Laboratory simulations with twin-disc machine on head check

Head check has been observed at the gauge corner of the high rail in shallow curve tracks for the last several years. Many head checks also develop into breaking out like flaking. Head check with breaking out causes increasing noise and rail breakage. Consequently the interest in countermeasures against head check with breaking out has been growing. Therefore, this paper reports the results of investigations of curved track with head check and laboratory simulations with a twin-disc machine simulated wheel/rail to find out the countermeasures. First, it was identified that head checks were mainly caused on curves whose radii were less than 800 m from analysis of rail inspection data. The high rails of the curved tracks are head hardened rail. Moreover, it was found that lateral forces at high rail of head hardened rail were about 10 kN from track inspection data. Next, laboratory simulations with the twin-disc machine were carried out five times. First laboratory simulation with a HH340 disc whose hardness was the same as head hardened rail was carried out by using the measured data at a curved track with head check. Head check with breaking out finally occurred on the rail disc. After that, laboratory simulations for countermeasure against head check were carried out with standard disc, bainite disc and hypereutectoid disc at the final condition of preliminary experiments. As a result, head check with severe breaking out did not occur on the bainite and hypereutectoid discs over 100 MGT but occurred on the standard disc. Therefore, we can discuss the factors causing head check from these simulations and these results indicate that laboratory simulations for the countermeasure can be performed with the twin-disc machine.