Eric Magel

The application of contact mechanics to rail profile design and rail grinding

Abstract While many railway engineers are exploring the benefits of the latest lubrication technologies, bogie types and metallurgies, the wheel/rail (w/r) contact mechanics are often overlooked or poorly controlled. But the geometry of the w/r contact permeates every facet of the w/r interaction, having profound effects on wear, fatigue, corrugation, stability and derailment potential. A pummelling model is being developed at the NRC Centre for Surface Transportation Technology to quantify the performance of rail profiles when loaded by a large number of measured new and worn wheels. Typical results are shown for the RE136-10″, UIC60 and RE141 rail profiles. Contact mechanics principles are further applied in a discussion of several aspects of rail grinding, including surface roughness, facet width and rail grinding interval.

Tribological interrelationship of seasonal fluctuations of freight car wheel wear, contact fatigue shelling and composition brakeshoe consumption

This paper proposes a novel theory which explains the strong linkage between brakeshoe metal pick-up and a corresponding increase in wheel tread wear and shelling during the wet winter months. The model suggests that pick-up metal forms through the tribo-reduction of oxidized wheel-rail wear debris. The presence of abundant carbonaceous residues and moisture is thought to promote this reaction. The consequent removal of carbon and wear debris from the wheel-rail interface increases friction during the dry periods to the range 0.4-0.6. This exacerbates wheel-rail wear and shelling. It is concluded that the most effective way to alleviate seasonal increases in wheel shelling and wear is to control friction in the range 0.2-0.4. This can be accomplished by inhibiting carbon depletion associated with metal pick-up or by applying commercial friction reducers.

Designing and assessing wheel/rail profiles for improved rolling contact fatigue and wear performance:

A quick survey of wheel and rail profiles used around the world reveals a huge range of options. Wheels come in cylindrical, conical, and concave variations, while rails range in shape from a very flat 14 in. (350 mm) head radius to a tightly crowned 6 in. (150 mm) head radius. The rationale for implementing one or the other is often institutional inertia—a strong tendency to continue doing what has been done in the past. But the impacts of wheel and rail profiles on the performance of the vehicle/track interaction are large and the decision should not be made lightly. Unfortunately, there are few well-matched “off-the-shelf” solutions from the existing commercially available profiles, such that new rails and wheels often suffer early failures or infant mortality. Through examples and case studies, this paper discusses the significant role that wheel and rail profiles play with respect to performance and safety and makes the case for wheel and rail profiles specifically suited to the needs of each railway. Various techniques for assessing the performance of systems of wheels and rails are reviewed and discussed.

Optimizing Wheel/Rail Performance on High Speed, Mixed Traffic Corridors

Between 2001 and 2009, a series of field, laboratory and theoretical studies were conducted with FRA sponsorship to better understand the wheel/rail interaction on Amtrak’s multi-user Northeast Corridor. The development of a new wheel profile, optimized rail profiles, friction management practices and a grinding strategy were key aspects of the program. The experience gathered over an eight year period, including many lessons learned, has been collected and provides a template for how optimization of the wheel/rail interaction can be undertaken on high speed, shared use railway corridors.Copyright