Gauge Corner Research Articles

Wheel-rail wear characteristics of a modern tram passing curves with small radius

The wheel-rail wear was predicted for modern trams with independently rotating wheelset running on a groove-shaped rail. The tram vehicle-track coupled dynamics model, considering the wheel-rail multi-point contact, was developed using software UM to evaluate the dynamic responses of the vehicle and track. Hertz contact theory, the FastSim algorithm, and Archard material wear model were used to solve the normal contact stress, tangential contact stress, and wheel-ail wear, respectively. The wheel and rail profiles were updated when the wear depth reached to 0.1 mm. In calculation, the wheel and rail wear was calculated and analyzed separately. The results of groove rail and independently rotating wheelset wear predicted by this model coincided with relevant literature, which proved the effectiveness of this model. The wheel and rail wear characteristics of modern trams passing through curved tracks with small radii and the influence of wheel-rail friction coefficient on wheel and rail wear were calculated and analyzed using this model. The results show that the wheel and rail wear on the circular curve and the rear transition curve is more intense. The wheel wear is the most intense on circular curve while the rail wear is on the rear transition curve. The wear of inner and outer rails and wheels of wheelset one increases with the increase of wheel-rail friction coefficient while the wear of inner and outer wheels of wheelset three have no obvious change. The wear of the inner and outer rails is the most intense at the gauge corner position while is the lightest at the guard rail. The wear of wheelset one is more intense than that of wheelset three and the inner wheel wear is more intense than that of the outer wheel. The present analysis contributes to improve the life of tram wheel and rail and reduce the frequency of wheel-rail maintenance during operation.

Numerical and experimental investigation on critical stresses due to rail cant

The track integrity is significantly affected by the internal stress state of the rail. The rail cant influences the flexural stress distribution on the rail foot, thereby shifting the critical stress locations. In this study, full-scale lab testing was done for heavy equivalent wheel loads (16–40 tonne) to measure the rail foot stresses. Further, the mathematical model for track design is modified considering the effect of rail cant on stress distribution and compared with the developed finite element model (FEM) and the experimental study conducted. It was observed that the FEM and modified model calculates the rail stresses with better accuracy of around 5% for heavy wheel loads. The rail cant cause redistribution of stresses, making the gauge corner critical to rail failures. It was observed that stresses at the gauge corner are 20% higher than at the field corner of the rail foot.

Prediction and analysis of wheel flange wear on small curved track considering wheel-rail conformal and lubricated contact

Wheel flange wear on curved tracks is a significant issue that poses a threat to the safety of rail vehicles and leads to increased maintenance costs for railway operators. This study aims to develop a numerical model to predict wheel flange wear on small radius curves. The model integrates an efficient wheel-rail conformal contact model with laboratory-tested wear coefficients. By using virtual penetration and influence coefficients for conformal geometries, the model accurately simulates the conformal contact between the wheel flange and the rail gauge corner. The validity of the wheel flange wear prediction model is confirmed through field tracking testing. Using the proposed model, the effects of track layout parameters and solid lubricants on wheel flange wear are investigated. This study provides theoretical guidance for the operation and maintenance of the wheel-rail system to reduce wear.

Finite element analyses of rail head cracks: Predicting direction and rate of rolling contact fatigue crack growth

A numerical framework in 3D for predicting crack growth direction and rate in a rail head is presented. An inclined semi-circular surface-breaking gauge corner crack with frictionless crack faces is incorporated into a 60E1 rail model. The investigated load scenarios are wheel–rail contact, rail bending, thermal loading, and combinations of these. The crack growth direction is predicted using an accumulative vector crack tip displacement criterion, and Paris-type equations are employed to estimate crack growth rates. Results are evaluated along the crack front for varying crack radii and crack plane inclinations. Under the combined load cases and in the presence of tractive forces, the crack is generally predicted to go deeper into the rail than under pure contact. Crack growth rates for the combined load cases are higher than (but still close to) that for pure contact. A tractive force will increase growth rates for smaller cracks, whereas a steeper (45°) inclination will decrease the growth rate under the studied conditions as compared to a shallower (25°) inclination. Results should be of use for rail maintenance planning where deeper cracks require more machining efforts.

Study on the Formation Mechanism for High Rail Corrugation

This research employed a tracking investigation and numerical study to examine the initiation of high rail corrugation. Beginning with the trial operation of Metro Line 6 in Chengdu, China, we conducted a follow-up investigation for 2½ years that recorded the rail surface wear morphology of a 600-m radius curved track. The field observation results show that high rail corrugation occurred 12–17 months after the subway was officially put into operation, whereas the low rail of the same track did not show any corrugation. The distribution of high rail corrugation was discontinuous. Due to wear, the profiles of the rails and wheels changed. Two points of contact may occur between the leading outer wheel and high rail, with one contact point at the gauge corner and the other in the vicinity of the railhead (hereafter referred to as two-point contact). We developed a finite-element model that used the measured worn profiles to predict the self-excited frictional vibrations of a leading wheelset–rails system under the condition of two-point contact. We predicted the occurrence trend of self-excited frictional vibrations via the complex eigenvalue analysis. The simulation results show that in the condition of two-point contact, the self-excited frictional oscillation produced at an outer wheel–high rail interface can induce high rail corrugation. The use of straight or double S-shaped web plate wheels and an increase in railpad damping can help to reduce high rail corrugation.

Effect of Cyclic Loading on the Surface Microstructure Evolution in the Pearlitic Rail

The effects of cyclic loading on the surface microstructure evolution of different contact locations in a used pearlitic rail were studied. Microstructures were analyzed using Scanning Electron Microscopy (SEM). Meanwhile, grain boundaries and crystallographic orientations were explored via Electron Backscatter Diffraction (EBSD). At last, wheel–rail contact probabilities and forces were calculated using rail profiles. The results indicate that the side wear region located in the gauge face was 71.5% in the high-angle grain boundaries (HAGBs) fraction, 0.88 in the Kernel Average Misorientation (KAM) value, 36% in the recrystallization (REX) fraction, and had a predominant orientation in grains. The rolling contact fatigue (RCF) region situated at the gauge corner was 66.3% in the HAGBs fraction, 0.92 in the KAM value, 33% in the REX fraction, and was mis-orientated in grains. The region located at the edge of the running band was 60.7% in the low-angle grain boundaries (LAGBs) fraction, 0.97 in the KAM value, 12% in the REX fraction, and was mis-orientated in grains. Continuous dynamic recrystallization (cDRX) took place in wear and RCF regions during the cyclic rolling contact loading, creating ultra-fine grains with a transformation from LAGBs to HAGBs, lower KAM values, and more REX. Grains oriented along [111] parallel to the vertical direction in the wear region were influenced by the dominant normal force, while grains in the RCF region were non-oriented, which was attributed to large lateral and vertical forces of similar magnitudes.

Rail wear rate on the Belgian railway network – a big-data analysis

ABSTRACT This paper presents a big data-based analysis of the rail wear of the whole Belgian railway network measured in 2012 and 2019. Wear rates are reported, discussed, and quantitatively formulated as functions of critical factors in terms of curve radius, annual tonnage (rail age), high rail in curves, an average from both rails in straight tracks at rail top (vertical wear) and gauge corner (45° wear) and for steel grade R200 and R260. The influence of preventive grinding is also analysed. The wear rates are derived in an aggregated manner for the whole network. The wear rates do not show significant change with changes in rolling stock over the years, implying that the wear rates could also hold for other networks. It is found that R200 shows, on average, a 34% higher wear rate than R260. Also, the wear rate per tonnage is lower for high-loaded tracks. Thus, time is a relevant factor in explaining the wear evolution of low-loaded tracks; for instance, the effect of corrosion may have an important role. The paper provides statistically significant information that can be used for wear modelling, understanding and treating rolling contact fatigue based on the wear rate and developing tailored rail maintenance strategies.

Comparison of Rail Head Checks Using Destructive and Non-Destructive Examination Methods

The development of railway transportation requires increased vehicle speeds and axle loads. The enhanced effects from the vehicle side and the new harder steel rails used in tracks lead to increased Rolling Contact Fatigue (RCF) crack initiation and propagation. One of the most frequently occurring RCF defects is the Head Checks (HC) around the rails’ gauge corner. These defects cause severe economic and safety issues. In-use maintenance is based on corrective and preventive approaches, which are neither cost-effective nor reliable. The development of new predictive methods and the improvement of the existing corrective and preventive approaches offer a solution to this issue. In this investigation, an HC-infected rail sample was examined with non-destructive Dye Penetration Testing, Eddy-current Testing, and Visual Microscopic Testing after the sectioning of the sample. In the future, an extensive HC database can be created from the results of the developed evaluation process, which may serve as the base validation tool for newly developed predictive maintenance methods.

Use of Surface Acoustic Waves for Crack Detection on Railway Track Components—Laboratory Tests

The present work investigates the technical feasibility of a condition monitoring setup aiming at the detection of gauge corner cracks (aka head checks) in pearlitic railway rails, using a wayside (i.e., stationary) setup with surface acoustic waves (SAW) as its detection principle. The experimental SAW setup consists of a pitch-catch setup using piezo transducers equipped with comb adaptors to excite and measure narrowband Rayleigh waves with a center frequency of 1 MHz. SAW experiments were performed on a rail subjected to cyclic loading in a 1:1 wheel–rail test rig yielding the specific rolling contact fatigue, i.e., head checks. Elastodynamic finite integration technique (EFIT) simulations were performed to analyze the surface and bulk wave propagation in the rail and to predict the signals at specific receiver positions. SAW transmission and reflection scenarios at cracks were analyzed numerically via modelled variations of gauge corner crack configurations according to number of cracks (0–3) and depth (0, 0.5 mm and 1 mm). The numerical and the experimental results each show a clear correlation between the appearance and intensity of head check damage and the wave attenuation in transmission mode.

An investigation into the influence of wheel–rail contact relationships on the carbody hunting stability of an electric locomotive

Carbody hunting stability has attracted more and more attention due to its great influence on the dynamic performance of a railway vehicle. To fully understand the correlation between the wheel–rail contact relationship and the carbody hunting stability of an electric locomotive, the wheel–rail contact geometry analysis and the multi-body dynamics simulation are carried out in this work. The focus is on the influences of track parameters (including rail profile, rail cant and track gauge) on wheel–rail contact relationships and carbody hunting stability. A group of rail profiles are obtained by interpolating between the standard CHN60 profile and the worn rail profiles. The nominal equivalent conicity, the effective equivalent conicity and the wheel–rail contact bandwidth for a wheelset lateral displacement of ±6 mm are used to evaluate the wheel–rail contact relationship, while the lateral continuous comfort index is used to evaluate the carbody hunting stability. The simulation results show that keeping the rail cant at about 1/40 and reducing the track gauge and the wear depth at the gauge corner of rail can improve the carbody hunting stability of the electric locomotive. Furthermore, the effective equivalent conicity is a good choice to establish the relationship between the wheel–rail contact geometry and the carbody hunting stability.

Damage mechanism of a long-wavelength corrugated rail associated with rolling contact fatigue

Corrugation is a common rail damage, which seriously affects the safety and reliability of wheel-rail operation. In this study, the rolling contact fatigue (RCF) damage mechanism of an ex-service small radius rail with long-wavelength corrugation was explored. The results showed that the cracks in the side abrasion area propagated parallel to the rail surface with a very small depth due to the severe wear. While the formation mechanism of cracks in the gauge corner area was the ratcheting of material. The cracks propagated to large length along the plastic deformation flow of microstructure and stopped inside the plastic deformation layer. The cracks in the rail top area propagated first along the plastic deformation flow and then turned at the bottom of the plastic deformation layer into the bulk with the direction which was almost perpendicular to the rail surface. The deflection of cracks was due to the presence of the oxides. The presence of residual austenite in the white etching layer (WEL) and slight plastic deformation area beneath the WEL indicated that the main reason for the formation of WEL was the combination of temperature rise and sustained plastic deformation. It is worth noting that a large number of cracks produced by work hardening made the spalling in the trough severer, leading to the aggravation of rail corrugation.

Effect of gauge corner lubrication on wheel/rail non-Hertzian contact and rail surface damage on the curves

Effect of gauge corner lubrication on wheel/rail non-Hertzian contact and rail surface damage on the curves

Effect of track curvature on the microstructure evolution and cracking in the longitudinal section of lower gauge corner flow lips formed in rails

The microstructure of the flow lips formed at the lower corner of gauge face in the longitudinal section of worn high rails serving in curved tracks has been investigated. The radii of the curved tracks are 1500 m (S1, sharper curve) and 4000 m (S2, milder curve). Sharper curves result in a higher angle of attack (AOA) between rail-wheel thus leading to higher lateral contact forces as well as tangential frictional forces thus facilitating plastic flow. Such conditions favour formation of flow lips where rail material flows from the rail upper gauge face to the lower corner of the gauge face. A combination of optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and nano-indentation hardness measurements have been used for the characterization of the flow lip. It is observed that the outermost region of the flow lip consists of a uniformly present white etching layer (WEL) followed by an intermittently present brown etching layer (BEL) where the WEL and BEL thickness is less for milder curves. The WEL has the highest hardness and consists of fine grains of ferrite and particles/fine fragments of cementite. The BEL is relatively softer than WEL and has a similar appearance to WEL, but patches of lamellar structure appear with increasing depth from the outer edge. Beyond the BEL region, layers of deformed pearlitic structure are observed, and a more intact pearlitic structure is observed at a much lower depth for the milder curve than the sharper curve. For both the curvatures at a given depth, the hardness of pearlite bears a Hall-Petch type of relationship to the pearlitic interlamellar spacing. However, the alignment of the deformed microstructure is heavily dependent on the curvature. It has been found to align almost parallel (4°–10°) to the rail longitudinal axis for the milder curvature and at around 21°–35° for the sharper curvature. Cracks originate from the brittle WEL region due to contact fatigue whereas crack propagation is driven by bending stresses. Cracks have been found to move parallel to the alignment of the deformed pearlite along longitudinal direction for the milder curvature. Alignment of pearlite also motivates the crack propagation trajectory for the sharper curvature and hence the crack moves at an angle between 21° and 35° with the longitudinal direction but becomes almost perpendicular after a distance. Shallow cracks travelling parallel to the rail outer edge in S2 can result in spalling of the rail material leading to wear, whereas for sharper curves, cracks run deeper into the railhead. Thus, the tendency for rail failure through 'Reverse Transverse Fracture' – which involves crack initiation at the lower gauge corner and propagation into the railhead – increases with the sharpness of the rail curvature.

Microstructural investigation along the transverse section of the lower gauge corner flow lips formed in high rails of mild curves

The microstructure of the ‘flow lip’ formed at the lower gauge face in high rails in curved tracks has been investigated along the transverse section. The rails served in tracks having radii of curvature of 1500 m(S1) and 2000 m(S2) respectively. Optical images reveal the formation of an outermost white etching layer (WEL) followed by a brown etching layer (BEL) and deformed sublayers. Cracks originated from the WEL regions and from the notches at the extreme end of the flow lip. The cracks originate from the WEL region due to exhaustion of ductility, whereas, at the extreme end of the flow lip the cracks originate due to stress concentration caused by the notches generated due to uneven plastic flow of material. Using SEM (scanning electron microscopy) and EBSD (electron back-scattered diffraction), the WEL region is identified to consist of fine grains of ferrite and particles/fine fragments of cementite. The cementite in the WEL region is present as particles in S1 and as broken fragments as well as particles in S2. From the SEM images, the BEL has a similar appearance to WEL but with intermittent patches of lamellae-type features. The lamellae type features are much larger in S2 than S1 implying that the radius of curvature can significantly affect the level of deformation. The deformation was lower in S2 than S1 for similar distances from the outer edge, possibly due to less severe shear loading in a less sharply curved rail.

A study on the countermeasure method for gauge corner cracking by applying the worn profiles of rail

A study on the countermeasure method for gauge corner cracking by applying the worn profiles of rail

EFFECTS OF SLIP RATIO ON WEAR PERFORMANCE OF CLASS B WHEEL STEELS AGAINST SOFTER R260 RAIL STEELS USING THE TWIN DISC SETUP

A train experiences different slip ratios at the wheel/rail contact point as it moves along the rail track, which influences the rolling contact fatigue (RCF) and wear properties of wheel and rail materials. This variation in slip ratios is caused by a change in contact area between the wheel and rail head at curves, as the slip ratio increases compared with when a train is moving on a straight track. When the train is moving on a straight track, the wheel is found to be in contact with the rail head; but that changes when moving around curves, as the wheel flange will now be in contact with the gauge corner of the rail, affecting the severity of wear. Therefore, more research needs to be done to understand the role that slip ratio plays in the wear performance of wheel and rail materials in order to be able to develop models or systems that could be used to predict preventive maintenance. The aim of this work was to investigate the effect of the slip ratio on the wear performance of class B wheels against softer R260 rail steels under rolling and sliding conditions, using a twin-disc setup developed at the University of Pretoria. The results showed that the severity of wear was heavily dependent on the slip ratio – i.e., it increased with the slip ratio, with class B wheels performing better than the softer R260 rail.

Proposal of the rail profile selection method to reduce gauge corner cracking initiation by mitigating contact conditions of wheel and rail

Proposal of the rail profile selection method to reduce gauge corner cracking initiation by mitigating contact conditions of wheel and rail

Rail degradation due to thermite weld discontinuities: Field experience

This paper details the field-testing approach and results of thermite welds used in railway applications. Rail steels made from R260 grades are welded by two different processes: the standard process according to the European standards, and a recent technology. Welds are introduced in the same testing location to ensure comparable loading conditions in the aim of studying their degradation behaviours. The total testing-period is 6 months. During the in-service period, the surface hardness of the running band, in the welded area, is recurrently measured. For an accurate assessment of field results, a vehicle/track interaction (VTI) model evaluated the expected dynamic loads induced by the initial vertical irregularities.The simulations show that the highest dynamic load at the wheel/rail contact happens at the location of the maximum absolute gradient, in accordance with previous research. Particularly, dipped welds show relatively high dynamic forces inducing a high loss of the transversal profile. In respect of the field results, the comparison of initial and final surface hardness indicates a significant increase for ‘ALFONS’ welds over the welded areas. Additionally, all welds depicted a cyclic increase and decrease of the running band hardness. This result is discussed according to the ratcheting susceptibility of welds and eventual wear progression. For a testing-period of 10 weeks, the gauge corner of one ‘ALFONS’ weld developed a crack. The assessment of the longitudinal profiles revealed changes of the vertical irregularities that may modify the dynamic loads, and further the rolling contact fatigue mechanisms and degradation rates.

A novel three-dimensional wheel–rail contact geometry method in the switch panel considering variable cross-sections and yaw angle

Solving the wheel-turnout contact geometry is complex because the rail section is varying along its longitudinal position. Besides, a large yaw angle will occur, especially when the vehicle passes the switch panel in a diverging route. However, previous researches seldom considered the aforementioned factors simultaneously in performing wheel–rail local contact analysis. This paper therefore proposes a novel three-dimensional (3D) contact geometry method considering the combined effects of varying rail profiles and the yaw angle. This study uses S1002CN wheels and the switch panel of a 1:12 turnout as research objects to study the contact geometry, normal and tangential contact solution. The results indicate that the combined influences of rail profiles varying within the contact patch and the yaw angle on the contact solution are significant. The variable rail profiles obviously affect the position of the contact point. With a yaw angle, the normal gap, contact patch shape and stress distribution calculated by the novel 3D contact geometry method are asymmetric along the lateral and longitudinal directions, especially when the wheel flange contacts with a rail gauge corner. The proposed method can improve the accuracy of the wheel–rail contact solution and help predict rail damage in switch panels.

Effect of in-service work hardening on the sliding wear resistance of a heavy haul rail in the gauge corner

This work evaluates the tribological behavior of three samples taken from a pearlitic steel rail with different hardness values (550, 450 and 370 HV0.1) due to the in-service work hardening effect. A pin-on-disc sliding wear test was selected to simulate the sliding wear conditions among the wheel flange and rail head corner and gauge face. The influence of the stress level was evaluated by varying the applied normal loads; the 50 and 500 N loads were associated with large and small radius curves, respectively. Pins were made from the rail samples, and the counter body (disc) used was H-13 steel (600 HV30). The mass loss was measured, and the coefficient of friction (COF) for each condition was calculated. Scanning electron microscopy (SEM) was carried out for microstructural characterization of the samples before and after the sliding wear test. The results showed a monotonic correlation between the superficial hardness and the sliding wear resistance under the low severity condition. The sample with the intermediate hardness (450 HV0.1) has the greatest sliding wear resistance under the low severity, 50 N condition, and under the high severity test condition (500 N). For the tests performed at 50 N, the wear facilitated crack propagation, and the preexisting cracks were removed from the pin (rail) interface. In contrast, for the tests performed with a 500 N load, the material removal rate did not overcome the crack propagation. In addition, the energy at the sliding interface was enough to promote a white etching layer (WEL), which reproduced the surface of the in-service rails, and the material removal was not sufficient to remove the cracks from the pin (rail) surface.