Initiation Of Corrugation Research Articles

New experimental evidences of corrugation formation due to rail longitudinal vibration mode

ABSTRACT This paper aims at identifying the formation mechanism of short pitch rail corrugation using an improved configuration of a 1/5 scaled V-Track test rig. The loading conditions of the V-Track are designed to simulate the wheel-rail dynamic interactions on the tangent track. Corrugation initiation and consistent growth are successfully produced on the rail surface with a characteristic wavelength of about 6.0 mm, equivalent to the field one of 30 mm. By analysing the wheel-rail dynamic forces, the wheel and track dynamic behaviours across different rotations, it is found that the rail longitudinal vibration mode and its induced longitudinal dynamic force determine the corrugation formation with the necessary initial excitation.

The influence of asymmetric rail cant on rail corrugation in a small-radius curve section

A suitably designed rail cant can improve the wheel-rail alignment, effectively reduce the wheel-rail contact pressure and reduce the wheel-rail wear. However, the rail base cant has rarely been specifically designed for suppressing rail corrugation. Furthermore, no studies have yet been conducted on using different inner and outer rail cants in small-radius curve sections from the perspective of suppressing rail corrugations and wear. In this study, the growth rate index of rail corrugation is obtained by combining an impact hammer origin admittance test and a coupled vehicle-track multi-body dynamic model simulations. The wear depth of rail surface is obtained by combining a three-dimensional transient wheel-rail rolling contact model and Archard wear theory. From the overall perspective of preventing rail corrugation and slowing down rail wear, based on the multi-objective optimization using a particle swarm optimization algorithm, the optimal configuration of inner and outer rail cants in a small-radius curve section were determined as 1/22 and 1/40, respectively, which provided effective suppression of rail corrugation initiation and further development of rail wear.

Mechanism of short pitch rail corrugation: initial excitation and frequency selection for consistent initiation and growth

ABSTRACT This paper proposes a new hypothesis for the formation process of short pitch rail corrugation. An FE wheel-track dynamic model is utilized to verify the hypothesis by reproducing corrugation initiation and consistent growth. It is found longitudinal compression modes are responsible for corrugation initiation with necessary initial excitation that allows flexibility for longitudinal vibration. Consistency between longitudinal compression and vertical bending eigenfrequencies of the wheel-track system is required for consistent corrugation growth, which also determines maximum corrugation amplitude. Corrugation initiates by frequency selection instead of wavelength fixing. The proposed mechanism can explain field observations including the wavelength and periodicity of corrugation in the Netherlands, why corrugation forms on continuously-supported tracks where pinned-pinned resonance does not exist, and the small variation between the corrugation wavelength and train speed.

Short pitch corrugation mitigation by rail constraint design

Short pitch corrugation is a quasi-periodic rail defect that induces a high level of noise and accelerates track degradation. This paper proposes a methodology to mitigate short pitch corrugation by rail constraint design, including four steps. In Step 1, corrugation is numerically reproduced by employing a three-dimensional (3D) finite element (FE) vehicle-track model with degraded fastenings. In Step 2, the corrugation initiation mechanism is identified by the operating deflection shapes (ODSs) approach. In Step 3, different types of rail constraints are designed and their effects on rail vibration modes are analysed. Then FE models of these rail constraints are built up and validated. In Step 4, rail constraint models from Step 3 are applied to the 3D FE vehicle-track interaction model and their effectiveness on corrugation mitigation is evaluated. The results indicate rail longitudinal compression modes and the induced longitudinal dynamic contact force dominate the initial differential wear and corrugation initiation. Based on this mechanism, a new rail constraint is designed in this work that can completely suppress longitudinal compression modes and significantly reduce the fluctuation amplitude of the longitudinal contact force so that corrugation can hardly initiate. This paper first points out a direction for field corrugation mitigation by strengthening the rail longitudinal constraint.

Effect of arc corrugation initiation on the thermo-hydraulic performance and entropy generation of the corrugated tube

It's important to know which corrugation start provides the best heat transfer performance with the least frictional losses. Thus, the present work focuses on the performance of corrugated tubes with different corrugation initiation. The different types of arc corrugations (outward arc, inward arc, outward arc-inward arc, and inward arc-outward arc) are used for assessing the entropy generation and thermo-hydraulic performance of the tubes under the application of constant wall heat flux. The different corrugation starts have a different effect on the thermo-hydraulic and entropy generation performance. For all the considered flow rates, the outward arc-inward arc configuration has the highest Nusselt number. The combination of inward and outward arc corrugations results in better heat transfer, but this improved heat transfer is at the expense of the pressure drop. The total and heat transfer entropy generation in the corrugated and smooth tubes reduce with an increment in the Reynolds number, while frictional entropy generation enhances. The outward arc-inward arc configuration results in the lowest total entropy generation at the highest Reynolds number and it is 0.398 W/K. All the corrugated tubes have entropy generation number less than unity, which is advantageous because of better heat transfer and lesser system irreversibility.

The dynamic resonance under multiple flexible wheelset-rail interactions and its influence on rail corrugation for high-speed railway

The wheel-rail dynamic resonance (W-RDR) under multi wheelset-rail nonlinear interactions in the mid-high frequency range is still unclear regarding wheelset flexibility, wave transmissions and reflections (W-TF) among each wheel-rail interaction. To clearly elucidate W-RDR and its induced modes, a double vehicle-track coupled dynamic model of multiple flexible wheelset-rail interactions is established. The validity of the model in the mid-high frequency range is verified by comparing the simulated axlebox acceleration with the measured data. Then, the W-RDR (vertical force, friction power) is calculated and analyzed. Furthermore, the W-RDR under the single/ double/ multiple wheelset-rail interactions is compared and the rail bending modes between bogie wheels are proposed. The influence of wheelset flexibility and W-TF among each wheel-rail interaction on W-RDR are clarified. Finally, the initiation mechanism of rail corrugation is revealed based on corrugation growth rate. The results show that the wheelset flexibility has limited influence on vertical force resonances but significant contribution to friction power resonances. The W-TF between bogie wheels produce three rail local bending modes. The W-TF between wheels of adjacent bogies further intensify response peaks but do not generate new resonances. The W-RDR is mainly caused by the P2 resonance mode, the rail bending modes between bogie wheels and the wheelset bending modes. The rail 3rd-order bending, pinned-pinned resonance between bogie wheels and the wheelset 2nd antisymmetric bending resonance are key factors in corrugation initiation. Moreover, the wheel-rail resonance at the bogie leading wheelset is more prone to produce corrugation than that at the rear wheelset.

On the coupling of the vertical, lateral and longitudinal wheel-rail interactions at high frequencies and the resulting irregular wear

A transient FE model of wheelset-rail rolling contact has been developed with ANSYS/Ls-dyna to simulate the high speed running of a free wheelset on a slab track. Applying vertical, lateral and longitudinal vibrations at the passing frequencies of typical short pitch corrugation to the wheelset with no initial lateral shift, it is found that the vertical and lateral wheel-rail interactions are coupled to a large extent, while the longitudinal relatively independent under rolling-sliding and dependent when approaching full-sliding. The resulting irregular wear calculated with implemented wear models of Archard, Tγ and Zobory increases in amplitude with the friction exploitation level, whereas its phase keeps rather stable under rolling-sliding. As full-sliding is approached, the phase shifts greatly in the presence of the vertical or lateral vibration, but not of the longitudinal vibration. Consequently, corrugation initiation from the vertical and lateral vibrations becomes harder if both full- and rolling-sliding wheels pass over.

New Insights into the Short Pitch Corrugation Enigma Based on 3D-FE Coupled Dynamic Vehicle-Track Modeling of Frictional Rolling Contact

A three-dimensional (3D) finite element (FE) dynamic frictional rolling contact model is presented for the study of short pitch corrugation that considers direct and instantaneous coupling between the contact mechanics and the structural dynamics in a vehicle-track system. In this study, we examine the system responses in terms of vibration modes, contact forces and the resulting wear with smooth rail and corrugated rail with progressively increasing amplitude to infer the conditions for consistent corrugation initiation and growth. Wear is assumed to be the damage mechanism, and short pitch corrugation is modeled using wavelengths from field observations of a Dutch railway. The contribution of this paper is a global perspective of the consistency conditions that govern the evolution of short pitch corrugation. The main insights are as follows: (1) the longitudinal vibration modes are probably dominant for short pitch corrugation initiation; (2) during short pitch corrugation evolution, the interaction and consistency between longitudinal and vertical modes should determine the development of short pitch corrugation, and once a certain severity is reached, vertical modes become dominant; and (3) in the case simulated in this paper, corrugation does not grow probably due to not only the different resulting main frequencies of the vertical and longitudinal contact forces, but also the inconsistency between the frequencies of the vertical and longitudinal vibration modes and the resulting wear. It is inferred that in the continuous process of initiation and growth of the corrugation, there should be a consistency between them, and this could be done by the control of certain track parameters.

Dynamic optimization of track components to minimize rail corrugation

In this paper, the influence on corrugation of the most significant track parameters has been examined. After this parametric study, the optimization of the track parameters to minimize the undulatory wear growth has been achieved. Finally, the influence of the dispersion of the track and contact parameters on corrugation growth has been studied. A method has been developed to obtain an optimal solution of the track parameters which minimizes corrugation growth, thus ensuring that this solution remains optimum despite dispersion of track parameters and wheel–rail contact uncertainties. This work is based on the computer application RACING (RAil Corrugation INitiation and Growth) which has been developed by the authors to predict rail corrugation features.

Wagon–track modelling and parametric study on rail corrugation initiation due to wheel stick-slip process on curved track

For the investigation of rail corrugation formation due to the wheel stick-slip process on curved tracks, a nonlinear wagon–track model is presented in this paper. In this model, the wagon movements were described using up to 78 degrees of freedom (Dofs). The two wheels in a wheelset are coupled through the stiffness coefficients corresponding to the natural torsional and bending modes of wheelset. The track is considered as a discretely supported distributed-parameter track modelling with one layer. In the wheel–rail interface, before the creep saturation point μ s N c ( μ s, static wheel–rail friction coefficient; N c, normal force), the creep forces and moments are calculated using Kalker's linear creep theory. After that point, the wheel slides on the rail and the friction force will be μ k N c ( μ k—kinetic friction coefficient). The simulations show that the frequency of wheel stick-slip process is composed of a basic frequency, which matches the sleeper-passing frequency and the combined torsional and bending frequency of the wheelset, forming the wavelength of rail corrugation at different situations. Generally, the wheel stick-slip process on the high rail oscillates at the basic frequency whilst the dominant frequency on the low rail is double the basic frequency. The effects of the curved track parameters, the wheel–rail friction characteristics and the wheel–rail profiles on the wheel stick-slip process were investigated.

Nonlinear three-dimensional wagon–track model for the investigation of rail corrugation initiation on curved track

A nonlinear wagon–track model on curved track has been developed to characterize rail corrugation formation due to self-excitation of the wheel–rail stick–slip process. In this model, wagon movements were described using up to 78 degrees of freedom (DOFs) to model a three-piece freight bogie. Innovatively, the wheelset movements are described using nine DOFs, including torsional and bending modes about the longitudinal and vertical directions. The track modelling is considered as a one-layer structure (two rail beams on discrete spring and damper elements). The wheel sliding after creepage saturation is considered in the wheel–rail interface modelling. Simulation of a case study shows that the frequencies of the wheel stick–slip process are composed of the basic frequency, which might come from the combined effect of sleeper-passing frequency and one-third of the combined torsional and bending frequency of the wheelset, and the double and triple basic frequencies, which form the wavelengths of rail corrugation at different situations.

Elastic-Plastic Finite Element Analysis of Nonsteady State Partial Slip Wheel-Rail Rolling Contact

A finite element analysis with the implementation of an advanced cyclic plasticity theory was conducted to study the elastic-plastic deformation under the nonsteady state rolling contact between a wheel and a rail. The consideration of nonsteady state rolling contact was restricted to a harmonic variation of the wheel-rail normal contact force. The normal contact pressure was idealized as the Hertzian distribution, and the tangential force presented by Carter was used. Detailed rolling contact stresses and strains were obtained for repeated rolling contact. The harmonic variation of the normal (vertical) contact force results in a wavy rolling contact surface profile. The results can help understand the influence of plastic deformation on the rail corrugation initiation and growth. The creepage or stick-slip condition greatly influences the residual stresses and strains. While the residual strains and surface displacements increased at a reduced rate with increasing rolling passes, the residual stresses stabilize after a limited number of rolling passes. The residual stresses and strains near the wave trough of the residual wavy deformation are higher than those near the wave crest.

The role of high positive friction (HPF) modifier in the control of short pitch corrugations and related phenomena

Vibration and noise from wheel–rail corrugations reduce the life of vehicle and track components and bring great discomfort to passengers and residents living in close proximity to the tracks. Roll–slip (stick–slip) oscillations are involved in a number of corrugation initiation and formation mechanisms, especially in systems that exhibit a high level of friction, and negative friction characteristics. HPF friction modifier has demonstrated the ability to change the negative friction characteristic of the wheel–rail interfacial layer to positive, and reduce and control friction to levels consistent with braking and traction requirements of the system. Depending on the circumstances of the system involved, HPF can always reduce top of rail noise by at least 3–4 dB and in some instances by as much as 25 dB.

Wheelset-track resonance as a possible source of corrugation wear

This paper reports on the on-going investigation of the interaction of the torsional dynamics of the wheelset and the longitudinal dynamics of the track, coupled through the contact patch, as a possible source of rail corrugation wear. Previously developed computer models have been up-dated to include the complete dynamic creepage characterization of the contact patch. Possible sources of wheel-rail excitation, such as wheel-to-wheel differential running radii, wheel tread defects, wheel-to-wheel differential tangential force and track lubrication, which could induce wheelset-torsional-track-longitudinal vibrational resonance and thus constitute potential sources of corrugation initiation, have been investigated analytically. Simulation examples demonstrate that the identified sources may generate dynamic resonance response(s) of the wheelset-torsional and/or tracklongitudinal vibrational modes. The amplitude, frequency, and duration of such resonance, in addition to being functions of the system inertia, stiffness parameters and the wheel-rail coupling through the contact patch creep force, are shown to be highly sensitive to the magnitude and time rate of change of the excitation input.

Investigation of rail corrugations on the Baltimore Metro

Rail corrugations have been a problem in certain sections of the relatively new Baltimore MTA rail transit system. A study was conducted to define rail corrugation initiation and growth processes on the system so that construction specifications for new trackage could be modified to reduce corrugations. The study included a literature review, experiments with both trackside and on-board instrumentation and analysis by means of computer modeling. Results from these three tasks are reviewed in this paper.

Fretting of polymer. (2nd report Direct observation of fretting phenomena)

Fretting damaged surfaces of PMMA (polymethyl methacrylate) and steel balls in contact are directly and microscopically observed by optical microscope for various level of normal load, amplitudes of steel balls and fretting frequencies. It is found that corrugation occurs on the surface of PMMA during fretting and it is closely related with the wear of steel balls. After the initiation of corrugation, two types of wear are observed in our experiments : (a) the steel ball continues to slide on PMMA and the wear debris of the steel ball is enveloped in the softened PMMA ; and (b) the steel ball adheres to the corrugation and the wear debris accumulates at the boundary of adhered area. To study the cause of corrugation, the distribution of temperature of the fretting surface is numerically analyzed by the nonlinear transient heat conduction equation with the heat generated by the dissipation of energy during fretting. As a result, the increase of temperature by the dissipation of energy is very little, and it may be attributed to the viscoelastic property of PMMA.