2.2.1 Common defects caused by inappropriate manufacturing and use

As per increasing of demand for HSR, rail defects have become a critical challenge in operation because an incident could cause more losses when trains run at higher speed. Many researchers have proposed classification methods for typical types of rail cracks derived from different propagation orientations of rail defects [15, 16]. The most common rail defects are caused by inappropriate manufacturing and inappropriate use of rails, and they mainly include transverse defects (TD), detail fractures (DF) and split heads. TD (Figure 1a) is one of the most critical type

Figure 1. Transverse defect and detail fracture [15]. (a) Transverse defect. (b) Detail fracture.

of cracks that appear in railheads propagating along lateral direction. DF (Figure 1b) has an origination point and grows radially from the origination point. These types of defects are caused by inappropriate use such as excessive stress concentrations. The vertical split heads (VSH) (Figure 2a), which usually originate from manufacturing anomalies, cause the second most train derailments (after TD).
