Wheel Polygonization Research Articles

Investigation on the characterisation of axle box resonance characteristics to wheel excitation

A growing number of studies have demonstrated the effectiveness and superiority of reverse engineering in using axle box vibration acceleration signals to deduce the operation state of wheelsets. However, there is a lack of discussion and summary on the overall mapping relationship between wheel excitation and axle box response, and there has been no detailed investigation on resonance characteristics of axle box. To address the deficiency, a novel resonant excitation loading method is proposed, which is applied to the vehicle model with flexible wheelset and axle box. Amplitude frequency response (AFR) curve of the resonance characteristics of axle box is obtained. AFR is used to characterise the characteristics of various excitation states of wheel, including wheel polygon, wheel tread flat, and wheel-rail separation state, and the corresponding evolution law is revealed. Finally, through two case studies, the guiding role of axle box resonance characteristics on wheel operation status detection is discussed in detail. Analyses show that mastering the resonance characteristics of axle box is an effective way to deduce the operation status of wheel based on the complex axle box vibration response signal, and it will provide a basis for the quantitative evaluation of wheel local damage.

A simulation investigation on the effect of wheel-polygonal wear on dynamic vibration characteristics of the axle-box system

With the increasing speed of high-speed trains and the deteriorating operation environment of axle-box system, the dynamic performance of axle-box bearing directly affects the stability and safety of operation. In this paper, a bearing-vehicle-track coupling dynamic model is established, and its effectiveness is verified by field tests. The simulation results of the coupling dynamic model including wheel-polygonal wear show that the effect of high order polygonal wheel wear (17th ∼ 21st order) on the axle-box system is greater than that of low order wheel wear (1st ∼ 5th order). The frequency domain of axle-box vertical vibration acceleration excited by high order wheel-polygonal wear is mainly distributed in 400 ∼ 600 Hz. The low order polygonal wheel wear amplitude has little effect on the bearing roller-outer raceway contact load. When the wear amplitude of 20th order polygonal wheel is 0.06 mm, the roller-outer raceway contact load is 27.22% higher than that when the wear amplitude is 0.04 mm. In order to avoid bearing failure caused by excessive bearing roller-raceway contact force, the amplitude of 20th order polygonal wheel wear should reduce to less than 0.04 mm.

Influence of wheel out‐of‐roundness on the remaining life of railway wheels under mixed‐mode fatigue loading

AbstractAs a common condition in train operation, the out‐of‐roundness (OOR) of wheels may have a great influence on the life of cracked wheels. In this study, the I–II mixed‐mode crack growth rate of different angles was tested, finite element analysis was carried out by using the test results, and the influence of different wheel roundness conditions on the life of cracked wheels was revealed. The results show that the mode II stress intensity factor of mixed‐mode cracks is the main driving force for crack propagation in the process of wheel rim crack growth. With an increase in the wheel scar length and the order of the wheel polygon, the crack propagation life decreases significantly.

Current signal characteristics analysis of transmission system in high-speed train under abnormal vibration conditions

Abnormal vibration monitoring of high-speed trains is usually performed by analysing the vibration acceleration of specific structures to identify characteristic signals. However, due to the harsh operating environment caused by multiple internal and external sources of compound excitation, vibration monitoring of high-speed trains faces numerous problems, such as easy damage to vibration sensors, limited installation space for testing equipment, and difficulty in vibration testing of rotating parts. This paper takes high-speed train transmission system as the research object, combines multi-body system dynamics and electric transmission control theory to establish an electromechanical model of high-speed train transmission system, and carries out simulation research for three typical working conditions of high-speed train, which are wheel flat, wheel polygon and hunting motion. By analysing the transmission response of wheel–track relationship, gearing and motor current under three operating conditions based on Motor Current Signal Analysis (MCSA), it can be concluded that the motor current signal can be used instead of the vibration signal to identify the above three abnormal operating conditions by analysing the characteristic frequencies in the motor stator current. While MCSA is commonly used to diagnose faults such as tooth surface pitting and tooth root cracking inside gearboxes, the results of this paper show that motor current signals can also be used to monitor any abnormal operating conditions of high-speed trains that can cause changes in motor load torque.

Quantitative detection of locomotive wheel polygonization under non-stationary conditions by adaptive chirp mode decomposition

Wheel polygonal wear is a common and severe defect, which seriously threatens the running safety and reliability of a railway vehicle especially a locomotive. Due to non-stationary running conditions (e.g., traction and braking) of the locomotive, the passing frequencies of a polygonal wheel will exhibit time-varying behaviors, which makes it too difficult to effectively detect the wheel defect. Moreover, most existing methods only achieve qualitative fault diagnosis and they cannot accurately identify defect levels. To address these issues, this paper reports a novel quantitative method for fault detection of wheel polygonization under non-stationary conditions based on a recently proposed adaptive chirp mode decomposition (ACMD) approach. Firstly, a coarse-to-fine method based on the time–frequency ridge detection and ACMD is developed to accurately estimate a time-varying gear meshing frequency and thus obtain a wheel rotating frequency from a vibration acceleration signal of a motor. After the rotating frequency is obtained, signal resampling and order analysis techniques are applied to an acceleration signal of an axle box to identify harmonic orders related to polygonal wear. Finally, the ACMD is combined with an inertial algorithm to estimate polygonal wear amplitudes. Not only a dynamics simulation but a field test was carried out to show that the proposed method can effectively detect both harmonic orders and their amplitudes of the wheel polygonization under non-stationary conditions.

Wheel polygonisation growth due to multiple wheelsets/track coupling vibration

This present study investigates wheel polygonisation growth on China’s high-speed trains from the perspective of multiple wheelsets/track coupling vibration. Two theoretical models were established: a simplified linear model for polygonal wear trend analysis in the frequency domain, and a detailed nonlinear model for reproducing polygonisation in the time domain. The simulation results suggest that both the amplitude–frequency and phase-frequency characteristics play vital roles in the development of polygonal wear. The rail localised bending resonances between adjacent wheels are the main contributors to the high-order wheel polygonisation. The third and second order rail localised bending modes induce a high amplitude of wear fluctuation at 645 and 400 Hz, respectively, while leading to the phase difference between the wear response and original excitation being closest to 180° at 565 and 330 Hz. Accordingly, wheel polygonisation with frequencies of 572 and 342 Hz achieved the largest wear growth rate. Then, the rail localised bending vibration was captured on-site through a train passing test. And a long-term tracking test of high-speed train was utilised to validate the evolution process of the wheel polygonisation, it was determined that the simulated development of wheel polygonal wear and axlebox acceleration reached agreements with the measured results.

Experimental and numerical investigation into development mechanism of wheel polygonalization

The polygonal wear is a significant concern in railway engineering, and the mechanism behind it remains elusive. In this study, the polygonal wear on a specific metro line in China is analyzed. The 7th-order and 8th-order wheel polygonal wear are commonly measured on the metro, in which corresponding excitation frequency is located in the 44.3–58.9 Hz interval at the operating speeds of 60–70 km/h. Meanwhile, an obvious natural resonance at 50.7 Hz is found by analyzing the acceleration of axle box, which is verified by the eigen analysis of the corresponding metro track. Moreover, the vehicle-track coupling model with polygonal wheel is established to analyze the vertical wheel/rail forces induced by polygonal wear. The result indicates that the P2 resonance is the main contributor to the high amplitude vertical wheel/rail forces, which is also the main factor for development of polygonal wear after formation.

Analysis on the formation cause for the high-order wheel polygonization of the high-speed trains based on the finite element method

The formation cause of high-order wheel polygonization of high-speed trains is investigated. A modelling of wheelset/track interaction based on the finite element method (FEM) is set up. The stability of the wheelset-track system (WTS) is studied by using the complex eigenvalue analysis (CEA) based on the modal coupling theory. The dynamic response of the wheelset rolling on the rails is simulated by the transient dynamic analysis (TDA). The results show that the friction-induced vibration (FIV) of the WTS at about 540 Hz, which is composed of the fifth-order bending mode of the wheel axle and the antisymmetric yaw of the wheels, is the principal cause of the 23-order wheel polygon. The frequency of the FIV responsible for the 23-order polygonal wear hardly changes with the vehicle speed and the coefficient of friction (COF) between the wheel and rail, which coincides with the fact that the wheel polygon of high-speed trains in China tends to be frequency-fixed. The order of wheel polygon is inversely proportional to vehicle speed. The higher the wheel-rail COF and the vehicle speed, the faster the wheel polygonization evolves.

Vibration and Stress Response of High-Speed Train Gearboxes under Different Excitations

The vibration data of the gearbox on a high-speed train was measured, and the vibration characteristics were analyzed in this paper. The dynamic stress of the gearbox under the internal and external excitation was examined by a railway vehicle dynamic model with a flexible gearbox and a flexible wheelset. The ideal 20th polygonal wear was considered, and dynamic stresses of the gearbox under different polygonal wear amplitudes were calculated. The gear transmission model was established to study the dynamic stress of the gearbox under the influence of the time-varying stiffness of the gear meshing. Based on the rigid–flexible coupling model, and considering the influence of wheel polygonization, gear meshing time-varying stiffness, and wheelset elastic deformation, the dynamic stress of the gearbox was investigated with consideration of the measured polygonal wear and measured rail excitation. The results show that the dynamic stress of the gearbox is dominated by the wheel polygonization. Moreover, not only the wheel polygonization excites the resonance of the gearbox, but also the flexible deformation of the wheelset leads to the deformation of the gearbox, which also increases the dynamic stress of the gearbox. Within the resonant bandwidth of the frequency, the amplitude of the dynamic stresses in the gearbox will increase considerably compared with the normal case.

Effect of polygon-shaped wheels on fatigue fracture of fastener clips in high-speed railway lines

This paper studies the effect of wheel polygonalization and material properties on the fatigue failure of fastener clips in high-speed railway lines and puts forward the corresponding inhibition measures. Vibration frequencies excited by 24th-order wheel out-of-roundness (OOR) were analysed by on-site tests of the axle box vertical vibration acceleration. A finite element modelling method of polygon-shaped wheels was proposed, which was verified by comparing the field measurement with the dynamic simulation. The dynamic response of the fastener clip was simulated by using a rigid–flexible coupled model of the wheelset-track system. The effect of amplitudes as well as typical wavelengths of wheel OOR on the fracture of the clip was analysed based on the Miner fatigue damage accumulation ruler. The results show that when the wheelset ran at 237 km/h on the track, the 24th-order wheel OOR had no obvious effect on the Mises equivalent stress of the clip. When the amplitude of the 24th-order wheel OOR reached 0.225 mm and above, excited vibrations of about 1172 Hz were transmitted from the wheelset-rail system to the fastener systems, thus reducing the safe operating life of the clips. This phenomenon can be inhibited by setting a reasonable amplitude threshold for wheel re-profiling. Wheel eccentric wear (first-order OOR) and 12th-order OOR had lesser effects on the fatigue failure of the clip. The decrease of Poisson’s ratio or the increase of Young’s modulus of the material could cause the maximum Mises equivalent stress at the clip to increase, which might induce cracks, thus leading to the fracture of the clip. Therefore, during the production process, the Poisson’s ratio and Young’s modulus of fastener clips should be strictly controlled to ensure that they are within the permitted range.

Gearless Track-Friendly Metro with Guided Independently Rotating Wheels

Track–vehicle severe interaction on track with small curve radius results in rail wear and corrugation, and wheel polygonization, which drain considerable resources for rail grinding and wheels re-profiling in metro lines. To reduce the damage caused by track-vehicle severe interaction, the paper analyzes the reasons leading to rail wear and then proposes an architecture of a metro vehicle with independently rotating wheels driven directly by permanent magnet synchronous motors. The architecture is axle guidance, offered by passive linkages, which ensures that all axles are oriented radially, while control strategy was kept as simple as possible, identifying only two basic traction conditions. The concept is first discussed and then validated through a comprehensive set of running dynamics simulation performed with a multibody software to evaluate rail wear and rolling contact fatigue in traction/braking, coasting with different cant deficiency/excess conditions. The multibody dynamics simulation shows that the proposed architecture is virtually capable of avoiding both wear and rolling contact fatigue damages, and achieves the highest possible track friendliness. The concept of the proposed architecture is a track-fiendly metro architecture and could be a good reference for reducing rail-track interaction damages and maintainace cost.

Full-scale test and numerical simulation of wheelset-gear box vibration excited by wheel polygon wear and track irregularity

The wheelset-gear box of high-speed train is the typical unsprung mass serving in the complex excitation environment. To investigate the independent and compounded influences of wheelset out-of-roundness, wheel polygon wear and track irregularity on the vibration performance of wheelset-gearbox system, the 1:1 high-frequency excitation test based on the rolling test rig is carried out within the speeds of 100 ∼ 500 km/h. The corresponding multi-body dynamic model is established and validated. The detailed wheel-wheel contact relations are discussed. The research results indicate that the test rig dynamic model can capture the vibration amplitude and main frequency characteristics well, especially for the vibration below 1000 Hz. For the wheelset-gearbox system without track excitation, its vibration energy is basically concentrated in the resonance region of test object. At higher speeds, the vibrations induced by wheelset and motor rotation gradually become dominant. Under excitation of the grinded polygon wear in rail wheel, the multiple-frequency vibration almost determines the system vibration level within the test speed ranges, whilst the vibration induced by the wheelset and motor rotation plays an important role only at the speed above 300 km/h. In comparison, the high-speed track random irregularity contributes very small vibration magnitude. For the axle box, the vibration amplitude composition ratios led by the excitations of wheelset out-of-roundness, rail wheel polygon wear and track irregularity are around 26.7%, 48.3% and 25% correspondingly. And for the gear box, the composition ratios reach 38.46%, 32.05% and 29.49% respectively. The wheel polygon wear has been the main excitation source in the high-frequency vibration of wheelset system, followed by the wheelset 1st-order out of round and track irregularity in sequence.

Effect of wheel polygonalization on the Degree of Non-linearity of dynamic response of high-speed vehicle system

Polygonalization of the wheel describes the growth of out-of-round profiles of the wheels of railway vehicle. This problem was identified in the 1980s but its mechanism is still not well understood. The wheel-rail disturbance formed by wheel polygonalization will accelerate the fatigue fracture of the key parts of rail vehicles and seriously threaten the safety of rail vehicle. This fact has led to significant efforts in detecting and diagnosing wheel polygonalization, in particular in setting the criteria for health monitoring. Currently, the time-domain feature parameters extraction method based on data statistics and frequency-domain feature parameters extraction method based on spectrum estimation are widely applied to detect wheel polygonalization. However, the basis of spectral estimation is the Fourier transform, which is not good at dealing with non-linear vibration systems (such as vehicle-track coupled system). Aiming at the wheel polygonalization problem existing in high-speed train, the non-linear extent of vibration response of vehicle system caused by wheel polygonalization is analyzed based on vehicle-track coupled dynamics and adaptive data analysis method. A typical high-speed train model is established according to the vehicle-track coupled dynamics theory. The wheel polygonalization model is introduced and vehicle system vibration response is calculated by numerical integration. The vibration response signal is decomposed by empirical mode decomposition (EMD) to produce the intrinsic mode functions (IMFs). By calculating the intra-wave frequency modulation of IMFs, that is, the difference between instantaneous and mean frequencies and amplitudes, the non-linearity of the dynamic response is quantified. Influences of wheel polygonalization on the non-linearity of steady-state and unsteady vibration responses of vehicle system are analyzed in detail. An objective criterion for wheel polygonalization health monitoring based on Degree of Non-linearity is proposed, which provides an effective tool for prognostics and health management of trains.

The effect of 3D wear state of wheel polygon on wheel–rail system dynamics

Wheel wear is a natural phenomenon of wheel–rail rolling contact during vehicle operation. The non-uniform wear in lateral and circumferential directions is normally occurred on wheels. The lateral non-uniform wear will lead to the unexpected hollow wear which can cause flange to flange vibration at low-frequency band, and the circumferential non-uniform wear will result in the vertical vibration which is the originate from the polygon phenomenon. These two forms of wear are coupled to each other on wheels and affect the dynamic behaviours of wheel–rail system. In this paper, a wheel–rail contact dynamics model which includes the 3D geometric shape of wheel profile is established and employed to vehicle system dynamics. The results show that the contact mechanical properties of wheel–rail are greatly affected by the 3D wheel profile. The low-frequency vibration of wheelset caused by hollow wear and the high-frequency vibration by polygonised wear are coupled, which increase the vibrational acceleration of wheel–rail system and even made for the main problem of the periodic separation of wheel and rail and aggravate the wear of wheel polygon.

Effects of wheelset flexibility on locomotive–track interaction due to rail weld irregularities

Irregularities of rail joints ordinarily induce high-frequency impacts on wheel–rail contact systems, which may further influence vehicle–track interaction. In this study, a three-dimensional locomotive-track coupled dynamics model that uses the wheelset flexibility was developed. The wheelset rigid motion and elastic deformation are calculated based on the multi-body dynamics theory and finite element method, respectively. The effectiveness of this model was validated. The effect of wheelset flexibility on locomotive–track interaction due to rail weld irregularities is analysed by comparing the dynamic responses obtained using the rigid model and the proposed rigid–flexible coupled model. The proposed model is applied to the sensitivity analysis of the wheelset response to the rail weld geometry irregularity. The results show that the dominant frequency of the wheel–rail force or axle–box acceleration is 81 Hz, which is the 1st bending modal frequency of the wheelset. The P2 resonance frequency is easily excited owing to impacts of rail weld irregularities, which may induce the formation of locomotive wheel polygonization. The wheelset acceleration was more sensitive to the wavelength than the depth of the rail weld irregularities. The wavelength characteristics can be significant in vehicle vibration-based condition monitoring of rail weld irregularities.

On the formation mechanism of high-order polygonal wear of metro train wheels: Experiment and simulation

Severe high-order polygonal wear has been found on metro train wheels of one metro line in China, which causes considerable vibration of vehicle components and disturbing interior noise. Field tests and numerical simulations were conducted to investigate the formation mechanism and key influencing factors of wheel high-order polygonisation. Wheel out-of-roundness (OOR), vibration behavior of vehicle components, and rail surface irregularities were tested. On-site measurement results indicate that the wheels exhibit 13th- to 16th-order polygonal wear. The dominant wavelengths are about 165–203 mm. The experimental results show that the wheel polygonisation is related to the first-order bending vibration of the wheelset and the P2 resonance generated on ladder sleeper tracks and steel spring floating slab tracks. A long-term wear model was developed to further study the cause of wheel polygonisation, which included a vehicle–track coupled dynamic model, considering the flexibility of the wheelset and track, as well as a wear model. The effects of operating speeds, P2 resonance frequencies for different tracks, and wheelset flexibility on the development of wheel polygonisation were investigated. Based on the experimental and simulation results, it is further believed that the P2 resonance is the main cause of the higher-order polygonal wear of wheels, and the first-order bending vibration of the wheelset can exacerbate the wheel polygonisation.

The impact of wheel polygonisation to the railway corrugation

The railway companies have been beset by rail corrugation for many years, especially those subway companies. Therefore, the formation mechanism of rail corrugation has been paid much attention in the last decades. It is believed that corrugation occurs when the vehicle runs over the track and excites its resonant vibration. Wheel polygonal wear (WPW), as a typical wheel tread defect, inevitably worsens the wheel-rail contact state and excites track vibration. However, little attention has been paid to the impact of the WPW to rail corrugation. In this paper, the impact of WPW to rail corrugation is considered. Firstly, the wheel-rail interaction with WPW is analysed, where the wheel-rail interactive force is treated as a moving harmonic load. Then, the impact of WPW to rail corrugation is investigated with the help of theoretical analysis and simulation experiments. The specific track with integrated ballast bed is considered as an example. The results show that the initial rail wear is largely due to WPW. And when the track resonance is excited by the moving harmonic excitation induced by WPW, the initial wear evolves into rail corrugation. In addition, WPW intensifies the development of existing corrugation and leads to some new corrugation.

Research on the Influence of Wheel Polygonization on Axle Stress

To study the influence of wheel polygonization on the dynamic stress of the wheel axle, a vehicle-track rigid-flexible coupling dynamic model was established. In the model, the wheelset, axle box, and track system were modelled as flexible bodies to consider the influence of elastic vibration. At the same time, the dynamic stress on key positions of the axle under the wheel polygonization excitation was measured on the high-frequency vibration test rig. The accuracy of the model was verified by comparison with the test results. The wheel axle stress under the excitation of the wheel polygonization with different orders, wave depths, and running speed was calculated. The results show that the wheel polygonization can increase the amplitude of the axle dynamic stress, and the larger the wave depth of the wheel polygonization, the larger the stress amplitude. When the wheel polygonization frequency is close to the frequency of the wheelset elastic vibration mode, the wheelset first-order bending and second-order bending modes have a great influence on the axle stress. The resonance vibration of the wheelset elastic modal can cause the dynamic stress on key positions of the axle increase sharply.

Formation process, key influencing factors, and countermeasures of high-order polygonal wear of locomotive wheels

Two types of high power alternating current (AC) locomotive in China are prone to serious high-order polygonal wear, which has significant negative effects on the operation of locomotives. This study investigates factors influencing polygonal wear in locomotive wheels and determines methods of minimizing operation damage. We designed experiments to analyze the process of polygonization formation of wheels to identify the key influencing factors, finding that natural vibration of wheelsets is the central inherent factor of wheel polygonization and that these vibrations can be easily stimulated by wheel or rail irregularities. We found that poor re-profiling quality is the key external factor in these irregularities. The wheelset bending resonance is activated when the remaining wheel polygonal wear has a wavelength of 200 mm in the 1/3 octave band, in turn leading to significant increases of wheel polygonal wear. In this study, we review a new wheelset design that can mitigate and/or eliminate the polygonal wheel wear due to increased stiffness in wheel bending. We evaluate the potential capacity of the newly designed wheelset and propose two proven effective measures to further improve the wheel re-profiling quality for polygonal wear.

Random vibration analysis of tram-track interaction on a curve due to the polygonal wheel and track irregularity

The vibration performance of a tram vehicle running on the curved track is influenced by the speed of the running vehicle, the geometry of the track, the roughness of the wheel and rail, and environmental characteristics. This paper investigates the random vibration analysis of tram-track interaction on a curved track due to the polygonal wheel and track irregularity by the pseudo excitation method (PEM). The dynamic behaviour of tram-track interaction on a curve is modelled using the finite element method (FEM) and multi-body system (MBS). The field tests were carried out to acquire the rail vibration and deformation response, and also measuring the polygonal wheel wear profile to analyse and validate the dynamic behaviour tram-curved track model. The influence of the polygonal wheel on the vibration of tram-curved track coupled system and the wheel-rail contact responses are investigated by considering the wheelset flexibility. The results are illustrated through comparison between with and without the polygonal wheel in terms of time and frequency domain. The numerical results suggest that the wheelset flexibility under the polygonal wheel wear excitation would aggravate the vibration mode of the rail, car-body and axle-box, and also increase the dynamic wheel-rail contact force and creepage.