RAIL WEAR DEVELOPMENT - MEASUREMENTS AND EVALUATION

As part of two separate research projects rail profile, rail surface hardness and track geometry have been measured on a railway track, which is almost exclusively devoted to commuter train traffic, for a total period of three and a half years. This report presents results from these measurements concerning rail wear and in what way different factors influence rail wear. Also the traffic situation at the test sites and the methodology concerning measurements and evaluation are presented. The shapes of rail profiles in curves with different radii and at different stages of accumulated traffic tonnage were compared to each other. From these comparisons it can be seen that the wear is distributed across the rail profile in a way that tends to promote a uniform or almost uniform rail profile shape. Also the influence of curve radius on rail wear rate has been investigated. Rail wear rates in different curves have been compared to rail wear rate on a straight track. The influence of curve radius on rail wear rate has been found to be substantial. Measurements performed at different sections in a curve show that vehicle behaviour probably influences rail wear significantly. When leaving a curve and heading for a straight track the acceleration of the vehicle may increase the rail wear. Weather data from nearby located meteorological stations has been compared to measured rail wear. Especially precipitation has been found to affect rail wear, but also air temperature may influence rail wear. Track-side lubrication of the rail in curves can significantly reduce rail wear. The reduction is however dependent on both the distance after the lubricant device and the radius of the curve. Weather conditions may also influence rail wear in lubricated curves differently than in non-lubricated curves. This is probably due to that the lubricant is affected by weather conditions such as precipitation and air temperature. Also the rail steel grade influences the rail wear. To investigate this test sites with both UIC 900A and UIC 1100 grade rail steel were examined. Higher rail steel grade was found to reduce rail wear. The effect of lubricating the rail compared to the use of different rail steel grades was also examined. New rails can have a different wear rate compared to old and worn rails who have already accumulated traffic tonnage. This may be due to the fact that worn rails usually have rail profile shapes that are different from that of new rails. This leads to altered contact conditions between wheel and rail and thus altered wear conditions. Another reason may be that accumulation of traffic tonnage results in plastic rail deformation which leads to increased surface hardness and thus increased wear resistance. (A)