| Two new technologies have recently been developed that can help to solve some of the wheel rail contact problems. The first is a method of top of rail lubrication (TOR) or friction modification (FM). The second is a technique of laser glazing of steel rails. Both technologies help in reducing friction, wear, and energy consumption in the wheel rail contact. This research introduces the two technologies and presents some specific aspects of both methods. A variety of testing machines, including a 1:12 scale wheel/rail simulator (LA4000) were used to study the potential of these two new technologies on energy savings. LA4000 friction/wear studies were conducted to evaluate the effect of laser glazing and TOR lubricant on the lateral slip forces between a simulated wheel/rail. Three conditions under dry and lubricated environments were studied: unglazed wheel and an unglazed rail, an unglazed wheel against a glazed rail, and a glazed wheel against a glazed rail. The results of the tests indicate that the use of TOR and laser glazing does indeed reduce the lateral forces, which are an indirect measure of the damage caused to the wheel, rail and track. In order to develop an efficient top of rail lubrication system, all parameters affecting FM consumption rates have been studied. These parameters include speed, angle of attack, load and lubricant quantity. Also, experimental studies included material microstructure and microhardness characterization. Results showed that laser-glazed layer consists of martensite microstructure and is two to three times harder than the substrate.; In order to assess the impact of laser glazing on the thermal residual stress build up in the laser-glazed layer, a one-dimensional thermal stress analytical model was introduced. Also, the modified Goodman's fatigue criterion was used to evaluate the impact of laser glazing on rail fatigue life. Results showed that laser glazing introduces a high tensile residual stress in the laser glazed region and exacerbate the surface initiated fatigue cracks leading to undesired shortening in fatigue life. In order to alleviate this problem, laser shock peening (LSP) can be employed. With this process, compressive residual stresses can be introduce in a region of a greater depth than the laser glazed layer. |
