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The paper describes the results of brake dynamometer experiments conducted to evaluate the influence of the tread temperature caused by tread braking on the wear rate of railway wheel tread. Employing a full-scale tread brake dynamometer composed of a brake block, a wheel, and a railwheel, wheel-rail rolling contact was imposed on the wheel tread surface heated under several braking scenarios. In dynamometer tests simulating the braking patterns of an actual vehicle exposed to unexpected hollow tread wear, no tread wear was observed after repetitive station stop braking, whereas tread wear was observed only for the rolling contact region after repetitive holding braking for load cases in which the internal tread temperature reached 300 °C. The wear rate of the rolling contact region was determined for various temperatures by performing experiments in which rolling contact was imposed at a constant tread temperature. The wear rate of the wheel tread increased rapidly with temperature at the tread surface for internal temperatures of 200 °C–300 °C. The wear volume obtained in the experiment was converted and generalized to determine the temperature dependence of the wear rate of the wheel tread as a function of the travel distance. The surface temperature of the tread and the internal temperature distribution were computed by FEM. The maximum temperature on the tread surface was estimated to range from 240 °C to 380 °C. The hollow wear of tread-braked railway wheels is primarily attributed to plastic deformation of the tread surface caused by hot rolling, i.e., rolling under a softened state with an increased temperature of the wheel steel on the tread surface. Verification of thermally activated process using Arrhenius equation confirms this conclusion.

The wear damage mechanisms occurring in the tribological pair bronze (CuSn12)-quenched and tempered steel (42CrMo4V) frequently used as reference materials for worm gearing power transmissions were investigated. Lubricated rolling sliding tests in the disk-on-disk configuration were performed. Different radial loads were applied in order to reach in the contact region Hertzian pressures close to the allowable design limit for bronze. The relative sliding speed was set to a level typical of screw-worm wheel transmissions. The tests were conducted up to a sliding distance of about 1800 km and periodically interrupted for measuring the specimen's weight loss and for inspecting the surface modifications. At the end of the test, the wear curves (specific weight loss vs. sliding distance) were built up and the surface damage was analyzed by means of optical and scanning electron microscopy. Different damage phenomena as scoring, pitting, spalling were identified, whose severity depends on the applied load. Microstructural features, i.e. the interdendritic phase, strongly dictate the subsurface crack path and crack branching .

Following research in 2000 in which the benefits of using lateral creep to establish friction levels in the wheel/rail contact region were established, the author and his team pushed the operating regime to include the smaller, slower realm of hand-operated tribometry. Implementing and managing of both flange lubrication, and top of rail friction modification programs have become more widely adopted and hence there is a growing need for measurements that assist in quantifying the effectiveness of these programs. Likewise, the need to measure the success of these programs has become paramount. The current design, hand-push tribometer widely used throughout the world has limitations previously outlined and operators have pressed for improvements both in operating convenience and, in particular, in controlling the operating regime that defines the values produced. The key element is in maintaining a low creep or percent slip condition that any particular measurement is associated with. The original tribometer and its predecessors were not capable of controlling creep in the few percent range. A related limitation in previous designs was the tendency to have the measuring wheel momentarily stop, thereby leaving one spot on the wheel susceptible to rapid changes to its local condition. In the new design, for each increment of forward motion, the measurement wheel always rolls to a new position of both the measurement wheel and the rail.

Researches on wear and fatigue in rolling contact from a tribological viewpoint are introduced. Transmission of traction and accompanying microslip in the contact region play critical roles in these phenomena. First, a quantitative analysis of wear in rolling contact with microslip is introduced, and it is shown that a simplified microslip theory can explain its behavior. Second, a marked change in contact fatigue life with traction is demonstrated, and a theory is introduced which relates the fatigue life with cumulative shear strain in the subsurface.

Recent studies show that pseudo-elastic TiNi alloy exhibits high resistance to wear, compared to many conventional wear-resistant materials. It is demonstrated that hardness is not crucial to the wear resistance of this alloy, since its hardness is lower than those of conventional wear-resistant materials. In order to understand the excellent wear behaviour of TiNi alloy and determine the factors responsible for wear resistance of the alloy, the performance of Ti–50.3 at.% Ni alloy during a dry sliding wear process was investigated and compared to a 2Cr13 steel. It was demonstrated that the TiNi alloy performed much better than the 2Cr13 steel, although the latter has a higher hardness. It is expected that the high wear resistance of TiNi alloy is attributable to its special mechanical behaviour, in particular its so-called pseudo-elasticity, caused by reversible martensitic transformation. Mechanical and thermal properties of Ti–50.3 at.% Ni alloy were studied and a FEM analysis was made to investigate the plastic strain in the contact region and to correlate the wear behaviour of TiNi alloy to its pseudo-elastic and thermal properties that are influenced by the martensitic transformation.

Wear tests of a silicon nitride ball pressed against a bearing steel rod were carried out at room temperature under lubrication with a light mineral oil using a lathe. The wear of the Si3N4 ball was measured at various fixed sliding distances up to a maximum distance of 3000 m. A mineral oil of low viscosity (base oil), and a mineral oil containing different amounts of phosphorus (added as tricresyl phosphate) and 0.2 wt.% S were supplied to the contact region between the Si3N4 ball and the steel rod. An addition of 0.5 wt.% P to the base oil reduced the wear volume of the Si3N4 ball by about 90% of that with the base oil. The reduction in the wear is ascribed to surface film formation. When using the base oil alone, the wear of the Si3N4 ball decreased more at high sliding velocities than at low sliding velocities.

The combined effect on railway wheels of a periodically varying contact pressure and an intermittent thermal brake loading is investigated in this paper. The development and redistribution of residual stresses in the wheel rim are clarified. Elasto-plastic strain cycles are calculated for some often occurring loading histories. These cycles are used as input to a damage mechanics model where the relative lifetime of the wheel rim can be estimated. Shakedown, cyclic plasticity and ratchetting are central phenomena discussed in the paper. A commercial finite element model computer programme for thermo-elasto-plastic analysis is employed. Temperature-dependent material data for a real wheel steel are used. Simulations with varying material data are carried out and measures to increase the lifetime of railway wheels are discussed.

Fretting wear of lubricated flat steel surfaces (100 mm × 100 mm ) was studied using a specially prepared test rig. The amplitudes of reciprocating sliding and the apparent contact pressure were 0.1–0.75 mm and 10 MPa respectively. The specimen surfaces were given various heat treatments and were mesh grooved for oil supply. Gear oil was fed to the sliding surfaces. Ungrooved surfaces gave severe fretting wear under the experimental sliding conditions used. However, significant reduction in fretting wear was obtained by grooving the surface. The effect could be obtained only when the spacing between the grooves was small, presumably because the oil was fed to the whole contact region owing to the smaller spacing.

The origin of fatigue cracks in fretting fatigue is the boundary between the slip and non-slip areas in the contact region. They arise at this boundary because of the high stress concentration. When a crack is formed it relieves the stress concentration at this point, and the boundary between the slip and non-slip areas moves inwards, resulting in the initiation of another crack which propagates more rapidly than the first crack because of the higher stress concentration. Crack formation can be prevented or retarded by ensuring that slip occurs over the entire contact region.

Measurements under potentiostatic control have been made of the increase in corrosion current when fretting occurs on the surface of various copper and aluminium alloys. Polarisation measurements on copper alloys indicate that the increase in corrosion current density due to fretting can be of the order of 1500 times. The increase in corrosion is attributed to continual rupture of oxide films and, to a lesser extent, to plastic deformation in the contact region.