Rolling Stock and Manufacturing The ring-groove rivets have been used in various wagon configurations.
Riveting new connection system A ring-groove rivet developed by CRRC adds high-strength connection and superior reliability to rail freight wagons. The fastening connections on railway freight wagons often come under a great deal of stress, emanating from a range of causes, incuding pressure from heavy loads, travelling over long marshalling yards, to harsh operation environments. Hot riveting is a commonly-used fastening mode for connections with dissimilar material and key parts, but the technique is not without problems, for example low-strength connection, complicated technology, timewasting, and pollution. To address fastening problems that exist in railway freight wagons, CRRC Fastening System has researched and developed the cold-extruding ring-groove rivet, which has demonstrated advantages of high-strength connection and superior reliability. The ring-groove rivet not only ensures the operation’s safety, but improves the overall quality of the wagon. At present, the ring-groove rivets have been used in various wagon configurations, such as open top, box, and double-layer depressed flat units. Total installation has reached 200 million sets.
The thread structure of a bolt (left) compared to that of the ring-groove rivet.
38 | ISSUE 5 - JUNE 2022 | RAIL EXPRESS
The assembly mainly consists of a ring-groove rivet and collar.
TECHNOLOGY ADVANTAGES • Superior mechanical property In comparison with high-strength bolts, the clamp force of the ring-groove rivet is increased by more than 10 per cent under the same specification, which can provide more reliable fastening connection. • Good consistency of clamp force The clamp force of bolts is easily affected by various factors, with the deviation of clamp force reaching to 20 per cent or above. But the clamp force of the rivet is generated by axial force through the riveting process, making it more stable. The wave range of clamp force is controlled within 3 per cent. • Reliable anti-loose performance When it comes to thread connection, there is no lateral clearance after rivet installation because the ring-lock structure existing in the
ring-groove rivet can prevent relative rotation and motion. Attenuation curves have demonstrated the attenuation speed of clamp force of the rivet is slower than the bolt under the same testing condition, which means the rivet is more suitable for parts connection under rugged conditions. • Better fatigue resistance The rivet uses an arc low stress integral structure, which can effectively increase shock resistance and fatigue resistance. Through the shock testing, shock resistance of the rivet is increased by 48 per cent over bolts. • Outstanding delayed fracture resistance The rivet uses a single ring groove to eliminate clearance after installation and effectively avoids hydrogen embrittlement, further improving corrosion resistance as well as delaying fracture resistance.
