Failure Causes Analytics of Rail Joint

Rail joint is also known as rail joint bar, rail fish plates. According to the various functions, the rail joint can be divided into common rail joint and compromise joint bar (include insulated rail joint, bugled rail joint, etc.) As the main rail track parts, the quality of rail joint have relative influence on the railway line safety. So before purchasing rail joint, or do the normal maintenance, check the quality and integrity of rail joint. Based on 20 years’ experience in manufacturing railroad fasteners, AGICO Rail analyzes the failure causes of rail joints.

The truth of rail joint bar

The rail joint is used to connect two ends of rails. Why choose rail joint instead of rail butt welding? Compared to the butt welding, the rail joint is more cost-effective and easy to install. In general, rail joint fastener rails with fish bolts together, there are some screw holes in the middle of rail joint. Rail joint can reduce the impact form wheel to rails, and increase the continuity of rail longitudinal deformation, what’s more, improve the smoothness of train operation.

Types of rail joint

1. By the size of rail track, rail joint can be classified into rail joint for light rail, heavy rail. The insulated rail joint for light rail include 8kg, 9kg, 12kg, 15kg, 18kg, 22kg, 24kg. The rail joint for heavy rail include 38kg, 43kg, 50kg, 60kg, QU70, QU80, QU100, QU120.
2. By the materials, rail joint is mainly made of medium carbon steel and high-carbon steel. Manufacturing methods of rail join include casting, rolling and forging.
3. By the international standard, there are UIC, BS, DIN, GB, AREMA and etc. Hot sale sizes of AGICO Rail include 115RE, 132RE, UIC45, UIC60, BS80A, etc.

Failure cause of rail joint

1. The crack on the surface of rail joint is closely related to the interaction between rail joint bar and rails. In the real working condition, the rail joint and fish bolt and end of rails are not a rigid integrity. The attack from wheel, exist of rail gap will result in the compaction of rail and rail joint bar and make the deformation of rail joint. Besides, the tightening force reduction caused by the abrasion between rails and rail joint also encourage the deformation of surface. The crack on the surface of rail joint is born in these situations. 

Therefore, the position, time, methods and rate of rail joint damage is decided by three elements, including interaction between rail and joint bar, the loading condition and the materials of rail joint. The interaction affects the position and time of crack, the loading condition and materials decide the extended mode and rate of cracks. When the crack appears on the upper open of rail joint, due to the less tensile stress, the extension is most affected by the materials of rail joint. When the crack appears on the lower open of rail joint, the tensile stress is bigger, the extension is most affected by the load condition of rail joint.

2. The season is another failure cause of rail joint. From the using status of rail joint, breakage of the rail joint in the winter is more than other three seasons. The breakage of rail joint might be related to the change of rail gap in the winter. The increase of rail gaps will improve the tensile stress of rail joint, especially in the position of the third and fourth screw holes. 1. The additional stress will lead to increase the failure of rail joint. The size, factor of additional stress and the threaten degree for service life of rail joint is unsure. 

3. Except for these two elements we mentioned above, some other reasons also can result in the failure cause of rail joint. As well know, there are some kinds of rail joint for special applications, such as the compromise rail joint bar, rail joint for tunnel. Because the stress state is more complicated, the maintenance is more difficult, meanwhile, the compromise rail joint is always affected by the corrosive air, so its failure rate is higher than the common fish plate’s.