Dynamic effect and safety limits of rail weld irregularity on high-speed railways

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By means of the vehicle-track coupled dynamics theory and the corresponding simulation software TTISIM, the effect of track concave irregularity located in rail weld zone on the dynamic responses of vehicle and track coupled system was investigated. The influence of the wavelength and amplitude of typical rail concave irregularity on wheel/rail dynamic responses was analyzed under high-speed operation. On this basis, the safety limits of rail concave irregularity were discussed. The results show that the rail concave irregularity will lead to obvious wheel/rail impact effect which is controlled by the shorter wavelength irregularity. Under high-speed operation, the wheel/rail dynamic responses decrease with the increase of irregularity wavelength, and grow gradually with the increase of running speed and irregularity amplitude. The wheelset decreasing ratio, which is the most affected dynamic index, becomes the controling index for running safety under the excitation of rail weld irregularity. The safety limits of rail weld irregularity decrease with the increase of running speed and rise with the increase of irregularity wavelength. For the overlapping shape weld irregularity, the safety limit is affected greatly by its short wavelength irregularity(wavelength is less than 0.2 m). At 200~250 km/h speed class and under 1m measurement scope, the safety limit of the cosine shape irregularity in rail weld zone is 0.82 mm, the maximum limit for the short wavelength irregularity of overlapping shape weld irregularity is 0.2 mm when the amplitude of the1 m wave is 0.3 mm(the acceptance tolerance of1 m wave), the maximum safety limit of the overlapping shape weld irregularity is 0.5 mm. At 250~350 km/h speed class, and under 1m measuremen scope, the safety limit of the cosine shape irregularity in rail weld zone is 0.62 mm, the maximum limit for the short wavelength irregularity of overlapping shape irregularity is 0.14 mm when the amplitude of the1 m wave is 0.2 mm(the acceptance tolerance of1 m wave), the maximum safety limit of the overlapping shape weld irregularity is 0.34 mm. The research results can provide theoretical references for the maintenance management of rail weld irregularities on high-speed railways.