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• Three dynamic indicators for predicting plastic flow in railway systems based on the mechanics of wheel-rail contact, Tresca's yielding criterion and shakedown theory. • A dynamic method that is simple to model and fast to compute for predicting plastic flow in railway systems. • Key parameters affecting plastic flow and rolling contact fatigue. • A dynamic approach for the impact of plastic flow on rolling contact fatigue damage. • Effect of different degrees of plastic flow on rolling contact fatigue. To analyze the plastic flow of wheels and its impact on rolling contact fatigue (RCF), this article proposes a multibody dynamics approach that is simple to model and fast to compute, based on the mechanics of wheel-rail contact and Tresca yield criterion. This method is used to study the plastic flow of the wheels and is validated by comparing it with plastic flow analysis based on the shakedown theory. The study shows that the dynamics indicators of maximum shear stress, adhesion saturation and stress ratio effectively reflect the plastic deformation of the wheel. Additionally, increasing wheel speed and curve radius, and decreasing wheel-rail friction coefficient, can effectively reduce the area and severity of plastic deformation in the wheel. Ignoring the impact of temperature effects on RCF, it is found that the more severe the plastic flow, the greater the likelihood of RCF. That is, alleviating the plastic flow of the wheel can reduce RCF damage in wheels. This approach to managing the health of wheels provides a comprehensive understanding of the interplay between operational parameters and the mechanical behavior of wheel materials, guiding maintenance strategies and operational decisions to enhance safety and extend the lifespan of railway components. [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]

• A two-stage simulation strategy was proposed to investigate the mechanisms of RCF cracks on the rail, consisting of a dynamic FEM for wheel and rail interaction and a coupled static FEM/BEM for crack growth. • The critical wheel positions for crack propagation during wheel approaching to and departing from the crack were determined and correlated with the different cracking mechanisms. • The orientation of the crack in rail played an essential role in crack growth behaviors. Rolling contact fatigue (RCF) crack is one of dominating damages on the rail surface due to repeated wheel and rail contact. RCF defects, including squats and head checks, can potentially cause rail fracture failure if not treated in time. It is critical to accurately predict the pertinent damage for different operational conditions. A two-stage simulation strategy was proposed to investigate the mechanisms of RCF-induced cracks on the rail, consisting of a dynamic FEM for wheel and rail interaction and a coupled static FEM/BEM for crack growth. It was found that there are two critical wheel positions for crack propagation during wheel approaching to and departing from the pre-existed crack. The different cracking mechanisms at these two critical wheel positions are correlated with the local physical phenomena, i.e. , the traction at the wheel/rail interface, the relative distance between the contact patch and crack, and the sliding at crack faces. The twisting of the cracks from the transverse plane to the longitudinal plane at the railhead significantly reduces crack growth in mode I, enhances crack propagation in modes II and III, and shifts the dominant crack growth from the crack front center to the crack corners. The increased incline of the crack in the rolling direction promotes the crack to grow downward in opening mode I. [ABSTRACT FROM AUTHOR]

• The wear performance of the defected rail materials under various slip ratios and contact stresses was investigated. • The surface damage of the defected rail materials under various slip ratios and contact stresses was studied. • The effect of slip ratio and contact stress on crack propagation mechanisms near the dent was discussed. The defects on rail surface may have negative effects on the rolling contact fatigue (RCF) performance of the rail materials. This investigation researched on the RCF behaviors of the defected rail materials under various slip ratios and contact stresses. The results show that both the wear loss and the average crack length increase if the slip ratio or the contact stress increases. Moreover, the surface damage characteristics change from simple adhesion spots to significant fatigue crack grouping when slip ratio and contact stress rise. Finally, the experimental results also highlight that the slip ratio provides the deformation area for crack initiation whereas the contact stress accelerates the crack propagation by emphasizing the geometric effects. [ABSTRACT FROM AUTHOR]

• Residual stress affects crack tip displacements of rail cracks. • CTSD amplitude increases with increasing wheel-rail friction coefficient. • Oblique crack propagates as the combined type of II/III dominated by type II. Fatigue crack is one of the main damages that reduce rail service life and raise rail maintenance costs. In this paper, a three-dimensional elastic–plastic finite element model of wheel-rail contact is established, in which a three-dimensional oblique crack is inserted in the rail. Taking crack tip displacements as fracture parameters, the effect of residual stress on fatigue crack propagation of rails is quantitatively analyzed, and the fatigue crack propagation mechanism of rails under the combined action of wheel load and residual stress are studied. Results show that crack tip displacements under the action of wheel load are quite different from that under the combined action of wheel load and residual stress. For the oblique crack with crack tip entering the residual tensile stress zone, crack tip sliding displacement amplitude increases with the increase of wheel-rail friction coefficient. Under the combined action of wheel load and residual stress, the oblique crack propagates as the combined type of II/III dominated by type II. [ABSTRACT FROM AUTHOR]