A singular rail or wheel surface irregularity, such as a squat, insulation joint or wheel flat, can cause large wheelrail impact force. Both the magnitude and frequency content of the impact force need to be correctly modelledbecause they are closely related to the formation, deterioration and detection of such irregularities. In this paper,we compare two types of commonly used wheel-track interaction models for wheel-rail impact problems, i.e., abeam and a continuum finite element model. We first reveal the differences between the impact forces predictedby the two models due to a typical rail squat using a time-frequency analysis. Subsequently, we identify thecauses for the differences by evaluating the effects of different model assumptions, as well as different modelparameters. Results show that the impact force consists of a forced vibration peak M1 followed by free vibrationrelated oscillations with three dominant frequencies: f1 (340 Hz), f2 (890 Hz) and f3 (1120 Hz). Compared withthe continuum model, the beam model with a Hertzian contact spring overestimates the M1 peak force. Thediscrepancy can be reduced by using a Winkler bedding contact model. For the track model, the beam model iscomparable to the continuum model up to about 800 Hz, beyond which the track damping starts to deviate. As aresult, above 500 Hz, the contact forces dominate at f2 for the beam while at f3 for the continuum model. Finally,we show that the continuum model is more accurate than the beam model by comparing to field observations.The effects of stress wave propagation on the differences are also discussed.@en

This study evaluates the degradation of wheels and rails at railway crossings. The evaluation method is composed of 1) finite element simulation of dynamic wheel/crossing interaction and 2) multi-criteria analysis of wheel/rail degradation in terms of yield behavior, rolling contact fatigue (RCF) and wear. With the aid of this method, we conducted a case study identifying the proper yield strength of rail steel material for a 54E1-1:9 crossing under a specified traffic condition. The case study indicates that the wear of contact bodies is more sensitive to train speed compared with yield and RCF; the increase of rail yield strength suppresses rail degradation while exacerbating wheel degradation; and rail yield strength in the range of 500–600 MPa is preferred to achieve a good trade-off between the wheel and rail degradations.

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This study compares various assumptions in different models to assess their capabilities to model vehicle-track interactions up to 2 kHz at a single rail-top defect. Field measurement data are used to evaluate discrepancies. The characteristics of contact force and axle-box acceleration (ABA) are first identified and qualitatively correlated with track, wheelset and contact models. Subsequently, the results from different models are quantitatively compared in terms of their capabilities to reproduce those characteristics. It is found that the differences in sleeper and wheel-rail contact models lead to the most significant discrepancies. The causes and physical implications of the quantified discrepancies are also discussed.@en

In this paper, we present a method for evaluating the performance of railway crossing rails after long-term service. The method includes 1) 3D profile and hardness measurements; 2) finite element simulation of wheel/rail interaction; and 3) numerical prediction of rail degradation. We conducted a case study on a crossing that had been in service for several years. The results indicate that the crossing experienced a run-in process in the major traffic direction, manifested as a widening of the running band, an enlargement of the contact patch size, a decrease in contact stress and eventually a reduction in plastic deformation and wear. However, the wheel/rail interaction was exacerbated in the minor traffic direction which induced more severe plastic deformation and wear.@en

This paper describes an approach for characterizing the dynamic behavior of the vehicle/track interaction at railway crossings. In the approach, we integrate in situ axle box acceleration (ABA) measurements with roving-accelerometer hammer tests to evaluate the influence of train speed, train moving direction (facing and trailing directions), sensor position (leading and rear wheels of a bogie), and the natural response of track structure on ABA signals. The analysis of data from multiple sensors contributes to the following findings: the major frequency bands of the vertical ABA are related to the natural frequencies of the crossing; thus, these ABA frequency bands are not greatly affected by variations in train speed, moving direction, and sensor position. The vibration energy concentrated at the major ABA frequency bands increases at higher train speeds, along the facing moving direction and from the leading wheel. The crossing rails vibrate as a combination of bending and torsion rather than solely bending at the major ABA frequency bands, since the vibrations of the wing rails are not synchronized. These results help enhance our understanding of the vehicle/track interaction at crossings and can be used to improve the dynamic response-based system for monitoring the condition of crossings.@en

This paper presents an analysis of the transient contact solutions of wheel-rail frictional rolling impacts calculated by an explicit finite element model of the wheel-insulated rail joint (IRJ) dynamic interaction. The ability of the model to simulate the dynamic behavior of an IRJ has been validated against a comprehensive field measurement in a recent paper (Yang et al., 2018). In addition to the measured railhead geometry and bi-linear elastoplastic material model used in Yang et al. (2018), this study adopts a nominal railhead geometry and an elastic material model for the simulations to provide an overall understanding of the transient contact behavior of wheel-IRJ impacts. Each simulation calculates the evolution of the contact patch area, stress magnitude and direction, micro-slip distribution, and railhead nodal vibration velocity in the vicinity of the joint during the wheel-IRJ impacts. The simulations apply small computational and output time steps to capture the high-frequency dynamic effects at the wheel-IRJ impact contact. Regular wave patterns that indicate wave generation, propagation and reflection are produced by the simulations; this has rarely been reported in previous research. The simulated waves reflect continuum vibrations excited by wheel-rail frictional rolling and indicate that the simulated impact contact solutions are reliable.@en

This dissertation aims to gain a better understanding of the dynamic wheel-rail interaction at crossings, including characterizing the wheel-rail contact behavior, evaluating the performance of crossings under traffic loads and monitoring the health condition of the structure. The first part of this dissertation focuses on an in-depth analysis of wheel-rail contact behavior and related rail degradation. An explicit 3D finite element (FE) model is developed to simulate the passage of a wheelset across a nominal crossing. The second part proposes a method to evaluate the performance of long-term serviced crossings. In the method, in-situ 3D profile and hardness measurements are conducted on a long-term serviced crossing and are used as the input for the FE modeling of dynamic wheel-rail interaction. The simulated wheel-rail contact parameters are then used to predict the distributions of plastic deformation and wear. The third part analyses the characteristic dynamic response of wheel-rail interaction at crossings. In-situ axle box acceleration (ABA) measurements were conducted on a nominal crossing with various test parameters. Thereafter, a roving-accelerometer hammer test was carried out to extract the relationship between the signature tune of the ABA and the natural frequencies of the crossing. The fourth part investigates the feasibility of the ABA system for monitoring the health condition of crossings. Information from multiple sensors was collected from both nominal and degraded crossings. By proper correlation of the gathered data, an algorithm was proposed to identify the characteristic ABA related to crossing degradation and then to evaluate the health condition of the structure.@en

In this paper, we investigate the capability of an axle box acceleration (ABA) system to evaluate the degradation at railway crossings. For this purpose, information from multiple sensors, namely, ABA signals, 3D rail profiles, Global Positioning System (GPS) and tachometer recordings, was collected from both nominal and degraded crossings. By proper correlation of the gathered data, an algorithm was proposed to distinguish the characteristic ABA related to the degradation and then to evaluate the health condition of crossings. The algorithm was then demonstrated on a crossing with an unknown degradation status, and its capability was verified via a 3D profile measurement. The results indicate that the ABA system is effective at monitoring two types of degradations. The first type is uneven deformation between the wing rail and crossing nose, corresponding to characteristic ABA frequencies of 230–350 and 460–650 Hz. The second type is local irregularity in the longitudinal slope of the crossing nose, corresponding to characteristic ABA frequencies of 460–650 Hz. The types and severity of the degradation can be evaluated by the spatial distribution and energy concentration of the characteristic frequencies of the ABA signals.

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Irregularities in the geometry and flexibility of railway crossings cause large impact forces, leading to rapid degradation of crossings. Precise stress and strain analysis is essential for understanding the behavior of dynamic frictional contact and the related failures at crossings. In this research, the wear and plastic deformation because of wheel-rail impact at railway crossings was investigated using the finite-element (FE) method. The simulated dynamic response was verified through comparisons with in situ axle box acceleration (ABA) measurements. Our focus was on the contact solution, taking account not only of the dynamic contact force but also the adhesion-slip regions, shear traction, and microslip. The contact solution was then used to calculate the plastic deformation and frictional work. The results suggest that the normal and tangential contact forces on the wing rail and crossing nose are out-of-sync during the impact, and that the maximum values of both the plastic deformation and frictional work at the crossing nose occur during two-point contact stage rather than, as widely believed, at the moment of maximum normal contact force. These findings could contribute to the analysis of nonproportional loading in the materials and lead to a deeper understanding of the damage mechanisms. The model provides a tool for both damage analysis and structure optimization of crossings.@en

Though numerical models based on multi-body dynamics (MBD) are often used to simulate the vehicle-track interaction at crossing impact, their relative capabilities and accuracy were not discussed. This paper aims to investigate the influence of wheelset flexibility on the result of crossing impact simulation in the frequency range 0–500 Hz. Two models are used: a MBD model with rigid wheelset and a reference finite element model that could fully account for the structural flexibility. Results of the two models as well as in-situ measurement show three characteristic frequencies of the vehicle-track interaction system induced by crossing impact. Based on the characteristic frequencies, the MBD model is tuned to resemble the reference FE model in terms of track and contact representation through a parametric analysis so that the influence of these differences can be isolated. It is found that the major influence of the wheelset flexibility is on the second characteristic frequency of the system, reflecting the second order bending of the wheelset. @en

In this paper, a finite element model is presented to investigate the wheel-rail impact-like interaction at crossing panel. Compared to existing work, the focus is on the accurate solution of the tangential contact problem, in an effort to obtain realistic stress and strain. Plastic deformation of the wheelset and the rail is accounted for, and the evolution of frictional rolling contact with respect to adhesion-slip regions, pressure, surface shear traction and micro-slip is elaborated during the impact. It is found that the variations of the pressure and surface shear traction from the closure rail to the wing rail are not synchronous; this could contribute to the non-proportional loading in the materials. Besides, the frictional contact upon the impact inherently contains high frequency vibrations, thus resulting in the cyclic loading on the local areas of the contact patch. The model can be applied to failure analysis and profile and structure optimization of crossings.@en