| Welding defects are an inevitable problem in the welding process of large structures.The more obvious and numerous the welding defects of the structure,the more it will reduce the fatigue life of the structure,resulting in premature fatigue cracking.The bogie structure,as the walking part of the rail vehicle,carries the safety of the train and passengers.In the manufacturing process of bogies,once the more complex and hidden welding defects appear,it is impossible to directly investigate them.If such defective bogies are put into use,it will definitely cause serious production safety accidents.Therefore,it is necessary to evaluate the fatigue life of bogie frames with welding defects.In this paper,we focus on the effect of misalignment defects on the fatigue performance of bogie frame,by combining the test and simulation,we can obtain the law of misalignment defects on the fatigue life of bogie frame,which will have important engineering significance.(1)In order to investigate the effect of misaligned defects on the fatigue performance of Q450 steel members,fatigue tests were designed for steel welded members with different misalignment heights,different tensile loads,with and without weld roots and other variables to obtain the fatigue life and cracking locations of steel members under different conditions;modeling and simulation were carried out in accordance with the actual test parameters to compare the test data,and the results showed that: the simulation of Q450 steel members The results show that the fatigue life and cracking location of Q450 steel members are similar to those obtained from the test,and the simulation results are slightly larger than the test results.(2)Taking a domestic high-speed train bogie as the research object,combined with the structural characteristics of the bogie itself,the bogie was subjected to the highest defect quality level of misalignment defects on the selected key parts of the weld,and the original model of the bogie frame and the model of the frame with misalignment defects were established;according to EN13749 standard,the frame with and without misalignment defects were subjected to extraordinary load conditions,and the bogie frame was compared and analyzed to see if it met the static strength standard.The results show that the static strength of the bogie frame meets the actual requirements of the project.(3)Simulating the fatigue test in UIC515-4 standard,four fatigue load conditions were applied to the bogie frame and a three-stage loading analysis was conducted to investigate the effect of different misalignment amounts on the fatigue life of the frame.Based on the equivalent structural stress method to extract the equivalent structural stress of the key welds,the fatigue life of each node is calculated,and then the fatigue damage of the welds in each working condition under the three loading stages is calculated.By superimposing the accumulated fatigue damage of each stage,the total accumulated damage of each weld at different misalignment heights is obtained.The results show that an increase in the amount of weld misalignment has a significant effect on the fatigue life of the key welds of the bogie frame structure.The larger the amount of misalignment,the greater the cumulative damage of the welds.This paper verifies the validity and feasibility of the finite element model through the analysis of test and simulation results,obtains the fatigue life and cracking location of the misaligned components,verifies the static strength results of the bogie frame to meet the actual engineering requirements,and derives the relationship between the amount of misalignment of the bogie frame welds and the accumulated damage and fatigue life.The simulation model can effectively calculate the effect of misalignment defects on the frame,which has some practical significance in engineering. |
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