Dwyer-Joyce, R.S., Lewis, R., Gao, N. and Grieve, D.G. (2003) Wear and Fatigue of Railway Track Caused by Contamination, Sanding and Surface Damage. In: 6th International Conference on Contact Mechanics and Wear of Rail/Sheel Systems : CM2003. CHARMEC , Gothenburg , pp. 211-220. ISBN 9163139286Full text available as:
The wheel rail contact operates in an arduous environment. Damage to the surface of either component is possible during manufacture, installation, or operation. The question arises as to how tolerant is the railway wheel or section of track to surface indentation or damage.
In this work a twin disc simulation has been used to relate the level of surface damage (as well as the way it is generated) to the fatigue life of the surfaces. A related problem is the presence of solid contamination on the track. Sand (applied for improved adhesion) or track ballast material can cause damage to the rail and wheel surfaces. These mechanisms have been explored to assess the effect on contact fatigue life and wear. The disc specimens have been either artificially damaged (with dents and scratches) or run with particles of sand or ballast material. The discs were then loaded and rotated at realistic conditions of contact pressure and controlled slip.
For normal operation of the contact, either dry or with water lubrication, surface dents and scratches have little effect on fatigue life. The normal plastic flow in the rail surface layer acts to close up dents. The failure of the disc is then by fatigue cracking across the whole surface with no particular preference to the dent location. Alternatively, if the contact is lubricated with oil then this plastic flow is greatly reduced and the dents act as stress raisers and fatigue cracks initiate from their trailing edge.
Sand or ballast particles are crushed as they enter the wheel/rail contact. The fragments indent the surfaces and rapidly roughen the contact faces. The surface indentation is relatively minor, but the presence of particles increases the level of traction (over the wet case) and promotes further surface plastic flow. This can reduce the residual fatigue life of the contact. Further, high concentrations of sand were shown to promote a low cycle fatigue process that caused very high wear by the spallation of material.
The twin disc simulations have shown that, under conditions similar to that of wheel/rail operation, surface damage is not a primary cause of fatigue failure. However, wear is greatly accelerated by the presence of solid contaminants and some evidence of a low cycle fatigue process was observed for sanded contacts.
|Item Type:||Book Section|
|Academic Units:||The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield)|
|Depositing User:||Repository Officer|
|Date Deposited:||12 Dec 2005|
|Last Modified:||08 Feb 2013 16:48|
Actions (login required)