Algorithm-based strategy to define an equivalent railway track for wear simulations

de Paula Pacheco P.A., Magelli M., Lopes M.V., Correa P.H., Zampieri N., Bosso N., dos Santos A.A.

AbstractRailway infrastructure relies on the dynamic interaction between wheels and rails; thus, assessing wheel wear is a critical aspect of maintenance and safety. This paper focuses on the wheel–rail wear indicator T-gamma (Tγ). Amidst its use, it becomes apparent that Tγ, while valuable, fails to provide a comprehensive reflection of the actual material removal and actual contact format, which means that using only Tγ as a target for optimization of profiles is not ideal. In this work, three different freight wagons are evaluated: a meter-gauge and a broad-gauge heavy haul vehicles from South American railways, and a standard-gauge freight vehicle operated in Europe, with different axle loads and dissimilar new wheel/rail profiles. These vehicles are subjected to comprehensive multibody simulations on various tracks. The simulations aimed to elucidate the intricate relationship between different wear indicators: Tγ, wear index, material removal, and maximum wear depth, under diverse curves, non-compensated lateral accelerations (Anc), and speeds. Some findings showed a correlation of 0.96 between Tγ and wear depth and 0.82 between wear index and material removed for the outer wheel. From the results, the Tγ is better than the wear index to be used when analyzing wear depth while the wear index is more suited to foresee the material lost. The results also show the low influence of Anc on wear index and Tγ. By considering these factors together, the study aims to improve the understanding of wheel–rail wear by selecting the best wear analysis approaches based on the effectiveness of each parameter.

Pacheco P., Lopes M.V., Correa P.H., Dos Santos A.A.

Bosso N., Magelli M., Zampieri N.

The development of an efficient freight railway system requires minimizing the travel time and maximizing the load capacity of trains. This objective can be achieved through three different strategies which can be adopted separately or in synergy. These strategies substantially consist of improvement of the load capacity of a single vehicle, increase in the train length, and increment of the vehicle velocity. The option to adopt simultaneously all three strategies is possible only when operating on dedicated infrastructures and specifically designing the vehicles and the track. This work shows the effect of the increment of the axle load, over the actual Italian limitation, on the most important indicators defined by the UIC regulation to homologate the vehicles. The calculations have been performed on a high-quality real track using a numerical model of a vehicle based on the Y25 bogie. In order to take into account higher axle loads, the vehicle primary suspension has been redesigned. The results show that an increment of the axle load is feasible until an axle load of 32.5 ton if speed is limited to 80 km/h, or until 30 ton if speed is limited to 120 km/h.

Bosso N., Magelli M., Zampieri N.

The development of numerical models able to compute the wheel and rail profile wear is essential to improve the scheduling of maintenance operations required to restore the original profile shapes. This work surveys the main numerical models in the literature for the evaluation of the uniform wear of wheel and rail profiles. The standard structure of these tools includes a multibody simulation of the wheel–track coupled dynamics and a wear module implementing an experimental wear law. Therefore, the models are classified according to the strategy adopted for the worn profile update, ranging from models performing a single computation to models based on an online communication between the dynamic and wear modules. Nevertheless, the most common strategy nowadays relies on an iteration of dynamic simulations in which the profiles are left unchanged, with co-simulation techniques often adopted to increase the computational performances. Work is still needed to improve the accuracy of the current models. New experimental campaigns should be carried out to obtain refined wear coefficients and models, while strategies for the evaluation of both longitudinal and transversal wear, also considering the effects of tread braking, should be implemented to obtain accurate damage models.

Ye Y., Hecht M.

Most of the existing railway wheel profile optimization methods involve the purpose of reducing wear, where the T-gamma value is often treated as an indicator to evaluate the degree of wear, considering a small T-gamma value representing less material loss. A small T-gamma value, however, implies that the wheel-rail contact points are likely to occur in the vicinity of the wheel’s nominal rolling circle, and the optimized wheel profile obtained with the target of minimizing the T-gamma value may result in a concentrated distribution of wheel-rail contact points around the nominal rolling circle, accelerating the formation of hollow wear. Using the T-gamma value as the optimization target, therefore, cannot guarantee that the wheel profile still has excellent wear performance during long-term service. Aiming at this issue, an indicator, named wear concentration index (WCI), is developed to assess the degree of wheel material loss and the shape stability of wheel profiles. Numerous simulations demonstrate the feasibility and superiority of the index WCI and indicate that this index can be used as an alternative to the target T-gamma in wheel profile optimization.

Luo R., Liu B., Qu S.

A fast calculation algorithm for the wear evolution of wheel profiles is proposed and results presented with a high-speed train as an example. The dynamics simulation includes the calculation of the vehicle running on a short straight track with random irregularities and the vehicle passing various curves without track excitation. The penetration curves of wheel/rail contact are assumed as the shape of wear distribution in a contact patch, which are calculated after the update of wheel profiles and interpolated in each step of wear calculation. The total wheel wear is the sum of the wear caused by track irregularities and the wear under smooth tracks, such as the straight and curved lines. After each dynamic simulation, several loops for wear calculation and profile update are carried out to smooth the wear curve. Simulation results show that the calculated distribution and average of the wear depth and the equivalent conicity in a reprofile cycle are in good agreement with the measured results. The predicted and measured wear shapes agree reasonably well in the area near the tape circle. Moreover, the proposed method is at least 15 times faster than the traditional wear calculation method and it can consider the influences of the stochastic parameters of the wheel/rail contact. • A fast algorithm for the wheel wear evolution is proposed using the wheel/rail penetration curves as wear distribution. • The nonlinear vehicle model and simplified dynamic simulation method are used to improve the speed of wear prediction. • The stochastic wheel/rail interactions are considered as the vital part in the wheel wear prediction. • There are good agreements in the wear evaluation between simulated and measured results with a travel distance in 300k km.

Pires A.C., Pacheco L.A., Dalvi I.L., Endlich C.S., Queiroz J.C., Antoniolli F.A., Santos G.F.

The aim of this study is to analyze how wheel wear affects the wheel reprofiling and service life and evaluate if these aspects can be improved by a new optimal wheel profile design. The NSGA-II multi-objective optimization algorithm was used to generate three optimal wheel profiles that are used alongside the current BRA profile for this analysis. After the optimization process, wear simulation was done to verify if the profiles performance will be maintained over time and to analyze how the worn profile shape affects reprofiling and service life. To quantify this, the worn profiles are used to simulate the reprofiling process in order to estimate the wheel's expected service life according to the wheels geometric tolerances. For this railway, an increase of at least 17% of service life can be expected by reducing the hollow wear maintenance limit from 3 mm to 2.5 mm while an increase of at least 29% can be expected from changing the limit from 3 mm to 2 mm. • Wear and reprofile simulation for data acquisition. • Large hollow wear values leads to decreased wheel life. • Large hollow wear worsens wheel reprofiling efficiency. • Improved wheel profile creation method. • Increase in wheel life by lowering permissible hollow wear limit.

Lima E.A., Baruffaldi L.B., Manetti J.L., Martins T.S., Santos A.A.

Shear pads are devices used to improve vehicle dynamics performance on heavy haul railways wagons. In this work, we present a method to determine the elastic properties of such components using exp...

BAKYT G., ABDULLAYEV S., SULEYEVA N., YELSHIBEKOV A., SEIDEMETOVA Z., SADVAKASSOVA Z.

Li Y., Ren Z., Enblom R., Stichel S., Li G.

The number of operating high-speed trains in China is around 2800 today and 179,200 wheels are under maintenance in one reprofiling period. To help researchers to understand the evolution of the wh ...

Molatefi H., Mazraeh A., Shadfar M., Yazdani H.

Owing to increases in route traffic, axle load, and incompatible combinations of wheel-rail profiles in freight wagons, the Iran railway network has encountered a tremendous increase in localized wheel flange wear. Thus, a strategy was applied to select a new wheel profile to improve wheel-rail interaction and decrease overall localized wheel flange wear. In this research, a practical method was applied for an optimal selection of a wheel profile to minimize wheel wear for three types of freight bogies commonly employed for freight open wagons, including the three-piece 18100, Y25, and H665 series. The research procedure to select the final candidates was based on a wear behaviour study of verified bogie vehicles’ numerical models in operation, as equipped with various wheel profiles via conventional wheel-rail wear models. Then, comprehensive field tests were conducted to monitor the flange wear depth and total wear rate of the final wheel profile candidates in operation conditions, from the aspects of one and multiple wheel-rail contact point distribution, wear rate, and stability of the worn wheel profile for 56,500 km. Eventually, the optimal wheel profile was recommended, in consideration of the population of each bogie type. Some technical and field study aspects of the work were also discussed.

Ma X., Jing L., Han L.

The dynamic wheel–rail responses during the rolling contact process for high-speed trains were investigated using the explicit finite element code LS-DYNA 971. The influence of train speed on the wheel–rail contact forces (including the vertical, longitudinal, and lateral forces), von Mises equivalent stress, equivalent plastic strain, vertical acceleration of the axle, and the lateral displacement of the initial contact point on the tread, were examined and discussed. Simulation results show that the lateral and longitudinal wheel–rail contact forces are very smaller than the corresponding vertical contact forces, and they seem to be insensitive to train speed. The peak value of dynamic vertical wheel–rail contact force is approximately 2.66 times larger than the average quasi-static value. The elliptical wheel–rail contact patches have multiple stress extreme points due to the plastic deformation of the wheel tread and top surface of the rail. The vertical acceleration value of the axle in the steady condition is around ±5 m/s2 for the perfected wheel–rail system with the running speed below 300 km/h.

Kuka N., Verardi R., Ariaudo C., Pombo J.

To improve the efficiency and competitiveness of railway transport, passenger and freight trains should travel faster and have increased payload, without losing the necessary levels of running safety and ride comfort, as well as assuring low aggressiveness on track and minimising the life cycle costs. Hence, the manufacturer’s challenge consists of improving the dynamic performance of the railway vehicles and reducing the loads on the track as well as on the rolling stock components. These objectives can be achieved through optimizing the design of the vehicle, while taking into consideration that the characteristics of the vehicle and of the track may change over time and space, and that they depend on the maintenance conditions of the vehicle and of the infrastructure. This work proposes a computational methodology to study how the varying vehicle component characteristics, on normal and degraded conditions, impact on the vehicle/track interaction loads and on the track damage. The purpose of this study is to trace a path towards a realistic definition of a load mission profile for the structural fatigue dimensioning of the vehicle components. The assessment criteria and the evaluated quantities are defined according to the EN14363 regulation.

Magel E., Kalousek J.

A quick survey of wheel and rail profiles used around the world reveals a huge range of options. Wheels come in cylindrical, conical, and concave variations, while rails range in shape from a very flat 14 in. (350 mm) head radius to a tightly crowned 6 in. (150 mm) head radius. The rationale for implementing one or the other is often institutional inertia—a strong tendency to continue doing what has been done in the past. But the impacts of wheel and rail profiles on the performance of the vehicle/track interaction are large and the decision should not be made lightly. Unfortunately, there are few well-matched “off-the-shelf” solutions from the existing commercially available profiles, such that new rails and wheels often suffer early failures or infant mortality. Through examples and case studies, this paper discusses the significant role that wheel and rail profiles play with respect to performance and safety and makes the case for wheel and rail profiles specifically suited to the needs of each railway. Various techniques for assessing the performance of systems of wheels and rails are reviewed and discussed.

Apezetxea I.S., Perez X., Casanueva C., Alonso A.

ABSTRACTIn railway applications wear prediction in the wheel–rail interface is a fundamental matter in order to study problems such as wheel lifespan and the evolution of vehicle dynamic characteristic with time. However, one of the principal drawbacks of the existing methodologies for calculating the wear evolution is the computational cost. This paper proposes a new wear prediction methodology with a reduced computational cost. This methodology is based on two main steps: the first one is the substitution of the calculations over the whole network by the calculation of the contact conditions in certain characteristic point from whose result the wheel wear evolution can be inferred. The second one is the substitution of the dynamic calculation (time integration calculations) by the quasi-static calculation (the solution of the quasi-static situation of a vehicle at a certain point which is the same that neglecting the acceleration terms in the dynamic equations). These simplifications allow a significant...