Research On The Lightweight Of EMU Car Body Based On The Hybrid Structure Of Composite Material And Aluminum Alloy

Countries with cutting-edge high-speed rail technology nowadays have embarked on the research and development of the next-generation EMUs,and China also set up efforts on an innovation project on CR450,a new generation of EMU that can run at400km/h.The top-level technical indicators have specified the lightweight requirements.Lightweight design is conducive to more efficient traction and operation,shorter distance of emergency braking,and less dynamic wheel-rail forces.The car body is a key component of an EMU,and its mass accounts for about 1/3 of the entire vehicle.Hence,it is of great significance to reduce weight of the entire vehicle,and the lightweight design of car body becomes the crucial research direction of the lightweight design of an EMU.Based on the head car structure of the high-speed EMU with a speed of 350 km/h,this paper proposes a lightweight design based on the composite material-aluminum alloy hybrid structure and the body mass has been reduced significantly.The main research contents are as follows:(1)The head car body of the high-speed EMU with a speed of 350km/h was numerically analyzed.The stress distributions of the car body under the action of static load and fatigue load were calculated.The stiffness and modal analysis were also carried out.And the strength and stiffness characteristics of the car body were obtained,which provides ideas and basis for carrying out lightweight design.(2)Based on the sub-model and NSGA-II genetic algorithm,the structural size optimization method was proposed.And the proposed method was employed to carry out the structural optimization of low-stress sheet areas such as roof,side wall,end wall and underframe.Taking the mass of the car body and the minimum structural stress under the specific working conditions as the optimization goal,and taking the thickness of the plate as the optimization design variable,the structure was optimized with the help of Isight and ANSYS programs.The mass of the optimized car body is reduced by 19.05%compared to the original car body.(3)Based on the three-dimensional Hashin failure criterion,a UMAT subprogram was written to simulate the damage progression process of carbon fiber composite bidirectional woven fabrics.The accuracy of the subroutine is verified by the existing literature test data.Furthermore,a comparison of glued,bolted,and glue-screw hybrid joints between carbon fiber composite laminates and laminates was completed.The research results show that the glue-screw hybrid connection can effectively improve the strength of the composite material connection.The simulation of multi-fastener connection structural strength was carried out,and it can be found that increasing the row spacing is beneficial to increase the connection strength.When the row spacing is 4 times the bolt diameter,the bearing effect of the connection structure is the best.(4)The research on carbon fiber composite cabs was completed.The strength,stiffness and modal calculation of the optimized composite material-aluminum alloy hybrid structure car body were carried out.For cabs with high stress level,lightweight and high-strength carbon fiber composite materials were used instead of aluminum alloys to reduce the weight of the car body.The weight of the proposed composite materialaluminum alloy hybrid structure lightweight head car body is 8661 kg,which is 21.01%lighter than the original car body.And the strength,stiffness and mode of the body meets the requirements of relevant standards.There are 66 figures,25 tables and 63 references.