Скачать или смотреть Creep in rails | theory of creep | Railway Engineering | GATE ESE IES SSC JE

follow us on instagram   / engineerscoach  

Creep:

The creep of rails is the longitudinal movement of rails in a track. It is also called as travel of rails.

Theories of creeps:-

1.Wave action or wave theory:-As train is passing under the rolling wheel, the portion under rolling wheel is compressed and depressed slightly due to wheel loads. As wheel moves, this depression also moves and the portion which is under depression previously comes back to its original position. This produces wave action which causes creep in forward direction.

2.Percussion theory:-This type of rail creep occurs mainly due to impact ofwheel. In this type, when wheel pass over joint, the trailing rail depresses down and wheel gives impact to the end of facing rail which results in creep.

3.Accelerating or starting of a train:-At time of acceleration, wheel gives backward thrust which causes creep.

4.De-accelerating or stopping of train, due to application of breaks:-If sudden stopping takes place, breaking effect tendsto push the rail forward and thus causes creep in forward direction.

5.Alignment of track:-Creep is more on curved portion than straight portion.

6.Expansion and contraction of rails is happens due to temperature variation. Creep may also cause due to expansion and contraction of rails.

Prevention of creep:-

1.Pulling back the rail to original position

2.Provision of anchors and anti-creepers should be done

3.One should increase number of sleepers per rail length

4.One should provide sufficient ballast and packing with care

5.For good grip steel sleepers are used

What is Rail Creep ?

Creep in rail is defined as the longitudinal movement of the rails in the track in the direction of motion of locomotives. Creep is common to all railways and its value varies from almost nothing to about 6 inches or 16cm.

Causes of Creep

The causes of rail creep can be broadly classified into two categories

Major Causes of Creep

Major causes of creep also known as principal causes of creep. Follows are the major causes of creep in rail

1.   Creep may be developed due to forces that come into operation when the train is starting or stopping by application of brakes. Increase of starting the wheels pushes the rail backward and hence the direction of creep is in backward direction.
When brakes are applied then the wheels of the vehicles push the rails in forward direction and hence the creep is in forward direction.

2.   Creep is also developed due to wave motions. When the wheels of the vehicles strikes the crests, creep is developed.

3.   Another reason creep develops because of unequal expansion and contraction owing to change in temperature.

Minor Causes Creep

Some of the minor causes of creep in rail are below:

Rails not properly fixed to sleepersBad drainage of ballastBad quality of sleepers usedImproper consolidation of formation bedGauge fixed too tight or too slackRails fixed too tight to carry the trafficIncorrect adjustment of super elevation on outer rails at curvesIncorrect allowance for rails expansionRail joints maintained in bad conditionMagnitude and Direction of Creep  

Creep is not constant over a given period, it is not continue in one direction or at uniform rate. Both the rails of the track may creep in same direction, perhaps both the rails reverse the direction of creep or one rail creep in opposite direction to that of other. 

Results and Consequences of Creep
Following are some of the undesirable consequences of creep

1.       The most serious effect of creep is the buckling of track in lateral directions.  If unattended and not properly removed then it causes derailments which leads to accidents.

Correction of Creep|Methods against Creep

There are two methods used for the correction of creep. These are

Pulling back Method
Use of Creep Anchors / Anti Creepers

Theory of Coning of Wheels

Coning of wheels

coning of wheels in railway engineering

flanges of wheel is never made flat,but they are in the shape of cone with a slope of 1 in 20.

coning of wheels is mainly done to maintain the vehicle in the central position with respect to the track.

What is coning of wheels?

wheels of the railway vehicles against general belief not flat but sloped, usually beveled by means of a cone semi-angle of the arrangement of 1/20 (rad.)this is to make the train run at the center of the railway track and to turn without slipping of its track. Since the wheels forms a part of a cone hence called conning of wheels. We will discuss here in detail why coning is provided and its benefits.
point and crossing in railway engineering.