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The rail profile milling process allows considerable thickness to be removed in a single pass. However, the residual waviness formation law after milling and its subsequent effect on rail performance remains uncertain. In this paper, the wavelength and wave height of the residual waviness are identified as the key characteristics. The relationship between milling speed and residual waviness is determined, and a numerical model of the residual waviness formed on the surface after milling is established based on the commonly used three milling speeds of 300, 600, and 1000 m/h, and its accuracy is verified using the parameters of the residual waviness detected by the milling experiments. A three-dimensional finite element analysis model of wheel-rail contact was employed to analyze the contact stresses and low fatigue cycles at a wheel load of 11.5 tons with no residual waviness on the rail profile surface and with three types of residual waviness, respectively. The results show that the residual waviness changes the wheel-rail contact position and the morphology of the contact area, reduces the maximum contact stress and increases the strain fatigue cycles. The application of elevated milling speeds reduces the wheel-rail contact stresses after milling, thereby increasing the low fatigue cycles. [ABSTRACT FROM AUTHOR]

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]

In experiments of aviation motor bearings, when the deep-groove ball bearings are subjected to an overturning moment at high speed, it often happens that the rivet on the cage breaks and the debris invades the raceway, resulting in bearing failure. To address the problem of early failure of deep-groove ball bearing cages and rivets in aviation motors, the causes of early failure were analyzed from the aspect of cage design in this study. The influence of the raceway and cage structure parameters on the dynamic contact characteristics of the rolling element and cage under the action of overturning torque were analyzed, the weak link of the cage was determined, and the cage design parameters were optimized. The results show that with an increase in the cage width and pocket radius, the impact force between the ball and cage first decreases and then increases, and the tilt angle of the cage gradually decreases. A larger channel radius and smaller clearance can slow down the interaction between the cage and the rolling element and make the cage run more smoothly. Increasing the thickness of the cage can ensure that the rivet part of the cage is at a low stress level, and the risk of premature fatigue failure at the rivet part can be reduced by maintaining a small gap–fit relationship between the rivet and rivet holes. The research results indicate that the working condition adaptability of the bearing cage for aviation motors can be improved, and the design method for this type of bearing can be enhanced. [ABSTRACT FROM AUTHOR]

Based on the cohesive zone model (CZM), a finite element model of the film–substrate bearing system in the rolling–sliding contact state is established. Through analyzing the normal and tangential bearing states of the film–substrate system, the effects of the sliding–rolling ratio and the film–substrate adhesion strength on the interfacial stress and the interfacial energy release rate of the film–substrate system are studied. The results show that there is an almost symmetric stress distribution at both sides of the contact zone in rolling contact. In rolling–sliding contact, obvious shear flow along the rolling–sliding direction occurs at the front edge of the contact zone, which results in a significant increase in the shear stress at the interface at the front edge of the contact zone, increasing the risk of interface damage and delamination failure. Meanwhile, the shear flow causes a normal tensile stress concentration along the film surface behind the contact zone, which very easily causes the emergence and expansion of the film surface cracks. In addition, there is a clear positive correlation between the adhesion strength and the load-bearing capacity of the film–substrate interface. The tangential delamination damage mainly occurs at the interface regardless of the rolling or rolling–sliding contact state. [ABSTRACT FROM AUTHOR]

To study the thermal ‐ force bulging behavior of roll profile electromagnetic control technology (RPECT), the variation laws of the comprehensive roll crown, the thermal ‐ force contribution roll crown and the ratio of the force crown with the heat of contact zone under different current densities and frequencies were analyzed by finite element method, and the mapping relationship and establishment condition between the heat of contact zone and the thermal‐force bulging ability were explored. The results show that, within the range of the middle and low values of the heat of contact zone, the thermal‐force control ability corresponding to the same value of the heat of contact zone cannot be affected by the magnetic parameters. Therefore, an efficient control strategy of RPECT can be proposed, which takes the heat of contact zone as the bridge value between the input parameter and the control ability. The strategy can quickly achieve the target temperature rise effect of the contact zone by increasing the magnetic parameters, and then obtain the target control ability. Taking the roll gap crown requirement of 20 μm as an example, the comparison between the original and the efficient control strategy shows that the control time of the new strategy can be effectively shortened to 19. 57% of the original control time. [ABSTRACT FROM AUTHOR]

The azimuth track is an important component of the radio telescope wheel–rail system. During operation, the azimuth track is inevitably subject to phenomena such as track wear, track fatigue cracks, and impact damage to welded joints, which can affect observation accuracy. The 110 m QiTai radio telescope (QTT) studied in this paper is the world's largest fully steerable radio telescope at present, and its track will bear the largest load ever. Since the welded joint of an azimuth track is the weakest part, an innovative welding method (multi-layer and multi-pass weld) is adopted for the thick welding section. Therefore, it is necessary to study the contact mechanical properties between the wheel and the azimuth track in this welded joint. In this study, tensile tests based on digital image correlation technology (DIC) and Vickers hardness tests are carried out in the metal zone (BM), heat-affected zone (HAZ), modified layer, and weld zone (WZ) of the welded joint, and the measured data are used to fit the elastic–plastic constitutive model for the different zones of the welded joint in the azimuth track. Based on the constitutive model established, a nonlinear finite element model is built and used to simulate the rolling mechanical performance between the wheel and azimuth track. Through the analysis of simulated data, we obtained the stress distribution of the track under different pre-designed loads and identified the locations most susceptible to damage during ordinary working conditions, braking conditions, and start-up conditions. The result can provide a significant theoretical basis for future research and for the monitoring of large track damage. [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]

This paper is concerned with the modeling of power dissipation due to friction and its relation with wear estimation in wheel–rail contact. Wear is a complex multi-scale and multi-physical phenomenon appearing in rolling contact. Wear is generated by high contact stress and the work of friction forces. This phenomenon leads to the appearing of the worn material in the form of wear debris between contacting surfaces. In contact models, wear is usually described in terms of the wear depth function. This function modifies the gap between the contacting bodies as well as the shape of the surfaces of the wheel and rail in contact. In this paper, besides the wear depth function, the dissipated energy, rather than the contact stress, is taken into account to evaluate the wear impact on rail or wheel surfaces. The dissipated energy allows us to more precisely evaluate the wear debris amount as well as the depth of wear and its distribution along the contact interface. A two-dimensional rolling contact problem with frictional heat flow is considered. The elasto-plastic deformation of the rail is considered. This contact problem is governed by a coupled system of mechanical and thermal equations in terms of generalized stresses, displacement and temperature. The finite element method is used to discretize this problem. A discretized system of equations with nonpenetration and friction conditions is transformed and formulated as a nonlinear complementarity problem. The generalized Newton method is applied to numerically solve this mechanical subproblem. The Cholesky method is used to find the solution of the heat-conductive problem. The dissipated power is evaluated based on the resultant force and slip at a reference point. Numerical results including the distribution of slip velocity, power factor and wear rate are provided and discussed. [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]

The manufacturing of thin films with structured surfaces by large-scale rolling has distinct advantages over other techniques, such as lithography, due to scalability. However, it is not well understood or quantified how processing conditions can affect the microstructure at different physical scales. Hence, the objective of this investigation is to develop a validated computational model of the symmetric forward-roll coating process to understand, predict, and control the morphology of carbon nanotube (CNT)-polydimethylsiloxane (PDMS) pastes. The effects of the thin-film rheological properties and the roller gap on the ribbing behavior are investigated and a ribbing instability prediction model is formulated from experimental measurements and computational predictions. The CNT-PDMS thin-film system is modeled by a nonlinear implicit dynamic finite-element method that accounts for ribbing instabilities, large displacements, rolling contact, and material viscoelasticity. Dynamic mechanical analysis is used to obtain the viscoelastic properties of the CNT-PDMS paste for various CNT weight distributions. Furthermore, a Morris sensitivity analysis is conducted to obtain insights on the dominant predicted characteristics pertaining to the ribbing microstructure. Based on the sensitivity analysis, a critical ribbing aspect ratio is identified for the CNT-PDMS system corresponding to a critical roller gap. [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]

At the entry of the pickling and tandem cold strip mill (PL-TCM), the unreasonable cut length of the head and tail of the strip often causes a thickness difference between the weld surfaces of the front and back strip, resulting in a weld seam with thickness difference after welding. This can easily lead to strip breaking at the weld seam in the cold rolling process. In this paper, a finite element model of roll and strip with weld seam is established to investigate the mechanism of strip breaking at weld seam due to thickness difference. By simulating the working conditions in the rolling process for weld seam with different thickness differences, the evolution of the stress state of the weld seam in the rolling process under each working condition is analyzed. The influence of thickness difference in the rolling process of the weld seam is revealed, and the effect of thickness difference on the risk of strip breaking at weld seam during the rolling process is further discussed. According to the research results, the optimization method of strip head and tail shear length was designed and applied to the industrial site. After application, the accident rate of strip breaking is reduced and the effect is as expected. [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]

This paper presents the design of a compliant rack and pinion mechanism with the support of a compliant rolling contact joint (CRCJ). The flexible strips are mounted to connect the rack and pinion to accelerate the mechanism. Two types of rack and pinion mechanism are proposed: rack and pinion mechanism and double rack and pinion actuator. The 3D model is created with finite element analysis (FEM) for structural analysis to observe the maximum strength and the deformation of the flexible strip. A 3D-printed model is proposed by using a fused deposition method (FDM) by printing layer by layer for experimental and demonstration purposes. In this study, we propose a set of examples to convert a traditional rigid body mechanism to complete a complaint mechanism to accumulate the actual function and also to increase the high possibilities of mounting. [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]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 hardness of the soft zone is much lower relative to the hardened surface of the raceway. • A hierarchical finite element modeling method of the main bearing is proposed. • The principle of selecting the optimum hardened depth is given. • The effect of the soft zone on the contact characteristics and fatigue life of the raceway is investigated. • This analyzing method can quickly and efficiently clarify the contact state in the soft zone during the rolling process. A hierarchical finite element modeling method is proposed to study the problem of fatigue spalling easily due to low hardness in the soft zone for the main bearing of a tunnel boring machine. Quasi-static analyses of the main bearing are performed based on the global symmetric model and verified by relative displacement tests of the rings. The invariant contact pressure is replaced by the rolling contact of the rollers in the local sub-model. The contact load is used as an input to solve the stress field, and then the effects of soft zone and hardened depth on the contact characteristics and fatigue lifetime of the sub-model are investigated. The results show there are stress peaks at the junction of the hardened and soft zones. The effect of hardened depth on the stress distribution and fatigue lifetime is relatively small. However, the optimum hardened depth is influenced by the contact load and the permissible stress of the material. The minimum lifetime of the raceway during rolling occurs in the soft zone. This paper achieves a fast and effective rolling contact fatigue analysis of the main bearing, which provides a theoretical basis for optimizing the main bearing design. [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]

In order to overcome the shortcomings of the steel spring floating slab track structure in the urban rail transit with short sleepers in the steel spring floating slab structure due to its poor maintenance accuracy, large adjustment workload, difficulty in assembling the rail row, and slow construction progress, the optimized double-block sleepers ballastless track technology is introduced into the steel spring floating slab structure to form a new double-block sleepers floating slab structure with high precision of the double-block sleepers ballastless track and high vibration damping effect of steel spring floating slab. The static characteristics under the four conditions of lifting, stacking, hoisting and construction are analyzed and studied by a finite element model established, optimal structural design parameters are determined, the overall and local reinforcement design of the structure is carried out according to the limit state design method of partial reinforcement design, and the test section is prepared and dynamic performance test is conducted. The results show that the new double-block sleeper can effectively reduce the cracks of the ballast bed on account of its better rail bottom slope accuracy and smoothness, simple construction and fast speed; within the speed range of 80~120 km/h, the maximum derailment coefficient is 0. 52, and the maximum wheel load reduction rate is 0. 28, which are all less than the specified limits, and the vibration reduction effect reaches 14 dB; and it has good driving safety indicators and vibration reduction performance. [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]

During measurements, the crankshafts of marine engines are usually supported on a set of rigid prisms. Such prisms maintain a constant height position, cause different values of reaction forces and, consequently, may cause elastic deformations of the crankshafts. Thus, the measurements of the dimensions and geometry of the crankshaft may be distorted. This article proposes a measuring system developed to support the crankshaft with a set of flexible supports. These supports implemented the given reaction forces, which ensured the elimination of the crankshaft deformations, regardless of the possible deviations, i.e., in the coaxiality of the main crankshaft journals. The values of these forces were calculated using the finite element method (FEM). These calculations showed that in order to eliminate the crankshaft deformations, the values of the reaction forces must change not only on individual supports, but also with the change of the shaft rotation angle during the measurement. The numerical experiments showed that the application of flexible supports results in uniform contact reaction forces on adjacent main journal supports. This uniformity occurs regardless of the quality of the crankshaft geometry. Thus, the necessity to use a set of flexible supports for measuring marine engine crankshafts was confirmed. The research also showed that the values of the reaction forces ensuring the elimination of shaft deflections under the assumption of nodal support can be treated as corresponding to the resultant reaction forces realized by the prismatic heads. [ABSTRACT FROM AUTHOR]

In rolling or gear contacts, truncation of the contact ellipse can occur, for example, when an undercut extends into the contact area. For an elastic calculation approach, the edge constitutes a mathematical singularity, which is revealed by a theoretically infinitely high pressure peak. However, when elastic–plastic material behavior is taken into account, the pressure peak is limited by local hardening and yielding of the material, leading to plastic deformations. As a result, those calculations are rather challenging and the results partly unexpected due to the discontinuity contained in the geometry. Nevertheless, to the authors' knowledge, hardly any published studies exist on elastic–plastic simulations of truncated contact ellipses. Therefore, a numerical study concerning the contact of a rigid ball with an elastic–plastic plane is presented. Due to an undercut in the plane, a quarter of the theoretical Hertzian contact ellipse is cut off. The aim of the study is to investigate the influence of the undercut angle on the pressure distribution and the elastic and plastic deformation at the edge. The use of FEM shows that the undercut angle has a significant effect on the characteristics of the contact. The results obtained using FEM are then used as a reference for comparison with a semi-analytical method (SAM). It is shown that the SAM, based on the half-space, provides comparable results only for very small undercut angles. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An investigation on the White Etching Crack (WEC) phenomenon as a severe damage mode in bearing applications led to the observation that in a latent pre-damage state period, visible alterations appear on the surface of the raceway. A detailed inspection of the microstructure underneath the alterations reveals the existence of plenty of nano-sized pores in a depth range of 80 µm to 200 µm. The depth of the maximum Hertzian stress is calculated to be at 127 µm subsurface. The present study investigates the effect of these nanopores on the fatigue crack initiation in SAE 52100 martensitic hardened bearing steel. In this sense, two micro-models by means of the Finite Element Method (FEM) are developed for both a sample with and a sample without pores. The number of cycles required for the crack initiation for both samples is calculated, using the physical-based Tanaka–Mura model. It is shown that pores reduce the number of cycles in bearing application to come to an earlier transition from microstructural short cracks (MSC) to long crack (LC) propagation significantly. [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 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 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]

The residual stress approximation methods formulated by McDowell and Moyar, Jiang and Sehitoglu, and McDowell for rolling and sliding contact problems are reconsidered in the context of single anisothermal loading cycles and isotropic hardening. A consistent extention to incorporate thermal softening is developed and the generalized thermoelastoplastic algorithms are cast into a proper predictor–corrector formulation. Detailed explicit and implicit numerical integration strategies are presented and validated using specifically designed finite element models that conform to the underlying mechanical assumptions. Then, the applicability of the approximate algorithms to anisothermal problems with isotropic hardening and thermal softening is analyzed by assuming a rate-independent Johnson–Cook-type yield stress model and by comparing the obtained transient and residual stresses to results from full-scale finite element half-space models under varying loading and strain-hardening intensities. An in-depth, comparative discussion on the adequacy of the algorithms in conjunction with the justification of their respective mechanical simplifications follows. Sufficiently strong strain hardening is found to be a prerequisite for accurate predictions, and Jiang and Sehitoglu's approach is deemed to be preferable for the considered type of problem. The conclusions drawn from the investigations are discussed in the context of common applications with particular emphasis on manufacturing process modeling and the corresponding guidelines are proposed for such use cases. [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]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

Rolling contact fatigue failure is one of the main fatigue damages in railway wheels caused by cyclic rolling contact with rails. This fatigue failure is caused by internal defects such as nonmetallic inclusions or voids and may occur in heavy haul freight car wheels. The subsurface crack propagation behaviors caused by the internal defects are evaluated by twin-disc-type rolling contact fatigue tests using test specimens with artificial defects. Finite element analyses involving simulated rolling contact fatigue tests are also conducted. The subsurface cracks are more likely to propagate in the test specimens with larger artificial defects. Moreover, cracks initiating from the trailing side of the defects propagate faster than those from the leading side. Shear mode equivalent stress intensity factors obtained from the finite element analyses correspond well to the results of the rolling contact fatigue tests. The test specimen models with larger defects have larger equivalent stress intensity factor ranges than the test specimen models with smaller defects in both the leading and trailing sides. The results of the finite element analyses also suggest that the crack propagations are affected by the deformation of the artificial defects, which leads to higher resistance to crack propagation in test specimens with smaller internal defects. [ABSTRACT FROM AUTHOR]