What damages may occur to steel rails after prolonged use
According to the famous Hertz theory, when two sliding bodies come into contact under high stress, the surface or subsurface of the contacting body will generate extremely high contact shear stress. This type of contact shear stress is the cause of fatigue on the surface of the rail wheel rail contact. The main manifestations of fatigue on the contact surface between rail and wheel rail are:
(1) Fish crack
If the occurrence of fish scale cracks is not controlled in the early stage, they may detach or fall off, and even develop into nuclear damage on the transverse surface of the rail head, leading to rail breakage.
(2) Rail head fat edge
The fine cracks at the fat edge of the rail head can expand into transverse cracks and break the rail.
(3) Collapse (creep, black spots)
A typical manifestation of contact fatigue, the development result is severe peeling and flaking.
On long slopes and signal lines, if the train climbs, brakes, starts or the driver operates improperly, severe sliding friction occurs between the wheel and rail, resulting in the formation of quenched martensitic microstructure on the surface of the rail. The high hardness and low strength mechanical properties of the martensitic structure determine its metal fracture under the action of wheel rail contact stress, leading to cracking and peeling. The tip of the peeling crack is highly likely to become a fatigue source and expand into a rail head nuclear damage.
summarize
In addition to the above forms, it also includes rail core damage, rail joint damage, horizontal, vertical, and diagonal cracks in the rail, rail bottom cracks, and rail welding joint damage. According to the types, locations, and causes of rail damage in China, there are a total of 9 categories and 32 types of damage, which are numbered with 2 digits. The 10 digits represent the location and status of the damage, and the 1 digit represents the cause of the damage.
