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Computer modelling of process of accumulation of rolling contact fatigue damage in railway wheels
Abstract
An algorithm for computer modelling of the process of accumulation of rolling contact fatigue (RCF) damage in railway vehicle wheels is introduced. The amplitude of maximum shear stress is adopted as a criterion for fatigue failure during rolling. RCF curves for wheel steels with a hardness 255–330 HB are obtained by processing the results of the RCF tests of the wheel steel specimens. Effect of the wheel steel hardness on accumulation of the RCF damage is investigated.
... При этом в расчете принималось, что в каждый момент времени приращение поврежденности не зависит от накопленной поврежденности. В этом случае контактно-усталостная поврежденность, накопленная в i-м узле конечно-элементной сетки, определялась по формуле [11]: ...
Heat-strengthened rails of the R65 type are the main type of rails used on the railway network of Russian Railways. Reducing the number of cropped and acutely defective rails is possible due to the rational use of the design features of intermediate rail fasteners and their current content. The article presents study results of the stiffness influence of intermediate fasteners on the operational durability of rails. The general statistics of the use of various types of intermediate rail fastenings on the network of Russian railways is considered. The main results of previously published studies on the effect of the stiffness of intermediate rail fasteners on the accumulation of contact fatigue damage in rails are briefly presented. Calculations of the accumulation of contact-fatigue damages in rails, carried out by the authors, are based on the data on the vertical and horizontal transverse stiffness of intermediate rail fastenings obtained from the results of bench tests. Calculations of the accumulation of contact-fatigue damage were carried out using the “Universal Mechanism” software package. In the process of modeling, four types of intermediate rail fasteners were considered: ARS-4, ZhBR-65Sh, ZhBR-65PShM and W-30. Calculation results were obtained for a curve with a radius of 650 m on a continuous welded track section.
... При этом в расчете принималось, что в каждый момент времени приращение поврежденности не зависит от накопленной поврежденности. В этом случае контактно-усталостная поврежденность, накопленная в i-м узле конечно-элементной сетки, определялась по формуле [11]: ...
Heat-strengthened rails of the R65 type are the main type of rails used on the railway network of Russian Railways. Reducing the number of cropped and acutely defective rails is possible due to the rational use of the design features of intermediate rail fasteners and their current content.
The article presents study results of the stiffness influence of intermediate fasteners on the operational durability of rails. The general statistics of the use of various types of intermediate rail fastenings on the network of Russian railways is considered. The main results of previously published studies on the effect of the stiffness of intermediate rail fasteners on the accumulation of contact fatigue damage in rails are briefly presented.
Calculations of the accumulation of contact-fatigue damages in rails, carried out by the authors, are based on the data on the vertical and horizontal transverse stiffness of intermediate rail fastenings obtained from the results of bench tests. Calculations of the accumulation of contact-fatigue damage were carried out using the “Universal Mechanism” software package. In the process of modeling, four types of intermediate rail fasteners were considered: ARS-4, ZhBR-65Sh, ZhBR-65PShM and W-30. Calculation results were obtained for a curve with a radius of 650 m on a continuous welded track section.
... According to these authors, their model considers microcrack initiation, coalescence, and propagation stages. Computer modeling of process of accumulation of RCF damage in railway wheels was also the subject of an investigation by Sakalo et al. 24 Cracks initiated and growing under rolling-sliding contact were also the subject of a study by Daves et al. 6 These authors used a two-dimensional finite-element model to evaluate the influence of contact pressure and slip on the crack driving force, crack growth rate and growth direction. ...
Fixed‐wheel gates with wheels mounted on both sides that roll on roller path plates are used in both emergency intake gates and spillway gates in hydrogenerating stations. Environmental corrosion along with high wheel loads cause differences in the profile of the roller path surface. Combined with the relatively high torsional stiffness of the gate end girders, a condition of wheel load redistribution occurs where some wheels are relieved of load while others are loaded beyond their maximum design values. Failure of one wheel could jeopardize the overall operation of the gate. Furthermore, frequent operation of these gates result in changes in the stress profile in both wheels and roller paths that, potentially, could lead to failure. Currently, design guidelines for gate wheels and roller paths do not consider the fatigue life of these elements. Research‐based evidence is provided to support changes to these guidelines. Fixed‐wheel gates with wheels mounted on both sides that roll on roller path plates are used in both emergency intake gates and spillway gates in hydro‐generating stations. Currently, design guidelines for gate wheels and roller paths do not consider the fatigue life of these elements. Research‐based evidence is provided to support changes to these guidelines.
... Рис. 8. Диаграмма приспособляемости материала [13]: 1 -граница зоны упругости; 2 -граница зоны упругой приспособляемости; 3 -зона упругой приспособляемости узлах трехмерной сетки определяются с применением приема наложения упругих связей на узлы, расположенные на поверхностях выделения фрагмента колеса [14]. Для позиций узла, занимаемых им при прохождении через область, прилегающую к контакту, совпадающих с узлами трехмерной сетки, определяются значения max τ . ...
The development of the methods for modeling the processes of accumulation of the rolling contact fatigue damage and wear of the wheels of the railway rolling stock and the rails is particularly relevant due to the increase in the number of damage in the recent times. The work is underway to improve the chemical composition and the technology of production of the wheel and rail steels in order to improve their mechanical properties and ability to resist the action of the cyclic loads. The methods of modeling allow predict the possibility of initiation of the fatigue cracks during operation with the sufficient accuracy in the short time. The selection of the contact fatigue criterion and the mathematical apparatus for calculating the stresses at points in the area adjacent to the contact patch to obtain the numerical values of the criterion components is the most important task in the development of modeling methods. The article focuses on the approaches based on the Dang Van criterion and the shakedown diagram for a material undergoing to the action of cyclic loads, which are widely used to assess the rolling contact fatigue of the wheels and rails. The assumptions that are used in the development of the algorithms concerning the models of the contacting bodies, the shape of the contact patch, the distribution of the contact pressures and the tangential forces are considered. The approach using the criterion — the amplitude value of the maximal shear stress is also considered. The example of modeling the process of accumulation of the rolling contact fatigue damage in the wheel of the freight car is given. The results of modeling are presented in the form of the isolines of the criterion values and the accumulated damage in the area adjacent to the contact patch. This work was supported by the Russian Foundation for Basic Research under Grant [17-01-00815A].
This paper evaluates the fatigue life of a roll-formed center sill part in a coil-carrying railway wagon underframe assembly. The loading cycles experienced by this rail wagon architecture are taken from a recorded railroad data available in the Association of American Railroads (AAR) Manual of Standards and Recommended Practices. To estimate the fatigue life of the roll-formed center sill under the given loading history, a two-step finite element (FE) analysis is carried out, considering the residual stresses and thinning introduced in the center sill due to roll forming. Firstly, a COPRA ® FEA RF model is used for roll forming analysis to predict the residual stresses in the center sill, followed by modeling of the actual loading history on the wagon underframe and prediction of fatigue life using commercial FE codes ABAQUS and fe-safe. To validate the results from fe-safe, experimental results of the fatigue tests of pre-strained lab-scale tensile specimens are compared with the predicted values obtained from fe-safe. Our prediction of the roll-formed center sill life shows that the residual stresses introduced due to roll forming are locally detrimental, as the fatigue life is reduced compared to the conventional center sill. This proposed method of evaluating the fatigue life of a part using railroad spectrum load data and roll forming residual stresses developed in the process of center sill fabrication, can be effectively used during the design phase of a rail wagon at both the part and assembly levels.
[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT The problem of uneven wear of a wheel set is considered by many scientists of the world, in the works related to car building. New software complexes for mathematical modeling are being created, and each follows its own theory of rolling stock dynamics. In this article the main provisions for deformation and wear of a wheel along the circle of rolling during car movement are considered. In this case, the elastic sliding model is described in more detail. During wheel rolling and in the presence of torque in the contact area, there is always a gripping area that is located at the entrance, and an area of slippage at the exit. It is proved that the coefficient of slippage is equal to deformation in the gripping area. Under certain kinematic and dynamic conditions, a stress distribution graph is plotted in the contact zone. On the basis of the theory of tangential stresses, a displacement formula is obtained, which is transformed into a new formula for the creep coefficient, which retains the physical meaning of the value found. Keywords: theory of rolling stock dynamics, wheel set, rail, creep coefficient, sliding, gripping, contact spot, wheel rolling, stress distribution.
The contact problem for a rolling elastic sphere and an elastic half-space covered with a viscoelastic layer (third body) is considered. The layer properties in normal and tangential directions are described by the Maxwell model. Based on the macroscopic approach of the contact fatigue damage accumulation the rate of damage accumulation in an elastic half-space is assumed depending on the amplitude values of the principal shear stresses or the equivalent von Mises stress. The influence of the relative longitudinal slippage, the sliding friction coefficient and the properties of the intermediate layer on the internal stresses and at the depth of contact fatigue cracks initiation is studied. The results indicate that the maximum damage can occur both on the surface of the elastic half-space and at a certain depth. The increase of the friction coefficient or relative longitudinal slippage leads to reaching the maximum value of the principal shear stress amplitude on the surface of the half-space, which results in contact fatigue surface fracture (wear). The results also demonstrate that the presence of a viscoelastic layer leads to a decrease of the principal shear stress amplitude within the elastic half-space.
The wear and fatigue competition mechanism of a bainitic rail steel was studied through rolling contact fatigue test. Results showed that the damage process could be divided into initial (before 2.0 × 10⁵ cycles), middle (around 2.0 × 10⁵ cycles) and late (after 2.0 × 10⁵ cycles) stages, with the dominant damage mechanisms of wear, wear and fatigue, and fatigue in each respectively. With increasing rolling cycles, the retained austenite transformation played an important role in achieving dynamic equilibrium between wear and fatigue. Moreover, the untransformed retained austenite could release crack tip stress and effectively control the excessive propagation of fatigue cracks.
Rolling contact fatigue is the main factor limiting the service performance of wind turbine gears. The inherent microstructure of the gear material has a significant impact on its contact fatigue behavior and service life. In this research, a two-dimensional contact fatigue model considering the gear material microstructure and the elasticity anisotropy characteristics of the crystals is established. The predicted results reveal a pronounced scatter phenomena of the stress distribution in the subsurface and the localized stress concentration at the grain boundaries caused by crystal elasticity anisotropy. Changes of initial grain orientations can cause a certain fluctuation in the critical stress and its depth in the subsurface. Under the same load level, the gear contact fatigue life calculated by the crystal elasticity anisotropy model is lower compared to isotropic material. Considering the anisotropic properties of the crystal elasticity, an S-N curve based on the maximum contact pressure for the wind turbine gear is drawn.
An algorithm for computer modeling of the processes of wear and accumulation of the rolling contact fatigue (RCF) damage in railway vehicle wheels is introduced. The combined criterion of contact fatigue is obtained on the basis of the specific strain energy and of the criterion theories of strength. The proposed criterion is tested on the Hertzian problem with full sliding. RCF curve for wheel steel with a hardness 295 HB using proposed criterion is constructed by processing the results of the RCF tests of the wheel steel specimens. The example of modeling of the processes of wear and accumulation of RCF damage in the car wheel using combined criterion is given.
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