The critical damage mechanism on many GB passenger train wheels is Rolling Contact Fatigue (RCF) cracking in the rim. Evidence from field observations suggests that RCF damage occurs much more quickly as the wheelsets near the end of their life. Wheel manufacturing processes induce a compressive hoop stress in the wheel rim; variations in residual stress through the life of a wheel may influence the observed RCF damage rates. This paper describes experiments to measure residual stresses in new and used wheel rims to identify whether this could be a significant factor, and compares the findings from neutron diffraction and ultrasonic birefringence methods. The scope goes beyond previous applications of neutron diffraction to railway wheels and identifies key considerations for future testing.Assuming that the as-manufactured stress distribution was similar for all three wheels tested, it is found that the stresses are redistributed within the wheel rim during its life as material is removed and plastic flow occurs. However, the hoop stress near the running surface remains compressive and may not have a large influence on the RCF damage rates.
Compared with the metal bristles, the flexible bristles can reduce the heat and wear caused by the friction between the bristles bundle and the rotor, and improve the working stability and working life of the brush seal. In this paper, the L-shaped numerical mode is established to analyze leakage characteristics of flexible bristle brush seal. The flow field of brush seal is analyzed, and the effects of differential pressure, rotating speed and temperature on the leakage rate were studied as well. The leakage rate of the flexible bristles brush seal under different pressure and rotating speed was measured and compared with the numerical results. The results show that: Pressure drop mainly occurred in bristles pack; Small pressure difference, high temperature and high speed can improve the sealing performance, which, shows that the flexible bristles brush seal can well adapt to high temperature and high speed conditions; The leakage rate after running-in is slightly lower than that before running-in, and has better sealing performance, and the brush bristles arrangement is complete and tight after test, indicating that the flexible bristle brush seal has the ability of lasting and stable seal; The error between experimental results and numerical simulation results is less than 10%, and the variation trend is consistent, confirming the accuracy of the leakage rate obtained by numerical simulation.
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