Fatigue Life Analysis Of High-speed Train Gearbox Housing

With the rapid development of China’s high-speed railway,"China’s speed"is constantly moving towards the world.The rapid development of high-speed railway and the continuous improvement of its operating speed have higher and higher requirements for its train performance.As the core unit of energy conversion and transmission,the gearbox in high-speed train bogie plays a very important role in the power transmission and safe operation of high-speed trains.Therefore,it is of great engineering significance to carry out the research on the fatigue life of high-speed train gearbox.The research contents of thesis are as follows:This thesis takes the CRH380A gearbox box of high-speed train as the research object,and takes the fatigue life analysis as the research purpose.First,the CRH380A box material was cut and made into a standard sample for fatigue test in the laboratory.The number of stress cycles of the material at different stress levels was obtained by combining the high-frequency fatigue testing machine and software.According to the data results,the S-N curve was drawn by using the least square fitting method.In addition,the P-S-N curve with survival rate P of 50%,90%and 99%was drawn by power function fitting,According to the lifting method,the fatigue limit of the box material is 110MPa.Then,the 3D data model of the gearbox was established by combining 3D scanning technology with Solid Works software,and the 3D data model was imported into the finite element software for static strength analysis under abnormal load condition.The results showed that the starting condition was the most dangerous condition,and the maximum stress value of the gearbox reached 139.07MPa.Less than the allowable stress of the box material 190MPa,that the box strength meets the requirements;In addition,in view of the possible resonance problems,the constrained modal analysis is carried out on the gear box.The analysis results show that the frequency range of the first eight modes of the box is between 628.52Hz and1166.6Hz,which is far less than the internal gear meshing frequency of 2450Hz in the box when the train runs smoothly at high speed,It is concluded that the internal structure of the box will not resonate.Then,UM multi-body dynamics software is used to establish the high-speed power bogie system model,gearbox transmission system and gearbox rigid-flexible coupling model.Taking the average running speed of a high-speed train of 300km/h as the analysis condition,the time history curve of the external excitation load on the gear box under the high-speed condition of 300km/h was obtained by considering the wheel-rail excitation in UM,and the load time history curve of the box under the high-speed condition was obtained by considering the internal and external excitation in ADAMS dynamic simulation software.The obtained S-N curve and load history data were combined with ANSYS finite element simulation to carry out transient analysis under this high-speed working condition,and the equivalent stress nemogram of the box was obtained.The results showed that the fatigue weak point of the box under this working condition was located at the lower right end of the connection between the pinion box and the lower box,and the maximum stress was21.23MPa.Finally,the finite element simulation results were mapped to the fatigue life analysis software n Code to analyze the fatigue life of the gearbox.By using P-S-N curves with different survival rates,the fatigue life cloud maps of the gearbox at P=50%,P=90%and P=99%were obtained,respectively.It is calculated that the minimum number of cycles required for fatigue failure at the dangerous failure point of the box is 2.361×10~8.The load stress spectrum of the dangerous node was processed by rain flow counting,and the 8-level program load spectrum was prepared.The load spectrum was modified by Goodman formula and the nominal stress method and Miner’s rule theory were used to calculate the fatigue life of the box body as2.137×10~8 cycles,and the finite element simulation results were compared and analyzed.