| Freight train are developing in the direction of further heavy-duty and high-speed,and the loads they bear are more severe,so frequent fatigue damage accidents occur during operation.Among them,during the maintenance of the bogie bolster,it is often found that multiple parts have fatigue cracks of different degrees,which seriously affects the safety of normal railway operation.This article takes the K6 bogie bolster running on the Daqin line as the research object,carries out the finite element strength analysis,and analyzes the crack propagation of the bolster with cracks.The research first established a reasonable finite element model of bolster stress analysis using ABAQUS finite element software,and on this basis,further conducted numerical simulation analysis of micro-crack growth and fracture of the weak part of the bolster fatigue strength.The research results can provide help for the improvement and maintenance of the bolster structure.It also provides a reference for the simulation analysis of fatigue crack growth and fatigue life of thin-walled complex structures such as bolsters.The main research contents and results are as follows:1.Combining the main parameters of the K6 type bolster,and based on the TB/T1959-2006 "Static Load and Fatigue Test of the Bolster" standard,a three-dimensional finite element model of the bolster based on nonlinear contact problems was established.Based on the comparison and analysis with the test results,the effects of loading form,test bench axis/surface distance,grid division and contact coefficient are discussed.The results show that the contact conditions have an important influence on the results of the finite element analysis.Among them,the reasonable friction coefficient μ=0.4;The reasonable division of the mesh for the high-stress parts can effectively improve the simulation accuracy;Under the load-bearing working condition,the reasonable shaft/surface distance L=160mm;the loading form has little effect on the calculated stress;the finite element analysis results obtained the dangerous parts where the fatigue cracks of the bolster may propagate under each working condition.2.According to the actual cracking position of the bolster,according to the loading condition of the bolster fatigue test in the standard.FRANC3 D three-dimensional fracture analysis software is used to insert cracks of different sizes at the weak fatigue position of a reasonable finite element model to establish a crack model.By calculating the stress intensity factor range under each working condition to determine whether the crack will propagate.The results show that the initial size of the crack propagation at the drain hole at the bottom of the bolster is 1 mm.The initial size of the crack propagation at the bottom of the outer hole is 2 mm.The initial size of the crack propagation at the arc transition is 3 mm.3.Insert initial cracks in each fatigue-dangerous part,and perform crack propagation simulation calculation for 106 loading cycles of 10 loading units respectively.The law of crack growth rate and stress intensity factors at different stages of growth were obtained.The results show that among the three dangerous positions,the cracks at the drain hole at the bottom of the bolster are the most dangerous,followed by the bottom of the outer hole,and the arc transition at the end is less dangerous;the crack growth life is mainly in the range of smaller crack size Therefore,in engineering practice,crack initiation should be suppressed as much as possible and casting defects should be reduced;the analysis verified the rationality of the bolster crack growth simulation analysis;and further discovered the surface crack growth law,that is,regardless of the shape of the initial crack,with The crack propagation will eventually expand into a semi-elliptical crack with a certain depth-to-length ratio. |
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