Numerical Simulation Research On Superplastic Forming Process For Aluminum Alloy Wallboard Of High-speed Train

With the development of rail transportation industry,stainless steel is gradually replaced by aluminum alloy in order to reduce the weight of the train.Aluminum alloy wallboard is the most typical part.However,because of the forming performance of aluminum alloy and the requirements of wallboard parts,the overall forming process of aluminum alloy wallboard parts has become a focus study.In this paper,an aluminum alloy wallboard of high-speed train was studied as a research object to research the forming process.Through analyzed the structural characteristics and technical requirements of aluminum alloy wallboard,a forming method by combining hot drawing process by gas and superplastic bulging was put forward.Then,the forming process of aluminum alloy wallboard was developed: negative hot gas drawing?positive bulge forming ? superplastic bulging forming ? trimming.By superplastic uniaxial tensile test,the hot forming performance of 5A02 aluminum alloy was studied to obtain the high temperature flow stress curves and analysis its superplastic deformation law.The results show that the material has a good superplastic forming characteristic and the maximum elongation reached 225% at 225? and 0.0001s-1 strain rate.Through metallographic analysis,the influence of heating time and temperature on the microstructure of 5A02 was studied.Research indicates that heating temperature is higher and heating time is longer,the grain size grows bigger.At the same time,based on the analysis of stress-strain curves,the real stress parameter equation of Fields Backofen was established.The superplastic forming process of aluminum alloy wallboard was analyzed by ABAQUS finite element analysis software.The deformation rules of process were studied from loading path of gas pressure,mold size and original blank size respectively.The study results show that the thickness distribution of the final forming wallboard parts is greatly influenced by the size of initial blank and the shape of preform mold.Through numerical simulation,the optimal process program of the aluminum alloy wallboard researched in this paper was worked out.