Research On Fatigue Crack Propagation In Key Position Of High-speed EMU

High-speed EMU in the actual operation process,the EMU car experience on the operation of the actual line by continuous random load,car body may appear tiny flaw in the manufacturing process,also key bearing component of car-body in long charge on a line in the actual effect of fatigue damage of the random load,when the damage accumulation to a certain degree will lead to bearing cracks,cause fatigue failure,affect the body organization safety and reliability,which will seriously threaten the safety of the running train.In this paper,we select the body of high-speed EMU CRH2 to create the three-dimensional model of the body and the finite element analysis model based on its two-dimensional diagram.According to JIS E7106 standard,the load under each working condition is determined,and the load calculation is carried out in ANSYS finite element software,and the static strength analysis of the vehicle body structure is carried out.The results show that the equivalent stress of each position of the car body structure is within the allowable stress range of the corresponding material,so the static strength of the car body structure meets the requirements.Under the action of torsion load,the maximum stress amplitude of the car body structure is lower than the fatigue allowable stress of the corresponding material,so the fatigue strength of the car body structure under the static strength loading is also full of requirements.Based on the calculation results of the whole vehicle body,the key positions of the vehicle body were selected and the sub-model research method was adopted for the key parts of the vehicle body.The detailed modeling of the parts of the vehicle body should reflect the detailed shape,and the detailed stress analysis of the key parts of the vehicle body was carried out.The submodel method is applied to the detailed stress analysis of the key position of the emu,which improves the calculation accuracy and provides an idea for the future research on the local static strength analysis of the emu body.The dynamic stress test based on the actual line was carried out on the key position of the high-speed emu body(five beams of the traction converter).NCODE software was used to process and analyze the obtained data to obtain the stress spectrum of each measuring point and the equivalent stress amplitude of the actual operation of this model.The key position of the body beam and the bolt matching structure were analyzed by using the extended finite element method in ABAQUS.The finite element model of fatigue analysis was established,and the crack propagation was simulated by presetting different initial cracks,establishing constraints and applying cyclic loads of different amplitudes.According to the analysis of the calculation of the fatigue crack propagation life and fatigue crack propagation critical dimension found that:under the different initial crack,the defect of extended life expectancy and critical size are different,through the crack of critical size range can determine the safety threshold value of the defect,for high-speed emu overhaul and replacement of parts to provide advice and reference.Figure 60,table 11,reference 55.