Compilation method of anti-fatigue design spectrum for welded frame of subway vehicle

XUE Hai; TIAN Aiqin; MA Long; ZHANG Yufan

doi:10.16579/j.issn.1001.9669.2025.10.013

Abstract：In view of the problem that the formulary design load based on the design standard can't truly reflect the actual service conditions of the welded frames of subway vehicles,and a large number of online measured data information has not been fully explored in the structural design of the frame,an anti-fatigue design spectrum compilation method based on the stress-time history sample information measured at the weak position of the subway vehicle frame was proposed.The small stress threshold value was determined by clustering ordered samples using the rain-flow counting method to compile measured stress spectrum reflecting structural damage,determining the stress-frequency-damage relation based on the fatigue damage theory,and using the methods of Bayesian parameter estimation and kernel density estimation to obtain stress extrapolation results.Considering the stress concentration caused by structural geometry changes in the cross-section of the welding site,the hot spot stress method and stress linearization method were used to obtain the stress concentration coefficient,and the measured stress spectrum was corrected to achieve the compilation of the design load spectrum.The research results show that the small stress threshold value is 3.18 MPa determined by extrapolation of stress extremes and the relation analysis between normalized stress-frequency-damage,which is 8.19%higher than the stress threshold value determined by traditional methods,the effect of discarding the number of small stress cycles is significant.Considering the load dispersion and stress concentration factor at the weld seam,while ensuring that the structure meets the current service conditions,the relation between the design mileage and equivalent stress is determined,the necessity of compiling the design spectrum is emphasized further.The above research builds the construction method of load spectrum compilation and the equal strength design of structures.