Wheel Polygonization Research Articles

Data-driven approach to study the polygonization of high-speed railway train wheel-sets using field data of China’s HSR train

Environmental factors, like seasonality, have been proved to exert significant impact on reliability of China high-speed rail train wheels in this article. Most studies on polygonization of train wheels are based on physical models, mathematical models or simulation systems. Normally, characteristics and mechanisms of wheel polygonization are studied under ideal conditions without considering the impact of the environment. However, in practical use, there are many irregular wear wheels and irregular wear cannot be explained by theoretical models with assumptions of ideal conditions. We look at two possible factors in polygonization: seasonality and proximity to engines. Our analysis of field data shows the environmental factor has more impact on wheel polygonization than the mechanical factor. Based on the Bayesian models, the mean time to failure of the wheels under different operation conditions is conducted. A case study of China’s HSR train wheels is conducted to confirm the finding. The case study shows the degree of polygonal wear is much more severe in summer than other seasons. The finding may give a totally new research perspective on polygonization of train wheels. We use Bayesian analysis because this method is useful for small and incomplete data sets. We propose three Bayesian data-driven models.

Wheel polygon evolution and dynamic influence on heavy haul locomotive

Wheel polygon evolution and dynamic influence on heavy haul locomotive

Analysis of wheel-rail dynamic characteristics due to polygonal wheel passing through rail weld zone in high-speed railways

Analysis of wheel-rail dynamic characteristics due to polygonal wheel passing through rail weld zone in high-speed railways

Comparison of wear models for simulation of railway wheel polygonization

This paper presents a comparative study on the applicability of existing popular wear models in simulation of railway wheel polygonization. Four representative wear models developed by BRR (British Rail Research), KTH (Royal Institute of Technology), USFD (University of Sheffield), and Professor Zobory respectively, are selected for the comparison with consideration of global and local methods. All the wear models are converted to calculate the instantaneous wear of one contact patch. Uniform expression of the converted wear functions is derived analytically with the equivalent wear coefficient as a useful index to identify the proportional relationship among the wear models quantitatively. Several scenarios grouped by harmonic excitation and random excitation are adopted to assess the fluctuation of the instantaneous wear depth calculated by different wear models. The evolved polygonal wear around the wheel circumference is also compared among the wear models based on a developed prediction program. Simulation results show that all the wear models being investigated in this paper present a similar ability to reflect the fluctuation of the instantaneous wear under various circumstances. Specifically, all wear models can correctly reflect the frequency characteristics of the excitation in a general sense, and the fluctuation phase of the instantaneous wear is obtained with almost the same result among the wear models. There is a very good consistency of trend for all local wear models to simulate the evolved polygonal wear. The mean value and the fluctuation amplitude of the instantaneous wear, as well as the roughness level of the evolved polygonal wear, are all determined by the original wear coefficients used. Besides, the global method is not suitable for calculating the polygonal wear of railway wheels as some sharp points might be generated by the absolute operation for the global WI (Wear Index).

Wheel flat can cause or exacerbate wheel polygonization

ABSTRACT Wheel flat is a common local defect occurring to railway wheels. The relevant standards have specified the operational limits for wheel flats in terms of the length. However, in the actual operation, wheel flats, the sizes of which are smaller than the specified criteria, often appear on wheels, and such flats are difficult to be completely erased by normal wheel-rail wear, resulting in a long-term cyclic wheel-rail impact with a followed damping oscillation. Besides, the mechanism of wheel polygonization has not been explained perfectly. Considering these two aspects, this paper aims to investigate whether wheel flats can cause or aggravate wheel polygonization as well as the influence of vehicle speeds and flat lengths on polygonal wear. Firstly, a parametric and automatic wear calculation model, which combines FaStrip and USFD wear function, is proposed. The simulation results prove that wheel flats can cause or exacerbate wheel polygonization, and vehicle speeds and flat lengths have a large influence on the polygonal wear. Furthermore, the conclusion that wheel flat can cause or exacerbate wheel polygonization is verified by a field test. It further states that those excitations or defects, which can cause long-term periodic wheel-rail impacts, may cause or aggravate wheel polygonization.

Influence of wheel-polygonal wear on the dynamic forces within the axle-box bearing of a high-speed train

ABSTRACT A three-dimensional vehicle-track coupled dynamics model, with the inclusion of the axle-box bearings, has been developed, which considers the coupling effects between the bearing and the vehicle components. Some non-linear factors, such as time-varying bearing stiffness, bearing clearance, wheel-polygonal wear and the non-linear wheel-rail contact forces, are also considered. Dynamic analysis has been implemented through numerical simulations that consider different amplitudes and harmonic orders of measured and idealised polygonal wheel wear. Both model analysis and validation were supported by field tests. Results show that the roller-raceway contact forces increases with vehicle speed and the amplitude of polygonal wear. However, the influence of wear upon the axle-box bearing is found to be small in the low-speed range, but at higher operating speeds, polygonal wear leads to a rapid increase in bearing contact forces and the potential for degradation. During vehicle operations, both high order (17th to 20th order) and lower order (1st to 4th order) wheel-polygonal wear patterns are generated. The former's influence on axle-box bearing forces is more significant. Hence, the identification and rectification of this order of wear should form part of maintenance practice and potentially also be considered in the design of axle-box bearings for high-speed trains.

Effect of wheel polygonization on the axle box vibrating and bolt self-loosening of high-speed trains

The wheel polygonization has become a great concern for the high speed rail vehicle owing to its highly adverse effects in high speed condition. Such periodic distributed wear along the wheel can give rise to high magnitude of high frequency impact loads at the wheel/rail interface and further contribute to severe fluctuations in axle box acceleration and the self-loosening for axle box bolts. In this study, the wheel polygonization-induced axle box vibrations and bolt self-loosening are thus initially investigated through the field tests and the roller test rig. Subsequently, a coupled vehicle/track dynamic model integrating a typical high speed rail vehicle and a flexible slab track is formulated to identify the mechanism of bolt self-loosening in the presence of wheel polygonization. The results suggest that the wheel polygonization can result in high magnitude accelerations in the axle box, and excite some of vibration modes of the axle box and its end cover. The accelerations on the axle box end cover are much larger than those obtained on the axle box, which is also comparable to the experimental results. It is thus believed that the self-loosening of axle box end cover’s bolts is mainly attributed to the severe oscillations on the axle box due to the wheel polygonization.

The influence of wheelset flexibility on polygonal wear of locomotive wheels

This paper reports on fundamental research to investigate the influence of wheelset flexibility on the development of wheel polygonization of a locomotive. After preparing a flexible wheelset model by importing a FE (Finite Element) model into the MBS (Multi-Body System) environment, the investigation work proceeded in 3 steps. Firstly, FRF (Frequency Response Function) of the contact responses against the track irregularity is analysed for a free wheelset and an on-track wheelset, with consideration of rotation effect. Secondly, the influence of the wheelset flexibility on the contact responses excited by white noise is investigated for straight and curved tracks. The final step is to check the influence of the wheelset flexibility on the development of wheel polygonization based on a developed prediction program for railway wheel polygonization. 6 scenarios are investigated with comparison between rigid and flexible wheelsets. Results show that, the wheelset flexibility cannot dominate the railway wheel polygonization in a general sense, unless some prerequisites are fulfilled to provide a suitable environment for the wheelset flexibility to be effectively and continually excited to fluctuate the contact responses, and thereby initiate wheel polygonization. The torsional mode of the wheelset can be effectively excited by stick-slip vibration due to saturated contact adhesion that can occur on track with small curve radii or by large traction torque. In this case, the developed wheel polygonization order will be exactly determined by the wheelset torsional modal frequency and the vehicle speed.

Study on effect of wheel polygonal wear on high-speed vehicle-track-subgrade vertical interactions

Wheel polygonal wear, as a form of wheel surface damage, is of great concern and potential threat to the deterioration and safety of railway systems. The experimentally measured polygonal wear can be treated as a superimposed wave with different harmonic orders, phases and wave depths, accordingly various frequency components are included. Most of the previous research is focused on vehicle-track vibrations caused by wheel polygon, while its influence on subgrade performance is rarely referred. With this consideration, a vertical model for vehicle-track-subgrade dynamic interactions is established by the Green function method with high accurateness and efficiency. In the numerical analysis, three types of excitations are considered, i.e., the measured polygon, the harmonic polygon and the track random irregularity. Numerical results show that the short wavelength excitation originated from the measured wheel polygon induce high-frequency wheel-rail interactions, which intensify the wheel and rail vibrations and have additional effects on the vibration modes of the displacement and stress curves of the subgrade surface; with the increased polygon order and wave depth, the wheel-rail vertical forces, wheel unloading rates, fastener forces and rail accelerations are significantly exacerbated; the vertical displacement and stress of the subgrade system are mainly affected by the lower orders of wheel polygon.

Torsional vibration analysis of the gear transmission system of high-speed trains with wheel defects

The gear transmission system of a high-speed train is the key component, which delivers the traction torque from the motor to the wheelset. It couples with the vehicle system via the suspension system, gear meshing and the wheel–rail interface. The dynamic performance of the transmission system directly affects the operational reliability or even the running safety of high-speed trains. In this study, the effects of wheel polygonalisation and wheel flat on the dynamic responses of the transmission system are investigated through simulations of a novel vehicle dynamics model. This model integrates the flexible gearbox housing, the time-varying mesh stiffness and the nonlinear gear tooth backlash, and the track irregularities to obtain more realistic responses of the traction transmission systems in a vehicle vibration environment, from motors to wheelsets, under the effects of the wheel flat and polygonal wear. The field experimental tests are implemented for a vehicle running along a main high-speed railway line in China. Subsequently, the developed dynamics model is validated with good agreement between the experimental and the theoretical results. The calculated results revealed that wheel flat and wheel polygonal wear caused a high-frequency fluctuation of both the longitudinal creep force and the gear mesh force, causing a violent and complex torsional vibration of the gear transmission system. Moreover, the flexible deformation of the gearbox housing, especially its resonance due to the wheel polygonal wear, contributed to the torsional vibration of the gear transmission system.

Effect of the unstable vibration of the disc brake system of high-speed trains on wheel polygonalization

This paper conducts a detailed investigation into the formation mechanism of wheel polygonalization in high-speed trains and its influence factors through numerical simulation. A finite element model including two rails, one wheelset, and three disc brake units is set up to study the formation mechanism of wheel polygonalization in high-speed trains based on the point of view of frictional self-excited vibration. Using the finite element complex analysis, the dynamic stability of the wheelset–track–disc brake system is studied. In addition, the influence factors on the wheel polygonalization are investigated. Results show that when the longitudinal creep force is unsaturated, the 21-order polygonal wear of wheels occurs easily due to the self-excited vibration of the disc brake unit. When the longitudinal creep force is saturated, the 12-order polygonal wear of wheels probably occurs due to the self-excited vibration of the disc brake unit. The bigger the friction coefficient between the brake disc and pad, the greater the occurrence propensity of the polygonal wear of wheels. Vertical fastener damping that is too large or too small is disadvantageous for suppressing wheel corrugation. However, increasing the lateral fastener damping is beneficial for reducing the polygonal wear of wheels. When the vertical fastener stiffness is 25 MN/m, 7-order, 9-order, and 14-order wheel polygonalization can easily occur. A higher lateral fastener stiffness is beneficial for the suppression of wheel polygonalization.

Fatigue analysis of the gearbox housing in high-speed trains under wheel polygonization using a multibody dynamics algorithm

To examine the effect of the wheel polygonization on the fatigue of the wheelset-mounted gearbox housing of a high-speed train, a three-dimensional multibody system (MBS) railway vehicle model, which accounts for the flexibilities of gearbox housing and wheelset and the nonlinear wheel-rail contact, is established to perform the finite element and multibody dynamics analysis simultaneously. Field measurements on the wheel wear, within a total running distance of 140,000 km, were conducted to state the evolution of polygonal wear with a dominant order of 20 on the wheel. Then this uneven wear on the wheel is treated as excitations in the wheel-rail interaction, followed by numerical analysis on the dynamics stress distribution on the gearbox housing under the effect of a variable amplitude of polygonal wear on the wheel. It shows that the stress distribution on the gearbox housing is significantly affected by the deformation of the wheelset. Furtherly, the Kernel density estimation (KDE) method is employed to extrapolating the dynamic stress on the gearbox to obtain the stress with a total running distance of 140,000 km, then its fatigue damage is estimated. Comparative analysis in the fatigue damage of gearbox housing with or without the wheel polygonization states that the fatigue damage with a 20th order polygonal wear is 63% larger than that without the polygonal wear on the wheel.

Variable frequency drive harmonics and interharmonics exciting axle torsional vibration resulting in railway wheel polygonisation

ABSTRACTSevere vibrations and an increase in structural component fatigue failures have been observed on a freight locomotive class operating on a heavy haul route within South Africa. The root cause of these severe vibrations were investigated experimentally and it was found that polygonised wheels were cuasing these severe vibrations. A coupled mode of vibration exists in the traction system that is a combination of traction motor pitching and wheelset axle torsion. Harmonics and interharmonics are features of an AC motor controlled by a variable frequency drive (VFD) and were confirmed to cause resonance of the coupled vibration mode. Interharmonics are a function of the fundamental frequency () of the VFD and the input AC frequency ( supplied to the VFD. It was found by experimentation that the interharmonic caused resonance of the coupled mode while the locomotive operated at 40 km/h. This running speed and frequency of vibration was found to fix the wavelength of a 20th order polygon on the wheels during approximately 11% of the locomotive’s load hauling time.

A study of formation of high order wheel polygonalization

High frequency and high magnitude wheel-rail impact forces caused by high order wheel polygonalization have been associated with service failures of different structural components in high-speed rail vehicles. In this study, a long-term wear iterative scheme was developed to identify primary contributors of high order wheel polygonalization and its propagation over the service period. The wear model was formulated by integrating an Archard wear model to a coupled vehicle/track dynamic model of a high-speed railway car. The effects of different vehicle and track parameters such as the flexibilities of wheelset and rail, vehicle speed, wheelbase, and rail pad stiffness and damping on the wheel wear were further investigated. The bending vibration mode of the rail segment between two wheelsets, regarded as three half wavelength bending vibration mode near 650 Hz, was identified as the primary contributor to high magnitude wheel/rail contact force in the 500–800 Hz frequency range. This represented a nearly fixed-frequency loading condition. Variations in the vehicle speed and the track could help distribute wheel circumferential irregularities over a broader range of wavelength and thereby mitigate the growth rate of wheel polygonalization of a single order. It is further shown that the wheelset flexibility and higher rail pad stiffness accelerate the wheel wear and more likely contribute to the lower order wheel polygonalization. Increasing the rail pad damping could effectively reduce the rate of growth of high order wheel polygonalization.

Research on Vibration Characteristics and Stress Analysis of Gearbox Housing in High-Speed Trains

Gearbox housing in high-speed trains has two kinds of excitation sources: the internal excitation of gear mesh excitation and the external excitation that contains the wheel polygonization and the input torque. To study the effect of the torque on the vibration and stress of the gearbox housing, a multibody dynamic model is established by the Simpack, in which the elastic deformation of the wheelset and the gearbox housing are considered. A traction drive system is modeled by the MATLAB/Simulink to calculate the traction torque, which is transformed to drive the high-speed train to overcome the basic resistance and run with a constant speed. The accuracy of the model is verified by comparing the simulation results with the measurement results. Based on the electromechanical model, the vibration acceleration of the gearbox housing in the case of without torque, with ideal torque, and with harmonic torque is calculated and analyzed, as well as its dynamic stress. The results show that the traction torque plays a role in amplifying the vibration acceleration and dynamic stress. When the fatigue damage of the gearbox housing is calculated, it will obtain a more accurate result to consider the effect of the traction torque.

Experimental and Numerical Investigation into Formation of Metro Wheel Polygonalization

We present a detailed investigation of the mechanism of metro wheel polygonal wear using on‐site experiments and numerical simulation. More than 70% of metro wheels exhibit 6th–8th harmonic‐order polygonal wear; the excitation frequency of the polygonal wear is located in the 50–70 Hz interval at an operating speed of 65–75 km/h. To determine the root cause of the polygonal wear, a dynamic train behavior test is conducted immediately after wheel reprofiling. The results suggest a natural mode resonance in the vehicle/track system, whose frequency coincides with the passing frequency of the 6th–8th order polygonalization. The magnitude of the resonance increases significantly when the vehicle runs on a monolithic concrete bed with DTVI2 fasteners. Thus, a corresponding coupled vehicle/track dynamic model is established and validated by comparing the calculated frequency response functions (FRFs) of tracks and dynamic responses of axlebox acceleration with the measured values. Using multiple timescales, the dynamic model and Archard wear model are integrated in a closed loop for long‐term polygonal wear prediction. The simulated and measured evolution of polygonal wear show good agreement. By combining simulation results and experimental data, we suggest that the P2 resonance is the main contributor to the high amplitude of wheel/rail contact forces in the 50–70 Hz frequency range and the reason for subsequent polygonal wear. Parametric studies show that the dominant order decreases as vehicle speeds increase, representing a “frequency‐constant” mechanism. The wheelset flexibility, especially the bending mode, would aggravate the wheel/rail creepage and further accelerate the formation of polygonal wear. Higher rail pad stiffness will increase P2 resonance frequency and shift the dominant wheel to higher polygonal orders.

Structural Improvement of the ω‐Type High‐Speed Rail Clip Based on a Study of Its Failure Mechanism

In the circumstances of high‐speed railways, the wheel‐rail vibration is significantly aggravated by polygonal wheel wear and rail corrugation, which subsequently leads to the wheel‐rail interaction at higher frequencies and potential failure of the rail fastening. In this paper, a ω‐type clip of the fastening in the CRH high‐speed rail was used to investigate the failure mechanism. First, a dynamic wheel‐rail coupling model and a finite element analysis of the rail clip were developed, from which the rail vibration frequency and modal frequencies of the clip with different installation torques were obtained. The experimental tests and modal simulation results were mutually verified. In addition, the real‐time vibration measurement and the wheel‐rail wear monitoring were carried out at a CRH high‐speed railway site. It was found that the resonant frequencies of the ω‐type clip in the installation condition coincided with the excitation frequencies of the wheel‐rail interaction induced by wheel‐rail wear. The high‐frequency dynamic failure mechanism of a typical ω‐type clip, W300‐1, is put forward for the first time. Moreover, a high‐frequency rail clip fatigue test system was designed and developed specifically for this study. The loading excitation frequency of the clip test used was set as 590 Hz, and the loading amplitude was 0.05 mm. After 125‐minute operation of the test system, the clip was broken at the expected location predicted by the FEA model. The high‐frequency fatigue test result further verified that the failure mechanism of the ω‐type clip was due to the resonance of the clip with its excitation force from the wheel‐rail interaction. Finally, the clip was then structurally improved taking into account the stiffness and mass, which led to its resonant frequencies shifting away from the high‐frequency excitation range, hence avoiding resonance failure of the subject clip.

Research of Wheel-Rail Coupled Vibration Excited by Wheel Polygon for Heavy-Haul Locomotive

In order to study the wheel-rail impact vibration of the heavy-haul locomotive with 25t axle-load, the typical wheel polygonal data for different running distance were field measured. The radial circular run-out, radial geometric deviation and harmonic composition of wheel polygon were analyzed. The vehicle-track vertical coupling dynamics model was established and verified by comparing the vibration test results and numerical simulation results. The research results show that, with the increase of service mileage, the wheel polygon wear deteriorates, leading to the violent wheel-rail dynamic interaction. The impact force caused by the wheel polygon has a great influence on the primary suspension force, and has almost no influence on the secondary suspension force. The maximum acceleration of the car body, frame and wheelset caused by the wheel polygon is 3.148g, 0.177g and 0.00149g, so the vibration attenuation phenomenon of the locomotive is very obvious. The maximum acceleration of the rail, sleeper, ballast is 3.38g, 2.81g, 2.1g, therefore, the track system vibration attenuation is weaker. The main frequency of the vibration is 30Hz, which corresponds to the 7th-order harmonics, the result is consistent with the analysis of the wheel polygonal harmonic components.

Effect of the turning characteristics of underfloor wheel lathes on the evolution of wheel polygonisation

During both running and wheel cut operations, wheels of railway vehicles and the friction rollers that support and drive the wheelset on a typical wheel cut lathe are subject to wear and hence are likely to develop out-of-round characteristics after sustained use. The resulting out-of-round wheels can significantly affect the ride quality and can potentially increase the incidence of fatigue-related component failures due to the resulting higher intensity loading cycles. Furthermore, the corresponding out-of-round characteristics of the lathe's friction rollers will continue to degrade the subsequent cut quality of wheels. For the analysis of the out-of-round characteristics caused by an underfloor wheel lathe used for the high-speed trains in China, a mathematical model based on a typical electric multiple unit (EMU) vehicle's wheelsets and their interactions with the wheel lathe friction rollers was established. Factors influencing the cut quality of the wheels, including the number of cuts, eccentricity forms of the friction rollers and the longitudinal spacing of the two rollers, have been analysed. The results show that two cuts can effectively remove the higher order polygon on the wheel surface. The eccentricity and phase angle of the friction rollers have no influence on the cut quality of higher order polygons, whereas they are the primary cause for the fourth-order polygons. The severity of the fourth-order polygon depends on the level and the phase of the eccentricity of the friction rollers. The space of the two rollers can also significantly affect the cut quality. Obtaining the theoretical and practical value for the maintenance of polygonised wheels using the underfloor lathe is the main outcome of this study.

Investigations on formation mechanisms of out-of-round wheel and its influences on the vehicle system

The railway wheels are invariably subjected to the uneven wear owing to the wheel/rail interaction, and always tend to be an out-of-round wheel. Such wear on the wheel circumference can be classified into the local defect and the periodic uneven wear. The local defects, including the wheel flat and wheel shell, have been well documented, while the formation mechanisms of wheel polygonalizations, especially for high-order polygonal wear, have not yet been explained clearly. The formation mechanisms of wheel polygonalizations are thus initially reviewed and discussed in this study, and the metal cutting theory is also employed to explain the formation procedure of wheel polygonalization. A coupled vehicle/track dynamic model integrating with the flexibilities of the wheelset, bogie and car body is subsequently formulated to investigate the influences of wheel polygonalization on the dynamic responses of vehicle system, in terms of wheel/rail normal forces, lateral forces and accelerations of wheelset and bogie frame. A maintenance strategy for wheel polygonalization considering the different peak-to-peak amplitudes and the number of harmonic waves is proposed on the basis of limit values of wheel/rail vertical force.