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Here a comprehensive 3-D wheel-rail rolling contact finite element model was developed to investigate the influence of wheel-rail material properties on the dynamic wheel-rail interaction. The wheel-rail contact responses induced by two typical wheel tread defects (i.e. wheel flat and tread spalling) were discussed and compared to the responses of perfect wheel in this work. The dynamic wheel-rail responses of three typical material models involved (i.e. rigid, elastic, and elastic-plastic models) were investigated in terms of contact force, contact pressure/stress, and wheel/rail degradation. Furthermore, the strain rate levels during wheel-rail rolling contact at various train speeds were estimated with emphasis on the elastic-plastic model, which was helpful for determining strain rate range of wheel/rail material property tests. Finally, the influences of strain rate effect and initial fatigue damage of wheel/rail materials on dynamic wheel-rail responses were discussed. These results illustrated that the rigid model grossly overestimated wheel-rail impact force caused by wheel tread defects, while the elastic model overestimated wheel-rail contact pressure/stress, damage index, and frictional work. The strain rate effect could significantly increase Mises stress and inhibit plastic deformation of wheel-rail system, while the initial fatigue damage would reduce Mises stress and aggravate plastic deformation. [ABSTRACT FROM AUTHOR]

High-order polygonal wear of wheels is one of the most severe technical challenges for China's high-speed trains at present, and its formation mechanism has not been thoroughly understood. The effect of train traction on the wheel polygonal wear of high-speed trains was studied based on a wheel/rail rolling contact finite element model. The frequency domain characteristics of unstable vibration of the wheel/rail system under rolling/sliding contact were studied by using the finite element complex modal analysis method. We also examined wheel/rail contact forces and friction in the time domain. The cause of the high-order polygonal wear of Chinese high-speed train wheels was revealed. The effect of the vehicle speed and the wheel diameter on wheel polygonal wear were investigated. The results show: the friction-induced vibration of the wheel/rail system will be excited when the rolling/sliding contact between the wheel and rail. The radial zoom modal of the wheel is an unstable mode, which is the main cause of the 21-22 order polygonal wear of the high-speed train wheels in China. Additionally, vehicle speed has a linear relationship with the order of polygonal wear. Reducing the vehicle speed helps to control the polygonal wear of the wheels. Wheels of different diameters exhibit varying degrees of polygonal wear, with smaller wheels being more resistant to friction-induced vibrations. [ABSTRACT FROM AUTHOR]

In this study, finite element method (FEM) is applied to investigate the effect of material defect orientation on subsurface crack initiation in rolling bearings. First, the history of stress intensity factors (SIFs) of a subsurface cubic material defect is calculated. SIFs calculation is conducted when it is parallel to the rolling surface of a bearing ring ( φ = 0 ∘ ) under a ball rolling on the ring. Then, the effect of defect orientation, varying from φ = 0 ∘ to φ = 30 , 45 and 60 ∘ , on the history of SIFs is investigated. It is deduced that changing the defect orientation results in a threefold increase in the equivalent SIF range compared to parallel orientation. [ABSTRACT FROM AUTHOR]

An improved moment of load path model for rolling contact fatigue life prediction is proposed in this paper. First, the complex multiaxial stress variation of the subsurface materials under rolling contact conditions was analyzed by the finite element method. Next, the equivalent stress parameter was presented to characterize the complex stress state based on the improved moment of load path method. The key concept of the proposed method is building a new coordinate system for analyzing the load path of the complex multiaxial stress state. The efficiency of the proposed model was validated with different kinds of fatigue test results in the existing literature. The model results show a good agreement with the test data. Finally, the model was used to obtain the relationship of the Hertz stress versus fatigue life under rolling contact conditions according to the fatigue life data. Highlights: The proposed multiaxial life prediction model considers the hydrostatic stress.The correlation of the multiaxial test data is built using a defined stress parameter.Rolling contact fatigue life is predicted by the proposed multiaxial model. [ABSTRACT FROM AUTHOR]

In this study, finite element method (FEM) is applied to investigate the effect of material defect orientation on subsurface crack initiation in rolling bearings. First, the history of stress intensity factors (SIFs) of a subsurface cubic material defect is calculated. SIFs calculation is conducted when it is parallel to the rolling surface of a bearing ring ( φ = 0 ∘ ) under a ball rolling on the ring. Then, the effect of defect orientation, varying from φ = 0 ∘ to φ = 30 , 45 and 60 ∘ , on the history of SIFs is investigated. It is deduced that changing the defect orientation results in a threefold increase in the equivalent SIF range compared to parallel orientation. [ABSTRACT FROM AUTHOR]

In this study, a tire-soil rolling contact model based on the finite element method was established to determine the traction characteristics of the tire on the loose soil. Considering the soil parameters and tire parameters (loads, slip, inflation pressure and tread pattern), the influence of traction characteristics of the tire was obtained, taking tire sinkage and gross traction as evaluation indexes. The correctness of the tire-soil rolling contact model was verified by carrying out the soil bin-single wheel experiments. The results of the simulation and test showed that with the increase of load and sinkage of the tire, the gross traction tended to increase, thus enhancing the tire traction characteristics. With the increase of slip, the tire sinkage and gross traction increased, and the best tire traction characteristics were exhibited at a slip of 20%. Within the rated inflation pressure, as the inflation pressure increased, the tire sinkage decreased, the tire gross traction decreased and the traction characteristics of the tire were weakened. Under simulated working conditions, the traction characteristics of the tire first increased and then decreased with the increase of the number of tire lug pairs, and 15 tire lug pairs performed best. This paper presents a further study on the interaction between tires and soil under different influencing factors, and its findings provide an effective reference for predicting the traction performance assessment of tractor tires on working roads. [ABSTRACT FROM AUTHOR]

The work rolls of CVC rolling mill usually adopt S-shaped roll profile curve in the rolling process of plate, which changes the contact between the rolls and causes the contact pressure distribution between the rolls to be uneven. The peak of the contact pressure between the rolls appears at the end of the roll, which leads to peeling or "meat loss" at the end of the roll and poor plate crown control effect. To solve those problems, a CVC rolling mill backup roll profile curve with parabolic chamfer was proposed, and the fusion model of plate crown based on mechanism and data-driven models was developed. Combining the parameters of the CVC roll profile curve, the theoretical calculation formula of the backup roll chamfering was deduced. According to the actual data of the plate rolling mill, the parameters of different types of backup roll chamfering were determined, and the distribution of contact pressure between the rolls under different backup roll chamfering was calculated and analyzed by finite element model. Based on the new parabolic chamfer curve of backup roll, the rolling force setting model based on Extreme Learning Machine (ELM) and roll wear model based on Genetic Algorithm Artificial Neural Network (GA-ANN) were constructed by using the nonlinear fitting ability of machine learning algorithm. Then, the predicted results of rolling force and roll wear were taken as the input variables of plate crown prediction. At the same time, the roll system deformation model and roll bending force model based on mechanism model were introduced as inputs to construct the plate crown Convolutional Neural Network (CNN) model based on mechanism and data-driven fusion. The simulation results show that the parabolic chamfer can significantly reduce the pressure between the backup rolls. When the rolled strip width is 2000 mm, 2400 mm, and 2800 mm, the parabolic chamfer can reduce the peak contact stress between the rolls by 8.6% and 10.8%. When the rolling bending force is 1600kN, 2100kN, and 2600kN, the parabolic chamfer can reduce the peak contact stress between the rolls by 8.6%, 8.9%, and 9.1%. The hit ratio of plate crown increased from 90.4% to 96.5%, and the product degradation rate caused by the shape problem decreased by 35.5%. [ABSTRACT FROM AUTHOR]

To reveal the characteristics of strip shape and roll change during the rolling process of six-high cold rolling mill (SHCRM), a three-dimensional finite element model of SHCRM was established by computer-aided design. The coupling deformation under various working conditions such as friction coefficient and bending roller force was analysed. Results show that the width of the plate, the amount of pressure, the friction coefficient, the rolling force, and the bending force are the key affecting factors of the deformation of the roller system, the shape of the load roll seam and the contact stress and strain. The deformation of the roll system, the shape change of the load roller seam and the stress and strain of the contact region are revealed. The obtained conclusions provide a reference for the development of rolling model of high cold rolling mill. [ABSTRACT FROM AUTHOR]

Angular contact ball bearings are common basic components in rotating machinery. During the operation of the bearing, the rolling slips, resulting in contact sliding friction between it and the raceway, which in turn causes wear in the rolling element and increase in the radial clearance of the bearing. The increase in clearance also affects the stiffness of the bearing, which in turn affects the natural frequency and fatigue life of the bearing. At present, there are few studies on the influence of bearing wear (variation of clearance) on life. In this paper, the finite element model based on the theory of contact mechanics is established for the angular contact ball bearing with medium- and high-speed rotation, and the mechanical properties and fatigue life influenced by the internal action of the bearing are analyzed. The effects of radial load and deflection angle on the mechanical properties and fatigue life of the bearing are also studied. Based on the analysis results of bearing contact mechanical properties and clearance changes, the calculation method of bearing life under rolling element wear is established. The influence of the variation of clearance and preload clearance on bearing life is analyzed, and the optimal preload is obtained. The research results of this paper can provide a theoretical basis for optimizing the installation of angular contact ball bearings, reasonably determining the service conditions, and prolonging the service life of bearings, which is necessary for engineering practice. [ABSTRACT FROM AUTHOR]

A three-dimensional wheel–rail rolling contact model (3D WRRCM) developed using the explicit finite element method (FEM) can be used to analyze the dynamic performances of wheelsets and tracks while considering the wheelset rotation and translation, as well as the real wheel–rail contact mechanism. When using the FEM with static initialisation (traditional model), the first step is to calculate the static wheel–rail displacement, strain, and stress when applying axle loading on the wheel and neglecting the wheelset rotation and translation. Then, using these results as the initial conditions, the dynamic wheel–rail displacement, strain, and stress are calculated while considering the wheelset rotation and translation by adopting the explicit dynamic solution method. However, obtaining a solution using this traditional method is time consuming, and the solution can be divergent because of the impulse produced by the suddenly increasing wheelset rotation when proceeding from the initial condition to the dynamic. The optimised method developed in this study can solve this problem. A comparison of the results from the traditional and optimised methods reveals that in the optimised method, the softer initial impulse effectively shortens the track length needed for the calculation and improves the solution efficiency. [ABSTRACT FROM AUTHOR]

Rail corrugation is very serious in Cologne egg fastener track; effective control measures are still lacking. The cause of the corrugation wear on a curved metro track is analyzed based on the friction-induced vibration theory. A finite element model is established to study the frequency domain and time domain features of the friction-induced oscillation of this system. The influences of the fastener spacing and the fastener support length on the corrugation wear are investigated to develop countermeasures. The simulation results show that the friction-induced vibration of the wheel-track system is the wavelength-fixed mechanism of the corrugation wear of rail of the curved Cologne egg fastener track. There are two reasons why the low rail corrugation wear is more serious. The contact resultant force between the low rail and the wheel is obviously bigger than that between the wheel and the high rail, resulting in a higher wear rate of the low rail. The contact force fluctuation of the low rail caused by the friction-induced vibration is more severe, resulting in a higher corrugation wear evolution speed on the low rail. The friction-induced oscillation cannot be eliminated only by adjusting the fastener support length and spacing. However, the long-wavelength corrugation wear instead of the more harmful short-wavelength corrugation wear can be produced by adjusting the fastener support length and the fastener spacing to alleviate the influence of corrugation wear on the vehicle-track system. [ABSTRACT FROM AUTHOR]

The abrasive belt grinding process is applied to grind aero-engine blades benefiting from the elastic contact between the tool and workpiece. The local material removal is difficult to be accurately controlled, resulting in poor surface integrity. A better understanding of the relations between key process parameters and the material removal is needed. In this study, a physical simulator of the abrasive belt grinding process was developed. Different contact wheel hardnesses and contact forces were applied to grind the titanium alloys. A finite element model of multi-abrasive grinding was established to predict the material removal. The characteristics of the stress distribution on the rubber wheel under the dynamic contact state of abrasive belt grinding were obtained. The results show that the contact force has a significant effect on material removal when the contact force is less than a critical value. When the contact force exceeds the critical value, the hardness of the rubber wheel has a more significant effect. The changes on material removal obtained by the finite element model are consistent with the experimental results within the range of presented process conditions. This study provides a basis for selecting grinding contact force and contact wheel hardness. • A physical simulator was developed for investigating this compliant grinding process. • A numerical model of local material removal was established. • Influence of rubber hardness on material removal is nonlinear with pressure variation. [ABSTRACT FROM AUTHOR]

The study of wear that occurs during operation in the wheel–rail assembly is a difficult process to analyze. The phenomena that accompany the wear process are extremely complex and involve many factors, which vary greatly over different periods of time and at different times of wheel–rail contact. Estimating the behavior of the system and its wear in operation is difficult to obtain. However, for common engineering applications, for which the determining factors, such as road profile, load, skid, speed and weather conditions, are known, useful results can be obtained by laboratory tests or by numerical simulation. The article aims to model the complex phenomena that take place in the rail wheel system, taking into account the impact that most essential operational factors have. For this, the Finite Element Method (FEM) is used, thus, trying to explain the wear mechanisms of the wheel–rail system. The obtained results are verified in the laboratory. The main observation in the paper refers to the fact that in the areas of maximum stress and deformation, cracks appear at the micro scale. FEM proved to be a method that can predict the appearance of these microcracks, the experimental results validating the numerical experiments. The research offers results that can prove to be of great importance in practice, for the analysis and improvement of railway safety. [ABSTRACT FROM AUTHOR]

In order to study the spatial-temporal distribution characteristics of electromagnetic rail gun temperature, based on moving grid processing method and mod function method, a 3-D geometric model of electromagnetic rail gun under single launch mode, a 2-D geometric model of electromagnetic rail gun under continuous-fire mode, and the corresponding transient electromagnetic field-temperature field coupling model are established by using the finite element analysis software COMSOL Multiphysics, and the temperature spatial-temporal distribution characteristics in the rail-armature contact area, cross section of rail, and along the rail axis is simulated under single launch and continuous launch. The results show that, under the conditions of single launch and natural cooling, the high temperature area in the rail-armature contact surface is located at the rear of the armature due to the skin effect. The temperature distribution along the axial inner side of rail tends to be higher near the tail and lower near the muzzle, it increases with time, but the peak temperature does not exceed the melting point of copper. Under the continuous launch and natural cooling, after five launches, the peak temperature of the rail increases to 709 °C, which is close to the melting point of copper. Continued launching will cause rapid accumulation of heat in the rail and a rapid increase of peak temperature, resulting in shortened life of the launcher and even launch failure. Therefore, without active cooling measures, the electromagnetic rail gun cannot be used in actual combat. The results of the study are an important guide for the design and thermal management of the cooling system of electromagnetic rail gun. [ABSTRACT FROM AUTHOR]

• A 3D FE model of wheelset-turnout-sleeper structure is established. • The ratcheting effect of turnout material is simulated. • A mixed implicit-explicit FE method is used to simulate the wheelset passing through the turnout. • The transient contact behavior of high-speed turnouts under cyclic loading is investigated. • The evolution of ratcheting strain of rail under different numbers of cycles and crossing speeds is discussed. The present work introduces a three-dimensional finite element model for the wheel-turnout-sleeper system, incorporating a cyclic constitutive model that accurately captures the nonlinear hardening behavior of rail steel under cyclic loadings. At the same time, a mixed implicit-explicit finite element method is employed to investigate the transient rolling contact behavior of wheel-turnout. Through dynamic analysis, the transient rolling contact status of the wheel-turnout, stress and strain responses of the turnout, and wheel-rail forces are investigated under varying crossing speeds and number of cycles. It is found that during the wheelset crossing, the contact stress remains relatively stable on the stock rail, and multi-point contact occurs at the wing rail and long point rail, and the contact stress on the surface of the long point rail is more significant. With an increase in crossing speed in the same cycle, there is a gradual rise in contact stress on the long point rail face. At the same crossing speed, with the increase in the number of cycles, the contact position between the wheelset and the long point rail gradually moves back, and the top width of the contact position gradually expands. Meanwhile, the fluctuation range of vertical displacement of the wheel center diminishes, and the wheel flange moves away from the long point rail. Additionally, a progressive accumulation of ratcheting strain is observed on the rail, and the ratcheting strain on the long point rail significantly exceeds that on the stock rail. The research results will help to provide a reference for the optimization and design of the critical cross-section profile of the long point rail and will have guiding significance for the maintenance and repair of turnouts. [ABSTRACT FROM AUTHOR]

A numerical method for the fast evaluation of ratcheting in solid-contaminated contact between rollers was developed. The physical problem was simplified with a plane-strain half-infinite body, with a distribution of pressure and tangential stress on the contact surface obtained by considering the presence of evenly spaced solid contaminant particles between the contacting bodies. Such a distribution was obtained by an analytical method, which considered the material of the contacting bodies as linear elastic. The stresses under the contact surfaces were calculated using the Boussinesq-Cerruti model. Subsequently, the plastic strain accumulated in the roller after each application of the contact load was calculated by means of a non-linear kinematic-hardening constitutive law, also considering the effect of wear in removing material layers from the surface. First, the effects of the introduced approximations were evaluated. In particular, the error in calculating the plastic strain using contact load distributions from a theory based on linear elastic behavior was evaluated by comparison with the results of finite element models. Subsequently, the method was used to assess the experimental results of previously published studies on sand-contaminated contact between rail and wheel materials. Despite the approximations and indetermination of some model constants, the method was proven to be able to qualitatively explain many of the damage mechanisms related to the interaction of the contacting bodies with the contaminant particles. • A numerical method for assessment of solid-contaminated contact was developed. • A contact pressure distribution with solid particle contamination was assumed. • The cyclic plastic strain was calculated by a non-linear kinematic-hardening model. • The error due to the approximations was evaluated. • This is a valuable tool for comparative design for ratcheting and wear damage. [ABSTRACT FROM AUTHOR]

A novel internal rotor bend actuator is presented that enables compensating strains to be applied about the rotor centre. Axial reaction tubes are used to maintain the structural stability of the bend actuator and to provide feedback on the level of actuation. The system is powered by an onboard battery and the actuation is derived from the operation of lead screw motors. The actuation is commanded wirelessly, thus providing the functionality for an autonomous rotor. The integrated rotor is demonstrated in isolation via laser tracker measurements and for the rotating prototype system. Actuated bending gave rise to radial displacements at the central point relative to shaft ends of approximately 50 µm peak-to-peak. These results validate a finite element deformation model. The rotor was levitated on active magnetic bearings, then rolling elements bearings, to demonstrate the synchronous vibration control achievable by static internal bending. The potential now exists for the commanded actuation to compensate for rotor eccentricities arising from manufacturing errors and dynamically induced unbalance for the cancellation of underlying synchronous vibration. • Novel structure bending concept. • Design of an experimental prototype. • Experimental validation of bending capabilities. • Results matching with finite element modelling. [ABSTRACT FROM AUTHOR]

The rail is subjected to cyclic stress and plastic deformation, excessive accumulation of which can promote rail degradation. A finite element (FE) model of three-dimensional (3D) cyclic rolling contact (CRC) with the implementation of an improved cyclic plasticity constitutive material model is developed to analyze the 3D elastic–plastic stress. Comparisons of the FE simulation results of 2D repeated moving pressure (RMP), 3D RMP, and 3D CRC models are conducted to elucidate the differences. The evolution and distribution patterns of the elastic–plastic mechanical behavior of wheel–rail contact with the number of cycles are also investigated. The FE results show that the 2D RMP model is conservative in predictions, and the results derived from the 3D RMP and 3D CRC models are comparable, while opposite results are available for some essential components. The 3D CRC model is a necessary choice especially for fatigue life prediction study. Due to the partial slip and cyclic rolling, the stresses and strains near the rail surface layer are significant and continuously accumulate. The residual equivalent plastic strain and the ratchetting strain increase with the increase of the tangential traction and the axle load, which will accelerate rail damage. • A 3D cyclic rolling contact FE model is proposed to study elastic–plastic stress. • Validation of the improved cyclic plasticity constitutive model by experiments. • FE simulation results and necessity choices are compared for three models. • The evolution of residual stresses and ratchetting strains in rail is revealed. [ABSTRACT FROM AUTHOR]

• A universal rotor-bearing-disk system model is established. • The model considers three types of maneuvering loads. • The special vibration responses of the system under rolling, pitching and yawing maneuver loads are compared and analyzed. It is an important embodiment of fighter's comprehensive ability to have high maneuverability. Therefore, it is necessary to study the coupling dynamic behavior of rotor system in typical maneuvering flight. Based on the finite element method, a 6-node rotor-bearing-disk system model with three kinds of maneuvering loads, nonlinear contact force of rolling bearing, eccentric unbalanced force of disk and gravity field is established in this paper, and the dynamic responses of the system under rolling, pitching and yawing maneuvering is analyzed in detail. The Newmark-β method is used to solve the system model. The system responses under different rotation speeds and two given rotation speeds are mainly analyzed. The system responses under three kinds of maneuvering loads are compared and analyzed. Finally, the 7-node stepped shaft system model is used to verify the universality of the analysis results in this paper. It is found that, under the same maneuvering load value, the possibility of rub-impact and frequency division components caused by different flight modes are different. The research in this paper can provide a cognitive basis for the mechanism of system rubbing fault under different maneuvers. [ABSTRACT FROM AUTHOR]

A semianalytical model is introduced to assess rolling contact fatigue problems in railway applications. The constitutive law is based on the nonlinear kinematic and isotropic hardening model of Chaboche–Lemaitre, which allows the cyclic elastoplastic strain under the contact surface to be evaluated. The much higher computational effectiveness in comparison with finite element (FE) analyses is quantified. The Dang Van multiaxial fatigue criterion is implemented to evaluate the rolling contact fatigue in the subsurface elastic region where cracking is relatively rare but more dangerous than surface cracks. The influence of the presence of sulfides in the wheel matrix in decreasing fatigue strength is also assessed by means of Murakami's approach. The model is used to compare conditions under small‐scale twin‐disk experiments to full‐scale wheel/rail contact conditions. It is found that, for the same Hertzian pressure, the small‐scale contact is more conservative in that it causes a deeper plasticized layer as compared with the elliptical full‐scale contact. In the investigated cases, crack initiation is also not expected according to Dang Van criterion in neither of the studied contact conditions. Highlights: A semianalytical model is developed to study the rail–wheel contact problem.Full‐scale rail–wheel contact and small‐scale twin‐disk contact problems are compared.The line contact problem experiences a deeper plasticized layer.The subsurface crack initiation is assessed using the Dang Van fatigue criterion. [ABSTRACT FROM AUTHOR]

The wheel-rail rolling contact finite element model has been generally considered to be a better choice for solving the high-frequency wheel-rail responses and local stress/strain states, compared to the traditional multi-body dynamics model. However, some thorny issues in the wheel-rail finite element analysis need to be solved or avoided, such as difficulties in geometry modelling especially for describing those multiple irregular wheel tread defects, possible computation termination by mesh distortion, and the balance between the computational efficiency and accuracy. Thus, an innovative computational method was proposed in this study, to transform the geometric irregularities induced by wheel out-of-roundness (wheel flat, tread spalling and wheel polygonization) to the randomly irregular displacement excitation of the wheel-rail contact, where the randomisation of the size, shape and distribution of wheel tread defects were considered. Based on geometrical relationships of the wheel-rail contact, the formulas of the wheel-rail contact displacement irregularity caused by various wheel tread defects, which was equivalent to the corresponding wheel-rail geometrical irregularity, were derived. And then the randomly irregular wheel-rail displacement satisfied to several various random distribution functions were generated by pseudo-random number sequence. Finally, the proposed method is demonstrated to facilitate applications of the explicit wheel-rail contact finite element model. [ABSTRACT FROM AUTHOR]

To improve the understanding of wheel/rail contact behaviour and damage mechanisms in turnouts, the 3D explicit finite element model of a wheelset rolling over a switch is introduced. This takes into account the arbitrary geometrical profile of the wheel-rail system, the relative motion between switch/stock rail, the nonlinear materials and actual moving postures of the wheelset. Precise frictional rolling contact solutions and dynamic response, including contact stress, surface shear stress, microslip, roll angle and lateral displacement, are all studied to obtain a better understanding of the wheel-rail frictional rolling contact behaviour in the switch panel. The simulated results are then verified through field tests on the Qingdao-Jinan line. The results indicate that the proposed explicit finite element method can be an efficient tool for solving the problems of frictional rolling contact behaviour and damage mechanism in switch panels. [ABSTRACT FROM AUTHOR]

Belgrospi-like damage is a special type of rolling contact fatigue (RCF) characterized by periodically grouped crack nests with short-pitch corrugation, which has been observed on sharp curved track in China. A 3D finite element model of the elastic–plastic wheel–rail transient rolling contact on a sharp curved track is developed to investigate the dynamic rolling interaction on corrugated rail. The competitive relationship between wear and RCF under cyclic loading is evaluated. Important findings include that the slope of corrugation geometry (CG) causes the center of the upslope the greatest dynamic contact solutions, which have a phase lead with respect to the CG. Under long-term cyclic loading, the rail material failure due to the continuous accumulation of plastic shear strain is RCF. [Display omitted] [ABSTRACT FROM AUTHOR]

Polygonal wear is a type of damage commonly observed on the railway wheel tread. It induces wheel-rail impacts and consequent train/track components failure. This study presents a finite element (FE) thermomechanical wheel-rail contact model, which is able to cope with the three possible generation and development mechanisms of polygonal wear: initial defects, thermal effect, and structural dynamics. The polygonal wear-induced impact contact and further development of wear are simulated. The simulated elastic contact solutions are verified against the program CONTACT. Different material properties (elastic, elasto-plastic and elasto-plastic-thermo, i.e. with thermal softening) and initial polygonal profiles are then applied to the FE model to investigate the influence of wheel/rail material and wear amplitude on wheel-rail contact stress and wear development. The simulations indicate that the wheel-rail impact-induced temperature may reach up to 362 ℃ at the contact interface, and the high temperature at the contact area influences wheel-rail contact stress and wear depth. • An innovative thermomechanical FE model is presented to study polygonal wear growth. • The simulated contact solutions are verified against the program CONTACT. • Using elastic material models causes overestimation of contact stress and wear depth. • Incorporating thermal effects is crucial for wear predication with high slip ratio. • The simulated contact temperature reaches up to 362 ℃ at the wheel-rail interface. [ABSTRACT FROM AUTHOR]

Tire design with respect to vibrational behavior and noise emission is a challenging task due to the large number of parameters and their coupling. Therefore, accurate high fidelity nonlinear Finite Element (FE) models are needed to aid in the design process. The widely used Arbitrary Lagrangian Eulerian (ALE) models, despite their computational efficiency, are limited to rib-slicked tires and require significant effort to consider inelastic material behavior and frictional phenomena. To overcome these limitations a novel nonlinear FE tire model is presented based on the Total Lagrangian (TL) formulation. The TL model is compared to the reference ALE model for the case of stationary rolling on a smooth and a rough road surface. The observed match of the TL model with respect to the hub and contact forces proves the feasibility of using the TL formulation in the context of rolling contact tire simulations. Therefore, the TL model can be seen as a valid alternative to the frequently used ALE models. • High fidelity nonlinear Finite Element models are required in the tire design process. • The Arbitrary Lagrangian Eulerian formulation poses limitations in modeling. • A nonlinear Finite Element Total Lagrangian tire model is presented. • The behavior of the Total Lagrangian matches the Arbitrary Lagrangian Eulerian model. [ABSTRACT FROM AUTHOR]

The adhesion at the wheel-rail contact is critical in train operation. Low adhesion leads to a longer distance for a train to accelerate and brake, and this may cause serious accidents. Sand particles are applied onboard trains at the wheel-rail contact to enhance the adhesion level. In this study, a finite element model is developed to investigate the mechanical behaviour of sand particles in a wheel-rail contact and how they affect the adhesion level. The acceleration and braking events using rolling/slipping and sliding contacts are simulated. Morphological properties of sand particles such as size and aspect ratio are considered. The adhesion enhancement is quantified from each simulation for comparison. The results indicate that the adhesion enhancement during the first contact between the wheel and sand particles is negligible and starts to increase when the wheel is rolling on the fragments. Its magnitude is controlled by the new third-body layers generated during the particle breakage under both rolling and sliding contacts. However, under sliding contact, when a similar amount of fragments is considered, the coarser particles with a larger aspect ratio tend to produce a higher adhesion enhancement. • Adhesion enhancement by sand can be correlated to newly generated surface area of third body. • Sand provide a higher adhesion enhancement during the acceleration compared to the braking. • During traction, the adhesion enhancement is influenced by the number of fragments. • During braking, the coarser and elongated particle generates a higher adhesion enhancement. [ABSTRACT FROM AUTHOR]

• The model can account for the non-linear lifting of the flange groove and the effects of wheelset traverse and side roll. • The wheel tread and flange are alternately loaded with two wheel load transition areas in the frog area. • Wear in the flange bearing area is significantly higher than in the tread bearing area, with an increase of 59.7%. • RCF damage dominates in the wing rail and the two wheelload transition areas. • Reducing the speed to 15 km/h significantly improves the service performance of the fixed frog. The tram No. 3 turnout fixed frog uses a variation in the depth of the flange groove so that the wheel rolls over the frog area in a continuous flange bearing. This method of travelling over the turnout requires the wheel load to transition back and forth between the tread and the flange, resulting in wheel-rail impact, which in turn affects service life. In order to investigate its service characteristics, this paper has established a transient wheel-rail rolling contact finite element model for the No. 3 turnout fixed frog. The macroscopic dynamic response and microscopic wheel-rail contact solution as the tram passes through the turnout at different axle weights and speeds are analysed in detail, and the changing patterns of wear and fatigue damage are investigated. The research shows that rail wear is particularly severe in the wheel flange bearing area, approximately 1.6 times greater than in the tread bearing area. In addition, when tram speeds are reduced to 15 km/h, there is a significant reduction in wheel-rail impact and wear, thereby improving ride smoothness and safety. The results of this study are of great significance to the operation and maintenance of the No.3 fixed frog turnout. [ABSTRACT FROM AUTHOR]

[Display omitted] Material microstructure plays a key role in crack initiation under rolling contact fatigue. When studying microstructure with crystal plasticity finite element method (CPFE), mesh sensitivity study is of great importance, as the surface-near region is under high uniaxial stresses. In this paper, a new structured mesh strategy is purposed and compared with the classical unstructured mesh strategy. Modelling tests on a bi-grain and a polycrystal model show the calculation of geometrically necessary dislocation (GND) density, recently proposed as a suitable fatigue damage indicator, is highly dependent on mesh morphology, when GND hotspots tend to appear near distorted elements even in homogeneous materials. With uniform mesh size and shape, structured mesh elements can provide physically more acceptable GND calculations, which is particularly important in loading scenarios with complex stresses, such as rolling contact fatigue. Computational efficiency is also improved compared to unstructured models because a smaller number of elements are required in a structured mesh model and pre-processing of the mesh is not required. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to reveal the friction and wear performance of grooves textured cylindrical roller thrust bearings with different groove dimensions under starved lubrication. Design/methodology/approach: The groove dimensions include: width of grooves (WOG, 50 µm, 100 µm and 150 µm), depth of grooves (DPOG, 7 µm, 11 µm and 15 µm) as well as groove deflection angle (GDA, 45°). A fiber laser marking system was used to prepare groove patterns on the raceways of shaft washers. The friction and wear properties of grooves textured bearings were researched through a vertical universal wear test rig using a customized roller bearing tribo-pair under starved lubrication. Static finite element analyses were conducted to reveal their surface stresses. Through the comprehensive comparison and analyses, the influence mechanism of grooves on the tribological behavior of cylindrical roller thrust bearings was proposed and discussed. Findings: When grooves textured bearings run under starved lubrication, their average coefficients of friction (COFs) and wear losses are all significantly reduced and much lower than those of smooth group. The influence of DPOG on the COF curves is significant, while the influence of WOG on the COF curves is a little weak. The influence of groove dimensions on the surface stresses of grooves textured bearings is weak, whether the WOG or DPOG. In this work, when the WOG is 100 µm and the DPOG is 15 µm, its average COF and wear loss are both the lowest, 0.0066 and 0.61 mg, respectively. Compared with the data of smooth group, its friction coefficient is reduced by 75.3% and its mass loss is reduced by 95.8%, showing a significant improvement in this condition. Originality/value: This work can provide a valuable reference for the raceway design and reliability optimization of rolling element bearings. [ABSTRACT FROM AUTHOR]

The dynamic effects, mainly including the inertia effect and strain-rate effect, on the dynamic wheel–rail contact behavior become more and more serious as the train speed increases. The inertia effect can be automatically taken into account in explicit finite element analysis codes, while the strain-rate effect needs to be considered via inputting the related material parameters. In the present paper, the influence of strain rate on the dynamic wheel–rail contact response for the straight track case was explored, based on a 3D wheel–rail rolling contact finite element model, via LS-DYNA/explicit algorithm. Effects of the axle load and train speed on typical dynamic wheel–rail responses were discussed, and the results indicate that the coupled train speed with strain rate has a non-negligible influence on dynamic contact responses. The strain rate hardening effect increases the maximum contact pressure and stress, and inhibits the plastic deformation of the wheel–rail system. A rate-sensitive factor (RSF) was then introduced to describe the strain rate hardening effect, confirming that the rail is more sensitive to strain rate compared to the wheel. Finally, an error analysis of the wheel–rail Hertz contact theory was conducted, which further verify the differences between elastic and elastic-plastic contact solutions. [ABSTRACT FROM AUTHOR]

Flange tip lift crossings are widely utilized in modern tramlines to replace traditional crossings to enhance commuters' comfort and prevent crossing nose failures. However, due to altered contact conditions between wheel flanges and ramps of crossings, the use of flange tip lift crossing has led to the critical issue of ramp wear. To resolve this issue, this paper investigated the dynamic contact response of a ramp during in-service loading, as well as the resultant wear of the ramp. With a dynamic finite element model, the local contact pressure and local sliding distance were computed and subsequently applied in a local contact-based wear model to evaluate the nominal wear of the ramp. Our findings indicate that under typical in-service loading conditions, the ramp exhibited up to 120 times more wear than the rail head, owing to increased contact pressure and reduced contact area during the ramp contact. To mitigate this issue, a design change of a gentler ramp inclination from the default 1:100 ramp to a 1:150 ramp could provide approximately 10% wear reduction. In addition, increasing the flange radius by 1 mm could reduce the wear by up to 13%. Conversely, increasing the speed to 45 km/h from the recommended 15 km/h speed may cause up to 5 times more wear. Furthermore, an empty tram showed 56% less wear on the ramp when compared to the condition of the maximum allowable axle load. These results offer an insight into the detrimental wear of ramps used in flange tip lift crossings of tramlines and can assist in the development of new designs and operating guidelines to mitigate ramp wear. • Ramp wear of a tram crossing was investigated using dynamic finite element simulation and a local contact-based wear model. • The wear of the ramp was found to be up to 120 times greater than that on the rail head of tram rails. • Gentler ramp inclination, increased flange radius, reduced vehicle speed and lower axle load can reduce the wear of the ramp. [ABSTRACT FROM AUTHOR]

The presence of fatigue crack is a common damage pattern in railway wheel-rail system, which will reduce service life and increase the maintenance costs of railway transportation. In this study, a two-stage simulation strategy was proposed to investigate the elastic-plastic fatigue crack growth behaviour of the wheel and rail, where a three-dimensional wheel-rail rolling contact finite element model was first built to solve the elastic-plastic wheel-rail contact pressure and tangential traction modification, and then a simplified three-dimensional finite element model of the wheel and rail inserted with vertical cracks under the equivalent moving load was built to explore the fatigue crack growth. Taking the J -integral at the crack tip as an elastic-plastic crack growth parameter, the influences of crack face friction, crack depth and traction coefficient on the crack growth were elucidated. Meanwhile, the competing mechanisms of wheel/rail wear and fatigue crack growth under rolling-sliding contact condition was illuminated based on the Archard wear model. The simulation results indicate that two critical locations for crack growth appear during the contact load approaching and departing from the crack. The Mises stress near the deepest crack tip exceeds the yield stress, causing a small plastic zone with the greatest crack growth rate. The reduction in the crack face friction, and/or the increase in crack depth and traction coefficient will accelerate the propagation of fatigue crack. In the case of only normal contact load or rolling-sliding contact (μ ≤ 0.375), the crack growth on the wheel and rail is dominant compared to wear and crack will continue to grow. • Proposed a two-stage simulation strategy to study wheel-rail fatigue crack growth. • Built 3-D finite element model of the wheel and rail inserted with vertical cracks. • Elucidated influences of key parameters on wheel-rail fatigue crack growth. • Illuminated competing mechanisms of wheel/rail wear and fatigue crack growth. [ABSTRACT FROM AUTHOR]

A time-domain finite element model is developed to study the transient rolling contact of a driving wheelset over a curved track with Low Adhesion Zones (LAZs) shorter than 1.0 m. LAZs on one rail, i.e., unilateral LAZs occurring more likely, is treated for a speed up to 500 km/h. Structural vibrations of wheelset are analyzed to explain the transient contact forces, creepages and the resulting irregular wear. LAZs on high rails are found more detrimental than those on low rails. The results explain the occurrence of flats and rolling contact fatigue in bad weather, although significant wheel idling is absent. • Dynamic curving of a wheelset over a track with short low adhesion zones simulated. • Low adhesion zones are applied on either high or low rail to study the difference. • Resulting creep fluctuation and traction redistribution are studied in detail. • RCF and unilateral flats on high speed wheels occurring in bad weather are explained. [ABSTRACT FROM AUTHOR]

• Local rolling contact fatigue (LRCF) is reproduced by scaled twin-disc tests. • Critical indentations over which LRCF initiates are found for test discs. • Influence of indenter geometry on plastic strain of indentations is analyzed. • Transferrable critical plastic strain for LRCF initiation is obtained. • Size-dependent critical depths are proposed for indentations in practice. Scaled twin-disc tests are conducted to study the initiation of local rolling contact fatigue (LRCF) from indentations on discs of U71MnG rail indented by sharp tap tips. Critical depths over which LRCF initiates are found for indentations of different geometries under oil lubrication. Simulating the indenting process with a static finite element modelling approach, a critical plastic strain of 170% corresponding to the critical depths is determined. Assuming this critical strain is transferrable, size-dependent critical depths are further derived for indentations on actual rails using the same modelling approach. After verification by LRCF damages in practice, a linearized relationship between the critical depth and the characteristic length is proposed for actual indentations, being 2.3–3.2 mm deep for ones with a characteristic length of 4.0–10.0 mm. [ABSTRACT FROM AUTHOR]

This paper proposes a semi-analytical fatigue life prediction method for the evolution of elastic–plastic cylindrical rolling contact fatigue mechanism under random surface topography, and reveals the evolution process of three contact fatigue mechanisms under high load conditions: micro-pitting, surface-originated pitting (SOP), and subsurface-originated spalling (SOS). Firstly, an elastic–plastic line contact model of random rough surface is proposed to analyze the contact condition between rolling elements considering random surface topography. Subsequently, a contact pressure spatial distribution model of rough surface is established, which can fully reflect the variation law of pressure distribution in the elastic–plastic stage. Finally, a semi-analytical life prediction (SALP) method is developed by combining the newly proposed analytical model with finite element method to illustrate the evolution process of the contact fatigue mechanism. The prediction accuracy of the SALP method is verified by comparing the results with those of the finite element method. Furthermore, the influence of random surface topography parameters (root mean square of roughness δ , correlation length λ) on contact fatigue life is further discussed, which helps to provide theoretical support for good surface process control for high-load rolling elements. [ABSTRACT FROM AUTHOR]

• Bearing's cavitation effects can affect the rotor dynamic response. • Stability threshold is changed due to bearing cavitation effects. • Cavitation effects has low influence in normal operational conditions. This work evaluates the influence of the cavitation effects of hydrodynamic journal bearings on the rotating system dynamic response. Several simulations were performed in order to determine in which operating conditions the cavitation effects become relevant to the rotors dynamic behavior. The rotating system model is constructed by means of the Finite Element Method (FEM), in which the rotor is supported by hydrodynamic journal bearings. Two different approaches were used to model the journal bearing, being Gumbels condition used for analyses without conservation of mass in cavitation and Elrods cavitation algorithm for analyses with conservation of mass. The results show that the inclusion of conservation of mass in cavitation does not lead to significant changes in the rotors dynamic response under normal operating conditions. However, conditions near to the instability threshold show a significant difference in dynamic response, since the model without conservation of mass reaches this limit before the model that includes these effects. [ABSTRACT FROM AUTHOR]

Bearing failure is one of the most important factors influencing performance, accuracy and reliability of rotating machineries. Bearing faults are commonly shown as the defects such as rolling body fracture, rolling body, and surface pitting, etc. Dynamic model of 6206 deep groove ball bearing with the above-mentioned bearing faults has been established by finite element method. Exponent Hardening Plasticity Cowper Symonds model related to strength and hardening coefficients is adopted for describing elastoplastic material model of rolling body. The smaller difference between simulated results obtained by EDM and theoretical results calculated by Hertzian point contact theory validates the reliability of explicit dynamic model established in this paper. Dynamic contact characteristics of rolling bearing with different faults such as rolling body fracture, rolling body peeling, and bearing pitting are investigated using explicit dynamic model above. By comparing contact characteristics of fault bearing with those of fault-free bearing, it provides a reference for fault diagnosis and failure prevention of rolling bearing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Positive Displacement Motor (PDM) is one of the most commonly used deep hole power drills. The thrust ball bearing unit is one of the vulnerable parts of the PDM. Failure of the thrust bearing greatly affects the PDM and can drastically reduce its drilling efficiency. In order to improve its service life, we have designed a new deep cavity tapered roller thrust bearing. In this analysis, we will evaluate the new product. In the past, results have shown that there is a serious stress concentration at both ends of the roller. The new deep cavity design will result in the improvement of the stress factor of tapered rollers. If the cavity depth and diameter are too small, the stress concentration at both ends of the roller becomes serious. If they are too large, the stress on the middle part of the roller is also too high. Deformation of the roller increases with an increase in the deep cavity's length and depth. Consequently, the deep cavity design can improve the PDM. [ABSTRACT FROM AUTHOR]

Although insulated rail joints (IRJs) are important railway track components and, because of their low bending rigidity, a dynamic wheel impact results as wheels pass over them. Proper attention is needed to address this problem. Focussing on this point, a 3D finite element analysis (FEA) is carried out on IRJs to evaluate on damage analysis of sub-surface railhead material for endpost materials: fiberglass (fb), nylon 66 (ny), and polytetrafluoroethylene (ptfe). A cyclic vertical wheel load up to a total of 2000 cycles in non-Hertzian pressure form is applied at the wheel/rail contact patch on an IRJ. The residual longitudinal stress damage parameter is considered to rank the endpost material based on sub-surface railhead damage. It exhibits a new pattern described as 'vertical flat type' for a depth up to 8 mm initially and, as the cyclic loading increases, the vertical flat pattern damage changes to an 'inclined flat type' pattern. • A few sub-surface damage patterns exist in railhead material. • The ptfe is a good endpost material for controlling the damage. • A decay in the ratchetting rate is established. • For a depth 1∼7 mm, the damage pattern changes as the loading cycle increase. [ABSTRACT FROM AUTHOR]

Nonlocal peridynamic (PD) theory is widely used in damage and thermomechanical coupling simulations. This study applied ordinary state-based PD thermomechanics to model the wheel-rail contact bringing temperature-dependent materials. A two-dimensional coupled thermomechanical model was developed to predict the evolution of the thermomechanical response, thermal damage, and wear in railway rail. The model was verified based on the displacement and temperature fields of the rail. The model results correlated well with the finite element model and analytical method results. The influence of the vehicle speed, rail surface cracks, and wheel idling on the thermomechanical response of the rail was also evaluated in detail. The results show that the influence of the vehicle speed on the temperature field is much greater than that of the contact stress. The contact temperature under the critical creepage could lead to the formation of a brittle white etching layer (WEL). Cracks on the rail surface increased the contact stress and temperature peaks. Thermomechanical loading also promoted rail surface damage. Continuous thermomechanical loading due to wheel idling softened and removed rail surface materials, forming wear pits and a WEL, known as wheel burns. • A 2D thermomechanical coupled PD model of the wheel-rail sliding contact is established. • A novel and concise wear prediction method is provided based on the PD damage model. • The interaction of rail surface cracks and contact thermomechanical loads is studied. • Rail wear and WEL formation (wheel burns) during wheel idling are explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dislocation-based model with a robust convergence is developed to investigate the contact problems. • A deterministic method is proposed to progressively evaluate the stick and slip contact conditions of crack faces. • The slip accumulation of crack faces during the loading process is accounted for the description of friction evolution. • The effects of friction coefficient, crack alignment and location on the shear behaviors of crack faces are analyzed. Mechanical transmission components are generally under the risk of contact fatigue, resulting in cracks initiated from the subsurface. When subject to compressive stress, these cracks might be forced to be closed, thus their faces are in partial slip contact. Under such conditions, the interactions of stick and slip zones cannot be directly determined, which is one of the greatest challenges of contact fatigue problems. In this study, the distributed dislocation technique is adopted to investigate the stick–slip friction along the alignment of shear cracks in arbitrary orientations in a half-plane under contact loading. The unknown dislocation density describing the crack face displacement is iteratively calculated based on the stress conditions and then introduced to update the surface gap between contacting bodies. The complex expressions of the influence coefficients used to determine the stress and displacement induced by the dislocations are derived and the FORTRAN codes are provided in the Supplementary Materials. A step-by-step loading method is proposed to progressively capture the slip history of crack faces. The model is also capable of simulating rolling contact problems. The results are comparable to those predicted using the finite element method with more robust convergence properties. The effects of friction coefficient, crack alignment, and locations of crack faces are discussed in detail. The model paves the foundation for further studies on competing mechanisms of crack propagation and crack face wear, and provides insights into the frictional fracture of materials under contact loading. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonic rolling and its finite element simulation on a bearing raceway was conducted. • Multi-objective process optimization for ultrasonic rolling on a bearing was performed. • Oriented martensitic grain stacking forms a flocculent plastic deformation layer. • Carbide particles are refined, and its size changes gradiently along the layer depth. For the first time, the ultrasonic surface rolling processing (USRP) technology was applied to a real bearing raceway, and a finite element simulation model for USRP on a bearing raceway was established. Practical tests were conducted to evaluate the surface integrity of the bearing raceway before and after USRP treatment. The USRP parameters were optimized using Taguchi-gray correlation analysis. The results show that the optimal process parameters for the 7224 bearing raceway are: an amplitude of 10 μm, a static pressure of 2400 N, a spindle speed of 45 rad/min, and rolling times of 7. In the process of USRP, residual compressive stress results from inhomogeneous elastic and plastic deformation. Adjacent tempered martensitic laths merge and deflect at a certain angle along the rolling direction to form directional grain stacks, resulting in a flocculent plastic deformation layer. The USRP based on the finishing mechanism of "peak-cutting and valley-filling" can improve the surface micro-morphology, reduce roughness value Ra to approximately 0.16 μm, and effectively eliminate microscopic cracks caused by grinding. The micro-hardness of the bearing raceway surface increased from 760 HV to 840 HV under the dual action of surface grain refinement and work hardening effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Common aerospace-quality bearing steels were studied under RCF and torsion fatigue. • An analytical model was developed and considered Fatemi-Socie failure criteria. • Good corroboration existed between simulation life and experimental results. • Calibrated analytical model offers 2/3rds time save compared to experiments. In this investigation common aerospace-quality bearing steels was evaluated in rolling contact fatigue both experimentally and analytically. Three aerospace-quality bearing steels was procured and evaluated. First, the bearing steels were evaluated using a 3 ball-on-rod rolling contact fatigue test rig. Next, the same bearing steels were evaluated using a torsion fatigue test rig in order to quantify these materials' performance against the damage causing stress in RCF – shear reversal. The torsion S-N data provided the foundation for the determination of material constants that were used in a continuum damage mechanics finite element model (CDM-FE model), which considered the Fatemi-Socie critical plane approach as the failure criteria. These material constants captured the material cleanliness effect between the various materials investigated. Additionally, the CDM-FE model utilized Voronoi tessellations to capture the material topological effect. RCF simulations were performed at the same operating conditions as in the 3 ball-on-rod test apparatus. Torsional fatigue results from this investigation indicated which material possessed the largest ultimate shear strength, and which material performed best in low cycle and high cycle fatigue. The three ball-on-rod results established experimentally which material performed superior in RCF. It was observed that good corroboration existed between the analytical simulation life predictions and the 3 ball-on-rod experimental results. [ABSTRACT FROM AUTHOR]

As traffic density and axle loads increase, the macroscopic wheel-rail contact can lead to severe rail wear. This paper constructs a multi-scale analysis framework from macroscopic force characteristics to microscopic wear mechanisms based on explicit finite element methods and molecular dynamics models. The study shows that the mutual proximity and annihilation of reverse dislocations in the rail material under the action of wheel-rail forces is an important cause of grain boundary fragmentation, while the proliferation of dislocations on the Subsurface leads to work hardening of the rail. The analytical framework proposed in this paper achieves a multiscale correlation between wheel-rail macroscopic contact and material microscopic response, and the conclusions obtained reveal the microscopic wear mechanism of rail materials. [ABSTRACT FROM AUTHOR]

Abstract The performance of the rolling element bearings operated at contaminated lubricant environment was simulated and analyzed in this research work. Artificial surface pits were created on the rolling element bearing inner track contact surface to simulate the effects of solid particle contaminants. The rolling element bearing consists of two Si 3 N 4 balls in compliment with regular steel balls has completed the defined test cycles. The Post-test surface analysis confirmed that the Si 3 N 4 balls had deformed the stress risers. The ball-on-disc experiment was conducted to simulate the repair mechanism produced by Si 3 N 4 balls. The Finite element method was utilized to understand the failure mechanism of the bearing. The higher stress concentration was observed at the edges of the artificial pits. Highlights • Mechanism of repairing the debris pits using few ceramic balls has been studied. • The surface initiated fatigue failure has explained visually by Finite Element analysis. • The theoretical calculations, experimental results are consistent and conclusive. • The 3D profile images of fresh, damaged and repaired surface give the visual treat to understand the contact analysis. • The material characterization techniques like SEM/EDS and surface scanning. • Profilometer are utilized for detailed analysis. [ABSTRACT FROM AUTHOR]

Abstract The aim of this paper is to develop a full Finite Element (FE) computational method for the dynamics of unstable frictional rolling contact systems in order to calculate reference solutions in many applications, especially curve squeal for railway transportation but also roller bearing or metal cutting. The proposed method is characterized by the use of a fine FE discretization of the contact surface in a Eulerian frame, nonlinear frictional contact laws and model reduction techniques. An application to the frictional rolling contact between two annular cylinders is presented in both quasi-static and dynamic cases with mode coupling instabilities. The validation of the approach in quasi-static conditions is carried out by comparison with CONTACT software. Stability and transient results show that the technique is able to simulate friction-induced vibrations at high frequencies. Reduced models are tested and show a good agreement with the full model. [ABSTRACT FROM AUTHOR]

Abstract The modeling of dynamic frictional rolling contact is crucial for accurately predicting behavior and deterioration of structures under dynamic interactions such as wheel/rail, tire/road, bearings and gears. However, reliable modeling of dynamic frictional rolling contact is challenging, because it requires a careful treatment of friction and a proper consideration of the dynamic effects of the structures on the contact. This study takes the wheel-rail dynamic interaction as an example to systematically explore the core algorithms for the modeling of dynamic frictional rolling contact by way of explicit finite element analyses. The study also theoretically demonstrates that the explicit finite element method handles nonlinearities in friction, material properties, arbitrary contact geometries and boundary conditions, and fully couples the calculation of frictional rolling contact with the calculation of high-frequency structural dynamics. An indirect validation method for dynamic contact solutions is proposed. To promote the broad use of the method, this paper proposes a detailed procedure for establishing robust wheel-rail dynamic interact tion models and obtaining dynamic contact responses. The proposed procedure can also be applied to the modeling of dynamic interactions occurring to tire-road, bearings and gears. Graphical abstract Image 1 Highlights • Systematically explore the core procedure for solution of dynamic rolling contact. • Dynamic analyses with nonlinearities in material, geometry and boundary conditions. • Couple calculation of friction rolling with calculation of structural dynamics. • Apply the procedure to the modeling of nonlinear wheel-rail dynamic interactions. [ABSTRACT FROM AUTHOR]

A precise study of stress state is crucial for an accurate evaluation of railway wheel defects. Wheel flats cause severe impact loads, which aggravate wheel failure. This paper describes 3D transient elasto-plastic finite element analyses of undamaged and flatted railway wheels using Chaboche's plasticity model as material model. The effect of the impact load is considered on contact region parameters that influence the stress. The results show that in a flatted wheel, the maximum contact force might not lead to a maximum von-Mises stress. It occurs in all cases considered, in a cross-section just above the leading edge of the wheel flat. [ABSTRACT FROM AUTHOR]

Short-pitch corrugation is a very common and frequent wear pattern on tight curved track of subway with complicated formation mechanism and various influencing factors. Service failures of structure components of the vehicle-track system and wheel-rail noise have been associated with short-pitch corrugation. Effective control measures against short-pitch corrugation are still limited. This study was driven by developing mitigation measures of the short-pitch corrugation by investigating the effect of the wheelset structure on rail corrugation. A 3D wheel-rail steady-state rolling contact finite element model was established with the consideration of the wheel inertia. The mixed Lagrangian/Eulerian method was used to describe the steady-state rolling of the wheel. Frequency domain characteristics of the friction-induced vibration of the wheel-rail system were studied by using complex eigenvalue analysis, and the relationship between the friction-induced vibration of the wheel-rail system and rail corrugation was revealed. Based on the stability analysis of wheel-rail system, the influence of the wheelset structure on short-pitch corrugation was studied. The numerical simulation results show that the shape of wheel web presents evident influence on the friction-induced vibration of wheel-rail system. The wheel-rail system with S-shape web is more prone to unstable than that with straight web. Rail corrugation is more likely to occur in the wheel-rail system with S-shape web. Further studies show that the axial distance between the rim and hub has a remarkable impact on the friction-induced vibration of the wheel-rail system. A significant reduction in the probability of rail corrugation can be achieved by reducing the axial distance between the rim and hub. When the rim-hub axial distance of the wheel with S-shape web is less than 0 mm, the friction-induced vibration of wheel-rail system will disappear, which means that the short-pitch corrugation caused by the friction-induced vibration of the wheel-rail system will no longer occur. As for the straight-web wheel, the friction-induced vibration will disappear when the axial distance is less than 6 mm. The rim thickness also has an obvious influence on the friction-induced vibration of the wheel-rail system. The probability of the friction-induced vibration increases with the decrease of the rim thickness, which indicates that the speed of rail corrugation will increase with the aggravation of wheel wear. • The structure of the wheel web has a significant impact on the short-pitch corrugation. • When the axial distance between the wheel rim and hub is reduced to a certain value, the corrugation caused by the friction-induced vibration of the wheel/rail system will not occur. • With the aggravation of the wear on the wheel tread, rail corrugation will become more serious. • The wheel with straight web is helpful to alleviate but con not eliminate the corrugation. [ABSTRACT FROM AUTHOR]