Technical Research On Vibration-assisted Stretch Forming Of Aircraft Skin Panel

In the stretch forming process of aircraft skin panel,different stresses will be generated inside the sheet,resulting in uneven forming of the skin panel.After the forming process,part of the stresses will remain in the skin panel to form residual stress,resulting in a larger amount of springback,and excessive amount of springback is the main problem for aircraft skin panel.These defects will seriously affect the quality of the skin panel.In order to solve these problems,a new technology of vibration-assisted stretch forming is proposed in this paper.The main contents are as follow:1.Combined with the mechanism of vibration reducing residual stress,the principle of vibration-assisted stretch forming process of aircraft skin is put forward.Through theoretical exploration,the selection ranges of vibration-assisted stretch forming parameters is determined.Also,the application method of vibration-assisted stretch forming is given.2.An experimental device of vibration-assisted stretch forming is designed.The main components of the structure are introduced,and the strength of the main structure is analyzed.Modal analysis is carried out to obtain the natural frequencies,which should keep away from the applied frequencies in prevent of resonance problems.The hydraulic system diagram is given.Combined with modal analysis,the structural design is optimized.3.The finite element model of vibration-assisted stretch forming is established.Finite element analysis of stretch forming and springback of AA2024 material has been completed.The forming limit figure,the thickness reduction rate and the springback of the whole process of vibration-assisted stretch forming is obtained.The influence of vibration-assisted stretch forming is investigated in terms of formability,thickness reduction rate and springback.The best parameters is determined in the whole process of vibration-assisted stretch forming.4.The model of stretch forming and springback simulation in elastic vibration-assisted stage and vibration-assisted plastic stage is established.The effect of vibration in elastic stage and in plastic stage on the springback of skin panel at the specific frequency and amplitude is studied.The specific impact of duration of vibration in plastic stage on springback of skin panel is explored.