Abstract: The head checks (HCs) at the gauge corner and shoulder of the rail from a heavy-haul railway in China are inspected by X-ray Computed Tomography scan technology (CT scanning). The three dimensional (3D) shape and space position of the real HCs are reconstructed by HCs planarization, HCs tip shape fitting and HCs plane space localization. The rail HCs propagation prediction method is presented in which the influence of the plastic zone at the HCs tip and are were considered. The results show that the CT scanning technology can get high-precision shape and characteristics of the real complete HCs, which realizes the 3D modeling of the nearly-flat HCs at the gauge corner and shoulder of the rail. The HCs propagation is predicted with the traffic accumulation according to the vehicle and track condition of the heavy-haul railway in China. It is shown that the maximum stress of the HCs by wheel/rail contact patch is at the rail surface and sub-surface with vertical distance of about 2-4 mm. There is no stress concentration at both the tip and the mouth of the HCs. The Von-Mises stress at the HCs tip by both leading outer wheels and both trailing outer wheels of the front and rear bogies in the same vehicle are close to each other respectively. The stress at HCs tip points below contact patch caused is by the front wheel smaller than that by the rear wheel when two-point contact happens between the front outer wheel and the high rail. The length and depth of HCs by prediction are close to those by microscopic observation. The propagation angle of the HCs along rail longitudinal direction by prediction includes the real propagation angles range of the HCs by microscopic observation.

Key words: crack propagation, rail, reconstruction, rolling contact fatigue crack, X-ray computed tomography scan