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SUMMER TRAININGON

Electric Loco Shed-North Central RailwaysTOPIC: GEAR FAILURE

Submitted By:Rajeev Yadav Submitted To: MR. Sulabh Nalwaya (Lecturer)IN GUIDELINES:MR. N.P. SINGH2Contents:About Electric loco shedGearTypes Of GearGear failure Recognition Of gear failureCauses of gear failure

About Electric Loco ShedThe electric loco shed, Kanpur was established in 1965 with the Electricification of Mughalsarai-kanpur.The shed started functioning with a meager holding of 11 imported WAM-1 type locomotives for passenger services.Present holding of shed is 201 locomotives (43-WAP4, 153WAG7, 02-WAG-9, &3-WAM4GEARAgearorcogwheelis arotatingmachinepart having cutteeth, orcogs, whichmeshwith another toothed part in order to transmittorque.

TYPES OF GEARSpur Gears

Spur gears are by far the most common type of gear and with the exceptions of the "cog" the type of gear that has been around the longestSpur gears have teeth that run perpendicular to the face of the gear.

Helical GearsHelical gears are very similar to spur gears except the teeth are not perpendicular to the face. The teeth are at an angle to the face giving helical gears more tooth contact in the same area.

Helical gears tend to run quieter and smoother than spur gears due to the increased number of teeth in constant contact at any one period of timeGEAR FAILURERECOGNITION Of GEAR FAILURE : A GEAR has failed when it can no longer efficiently do the job for which it was designed. 2. Cause of failure may range from excessive wear to catastrophic breakage.

CAUSES OF GEAR FAILURE:POLISHING.WEAR.PITTING.SCORINGFROSTINGFRACTURE. PLASTIC FLOW.RIPPLING.RIDGINGPolishing

Polishing is a very slow wearing-in process in which the asperities of the contacting surfaces are gradually worn off until a very fine, smooth surface develops.

Cause: This condition is usually caused by metal to-metal contact during operation.

WEAR:

A surface phenomenon in which layers of metal are removed, or "worn away," more or less uniformly from the con tacting surfaces of the gear teeth

Cause: Foreign material in the lubrication system ordinarily causes abrasive wear.PITTING: A surface fatigue failure which occurs when the endurance limit of the material is exceeded, a failure of this nature depends on surface contact stress and number of stress cycles.

Cause: Pitting is usually caused by gear tooth surfaces not properly conforming with each other or not fitting together properly

SCORING:Rapid wear resulting from a failure of the oil film due to overheating of the mesh, permitting metal-to-metal contact; this contact produces alternate welding and tearing which removes metal rapidly fromthe tooth surfaces

Frosting :

Frosting occurs in the early stages of scoring. Usually the dedendum section of the driving gear is the first to show signs of surface distress, al though frosting can first show up on the addendum section.Cause: Frosting is caused by heat in the mesh, which results in only marginal lubrication.FRACTURE:Failure caused by breakage of a whole tooth or a substantial portion of a tooth; this can result from overload or, more commonly, by cyclic stressing of the gear tooth beyond the endurance limit of the material.

Cause: Failures of this kind are often caused by deficiencies in the gear tooth which result in a high stress concentration at a particular area. PLASTIC FLOW:It is caused by high contact stresses and the rolling and sliding action of the mesh.It is usually associated with the softer gear materialsCAUSES: It often occurs in heavily loaded case-hardened and through-hardened gearsRIDGING:This is the formation of deep ridges by plastic flow of surface and subsurface material.It shows definite peaks and valleys or ridges across the tooth surface in the direction of sliding.

Cause: Ridging is caused by the plastic flow of surface and subsurface material due to high contact compressive stresses and high relative sliding velocities. REFERENCE:N.P. SINGH (S.S.E.)WikipediaGogglewww. Northern central railway.com

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