| The bogie is the main load-bearing component of the D-Series High-Speed Train,and the reliability of its structure directly affects the safety of the D-Series High-Speed Train operation.Considering that most of the current studies on the bogies of D-Series High-Speed Train have not given in-depth analysis and reasonable optimization to the reliability of the truck frame structure.In this paper,the truck frame of China Railways High-speed CRH3 is taken as the research object,and based on the modal analysis,static strength analysis and fatigue strength analysis to identify the weak points under the actual operating conditions,the structural reliability analysis is carried out with the help of Six Sigma Analysis module in the finite element analysis software,and the reliability of each response under the operating conditions is obtained,and the multi-objective reliability analysis and optimization design are carried out based on GA weighted neural network.The main research work done in this paper is as follows:1.The three-dimensional solid model of the truck frame was established using Solid Works,a three-dimensional modeling software,based on the geometric dimensions in the truck frame drawing.Then,the solid model was appropriately simplified and repaired in the Design Modeler module of the finite element analysis software ANSYS Workbench,and the mesh quality of the frame model was controlled by global meshing and local meshing,and finally the finite element model of the truck frame structure was obtained.2.According to the modal analysis theory,the first 20 orders of free and restrained modes of the truck frame of China Railways High-speed CRH3 are calculated,and the inherent frequencies and vibration patterns of each order of the truck frame are derived,and the vibration frequencies and vibration patterns of each order of the truck frame under the free and restrained modes are compared.The results show that the overall stiffness of the truck frame increases when the constraints of the actual operating state are applied to the truck frame,resulting in an increase in the modal frequency of the truck frame,but the increase in frequency gradually decreases with the gradual increase in the modal order.According to the weak link determination method,combined with the modal vibration pattern,the weak links of the truck frame in actual operation are mainly located in the connection area between the side sill and the transverse beam,the transverse beam tube mid-section,the connection arc area between the lower cover of the side sill and the rotary arm positioning seat,the sleeve,the end plate and the vertical plate,etc.3.According to UIC515-4 standard,the static strength analysis and fatigue reliability assessment of the truck frame of China Railways High-speed CRH3 were carried out.The analysis results show that under the three extraordinary load conditions,the area where the maximum stress is generated on the truck frame structure is located at the connection arc between the lower cover of the side sill and the rotary arm positioning seat,and the maximum stress value is 284.04 MPa,which is less than the material yield limit of 345 MPa.Under the13 simulated operating load conditions,the area of maximum stress on the truck frame structure is also located at the connection arc between the lower cover of the side sill and the rotary arm positioning seat,with a maximum stress value of 233.56 MPa,which is less than the allowable material stress of 240 MPa.After linear superposition of the damage values of the three stages,the total damage value is 0.8117,which is less than 1,indicating that the structural static strength and fatigue strength of the truck frame meet the design requirements.4.With the help of ANSYS Workbench finite element analysis software,the reliability analysis of the truck frame structure was carried out with the structural parameters of the truck frame as input variables and the maximum stress response and mass of the truck frame as output variables.From the results of the sensitivity analysis,it can be seen that for the maximum stress response,the greatest sensitivity is the input variable T1,the maximum stress response decreases sharply when the thickness of the connecting arc area between the lower cover of the side sill and the rotary arm positioning seat increases.The least sensitive is the input variable T3,which means that the maximum stress response is essentially constant when the wall thickness in the area where the side sill is connected to the transverse beam is varied.For the mass response,the maximum sensitivity is the input variable T3 and the minimum sensitivity is the input variable T1,and both are positive,the mass response increases when the wall thickness of the connection area between the side sill and the transverse beam increases or when the thickness of the connection arc area between the lower cover of the side sill and the rotary arm positioning seat increases.From the results of the reliability analysis,the probability that the maximum stress of the truck frame is less than 240 MPa,the stress reliability of the truck frame is 0.702.The probability that the mass of the truck frame is less than 3684 kg is 0.98924,and the probability that it is less than 3694.8 kg is0.99993.5.A BP network model based on GA weighting is proposed.Compared with the traditional BP network prediction model,the computational efficiency and prediction accuracy of this model are substantially improved.In the prediction model for the stress response,the prediction error of the improved model is reduced from within 10 MPa to within1 MPa;In the prediction model for displacement response,the prediction error of the improved model was reduced from within 0.09 mm to within 0.01 mm;in the prediction model for mass response,the prediction error of the improved model was reduced from within152.51 kg to within 13.00 kg.The multi-objective optimization design theory is used as the basis for the multi-objective optimization design of the truck frame structure.The optimization results showed that the truck frame stress response decreased by 40.865 %,the mass response decreased by 0.289 %,the displacement response decreased by 32.533 %,and the reliability of the three responses improved to 0.992,0.976,and 0.987,respectively.It can be seen that the reliability of the stress and displacement response of the truck frame structure is significantly improved after the optimized design while the mass is reduced.This result not only conforms to the lightweight design concept,but also provides a reference basis for the improved design of this type of truck frame. |
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