types of rail damage

What are the Main Types of Rail Damage and What are the Preventive Measures?

Generally speaking, the main types of rail damage are rail crushing, side grinding, wave running-in and stripping, and these types of damage account for more than 80% of rail damage. For high-speed railways, the common damage types of high-speed railways include wavy wear, tread contact fatigue cracks, nuclear damage, and internal defects of welds.

Rail crush

Rail crushing is caused by the continuous plastic deformation of the rail due to excessive pressure on the rail surface. This is often a type of rail damage on heavy-duty lines, especially in the curved section of heavy-duty lines, rail crushing often occurs. The judgment is based on the stability limit value of the rail as the criterion, and the main method to prevent rail crushing is to increase the yield limit value of the rail.

Rail side grinding

Rails with side grinding are often on curved lines. Generally, for trains running on straight lines, the wheel treads are in contact with the top surface of the rails, and the contact mode is point contact. However, if the train runs on a curved line, due to the inertial force of the train, the wheel rim may also contact the rail, forming a two-point contact, which will cause side wear of the rail.

For the prevention of this kind of damage, at present, the main methods are to adjust the bottom slope of the rail and the superelevation of the curve, to adjust the gauge, to use wear-shaped treads, and to asymmetrically grind the curved rail head. In addition, the use of high-strength rail materials is also the main measure to effectively reduce rail side wear.

Rail corrugation

Rail corrugation is mainly due to the fact that after the rail is put into use, a certain regular waveform appears along the longitudinal direction of the rail, which leads to the unevenness of the track. At present, rail corrugation has become a major damage form of rails. Even if the railway with 60kg/m rail is adopted, the phenomenon of rail corrugation still continues unabated.

Preventive measures: usually by increasing the elasticity of sleepers and ballast beds, can significantly reduce the force the force of vertical action, thereby reducing the impact force of wheels on the track during high-speed driving, and slowing down the formation of rail corrugation.

Rail stripping

Same as rail side grinding, rail peeling also occurs in curved sections, which is also a common type of damage to rails. Rail peeling also occurs on general lines, but it is not as serious as curved sections. The main preventive measures are to increase the strength of the rail material and reduce the friction between the wheel and rail.

Nuclear damage to the rail

Rail nuclear injury, also known as black or white core, mostly occurs in the rail head, which is one of the most harmful rail injuries in all kinds of injuries.

The cause of nuclear damage: due to the existence of white spots, bubbles and non-metallic inclusions or serious segregation in the rail itself, under the repeated action of the train dynamic load, these fine fatigue sources gradually expand, so that these fatigue sections have a flat and bridge surface, usually called white core. When the white nucleus develops to the orbital plane, the fatigue stain is oxidized and gradually develops into the black nucleus.

In addition to material factors, there are other factors caused by nuclear damage: nuclear damage caused by contact fatigue, nuclear damage caused by rail stripping, nuclear damage caused by scrapes(welding repair), and nuclear damage caused by poor welding.

Rail joint damage

The rail joint is the weakest link on the line. The maximum inertial impact force of the wheel acting on the rigid rail joint is about 60% greater than that of other parts. The main damage to the rail joint is screw hole cracks, followed by cracks in the lower jaw, joint loss, saddle wear, etc.

(1) The main reasons for screw hole cracks are: unreasonable track structure, excessive impact on joints, poor maintenance status, etc.

(2) The main reason for the formation of cracks in the lower jaw is: the rail head has been subjected to excessive partial load for a long time, the combined effect of horizontal thrust and the deflection stress of the rail head, etc.

(3) The main reasons for joint drop and saddle-shaped wear are: there is a large difference in hardness between the quenched layer of the rail and the base metal of the rail, and there is no uniform transition. The rail end of the large rail joint is subjected to a large impact force from the wheel, and the line is suspended.

Rail bottom crack

There are generally three forms of rail bottom cracks: rail bottom transverse cracks formed by the development of rail bottom potholes (or scratches), rail bottom cracks formed by the development of rail waist longitudinal cracks downward, and rail bottom transverse cracks caused by poor welding technology. Rail bottom transverse cracks are very easy to occur in the heat-affected zone of the rail bottom.