Question

what is creep ? Discuss the theories propounded to explain probable causes of creep.

Answer 1

In railway engineering, Creep is termed as the longitudinal movement of the rail relative to the sleepers. Rails have a tendency to gradually move along the direction of dominant traffic.

Theories propounded to explain causes of creep-

1. Wave theory- According to this theory, wave motion is set up in the rail tracks because of moving loads, causing a deflection in the rail under load. The portion of the rail under the wheel gets slightly depressed due to the wheel load. Therefore the rails generally have a wavy formation.

2. Percussion theory- According to this theory, creep is developed due to the impact of wheels at the rail end ahead of a joint. As the wheels of the moving train leave the trailing rail at the joint, the rail gets pushed forward, causing it to move longitudinally in the traffic's direction, and creep develops.

3. Drag theory- According to this theory, the backward thrust of the driving wheels of a locomotive has the tendency to push the rail backwards, while the thrust of the other wheels of the locomotive pushes the rail in the direction in which the locomotive is moving. This results in the longitudinal movement of the rail in the direction of traffic, thereby causing creep.