| The lightweight design of the railway vehicle structure can effectively reduce the dynamic force of the wheel and rail,reduce the manufacturing cost of the vehicle,and thereby improve the safety and reliability of the vehicle.The carbody is the main loadbearing component of the railway locomotive.It has the characteristics of complex structure,large weight,welding forming overall load,and multi-axle complex fatigue load.The lightweight design of the carbody has a significant effect on the weight reduction of the entire vehicle.The lightweight design of the carbody must meet its own multi-performance requirements,and the failure of the carbody is a typical fatigue failure.Therefore,the fatigue strength analysis of the carbody has important guiding significance for the lightweight design of the carbody.The design of the same type of carbody has reference value.This paper takes the middle car body of the 25 T passenger car as the research object,and compares and analyzes the static strength,stiffness,fatigue strength and fatigue life of the body before and after the weight reduction.First,the finite element model of the car body structure before and after weight reduction was established.The static strength and stiffness load conditions of the car body were determined according to the design standard EN12663-1/2010,and the static strength and stiffness of the car body before and after the weight reduction were calculated and analyzed.The analysis found that before the lightweight car body has a lot of performance indicators,it provides a reference and direction for the optimization design.The lightweight car body meets the requirements of the standard;the fatigue strength of the car body is determined according to the design standard EN12663-1/2010 For the load condition,the maximum principal stress method was adopted to convert the multi-axial stress of the car body into uniaxial stress,and the Goodman fatigue limit diagram of the car body material was determined.The fatigue strength of the car body before and after the weight reduction was compared and analyzed.According to the characteristics of the large-scale welded structure of the car body under dynamic load,a vehicle multi-body system dynamic model was established,and the American five-level track spectrum was applied to calculate the load spectrum at the four hollow springs,traction rods and couplers of the car body;The Box-Behnken matrix design method and polynomial fitting method establish a proxy model of the car body,which realizes the transformation from the load spectrum of the car body to the dynamic structural stress history;due to the difference between the car body plate and shell model to analyze the weld structure stress and the actual welded joint,The geometric concentration factor of welded joints is introduced for correction,and the structural stress calculated by the plate and shell model is corrected to the structural stress considering the stress concentration of welded joints.The method of structural stress and proxy model is used to calculate the dynamic structural stress history of the car body welds efficiently and accurately.Combining the equivalent structural stress and the main SN curve,the fatigue damage of the car body welds is calculated and analyzed.The fatigue life of the car body before and after the weight reduction is analyzed.The results show that the research method in this paper is used to effectively evaluate the multi-performance of the carbody before and after the lightweight design,and the dynamic structural stress calculation method combined with the equivalent structural stress and the main S-N curve method is used to damage the carbody weld.Fatigue life prediction for larger parts provides a method reference for the design of the carbody. |
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