Characterisation of plastic deformation and thermal softening of the surface layer of railway passenger wheel treads

Characterization of deformed pearlitic rail steel

“…The plastic shear strain was evaluated by measuring the angle α of the shear lines relative to the surface normal, see e.g. [4] and [5]. The angles α are obtained by manually tracing visible lines, and then using image analysis with linear regression to calculate the tangent direction of those lines at different depths.…”

“…The accumulation of strains has been investigated by e.g. [4] and [5] for rails and wheels respectively, where the strains were measured using the shear lines visible after etching. Micro hardness measurements also showed that the material had work hardened close to the surface, and in some cases [4], phase transformation to martensite had occurred (i.e.…”

The role of microstructure and its stability in performance of wheels in heavy haul service

“…The kinetics of this process are influenced by the time-temperature history during the skid event, composition and the condition of the pre-existing microstructure. For example, at elevated temperatures, the presence of carbide formers such as chromium will retard carbide dissolution [14], while carbide dissolution occurs at a greater rate in pearlitic microstructures that have sustained plastic deformation as a result of normal service conditions [2]. This is further complicated by the severe local plastic deformation, which itself can cause the dissolution of cementite [15][16][17][18].…”

“…The service conditions impose high contact stresses and severe thermal loads on the wheel rim. It is also well known that thermal inputs can be generated from wheel lockup (skid events), friction drag braking, traction forces, curving, hunting oscillation, etc., due to slip or creepage from wheel-rail interaction and wheel to brake block friction [1][2][3]. The combination of these thermal and mechanical loading conditions to the wheel rim can result in degradation or failure from one or more of the following modes:…”

Damage evaluation regarding to contact zones of high-speed train wheel subjected to thermal fatigue

“…Traditionally the main concern has been about martensite transformation due to its brittleness [15,[17][18]. Cvetkovskin et al noted that investigation of railway wheels taken out of service showed a deformed surface layer up to 5~10 mm below the wheel tread depending on tread position [19]. D. Peng et al described that under service conditions, the alterative thermal stress resulting in tensile circumferential stresses can be enhanced fatigue crack initiation and growth [20].…”