Study On Stretch Forming Process Of Multi-Curvature Skin Parts For High-Speed Train

As the key parts of high-speed train,the service life and performance of the skin parts are directly determined by the quality of the skin.In the choice of materials,aluminum alloy material is used to achieve the purpose of lightweight body;In its manufacturing process,skin stretch forming process is widely used because of its simple forming process and high forming accuracy and small springback.However,due to the material properties of aluminum alloy itself,section distortion and springback are unavoidable in the process of tensile forming.Therefore,the study of aluminum alloy skin tensile forming technology is of great significance to the manufacturing of rail trains in China.In this paper,the front skin of high-speed train is taken as the research object,and the influence of process parameters on the drawing forming process of stiffened surface skin is analyzed by using the finite element software.The forming accuracy is improved by optimizing the clamp track,process parameters and die surface.The main work contents are as follows:The elastic refolding equation of the skin parts was obtained and the forming defects of the skin parts were analyzed.The surface skin was formed by predrawing,stretching and filling.The mathematical model of clamp track was established,and the force of surface skin friction unit was analyzed.The influence of friction coefficient was introduced into the calculation of clamp track,and the mechanical model of stretching track was established.The clamping track was optimized under the premise of satisfying the calculation assumptions.The finite element model of stiffened surface skin drawing forming was established,and the finite element simulation of three stages of surface skin predrawing,stretching bending and filling and the springback process were carried out.The stress at the T-bar position of the surface skin and the stress distribution of the surface skin as a whole were analyzed.By comparing the simulation results before and after trajectory optimization,the change law of stress distribution,equivalent strain and springback amount was obtained.The influence law of different pretension amount,supplementary tension amount and die groove depth on the equivalent stress,equivalent plastic strain and springback of surface skin was analyzed.And by studying the forming defects at the surface skin reinforcing bars,The influence law of different drawing forming technology on the cross-section distortion of surface skin is obtained.The springback compensation of curved skin was studied according to the springback law of skin.Select appropriate springback iteration parameters mould compensation,curved surface is obtained by curve fitting skin elastic resilience curve equation of iterative compensation,and aiming at play renaturation equation curve of difference,string section,the three kinds of tangent iteration method in finite element simulation and optimization,so as to get the most suitable surface skin stretch forming compensation method;According to the results of mold curvature optimization,the influence of mold curvature optimization on the T-bar position and section distortion of curved skin and the precision of skin forming profile was explored,and the influence rule before and after the modification of mold surface was summarized.This paper studies the drawing forming process of the body skin in high-speed train,analyzes the influence of process parameters on the forming precision of drawing forming,and optimizes the drawing track and die,which provides technical support for the forming precision of aluminum alloy curved skin parts.