Strength Analysis And Structural Optimization Of Key Components Of Portal Bogie

ULF is a 100% ultra low floor light rail vehicle,which has attracted increasing attention due to its low floor characteristics,good curve negotiation characteristics and flexible grouping characteristics.The portal bogie used is the key to achieve these characteristics.In the paper,a detailed structural analysis is carried out for the portal bogie,especially the important load-bearing components such as bogie frame,outer wheel shell and inner wheel shell.According to the EN13749 strength standard,the static bearing loads of important carriers are calculated and the static strength is evaluated with the finite element method.The rationality of the structure is judged based on the static strength evaluation results.The theoretical optimization design of the frame and the outer wheel shell is carried out with the method of modern structural optimization theory.The structure is secondarily optimized with the actual processing and manufacturing technology based on the concept cloud map.The static strength,fatigue strength and dynamic stiffness of the optimized model are checked,and then the optimized structure performance is comprehensively evaluated.The research focuses and conclusions of this paper are as follows:1.On the basis of the structural characteristics of portal bogie and the strength standard of EN13749,the influence of rolling and bounce movement of the car body on the loading of bogies is considered.The static strength evaluation of key components of bogies is carried out.The calculation results show that the static strength of the outer and inner wheel shells meet the requirements and the strength allowance of the outer wheel shell is large.But the maximum equivalent stress value of the frame exceeds the allowable stress and does not meet the requirements of the strength.Considering the stress distribution and the stress value,the frame and the outer wheel shell have the space for structural optimization.2.For the load-bearing beam of the frame with high static stress value,the beam section is adjusted with the material mechanics method to reduce the bending stress level,and then the entire frame is light-weighted using the method of size optimization.The topological optimization method is used to redistribute the materials of the shell which play a connecting role in outer wheel shell.Considering two levels of strength and stiffness,the two topological optimization methods,which take material allowable stress as constraint function and minimum deformation energy as objective function,are used to optimize the shell theoretically.And then,combined with the two optimization results and manufacturing process,the final optimization model is determined.3.The static strength check and fatigue strength calculation are carried out for the optimized frame and the outer wheel shell.The analysis results indicate that the stress distribution is improved and that the stress level of the optimized structure meets the strength requirements.The quality of the frame is reduced by 45.8% and the quality of the outer wheel shell is reduced by 6.4%,which improves the overall lightweight level of the bogie.The results of constrained modal analysis indicate that the stiffness is reduced after optimization of the structure,but the fundamental frequency value meets the requirements.The dynamic stiffness of each part of the structure is reasonable and the overall dynamic stiffness of the optimized structure performs good.