Study On Load Characteristics Of EMU Bogie Frame Based On Dynamic Simulation

As an important load-bearing structure of high-speed EMUs,the structure bears complex multi-source load excitation during its service.Currently,architectures are often designed for fatigue strength based on standard guidelines such as EN 13749,JIE 4207 and TB/T3549.1.Although fatigue strength design according to the standard can ensure the fatigue strength of the structure,the fatigue strength assessment according to the load type and working condition combination in the standard results in a large margin.In order to evaluate the load of the fatigue strength of the bogie frame to fit the load in the actual running line and operating state of the vehicle,it is necessary to carry out a study of the load characteristics of the frame that meets the operation of the vehicle.In this paper,the load characteristics of the structure under different operating speeds and different curve conditions are obtained through dynamic simulation,and the load spectrum is compiled and the fatigue strength of the structure is evaluated based on the load spectrum.Taking CR400 BF trailer bogies as the research object,this paper through vehicle dynamics analysis model based on SIMPACK dynamics simulation software.Taking the line from Bishan to Jianyangnan Station of Chengdu-Chongqing high-speed railway as input,the influence of line and running speed on the load of the frame was determined.The results show that the load borne by the bogie frame increases with the increase of the vehicle speed,and the influence of curve radius on the load is not obvious.The cyclic counting of the load time history of the structure is carried out by the rainflow counting method,and the three-dimensional load spectrum of the main load of the structure is compiled.Based on the Haigh fatigue curve with the average stress value greater than 0,an average load correction method is constructed to convert the three-dimensional load spectrum into a two-dimensional load spectrum.Through the kernel density estimation theory,the test load spectrum is extended to the whole life operating mileage.Referring to the method provided by FKM,the luffing cycle coefficient was calculated,the equivalent constant amplitude load calculation method of the luffing cycle was determined,and the constant amplitude load spectrum of the typical load fatigue test load of the frame was constructed.Comparison with standard load shows that the amplitude of the random load spectrum based on line test is much smaller than the amplitude of the standard test load spectrum.Based on the ANSYS platform,the framework finite element analysis model was created,the program was compiled to create the node weld coordinate system,and the nodal stress component per unit load under the weld coordinate system was obtained through the weld coordinate system.Referring to the multiaxial fatigue analysis method provided by IIW,the material utilization of each node of typical welded joints under the random load spectrum of the frame and the standard test load spectrum was evaluated.Whether it is a random load spectrum or a standard test load spectrum,the distribution trend of material utilization at each node is consistent when fatigue strength is evaluated,and the maximum point of material utilization is the same.The fatigue strength evaluation based on the standard test load spectrum is more conservative than the random load spectrum evaluation.Therefore,by testing the load characteristics of the structure and evaluating the fatigue strength based on the random load spectrum,the lightweight design of the structure can be effectively carried out.