2022 Heavy Haul Session
Wear and Contact Fatigue Model for Rail
National Research Council - Canada
The presentation is based on a research program concerned with the life of rail carried out at National Research Council of Canada between 1984 and 1986. The program was concerned with four basic forms of wear: severe adhesive, mild adhesive, oxidative and abrasive. The laboratory tests were performed on 1/10th scale wheelset on pair or rail discs apparatus. The correlation between laboratory tests and field wear tests on rail steel of different hardness was found to be satisfactory. It was found that lubrication controls gauge face wear most effectively, however, it reduces wear rate on top rail surfaces to unacceptably low level which contributes to development of contact fatigue cracks. Comparative performance tests were carried out on several experimental batches of rail grease. To find out the rate at which the grease is consumed in the wheel rail interface a series of laboratory retentiveness tests were also performed.
The contact fatigue portion of our research program noted that although the load has strong negative effect on contact fatigue, the negative effect of counterformal wheel/rail geometry is disastrous. Mechanism of surface crack initiation by plastic instability was explored using especially designed test specimen which was subject to biaxial compressive and shear cyclic stress environment. It was found that, in case of plastic instability, lubrication decreases the onset of crack initiation which, when related to wear rates, was used to estimate the grinding interval. The results of these tests brought forward arguments in support of light but frequent grinding. This is called preventive grinding and the desirable grinding depth, period and patterns are described and discussed.
In the final discussion the author expressed his belief that the combination of thorough lubrication and preventive grinding will provide the railway industry with a means to substantially increase the rail life in curves and tangent tracks alike. It will also enable the railways to be in full control over the rail corrugation problem and a rail grinding program.