What Is a Longitudinal Wave?

The rail frame is the main component of the railway track. The main material is manganese alloy. Its function is to guide the wheels of locomotive vehicles forward, withstand the huge pressure of the wheels, and transmit to the sleepers. Its main material is carbon steel, which has high strength and hardness, high elastic limit and fatigue limit.

The type of rail is expressed in kilograms per metre of rail mass. There are several types of steel rails used in China's railways, such as 75kg / m, 60kg / m, 50kg / m, 43kg / m, and 38kg / m. The cross-sectional shape of the steel rail adopts an I-shaped cross-section with the best bending resistance performance, which is composed of a rail head, a rail waist and a rail bottom. In order to make the rail better withstand the forces from various aspects and ensure the necessary strength conditions, the rail should have sufficient height, its head and bottom should have sufficient area and height, and the waist and bottom should not be too thin. Among the above-mentioned various types of rails, production of 38kg / m rails has been stopped, 60kg / m, 50kg / m rails have been laid on main trunk lines, and 43kg / m rails are generally laid on station lines and special lines. For heavy-load railways and railways in particularly busy sections, 75kg / m steel rails are laid. In addition, in order to meet the needs of structures such as turnouts, super bridges, and seamless railroads, China's railways also use special sections (asymmetric I-shaped rails with the central axis). At present, a lot of short special section steel rails are used, referred to as AT rails.

Rail damage is a more serious problem in rail transit, which directly affects

(1) After using the rail for a period of time, the rail tread surface is polished to a shape closer to the original shape (shape) of the rail, so that the contact point of the wheel and rail can be transferred to the center of the rail tread surface to reduce contact stress. Control the formation and propagation of contact fatigue cracks. By changing the position and shape of wheel-rail contact, the wheels of a train can also be polished to wear-shaped treads to change the position and shape of wheel-rail contact. After the wear-shaped wheel is used, the original tapered contact is changed into a circular arc contact, which reduces the lateral pressure and also reduces the wheel / rail contact stress. The wear-shaped tread is in contact with the rail surface because it is a circular arc contact. The tapered tread has been reduced by 70%, preventing the formation and propagation of fatigue cracks in the rail head.

(2) By improving the line conditions (such as the setting of the line parameters, the design of the bottom slope of the lower rail of the original line can be changed according to the actual conditions of the line. Changing the original 1/40 to 1/20 can reduce the lateral pressure on the stock, that is, reduce The contact stress between the wheel and rail contact; improve the smoothness of the track bed, strengthen the cleaning of ballast slag and other measures to improve the maintenance and maintenance of the line, the quality of the repair and maintenance is directly related to the size of the wheel and rail contact stress, which directly affects the generation of rail Contact fatigue damage time), can also change the wheel-rail contact shape, improve and reduce wheel-rail contact stress and lateral pressure, so as to achieve the purpose of reducing and eliminating contact fatigue damage.

(3) U71Mn steel rails with ordinary wear resistance can be selected on the line. ^[1]