carried out under three water conditions.The static strength of the main structure of the aircraft fuselage and the connection strength of riveting and welding are analyzed.The specific work is as follows:Firstly,according to the actual size of the fuselage,a three-dimensional geometric model was established in CATIA,and then imported into Hyper Mesh14.0 to establish a refined finite element model.The RBE 2 rigid body element was used to establish a mesh welding structure to simulate the two welding forms of friction stir spot welding and butt welding.Through the free modal analysis,the vibration mode diagram of the aircraft body is checked,and the connection structure of the finite element model of the aircraft is checked.The connection form between the structures is improved to avoid the connection failure.Secondly,the finite element model of the aircraft fuselage is subjected to three kinds of limited loads under three water conditions,and the static analysis is carried out by Opti Struct solver.The stress and deformation of the main structure of the aircraft fuselage are analyzed,including the 1-31 partition frames,fuselage skin,fuselage main beam and bottom keel beam structure.Based on the fourth strength theory,the results under different working conditions are compared and analyzed to find the dangerous positions of each main structure under dangerous working conditions.The safety margin value of the fuselage structure is calculated by the safety margin formula to ensure the safety of the fuselage structure.Finally,this paper gives the engineering method of riveting strength and friction stir welding strength check.Based on the static strength analysis of the main structure of the fuselage,the connection strength of riveting and welding at the dangerous structure is further analyzed.The results show that the stress of the rivet is uneven in the elastic range,and the overall stress situation shows the characteristics: large at both ends and small in the middle.The larger the rivet spacing,the more uneven the stress distribution.The overall force level of the rivet under the symmetrical stern water condition is higher than that under other working conditions,and the rivet does not fail under the three water conditions.In addition,the engineering method is used to check and analyze the strength of friction stir welding at the dangerous partition frame.The results show that both forms of welded joints meet the strength requirements,which further verifies the feasibility of the application of friction stir welding technology and provides guidance for aircraft structural design and static strength test of the whole aircraft.