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Rail corrugation is very serious in Cologne egg fastener track; effective control measures are still lacking. The cause of the corrugation wear on a curved metro track is analyzed based on the friction-induced vibration theory. A finite element model is established to study the frequency domain and time domain features of the friction-induced oscillation of this system. The influences of the fastener spacing and the fastener support length on the corrugation wear are investigated to develop countermeasures. The simulation results show that the friction-induced vibration of the wheel-track system is the wavelength-fixed mechanism of the corrugation wear of rail of the curved Cologne egg fastener track. There are two reasons why the low rail corrugation wear is more serious. The contact resultant force between the low rail and the wheel is obviously bigger than that between the wheel and the high rail, resulting in a higher wear rate of the low rail. The contact force fluctuation of the low rail caused by the friction-induced vibration is more severe, resulting in a higher corrugation wear evolution speed on the low rail. The friction-induced oscillation cannot be eliminated only by adjusting the fastener support length and spacing. However, the long-wavelength corrugation wear instead of the more harmful short-wavelength corrugation wear can be produced by adjusting the fastener support length and the fastener spacing to alleviate the influence of corrugation wear on the vehicle-track system. [ABSTRACT FROM AUTHOR]

Polygonal wear is a type of damage commonly observed on the railway wheel tread. It induces wheel-rail impacts and consequent train/track components failure. This study presents a finite element (FE) thermomechanical wheel-rail contact model, which is able to cope with the three possible generation and development mechanisms of polygonal wear: initial defects, thermal effect, and structural dynamics. The polygonal wear-induced impact contact and further development of wear are simulated. The simulated elastic contact solutions are verified against the program CONTACT. Different material properties (elastic, elasto-plastic and elasto-plastic-thermo, i.e. with thermal softening) and initial polygonal profiles are then applied to the FE model to investigate the influence of wheel/rail material and wear amplitude on wheel-rail contact stress and wear development. The simulations indicate that the wheel-rail impact-induced temperature may reach up to 362 ℃ at the contact interface, and the high temperature at the contact area influences wheel-rail contact stress and wear depth. • An innovative thermomechanical FE model is presented to study polygonal wear growth. • The simulated contact solutions are verified against the program CONTACT. • Using elastic material models causes overestimation of contact stress and wear depth. • Incorporating thermal effects is crucial for wear predication with high slip ratio. • The simulated contact temperature reaches up to 362 ℃ at the wheel-rail interface. [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]

Purpose: The purpose of this paper is to reveal the friction and wear performance of grooves textured cylindrical roller thrust bearings with different groove dimensions under starved lubrication. Design/methodology/approach: The groove dimensions include: width of grooves (WOG, 50 µm, 100 µm and 150 µm), depth of grooves (DPOG, 7 µm, 11 µm and 15 µm) as well as groove deflection angle (GDA, 45°). A fiber laser marking system was used to prepare groove patterns on the raceways of shaft washers. The friction and wear properties of grooves textured bearings were researched through a vertical universal wear test rig using a customized roller bearing tribo-pair under starved lubrication. Static finite element analyses were conducted to reveal their surface stresses. Through the comprehensive comparison and analyses, the influence mechanism of grooves on the tribological behavior of cylindrical roller thrust bearings was proposed and discussed. Findings: When grooves textured bearings run under starved lubrication, their average coefficients of friction (COFs) and wear losses are all significantly reduced and much lower than those of smooth group. The influence of DPOG on the COF curves is significant, while the influence of WOG on the COF curves is a little weak. The influence of groove dimensions on the surface stresses of grooves textured bearings is weak, whether the WOG or DPOG. In this work, when the WOG is 100 µm and the DPOG is 15 µm, its average COF and wear loss are both the lowest, 0.0066 and 0.61 mg, respectively. Compared with the data of smooth group, its friction coefficient is reduced by 75.3% and its mass loss is reduced by 95.8%, showing a significant improvement in this condition. Originality/value: This work can provide a valuable reference for the raceway design and reliability optimization of rolling element bearings. [ABSTRACT FROM AUTHOR]

Flange tip lift crossings are widely utilized in modern tramlines to replace traditional crossings to enhance commuters' comfort and prevent crossing nose failures. However, due to altered contact conditions between wheel flanges and ramps of crossings, the use of flange tip lift crossing has led to the critical issue of ramp wear. To resolve this issue, this paper investigated the dynamic contact response of a ramp during in-service loading, as well as the resultant wear of the ramp. With a dynamic finite element model, the local contact pressure and local sliding distance were computed and subsequently applied in a local contact-based wear model to evaluate the nominal wear of the ramp. Our findings indicate that under typical in-service loading conditions, the ramp exhibited up to 120 times more wear than the rail head, owing to increased contact pressure and reduced contact area during the ramp contact. To mitigate this issue, a design change of a gentler ramp inclination from the default 1:100 ramp to a 1:150 ramp could provide approximately 10% wear reduction. In addition, increasing the flange radius by 1 mm could reduce the wear by up to 13%. Conversely, increasing the speed to 45 km/h from the recommended 15 km/h speed may cause up to 5 times more wear. Furthermore, an empty tram showed 56% less wear on the ramp when compared to the condition of the maximum allowable axle load. These results offer an insight into the detrimental wear of ramps used in flange tip lift crossings of tramlines and can assist in the development of new designs and operating guidelines to mitigate ramp wear. • Ramp wear of a tram crossing was investigated using dynamic finite element simulation and a local contact-based wear model. • The wear of the ramp was found to be up to 120 times greater than that on the rail head of tram rails. • Gentler ramp inclination, increased flange radius, reduced vehicle speed and lower axle load can reduce the wear of the ramp. [ABSTRACT FROM AUTHOR]

The presence of fatigue crack is a common damage pattern in railway wheel-rail system, which will reduce service life and increase the maintenance costs of railway transportation. In this study, a two-stage simulation strategy was proposed to investigate the elastic-plastic fatigue crack growth behaviour of the wheel and rail, where a three-dimensional wheel-rail rolling contact finite element model was first built to solve the elastic-plastic wheel-rail contact pressure and tangential traction modification, and then a simplified three-dimensional finite element model of the wheel and rail inserted with vertical cracks under the equivalent moving load was built to explore the fatigue crack growth. Taking the J -integral at the crack tip as an elastic-plastic crack growth parameter, the influences of crack face friction, crack depth and traction coefficient on the crack growth were elucidated. Meanwhile, the competing mechanisms of wheel/rail wear and fatigue crack growth under rolling-sliding contact condition was illuminated based on the Archard wear model. The simulation results indicate that two critical locations for crack growth appear during the contact load approaching and departing from the crack. The Mises stress near the deepest crack tip exceeds the yield stress, causing a small plastic zone with the greatest crack growth rate. The reduction in the crack face friction, and/or the increase in crack depth and traction coefficient will accelerate the propagation of fatigue crack. In the case of only normal contact load or rolling-sliding contact (μ ≤ 0.375), the crack growth on the wheel and rail is dominant compared to wear and crack will continue to grow. • Proposed a two-stage simulation strategy to study wheel-rail fatigue crack growth. • Built 3-D finite element model of the wheel and rail inserted with vertical cracks. • Elucidated influences of key parameters on wheel-rail fatigue crack growth. • Illuminated competing mechanisms of wheel/rail wear and fatigue crack growth. [ABSTRACT FROM AUTHOR]

Nonlocal peridynamic (PD) theory is widely used in damage and thermomechanical coupling simulations. This study applied ordinary state-based PD thermomechanics to model the wheel-rail contact bringing temperature-dependent materials. A two-dimensional coupled thermomechanical model was developed to predict the evolution of the thermomechanical response, thermal damage, and wear in railway rail. The model was verified based on the displacement and temperature fields of the rail. The model results correlated well with the finite element model and analytical method results. The influence of the vehicle speed, rail surface cracks, and wheel idling on the thermomechanical response of the rail was also evaluated in detail. The results show that the influence of the vehicle speed on the temperature field is much greater than that of the contact stress. The contact temperature under the critical creepage could lead to the formation of a brittle white etching layer (WEL). Cracks on the rail surface increased the contact stress and temperature peaks. Thermomechanical loading also promoted rail surface damage. Continuous thermomechanical loading due to wheel idling softened and removed rail surface materials, forming wear pits and a WEL, known as wheel burns. • A 2D thermomechanical coupled PD model of the wheel-rail sliding contact is established. • A novel and concise wear prediction method is provided based on the PD damage model. • The interaction of rail surface cracks and contact thermomechanical loads is studied. • Rail wear and WEL formation (wheel burns) during wheel idling are explored. [ABSTRACT FROM AUTHOR]

As traffic density and axle loads increase, the macroscopic wheel-rail contact can lead to severe rail wear. This paper constructs a multi-scale analysis framework from macroscopic force characteristics to microscopic wear mechanisms based on explicit finite element methods and molecular dynamics models. The study shows that the mutual proximity and annihilation of reverse dislocations in the rail material under the action of wheel-rail forces is an important cause of grain boundary fragmentation, while the proliferation of dislocations on the Subsurface leads to work hardening of the rail. The analytical framework proposed in this paper achieves a multiscale correlation between wheel-rail macroscopic contact and material microscopic response, and the conclusions obtained reveal the microscopic wear mechanism of rail materials. [ABSTRACT FROM AUTHOR]

Sliding wear tests were carried out with a pin-on-disc machine to study the tribological behavior of EN ER7 and AAR CLASS B wheel steels paired with cast iron and organic composite brake block materials. The contact stress was 0.61 MPa and the sliding speeds were 0.52 m/s and 0.62 m/s. The wear behavior was related to the friction coefficient recorded during the tests, the specific wear rate calculated at the end of the experiments and the microhardness profile obtained on the cross-section of the wheel pins. The worn surface and cross-section of the pins were analyzed by optical and scanning electron microscopy to investigate the main damage mechanisms. A stationary finite element model was proposed to estimate the contact temperature of the pin. The test results showed the same damage mechanisms for both steels, such as oxidative wear, delamination, abrasive wear and material transfer from the brake disc to the wheel pin, which led to adhesive wear. Overall, ER7 steel performed better when paired with the composite material as the pins showed lower specific wear rate; on the contrary, CLASS B pins had lower specific wear rate when the counterpart was cast iron. The tribological behavior of both steels was not influenced by the sliding speed. The simulations showed that the contact temperature was always higher when the disc in composite material was used, regardless of the pin material. Furthermore, ER7 steel demonstrated lower contact temperatures than CLASS B due to the lower friction coefficients in the experiments. • The wheel/brake tribology was investigated using a pin-on-disc setup. • ER7 and CLASS B steels were tested against cast iron and organic composite material. • The damage mechanisms of the wheel steels were identified. • A finite element model was proposed to estimate the steel pin contact temperature. • The contact temperature was always higher in the tests with the composite discs. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyze the influence of the load direction and the phenomenon of wear on rolling contact fatigue crack growth. For this purpose, a UIC60 rail with accurate geometry using FEM is studied. In this regard, a three-dimensional finite element model is provided. The maximum stress caused by wheel/rail contact for a new/worn wheel profiles was obtained using such model. Then, using Franc 3D software, during stress analysis for different situations of wheel, different values of stress intensity factors are obtained. The behavior of crack under fatigue loading was studied using a three-dimensional modeling. [ABSTRACT FROM AUTHOR]

A multi-step FE modeling strategy has been proposed to predict the temperature evolution, thermo-mechanical response, surface fatigue life and wear behaviors in railway rail for multi wheel passages. Equivalent contact pressure and heat source were coupled and moved simultaneously on rail surface to achieve a balanced advantage of low computational cost and high accuracy. Wheel configuration at locomotive plays a significant role on rail temperature. The highest temperature of 776.05 °C was developed with a slip ratio of 9.43% after 9 wheel passages. Rolling contact fatigue life of rail material decreased quickly with slip ratio due to significant thermal softening effect. Transition from mild to severe wear was found at slip ratio of 2.38% according to the corresponding rail flash temperatures. • A modelfor multi wheel passages of train locomotives considering both contact pressure and thermal effects was proposed. • Practical scenario of two locomotives was introduced to study the temperature evolution on rail surface. • Relation between slip ratio and rolling contact fatigue life of rail material was predicted. • Wear of rail was mild when slip ratio was ≤2.38% but transited into severe wear when slip ratio was higher. [ABSTRACT FROM AUTHOR]