THE WEAR AND FATIGUE BEHAVIOUR INVESTIGATION OF FILLET WELDING AND BRAKES IN WHEEL TYRE-RAIL SYSTEM OF RAILWAY VEHICLES SUMMARY Keywords: Wear, Fatigue, Wheel/Rail Interactions, Fillet Welding Steel wheels rolling on steel rails are the principal characteristic that distinguishes railways from other forms of transport. For effective and economical railway operation, important tribological issues must be addressed at the wheel/rail interface. Wheel and rail meet at a contact patch that is small and carries the full wheel load through which all steering, traction and breaking forces are transmitted. This contact patch sees a severe working environment. Stresses normal to the plane of contact can reach values several times the wheel or rail tensile strength and sometimes shear.s&esses in the plane of contact can exceed the shear yield stress. Rapid temperature rises, caused by relative slip between the wheel and rail, can reach several hundred degrees Celsius in routine operation, and over 10.00 °C in extreme circumstances. These stress and temperature conditions inevitably lead to wear, deformation and damage to the wheels and rails and a major goal of railroads is to arrange service conditions and maintenance procedures to minimize deterioration and hence extend component life. This is important, because rails-and to lesser extent wheels- constitute a large part of a railroad's asset base. Railways have more money invested in rail than in any other asset. Extending the life of these components and especially that of the rail, has a major impact on railroad profitability. An understanding of the tribology of the wheel/rail system is essential if wheel/rail life is to be extended. This system is complex and its behaviours depends on interactions between the materials (wheel, rail and any third body introduced, such as lubricant/debris mixtures) and environmental factors such as rain, snow, ice, etc. The material in and around the contact area is therefore highly stressed. High rates of wear might be expected for such a contact but. in addition, because the load is applied and removed many times during the passage of each train, there is the possibility of fatigue of the rail surface. The ideal material, which does not wear or suffer fatigue and yet is economically viable as a rail or wheel material, has not yet been found. However, service life extension of railroad components such as rail, wheel, wheel tyre and brake pads becomes an important achievement for engineers dealing with railways. XVIITherefore, the wear and fatigue behaviour investigations of rails, wheel tyres and brake pads were performed and occurred damages were characterized in this study. Then fillet welding operation was applied to worn surfaces of wheel tyres with two different electrodes by electric arc welding technique and by Gas Metal Arc welding method used in industry called Boden welding. After that wear and fatigue tests of specimens obtained from welded surfaces and joints were done. For wear tests, pin- on-disc testing method was used and the experiments were performed at four different loads as ION, 20N, 30N and 40N with 1 m/s constant sliding speed. The total sliding distance was 3600 m for every experiment. In the light of results of wear experiments, coefficient of friction, weight loss (mg), volumetric loss (mm3) and specific wear rate (g/N.m) values of specimens were calculated and advices were submitted to users. In addition, fatigue strengths and endurance limits of specimens were tried to detect during the fatigue tests performed for 300, 400 and 500 MPa stress amplitudes. XVIII.

THE WEAR AND FATIGUE BEHAVIOUR INVESTIGATION OF FILLET WELDING AND BRAKES IN WHEEL TYRE-RAIL SYSTEM OF RAILWAY VEHICLES SUMMARY Keywords: Wear, Fatigue, Wheel/Rail Interactions, Fillet Welding Steel wheels rolling on steel rails are the principal characteristic that distinguishes railways from other forms of transport. For effective and economical railway operation, important tribological issues must be addressed at the wheel/rail interface. Wheel and rail meet at a contact patch that is small and carries the full wheel load through which all steering, traction and breaking forces are transmitted. This contact patch sees a severe working environment. Stresses normal to the plane of contact can reach values several times the wheel or rail tensile strength and sometimes shear.s&esses in the plane of contact can exceed the shear yield stress. Rapid temperature rises, caused by relative slip between the wheel and rail, can reach several hundred degrees Celsius in routine operation, and over 10.00 °C in extreme circumstances. These stress and temperature conditions inevitably lead to wear, deformation and damage to the wheels and rails and a major goal of railroads is to arrange service conditions and maintenance procedures to minimize deterioration and hence extend component life. This is important, because rails-and to lesser extent wheels- constitute a large part of a railroad's asset base. Railways have more money invested in rail than in any other asset. Extending the life of these components and especially that of the rail, has a major impact on railroad profitability. An understanding of the tribology of the wheel/rail system is essential if wheel/rail life is to be extended. This system is complex and its behaviours depends on interactions between the materials (wheel, rail and any third body introduced, such as lubricant/debris mixtures) and environmental factors such as rain, snow, ice, etc. The material in and around the contact area is therefore highly stressed. High rates of wear might be expected for such a contact but. in addition, because the load is applied and removed many times during the passage of each train, there is the possibility of fatigue of the rail surface. The ideal material, which does not wear or suffer fatigue and yet is economically viable as a rail or wheel material, has not yet been found. However, service life extension of railroad components such as rail, wheel, wheel tyre and brake pads becomes an important achievement for engineers dealing with railways. XVIITherefore, the wear and fatigue behaviour investigations of rails, wheel tyres and brake pads were performed and occurred damages were characterized in this study. Then fillet welding operation was applied to worn surfaces of wheel tyres with two different electrodes by electric arc welding technique and by Gas Metal Arc welding method used in industry called Boden welding. After that wear and fatigue tests of specimens obtained from welded surfaces and joints were done. For wear tests, pin- on-disc testing method was used and the experiments were performed at four different loads as ION, 20N, 30N and 40N with 1 m/s constant sliding speed. The total sliding distance was 3600 m for every experiment. In the light of results of wear experiments, coefficient of friction, weight loss (mg), volumetric loss (mm3) and specific wear rate (g/N.m) values of specimens were calculated and advices were submitted to users. In addition, fatigue strengths and endurance limits of specimens were tried to detect during the fatigue tests performed for 300, 400 and 500 MPa stress amplitudes. XVIII.