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• The wear resistance of U75V rail treated by laminar plasma was significantly improved in actual line. • The generation of internal cracks in quenched area is related to the central ablation during preparation process. • The interface crack is closely related to the microstructure inhomogeneity caused by decarburization on the rail surface. The surface discrete hardening of laminar plasma (HLP) is an effective method of improving wear resistance for rails. While fracture failures on as-treated rail heads are still unavoidable and the related crack mechanism is unclear. As-treated U75V rail and untreated standard U75V rail were installed simultaneously on railway for comparison. The wear form and cracking mechanism of the rails after service are studied in detail. The results show that wear resistance of HLP-treated rail is improved dramatically compared with untreated ones. The wear depth of HLP-treated rail serviced for 9 months is still less than that of standard rail serviced for only 3 months. Central ablation induces overheated structures and hot cracks, resulting in cracks within the quenched area. Decarburized layer is the main reason for a ring-shaped reticular ferrite existing at the quenched area edge. Crack initiation at the interface is facilitated by the presence of reticulated ferrite and a non-uniform microstructure formed at the surface edge of the quenched area. These cracks propagate solely within the quenched area, preventing their propagation into the interior of the HLP-treated rail. [ABSTRACT FROM AUTHOR]

• Coupled rolling contact fatigue elastic-plastic damage model for carburized bearing steel. • Characterization of rolling contact fatigue with different thicknesses of carburized layer. • Relationship between the number of load cycles and the degree of subsequent material damage. • Optimization of carburizing heat treatment process for bearing steel. Being a pivotal element within high-speed train transmission systems, the mechanical attributes of bearings are of great significance to ensure the quality and safety of train operation. In this study, the rolling contact fatigue performance of bearing materials was tested to investigate the effects of different carbon layer characteristics on the rolling contact fatigue behavior. Combined with the thickness of carburizing layer, the elastoplastic coupling model of rolling contact fatigue damage of G20CrNi2MoA carburizing bearing steel was established. The model revealed the relationship between the number of load cycles and the degree of subsequent material damage. The model was used to calculate and predict the loading frequency of G20CrNi2MoA carburized bearing steel with excellent fatigue characteristics, which was 2.02 × 108 times before spalling. In addition, the carburizing heat treatment process for bearings was optimized based on the hardness gradient curves obtained, which provided valuable insights for improving the actual production process. [ABSTRACT FROM AUTHOR]

• Typical factors affecting the wheel-rail dynamic response are comprehensively considered to reveal the short-term load characteristics of frog under complex conditions. Meanwhile, based on the ellipsoidal Gaussian extrapolation theory, long-term wheel-rail load characteristics are obtained. • Combined with the strain energy fatigue parameter theory, a prediction method for the fatigue life of nose rail under complex conditions based on load spectrum preparation was proposed. • The location between the 30 mm and 35 mm sections of the nose rail has the shortest rolling contact fatigue crack initiation life and should be focused on during damage inspection. The rail profile irregular variation and wheel-rail relationships complexity at the gap in the frog enhance the wheel-rail impact forces, frequently resulting in rolling fatigue damage under complex cyclic loads. Therefore, it is particularly important to study the transient rolling contact load characteristics of fixed frog and to compile load spectrum considering various complex conditions for analyzing the fatigue damage of frog and extending the service life of structure. In this paper, a 3D transient FE model of wheelset and fixed frog is established, revealing rolling contact behavior of wheel-rail in frog area from both macro and mesoscopic perspectives. In order to investigate long-term load characteristics of wheel and rail under complex service conditions, the changes of line conditions, load conditions, rail wear state and other influencing factors in actual operation are taken into account. Based on elliptic Gaussian kernel density theory, a method for compiling the load spectrum of fixed frog nose rail is proposed, and the FP method is used for fatigue crack initiation life prediction of nose rail in fixed frog. The results show that the force state is more severe when passing through the frog in straight reverse direction, and resonance is prone to occur in the third and fifth vertical bending modes of the frog, as well as the fourth and sixth vertical bending modes of the stock rail. The increase in factors such as speed, axle load, wheelset lateral displacement towards frog side and wing rail wear will exacerbate wheel-rail impact and shorten frog service life. Different factors have an impact on the overall amplitude, oscillation center range, and maximum frequency load of the wheel-rail force in the long-term load spectrum of the frog. The fatigue crack initiation area of nose rail is mainly in 30 mm–35 mm sections, which is consistent with the on-site flaw detection results, verifying the accuracy of the calculation method developed in this paper. [ABSTRACT FROM AUTHOR]

• Local quenching causes gradient distribution of microstructure and hardness in wheel. • The statistical correlation is: Hardness = −2.77 × Fraction of proeutectoid ferrite + 328.07. • Wear and rolling contact causes microstructure evolution of wheel. • Microstructure and hardness show a significant synergistic evolution law. High-speed train wheels have complex service environments during wheel–rail contact, and a comprehensive understanding of the microstructural inhomogeneity at the rim is critical for service safety assessment. The local quenching process in the vicinity of the rim will cause a difference in microstructure, directly affecting the service performance of the material. In this study, high-throughput characterization method based on material genome engineering was used, the methods for characterising and identifying the microstructure of wheel steel were developed using high-throughput scanning electron microscopy, and the accuracy and reproducibility of the methods were evaluated. A point-to-point research scheme for microstructure image and hardness data was designed based on the concept of statistical mapping characterization. The area fraction of the proeutectoid ferrite and micro-Vickers hardness distribution in a large size range of the key area of the rim and their internal correlation was obtained, these helped avoid statistical and representativeness limitations of traditional local selection analysis of microstructure and hardness. The results indicates that the area fraction of proeutectoid ferrite and micro-Vickers hardness showed a clear gradient distribution, and opposite distribution trend, with a high negative correlation. In addition, by observing the correlation between microstructure and hardness, and studying the evolution of microstructure, it was found that the microstructure and hardness of the rim near the tread demonstrated a significant synergistic evolution law under the influence of service, this was observed both statistically and microscopically. These findings enhanced the application prospects of the microstructure-performance statistical mapping method, and were beneficial in efficiently evaluating the service life and safety of key components. [ABSTRACT FROM AUTHOR]

• The model can account for the non-linear lifting of the flange groove and the effects of wheelset traverse and side roll. • The wheel tread and flange are alternately loaded with two wheel load transition areas in the frog area. • Wear in the flange bearing area is significantly higher than in the tread bearing area, with an increase of 59.7%. • RCF damage dominates in the wing rail and the two wheelload transition areas. • Reducing the speed to 15 km/h significantly improves the service performance of the fixed frog. The tram No. 3 turnout fixed frog uses a variation in the depth of the flange groove so that the wheel rolls over the frog area in a continuous flange bearing. This method of travelling over the turnout requires the wheel load to transition back and forth between the tread and the flange, resulting in wheel-rail impact, which in turn affects service life. In order to investigate its service characteristics, this paper has established a transient wheel-rail rolling contact finite element model for the No. 3 turnout fixed frog. The macroscopic dynamic response and microscopic wheel-rail contact solution as the tram passes through the turnout at different axle weights and speeds are analysed in detail, and the changing patterns of wear and fatigue damage are investigated. The research shows that rail wear is particularly severe in the wheel flange bearing area, approximately 1.6 times greater than in the tread bearing area. In addition, when tram speeds are reduced to 15 km/h, there is a significant reduction in wheel-rail impact and wear, thereby improving ride smoothness and safety. The results of this study are of great significance to the operation and maintenance of the No.3 fixed frog turnout. [ABSTRACT FROM AUTHOR]

• Generation arc is subjected to triple acceleration of P - v - I. • Surface damage is a combination of mechanical and electrical damages after arcing. • Conductive AFM visually confirm the harmful effects of oxidation on conductivity. This study employs copper (Cu)-Cu rolling pairs to investigate the failure characteristics and surface damage mechanism of current-carrying tribological contacts under various conditions (contact load P = 40–180 N, rotation speed v = 4–600 rpm, and current I = 0–2.5 A). Based on synchronous current curves and video observations, the severe current fluctuations caused by the electric arc can be considered a criterion for the failure of rolling electrical contacts. Surface damage assessment through scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM), reveal ablation pits, oxidation, and roughening as primary manifestations of electrical damage. Post-rolling, the Cu on the surface was oxidized to copper (II) oxide. As the degree of oxidation increased, the conductive area in the AFM current map decreased significantly at a sample bias voltage of 1.5 V. Notably, arc generation was subjected to the triple acceleration of the contact load, rotation speed, and current. A back propagation (BP) neural network model was established to predict the running cycles before arc generation. Based on independent validation experiments under P = 120 N, I = 1.0 A, v = 400, and 600 rpm, the average prediction error of the proposed BP neural network model was 8.13 %. The results of this study facilitate the understanding of failure mechanism and predicting life cycles of rolling electrical contacts. [ABSTRACT FROM AUTHOR]

• Based on the Hertzian contact distribution and creep-slip characteristics, the fatigue life of spinning bearings is predicted using the damage parameter theory of the critical plane method and the L-P theory. • The deviation rate between the finite element simulation and the theoretical calculation results is 6.61% • The rotation speed, friction coefficient and external load affect the fatigue life of spinning bearings, and better lubrication and excellent contact surface to extend the life. • A rotary bearing life experimental device verified the reliability of the theoretically calculated deviation rate is 3.86%. In order to ensure the longer working life of rolling guide bushing, this work proposed a fatigue life prediction model of spinning bearings based on the Hertzian contact distribution and creep-slip characteristic. The influence of different parameters on the fatigue life of spinning bearings was analyzed according to the damage parameter theory of the critical plane method and the L-P theory. Finally, the fatigue life prediction model of spinning bearings was verified through the finite element simulation combined with the experiments. The reliability results show that creep-slip characteristic and deformation lead to the contact zone stress of the spinning bearing firstly increases, decreases subsequently to zero and then increases to the peak value. The increase of rotational speed will make the fatigue life of the spinning bearing firstly increases and then decreases. With the increase of friction coefficient, its fatigue life will become smaller and smaller, and the increase of the external load will decrease its fatigue life. Meanwhile, the prediction error rate of the fatigue life prediction model proposed in this study is 4.60%, which is within the error tolerance. This study provides certain methods and ideas for fatigue life prediction of spinning bearings, and lays a theoretical foundation for the design of highly reliable spinning bearings. [ABSTRACT FROM AUTHOR]

• Extreme load and welding defects lead to fatigue failure of wire bracket. • The stress of the optimized wire bracket is reduced and the service life is increased. • Different forms of the same acceleration load have different effects on structural damage. • Vibration fatigue analysis based on safety factors can predict the fatigue life well. Fracture analysis and structure optimization of faulty wire bracket to improve service life. Bench tests and simulation analysis are carried out to evaluate the vibration fatigue damage of optimized structures. The failure reason for wire bracket is the synergistic effect of extreme load and welding defect and the optimized configuration demonstrates reduced stress and a protracted service lifespan. Multi-mode bench tests indicate that only the damage under on-track multiaxial load in time domain is greater than that of the on-track test, and there is a safety margin of at least 10 %. The damage of standard, frequency domain and uniaxial cumulative load are about 0.07, 0.46 and 0.45 times of the on-track test, respectively. The vibration fatigue analysis results show that the variance between the beach tests and simulation outcomes is below 20 %. The life of the wire bracket can be evaluated by vibration fatigue simulation with appropriate safety factor adjustments. [ABSTRACT FROM AUTHOR]