Fatigue life assessment of key defective structures of locomotive body sleeper beam
In order to study the service safety of structures of sleeper beam with defects,firstly,the structural stiffness and deflection characteristics of the sleeper beam in bottom under different sizes were compared based on finite element simulation.According to the optimal structural test size,the equivalent fatigue bench test was carried out to obtain the stress distribution state and the potential crack position of the weld focus,and the consistency between the structure of sleeper beam and the simulation model was verified.Then,based on the structural integrity assessment method in BS 7910:2019 standard,the critical failure state of the structure was obtained by introducing the quantified crack defect,and the life prediction of the key weld area was realized.Combined with the numerical simulation method of fracture mechanics,the crack growth simulation of the local model structure was realized from the perspective of simulation,and the damage tolerance analysis of the structure with crack defects was completed.Finally,the reliability and difference of the results of the theoretical method based on standard evaluation and the numerical simulation method were compared and analyzed.The results show that the stress distribution of the submodel structure bench test of sleeper beam is consistent with that of the simulation model.The weak area of the submodel is concentrated in the fillet weld of the vertical shock absorber.Based on the BS 7910:2019 standard and numerical simulation calculations,the critical depths of the surface defects of the fillet weld of the shock absorber seat are 6.50 mm and 7.85 mm,respectively,and the corresponding fatigue load cycles are 1.029×105 and 1.121×105.The results of the two evaluations are in good agreement.
locomotive bodywelded structure defectFAD diagramfatigue life assessmentstress intensity factor
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