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In this article, considering the coupled interaction of heat, stress, material wear, and wheel–rail force transmission in the disc-braking process, a complex multifield coupled method was proposed to study thermal mechanical properties and contact state of brake discs. First, a coupled dynamic model of train, track, and brake gear was established to analyze the force transmission between brake friction pairs and wheel–rail system. Based on the coupled dynamics simulation results, a thermomechanical wear coupled model of the friction pair was established. It is found that the track irregularity results in vertical relative displacements with a range of (–2.6 mm, 2.8 mm) and makes the maximum brake force increase to 24.1 kN. As a comparison, brake bench tests without wheel–rail interaction were carried out. This showed that there was no vertical relative displacement between the friction pair, and the braking force had a stable value of 22.5 kN. The simulation results of the brake disc temperature distribution, and the friction pair contact state are consistent with the bench test results. In addition, different thermal simulation methods of the brake disc were used to verify the validity of the complex multifield coupled simulation results. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology 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.)

False brinelling damage in rolling bearings can lead to reduced component lifetimes and increased noise emissions, adversely affecting machine performance. Therefore, minimizing or avoiding such damage is very important. Environmental or operating conditions that can lead to false brinelling damage often cannot be avoided. Alternatively, such damage can be significantly reduced with suitable lubricants. This study utilized a test method from the research project FVA 540 to examine the impact of the base oil viscosity and NLGI class of greases on false brinelling damage at different temperatures. The results showed a clear dependency between the base oil viscosity of greases and the extent of false brinelling damage. Two different thickeners (lithium hydroxystearate/diurea) and different base oil types (PAO/esters) were investigated for this purpose. The results indicate that temperature had a significant effect on the physical and rheological properties of greases and show the potential for reducing false brinelling damage through the selection of appropriate lubricants. These results provide valuable information to improve the performance and lifetime of rolling bearings in industrial settings. [ABSTRACT FROM AUTHOR]

A dual chemically reactive multilayer coating is rationally subjected to mono- and dual-functionalization through a 1,4-conjugate addition reaction at ambient conditions to depict the raising of the oil contact angle and rolling of a beaded oil-droplet underwater, respectively, only in the presence of targeted toxic chemicals (e.g. nitrite ion and hydrazine). Rational switching of the hydrophobic aromatic moiety into a hydrophilic moiety in the modified multilayer coatings via selected modified Griess reaction and Schiff base reaction contributed to the desired change in underwater oil-wettability and oil-adhesion. Eventually, this approach allowed equipment-free and naked-eye chemical sensing with high selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

Wheel burn can affect the wheel–rail contact state and ride quality. With long-term operation, it can cause rail head spalling or transverse cracking, which will lead to rail breakage. By analyzing the relevant literature on wheel burn, this paper reviews the characteristics, mechanism of formation, crack extension, and NDT methods of wheel burn. The results are as follows: Thermal-induced, plastic-deformation-induced, and thermomechanical-induced mechanisms have been proposed by researchers; among them, the thermomechanical-induced wheel burn mechanism is more probable and convincing. Initially, the wheel burns appear as an elliptical or strip-shaped white etching layer with or without deformation on the running surface of the rails. In the latter stages of development, this may cause cracks, spalling, etc. Magnetic Flux Leakage Testing, Magnetic Barkhausen Noise Testing, Eddy Current Testing, Acoustic Emission Testing, and Infrared Thermography Testing can identify the white etching layer, and surface and near-surface cracks. Automatic Visual Testing can detect the white etching layer, surface cracks, spalling, and indentation, but cannot detect the depth of rail defects. Axle Box Acceleration Measurement can be used to detect severe wheel burn with deformation. [ABSTRACT FROM AUTHOR]

Rail wear occurs continuously owing to the rolling contact load of trains and is fundamental for railway operational safety. A point‐based manual rail wear inspection cannot satisfy the increasing demand for rapid, low‐cost, and continuous monitoring. This paper proposes a depth‐plus‐region fusion network for detecting rail wear on a running band, which is a collection of wheel–rail interaction traces. The following steps are involved in the proposed method. (i) A depth map estimated by a modified MiDaS model is utilized as guidance for exploiting the depth information of the running band for rail wear detection. (ii) The running band of a rail is segmented and extracted from images using an improved mask region‐based convolutional neural network that uses the scale and ratio information to perform instance segmentation of the running band images. (iii) A two‐channel attention–fusion network that classifies rail wear is constructed. In this study, we collected real‐world running band images and rail wear‐related data to validate our approach using a high‐accuracy rail‐profile measurement tool. The case‐study results demonstrated that the proposed method can rapidly and accurately detect rail wear under different ambient light conditions. Moreover, the recall rate of severe wear detection was 84.21%. [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]

Continuum manipulators, with their characteristics of flexibility and dexterity, have gained significant interest in various applications across industries such as inspection, manufacturing, space exploration, and medical surgery. However, because of their inherent compliance, handling payloads may prove challenging due to shape distortion and deflection. This demonstrates the need to optimize the manipulator's stiffness. The primary objective of this work was to show the merits of sensitivity analysis in the design of flexible surgical manipulators. Such analysis can guide important design decisions and enable the more efficient use of available resources, contributing to designing more effective prototypes. A new sensitivity analysis framework based on a multi-model and a multi-method approach was proposed to achieve this. This framework was then demonstrated by studying a tendon-driven rolling contact joint hyper-redundant manipulator for transoral laser microsurgery. In this analysis, the effects of independent design parameters on the stiffness of the manipulator were examined. Then, scaled-up 3D-printed prototypes were used to validate the accuracy of the stiffness model experimentally, which enabled us to assess the outcome of the sensitivity analysis framework. The results demonstrated that only two out of five design parameters for the considered manipulator significantly impacted the device's performance. This information could enable the designer to efficiently allocate resources toward correctly setting these two most important parameters to achieve the desired system. Overall, the proposed analysis framework is a general tool that can be applied to any design architecture, helping to develop optimal manipulators for various applications. [ABSTRACT FROM AUTHOR]

Abstract Sliding and spinning behaviors significantly affect the performance of rolling bearings, especially for dry-lubricated bearings, micro and macro sliding may lead to increased wear of the solid lubricating film. A unified rolling contact tribology analytical model is proposed for dry-lubricated angular contact ball bearings (ACBBs) considering the extreme conditions including high combined loads and rolling contact effects. A comprehensive solution framework is proposed to ensure the robustness of the model under different loading conditions. Equilibrium equations are solved to study the effects of friction coefficients, rotating speeds, and combined loads on the skidding and spinning characteristics of the ACBB. The results show that the rolling contact effects and combined loads significantly affect the skidding and spinning performance of the ACBB. Further analysis reveals that the skidding mechanism is related to the interaction between ball kinematical motion and traction forces. The developed analytical model is proved to more accurately predict the bearing kinematical and tribological behavior as it discards the raceway control hypothesis and considers the macro/micro-slipping, creepage, and self-spinning motions of the ball, which is validated using both the existing pure axial loading dry-lubricated ACBB model and the classical Jones—Harris model. The study would provide some guidance for the structure and lubrication design of dry-lubricated ACBBs.

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 Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering 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.)

This study investigated the effectiveness of lubricants and additives in preventing surface damage and wear, which is critical for numerous industrial applications. The ASTM standard operation conditions were employed for a series of experiments using a four-ball friction and wear tester, testing three different oils (A, B, and C) with and without 0.5% fly ash additive. The experiments were analyzed using a microscope to evaluate the effectiveness of oils and additives in preventing surface damage. The study found that certain anti-wear additives significantly reduced the size of wear scars on the balls, indicating their effectiveness in reducing surface damage. These findings have important implications for developing new lubricant formulations and optimizing industrial processes that involve sliding and rolling contacts. The study emphasizes the importance of selecting appropriate oils and additives for specific applications to minimize surface damage and wear, which is crucial for improving the performance and lifespan of machine components. [ABSTRACT FROM AUTHOR]

The article discusses the importance of improving environmental, social, and governance (ESG) performance in industrial companies and the responsibility of heavy industry sectors to support initiatives for reducing greenhouse gas emissions. It explores the role of reliability engineers in minimizing energy consumption and targeting specific types of energy losses in equipment asset-dependent industries.

The generation of wheel–rail-sliding frictional heat is often accompanied by transverse displacement of a wheel. To study the thermal problem of wheel–rail sliding friction at two-point contact, this paper uses an LM tread wheel and a 60 kg·m−1 rail as examples. A thermal–mechanical-coupled finite-element model of equal proportion wheel–rail sliding is established. A direct-coupling method is used to analyze the thermal–mechanical coupling of the wheel–rail interface under sliding contact. This model considers the temperature-dependent material properties and boundary conditions, such as thermal convection and thermal dissipation, in the process of nonstationary frictional-heat conduction. Firstly, the effects of different sliding speeds, axle loads, and contact modes on the temperature and stress fields of the contact area are analyzed. Then, the lubrication and cooling effects of friction modifiers on the rail top and rail gauge angle are compared. The results show that, at a sliding speed of 2 m/s and an axle load of 30 t under a sliding condition of 200 mm, on the top and side of the rail, the temperatures at the contact patch centers are 813 °C and 547.7 °C, respectively. Under different operating conditions, the rail-side temperature is 55–75% of that of the temperature at the rail top, and the rail-side contact and friction stress values are 76–96% of those at the rail top. This indicates that frictional thermal damage on the rail side cannot be ignored. With a lower sliding speed, the thermal response of the two contact patches is closer. The impact of axle load on the frictional temperature and stress on the rail side is more critical than the sliding speed. The optimal lubrication choice is overall lubrication, which can decrease the rail top temperature by 47.2% and frictional stress by 56.2%, as well as decreasing the rail side temperature by 70.3% and frictional stress by 77.4%. [ABSTRACT FROM AUTHOR]

Most of the published documents on the friction and wear properties of textured contact surfaces with partially distributed units (e.g., dots, grooves) are focused on sliding tribo-pairs or journal bearings. To study the friction and wear performance of rolling bearings with different distributions of pits, several patterns were introduced: OS-1/4 (Outside, 1/4 of raceway), OS-1/2 (Outside, 1/2 of raceway), OS-3/4 (Outside, 3/4 of raceway), IS-1/4 (Inside, 1/4 of raceway), IS-1/2 (Inside, 1/2 of raceway), IS-3/4 (Inside, 3/4 of raceway), TS (Two sides, 2/3 of raceway), FT (fully textured) and SR (Smooth reference), with two circumferential interval angles (CFIAs, 1.5° and 2.0°). The dimensions of the pits are the same in all patterns (diameter of 300 μm and depth of 15 μm), which were only prepared on the raceways of the shaft washers of 81107 bearings (nylon cages) using the laser marking method. All bearings were tested under 4000 N, 250 RPM and starved lubrication using a vertical universal wear test rig. Their mass losses and worn raceways were measured and observed. Their surface equivalent stresses were also analyzed and compared. The obtained results show that the influence of different distributions of pits on the tribological properties of rolling bearings is significant. The friction-reducing and anti-wear performance of TS is acceptable, whether the CFIA is 1.5° or 2.0°. A fully textured pattern cannot provide the best tribological properties and its behavior even becomes worse when the CFIA is 2.0°. In this work, when the CFIA is 1.5°, the friction-reducing and anti-wear performance of OS-1/4 is the best among all patterns. Using a smooth reference as a benchmark for comparison, its friction-reducing and anti-wear performance can be enhanced by 60.46% and 16.05%, respectively. The results of this work will be an important reference for the optimal design of the "washers-cage-rollers" contact system for rolling bearings. [ABSTRACT FROM AUTHOR]

Affected by the service environment, the actual service conditions of rail steel are complex, and the safety evaluation methods are limited. In this study, the fatigue crack propagation in the U71MnG rail steel crack tip was analysed by means of the DIC method, focusing on the shielding effect of the plastic zone at the crack tip. The crack propagation in the steel was analysed based on a microstructural approach. The results show that the maximum value of stress of the wheel–rail static contact and rolling contact is in the subsurface of the rail. The test grain size of the material selected along the L–T direction is smaller than that in the L–S one. Within a unit distance, if the grain size is smaller, the number of grains or grain boundaries will be greater so that the driving force required for a crack to pass through the grain boundary barriers will be larger. The Christopher–James–Patterson (CJP) model can well describe the contour of the plastic zone and can well characterize the influence of crack tip compatible stress and the crack closure effect on crack propagation under different stress ratios. The crack growth rate curve at the high-stress ratio is shifted to the left relative to the low-stress ratio, and the crack growth rate curves obtained under different sampling methods have good normalization. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering 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 deformation and degradation behavior of unstabilized ballast and that stabilized with elastomer and geogrid was evaluated using process simulation test (PST) apparatus at various loading frequencies (f). The results indicated that elastomer has significantly reduced the extent of both vertical and lateral deformations of ballast. For example, elastomer reduced the extent of vertical settlement (Sv) in ballast from 22.76 to 9.83 mm, and the lateral deformation (ld) from 8.14 to 1.95 mm (f=15 Hz). It was also seen that the deformation and degradation of both stabilized and unstabilized ballast increased nonlinearly with the increase in the applied loading frequency (f). Further, the beneficial effect of elastomer in restraining the lateral flow of ballast was seen over the entire depth of treated ballast, unlike the geogrid, whose efficiency was maximum at its placement location and then reduced at farther locations. Moreover, elastomer has significantly enhanced the resilient modulus (Mr) and damping ratio (D) of ballast when compared with geogrid-reinforced ballast. For example, the elastomer increased the Mr and D of ballast by 25.9% and 66.6%, respectively, in comparison with an increment of only 15.1% and 25.3% in the case of geogrids (f:15 Hz). The Mr and D of ballast were found to be influenced by the effectiveness of the ballast stabilization technique in reducing lateral displacements. Additionally, elastomer has significantly reduced the vertical stress (σv) at the ballast–subballast interface by 34%. Further, elastomer was found to be more efficient than the geogrid in reducing the dynamic amplification factor (DAF) at any loading frequency. Similarly, elastomer reduced the breakage of ballast by 71% compared with the 40% of geogrid reinforcement (f=15 Hz). [ABSTRACT FROM AUTHOR]

The friction and wear performance of high-performance bearings directly affects the accuracy and maneuverability of weapons and equipment. In this study, high-speed, high-temperature, and heavy-load durability experiments of weapon bearings were carried out, and their wear properties (i.e., surface wear, metamorphic layer, scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), residual stress, and retained austenite) were analyzed in multiple dimensions. The results showed the following: (1) The experimental temperature of the serviced front-end bearing is always lower than that of the rear bearing. (2) The metamorphic layer of the serviced rear bearing (i.e., inner ring, outer ring, rolling body, and cage) > the metamorphic layer of the serviced front-end bearing > the metamorphic layer of the unserviced bearing. (3) The rolling body of the rear bearing at high experimental temperatures contains not only elemental O, but also elemental P and Sr. (4) In the EDS analysis of the rolling elements, with the migration from the "ball edge" to the "ball center", the elemental C in the rolling elements of serviced or unserviced bearings decreases slowly, while the elemental Fe content increases slowly. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering 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.)

In order to improve the service life of the needle roller bearing used in a precision cycloid reducer, and to reveal the skew and collision phenomenon of the needle roller bearing, based on the force analysis of the transmission mechanism of the cycloid reducer and considering the friction between the cycloid wheel, needle roller, cage, and crank shaft, the dynamic contact between the rolling bodies is simulated by the Hertz elastic contact, where the contact between the cage pocket hole and needle roller is equivalent to the spring and damping, and a nonlinear dynamic model of the needle roller bearing is established. The influence of different load and cage clearances on the deflection impact of the rotating needle roller bearing is calculated. The results show that the inclination of rollers is different under different pocket clearances, and the larger the pocket gap, the greater the fluctuation of the roller inclination angle; the action force of the crank shaft on the roller suppresses the deflection of the roller; the impact force of the roller on the cage has periodicity, which is consistent with the impact force of the crank shaft on the roller. The impact force of the cage is different under different loads, and the greater the load, the more rollers there are in the bearing area, the larger the impact force is, and the smaller the impact force of the rollers in the middle of the bearing zone is, compared with that of the rollers on the two sides; when the load is small, a pocket cage gap of 0.3 mm is selected, and when the load is heavy, a pocket cage gap of 0.2 mm is selected in order to make the bearing run more smoothly. [ABSTRACT FROM AUTHOR]

In bearing applications, the presence of stray and parasitic currents in combination with lubricants has been studied for almost a century and has been found to cause fluting and corrugation damages under high current densities. However, recent research has suggested that at low current densities (<1 mA/mm2) under specific operating conditions, electrical discharges can substantially reduce bearing life due to the formation of white etching cracks (WECs). To date, limited studies have investigated the critical operating and electrical conditions for WEC formation and demonstrated effective fault detection techniques. This study uses a novel monitoring technique known as the electrostatic sensing technique to detect, monitor and characterise electrical discharges in an oil-lubricated steel–steel rolling contact on a TE74 twin-roller machine. The findings demonstrate that WECs can be formed under the influence of electrical discharges in less than 50 h, and the electrostatic sensors are effective for the early detection of critical electrical discharges related to WEC-induced failures. [ABSTRACT FROM AUTHOR]

Differing from the published documents on the effect of texture distributions of sliding tribo-pairs on their friction and wear properties, this study introduced eight patterns to reveal the influence of different distributions of pits on the tribological behavior of textured rolling element bearings with nylon cages under dry condition, namely: Outside-1/4 (OS1/4), Outside-1/2 (OS1/2), Outside-3/4 (OS3/4), Inside-1/4 (IS1/4), Inside-1/2 (IS1/2), Inside-3/4 (IS3/4), Bothside-1/3 (BS) and full (FP). A fiber laser marking system was used to prepare them on the raceways of the shaft washers of cylindrical roller thrust bearings (81107TN). A vertical universal wear test rig was used to obtain their coefficients of friction under an axial load of 2600 N and a rotating speed of 250 RPM, without any lubricant provided. Their wear losses and worn surfaces were characterized. The influence mechanism of different distributions on the tribological properties was also discussed. The results show that the self-lubricating performance of nylon cages can ensure the continuous operation (≥5 h) of cylindrical roller thrust bearings under dry condition. The influence of outside-distributed patterns on the friction and wear properties of bearings is significant. The friction-reducing effect and wear resistance of full textured group is improved but not the best. The friction-reducing and anti-wear behavior of OS1/2 is similar to that of FP. In this work, OS3/4 can provide the best tribological performance under self-lubricating conditions. Compared with the data of smooth bearings, its average coefficient of friction and wear loss can be reduced by 37.68% and 38.85%, respectively. This work would provide a valuable reference for the raceway design and reliability optimization of rolling element bearings. [ABSTRACT FROM AUTHOR]

Vehicle-track interaction in a switch panel diverging route is studied with a focus on the way its components may interact in the lateral direction. Taking one of the cases of S&C benchmark as the base model, several variants of the co-running track model are considered. In the first series of simulation, the effect of the lateral separation of the switch rail and stock rail is investigated, showing that only small differences are found in terms of wheel/rail forces between a track model where both rails are coupled, and one where they are free to move with respect to one another. Only transient effects are visible at the beginning and at the end of the two-point contact on both rails. While small, these differences can have some influence in terms of rolling contact fatigue and wear prediction. In the second series of simulation, co-running track models are developed including the baseplate and taking into account such effects as switch rail/stock rail contact at the undercut plane and dry friction. Significant changes are observed in the load distribution within the switch panel. Conclusions should be consolidated through experimental field measurement and using more realistic track models, e.g. discretely supported rail beam models. [ABSTRACT FROM AUTHOR]

The analysis of rail/wheel sliding friction heat is a very important research field. The numerical simulation is often adopted to calculate the friction heat, and experimental method is relatively few. In this paper, an experimental machine is designed to simulate the rail/wheel sliding contact. At the same time, a rail/wheel contact wear model and a friction heat transfer model are established. The characteristics of temperature on rail/wheel sliding contact are analyzed by experimental test and numerical calculation. The research results show that the temperature rise of wheel and rail is quick in the initial sliding contact stage, then gradually slows down. The temperature of wheel is higher than that of rail at the same depth from the contact surface. In the initial sliding stage, the wheel temperature rises faster than the rail temperature, which is related to the size of contact surface and the concentration degree of friction heat. Moreover, the results of this paper show that the temperature values of the rail/wheel obtained through experimental test and numerical calculation are in good agreement. The experimental and numerical calculation methods used in this article can be adopted to analyze the contact problems of other sliding friction pairs. [ABSTRACT FROM AUTHOR]

New demands placed on industry make it necessary to improve design, real-time monitoring and failure prediction methods for rolling bearings. This paper presents an approach for assessing how contact surface damage affects the vibration response of rolling bearings and how vibration-based monitoring shows the damage level of rolling element bearings. A new parameter named the damage factor is introduced to quantify the vibration response of rolling bearings. The analytical–numerical method for calculation of this parameter is developed based on nonlinear dynamics postulates. The developed method for damage factor calculation is tested on a particular type of radial deep groove ball bearing, and an experimental verification is performed, showing a maximum deviation of 7% in the results. The conclusions drawn from the obtained results and the potential contributions of the introduced parameters for rolling bearing design are discussed. The chosen polynomial function keeps deviations in relation to the calculated damage factor within 3% for failed areas of different sizes. [ABSTRACT FROM AUTHOR]

Next generation rolls such as super-cermet rolls and all-ceramic rolls can be only manufactured as sleeve rolls, although the circumferential slippage appears at the shrink-fit interface. In this study, the fatigue strength of the sleeve roll is evaluated by applying the load shifting method on the fixed roll to realize the local slip accumulation during roll rotation. The simulation shows that the fatigue-inducing stress amplitude remains constant although the accumulated slip amount increases. Based on those results, the fatigue strength of standard rolling rolls is estimated considering the slip defect. The defect dimension can be characterized by the root area parameter and the value area =1254 μ m can be estimated from smaller roll experimental results and the previous report for larger diameter sleeve rolls. The results show that in the absence of slip damage, the fatigue strength of sleeve rolls is not much lower than that of solid rolls without shrink-fit. [ABSTRACT FROM AUTHOR]

The ANSYS finite element software is introduced to simulate the cooling efficiency and thermal conductivity of the internal structure of the roll to study the influence of cooling water temperature, flow rate and aluminum melt on the roll temperature field and thermal conductivity. The research results show that in the process of casting and rolling, the aluminum melt is in contact with the rolls in the casting and rolling area, where the maximum temperature of the rolls is 520 °C. The temperature of the roll is gradually reduced to 40 °C, and then the roll continues to rotate until it enters the casting and rolling area, and the cycle is repeated. The reduction of the cooling water temperature could not significantly improve the roll temperature field. The increase of the cooling water flow rate can reduce the temperature field of the cooling water channel in the roll core. The temperature of aluminum melt at the exit of the casting nozzle can significantly increase the temperature field of the roll and the rolling temperature of the aluminum melt at the center of the roll gap, but it does not affect the temperature distribution at the exit of the roll gap after the aluminum melt is cooled by the roll. [ABSTRACT FROM AUTHOR]

Cetaceans are known for their intelligence and display of complex behaviours including object use. For example, bowhead whales (Balaena mysticetus) are known to rub on rocks and some humpback whale (Megaptera novaeangliae) populations undertake lateral bottom feeding. Such underwater behaviour is difficult to observe but can play a critical role in the whales' survival and well-being. Distinguishing social behaviours from those which serve a specific function remains challenging due to a lack of direct observations and detailed descriptions of such behaviours. A CATS (Customized Animal Tracking Solutions) suction cup tag with on board video and a 3D inertial measurement unit was deployed on three different humpback whales to assess their behaviour in the Gold Coast bay, Australia. Here, we present evidence of humpback whales (tagged and untagged individuals) performing bottom contact with prolonged rolling on sandy substrate. In addition, we showed that fish were actively feeding from the whales' skin during this behaviour. We detail the behaviour and discuss possible drivers, with a focus on cetacean innovation, possible ectoparasite removal, and habitat preferences. [ABSTRACT FROM AUTHOR]

False brinelling is a type of fretting wear that occurs in rolling bearings when the contacts of bearing rings and rolling elements are subjected to small-amplitude oscillatory motion. It manifests itself as deep craters with relatively polished bottoms that are evenly spaced around the bearing rings. This work investigates the influence of lubricant properties and contact conditions, including oil viscosity, applied load, and amplitude and frequency of oscillations, on the onset and progression of false brinelling damage. Experiments were conducted with AISI 52100 bearing steel specimens in a ball-on-flat configuration under small-amplitude oscillating conditions. A set of base oils and a group of custom-made greases with systematically varying properties were employed. Importantly, the same ball-on-flat setup was adapted to allow optical access to the contact by employing a sapphire disc instead of a steel one. This allowed direct observation of the damage onset and progression to better elucidate the mechanisms taking place. Additional experiments were conducted with the same lubricants on a thrust ball bearing rig and the observed trends were compared to those from the ball-on-disc setup. Results show that false brinelling damage initiates locally at discrete asperity microcontacts and then spreads relatively quickly with continued rubbing to cover the whole contact area. Oscillation amplitudes shorter than the Hertz contact width (A/D < 1) were shown to be most damaging, while the damage reduces drastically for amplitudes larger than the Hertz contact width (A/D > 1). For the more important case of A/D < 1, oils and greases with lower viscosities produced less damage. Oils in general produced somewhat less damage than the equivalent lithium- or urea-thickened greases with the same base oil. Lower oscillation frequencies and lower contact pressures also produced less damage. The corresponding friction and electrical contact resistance measurements indicate that under these conditions of A/D < 1 the contact operates under boundary lubrication at best but can intermittently approach effectively dry conditions, depending on lubricant properties and applied conditions. These observations indicate that the key variable that controls damage when the oscillation amplitude is less than the contact width is the ability of the lubricant to penetrate and remain in the oscillating contact. Therefore, lubricant properties and contact conditions that promote this penetration, which may be different from those that promote hydrodynamic film formation, can mitigate against false brinelling. [ABSTRACT FROM AUTHOR]

A multiscale approach for the fatigue life estimation of rolling bearings is presented in this paper and applied to inner rings of cylindrical roller bearings of the type NU208. The forces acting in the rolling contact are determined from system-oriented modeling at the macro level. The microscale contact simulations are carried out in a half-space contact model. The stresses on the inner ring are determined and used in the local fatigue approach, according to Fatemi–Socie, for fatigue life estimation. Four surface variants were investigated, one ideally smooth surface and three real (rough) surfaces. The three rough surface variants used different finishing processes: fine ground, hard turned, and rough ground were produced. A load case with a maximum pressure of 2.4 GPa in the roller-inner ring contact was investigated. In addition to the fatigue life estimation, the plasticity behavior (surface topography, resulting contact pressure, and residual stress) of the three manufactured surfaces stood in the focus of the work. As the comparison between experimental and simulated results confirms, good predictions can be made with the simulation model. [ABSTRACT FROM AUTHOR]

Grease-lubricated rolling element bearings can suffer from wear due to lubricant starvation under certain oscillating operating conditions. Especially for large-scale slewing bearings, such as blade bearings in wind turbines, experimental investigations are complex compared to small-scale reference testing. For an easier manner of testing, it is desirable to know whether the results of small-scale testing are applicable to larger-sized bearings. In this work, three different bearing types were tested and compared to already published results from a small-scale ACBB with a pitch diameter of 60 mm. The newly tested bearing types comprise a downscaled blade bearing (4-point contact double row ball bearing) with a pitch diameter of 673 mm, a small-scale CRTB with a pitch diameter of 77.5 mm and another ACBB with a pitch diameter of 95 mm. Qualitatively, all tested bearings show similar wear behaviour in terms of friction energy when operation parameters are varied. With higher oscillation frequency, damage becomes more severe. The oscillation amplitude shows three distinctive regimes. Within the range of small amplitudes, an increase in amplitude leads to more pronounced damage. We observe a threshold amplitude where this is no longer the case; a further increase in amplitude counteracts wear initiation until a final threshold is reached, beyond which no more wear is observed. These findings are in accordance with the reference results of the small-scale ACBB. Direct comparison between point and line contact shows that the latter is more prone to wear initiation under grease-lubricated, oscillating operating conditions. Furthermore, a previously introduced empirical number shows good performance in assessing critical operating parameters of the different bearing types. Specifically, harmful operating conditions can be classified for all studied bearing types with an accuracy of 78%. This method can be useful to assess operating conditions of greased, oscillating, rolling element bearings, e.g., to assess different pitch controllers or designs of slewing bearings. [ABSTRACT FROM AUTHOR]

The tribological contact between raceways and rolling elements is essential for rolling bearing performance and lifetime. The geometrical description of these contacts is well known and can be used in several mechanical simulation tools. The material description, especially of the near-surface volume after interaction with lubricants, is not as simple. In particular, the Schaeffler FE8-25 test with cylindrical roller thrust bearings exhibits different failure modes depending on the lubricant chemistry. The main failure mechanisms of this test are sub-surface fatigue damage due to WECs (White Etching Cracks) and/or surface-induced fatigue damage (SIF). The harsh test conditions with mixed friction at high speeds and multiple slip conditions over the raceway width additionally provides different tribological conditions on a small area. This leads finally to the formation of certain tribological layers on the raceway because of the interaction of the surface with the lubricant chemistry under local frictional energies, which are worth investigating. The characterization of the layers was performed by the two less time-consuming, spatially resolved analysis methods of µXRF and ATR FTIR microscopy adapted by Schaeffler. This paper shows the results of this research and offers new approaches to optimizing rolling bearing testing and predicting the risk of early failures. [ABSTRACT FROM AUTHOR]

Increasingly restricted availability and environmental impact of mineral oils have boosted the interest in sustainable lubrication. In this study, the thickening properties of sodium carboxymethyl celluloses (CMCs) were investigated in order to assess their potential as viscosity modifiers in aqueous gear and bearing fluids. The pressure, temperature and shear dependence of viscosity was studied at different concentrations and molecular weights M W . The tribological properties were investigated at different viscosity grades in both sliding and rolling contact, and compared to rapeseed oil and polyethylene glycol 400. The viscosity of the CMC solutions was adjustable to all application-relevant viscosity grades. Viscosity indices were similar or higher compared to the reference fluids and mineral oil. Temporary and permanent viscosity losses increased with M W . Permanent viscosity loss was highest for high M W derivatives, up to 70%. The pressure-viscosity coefficients α were low and showed a high dependency on shear and concentration. In rolling contact, low M W CMC showed up to 35% lower friction values compared to high M W , whereas no improvement of lubricating properties was observed in sliding contact. The results suggest that low M W CMC has great potential as bio-based thickener in aqueous lubrication. [ABSTRACT FROM AUTHOR]

10.3390/lubricants11040164 8 Holweger W., Bobbio L., Mo Z., Fliege J., Goerlach B., Simon B. A Validated Computational Study of Lubricants under White Etching Crack Conditions Exposed to Electrical Fields. Lubricants have taken a leading role as drive- train system components in recent years, mainly attributed to their viscosity as a quality criterion. 10.1007/s11426-021-1089-6 4 Holweger W., Bobbio L., Mo Z., Fliege J., Goerlach B., Simon B. A Computational Study on the Role of Lubricants under Boundary Lubrication. [Extracted from the article]

Aiming at the problem of low control accuracy caused by nonlinear disturbances in the operation of the PLS-160 wheel–rail adhesion test rig, a linear active disturbance rejection controller (LADRC) suitable for the wheel–rail adhesion test rig was designed. The influence of nonlinear disturbances during the operation of the test rig on the control accuracy was analyzed based on SIMPACK. The SIMAT co-simulation platform was established to verify the control performance of the LADRC designed in this paper. The simulation results show that the speed and creepage errors of the test rig under the control of the LADRC met the adhesion test technical indicators under four different conditions. Compared with the traditional PID controller, the creepage overshoot and response time with the LADRC were reduced by 1.27% and 60%, respectively, under the constant creepage condition, and the stability recovery time was shorter under the condition of a sudden decrease in the adhesion coefficient. The LADRC designed in this paper shows better dynamic and anti-interference performance; therefore, it is more suitable for a follow-up study of the PLS-160 wheel–rail adhesion test rig. [ABSTRACT FROM AUTHOR]

With the increasing applications of the planetary roller screw mechanism (PRSM) in mechanical systems particularly machine tools, a comprehensive mathematical model is required to define the kinematic characteristics and relations of the PRSM, such that its performances can be predicted for reliability analysis and design of machine tools. In this paper, the influences of machining and assembly errors on the motion characteristics of the PRSM are analyzed, and the kinematic model of the PRSM is established considering runout errors and elastic deformation. The planetary roller screw mechanism can be considered as a spring-mass system for analysis of the elastic deformation of the ball screw's thread under inertial force. For the spring-mass system, adjacency matrix is introduced to define the relationships between the elastic displacements of the joints and the deformations of the elements. Then, by considering the balance of force and the coordination of deformation, the nonlinear motion model of the double-nut roller screw is established. The effectiveness of the proposed model is verified by comparing the analytical results with the experimental data. [ABSTRACT FROM AUTHOR]

Radial clearance critically affects journal bearing performance, specifically the lubrication performance. This study investigates the lubrication characteristics of a journal bearing with adjustable radial clearance and compares the dynamic behavior of the bearing under laminar and turbulent flow regimes. The adjustable bearing exhibits two states of oil film pressure at different radial clearances. When the radial clearance is reduced from 100%cr to 80%cr, the oil film pressure is present only on the lower bearing bush; after being reduced to 70%cr, the upper bearing bush achieves effective lubrication; and after reduction from 70%cr to 30%cr, the oil film pressure increases more than six-fold. The turbulent flow model of the clearance adjustable bearing is then established considering the lubricant flow state, and the turbulence correction factors for different flow states are calculated. The journal bearing exhibits better lubrication characteristics under laminar than under turbulent flow conditions, and in some operating conditions, the stable velocity range calculated according to laminar flow theory may become unstable in turbulent flow conditions. Therefore, applying turbulence assumptions to design the operating speed range of rotating machinery under such conditions yields a greater safety threshold, which can reduce the risk of instability. The stability of the rotor bearing system is closely related to the radial clearance, and reducing the radial clearance will improve the stability of the system. In the turbulent flow state, the oil film pressure changes drastically, thus reducing the system stability. Moreover, the larger the radial clearance of the bearing, the more prominent the turbulence effect. Thus, reducing the bearing clearance prevents drastic changes in oil film pressure and improves the stability of the system. [ABSTRACT FROM AUTHOR]

This investigation integrates an alternative fully-parameterized approximation of nonlinear wheel/rail interaction into a simplified vehicle model, and a two-parameter Hopf bifurcation analysis is conducted to reveal the influence of the wheel/rail contact geometry and secondary suspension parameters for high-speed rail vehicles. The bifurcation diagram is compared among the 6 DOFs bogie model, linear and nonlinear 7 DOFs vehicle model, nonlinear 17 DOFs vehicle model, and 3D full DOFs vehicle model. It shows that the nonlinear 7 DOFs vehicle model can meet the requirement of both carbody hunting and bogie hunting simulations. 6 DOFs bogie model can only be used in bogie hunting bifurcation analysis. Linear vehicle model would bring errors in either critical speed or limit circle magnitude. The divergences in the linear terms of rolling radius and contact angle polynomials are significant enough in field operation to cause a noticeable difference in Hopf bifurcation speed. Attention shall be paid to the shape of equivalent conicity and contact angle curve. The crucial parameters to the Hopf bifurcation include the series stiffness and damping coefficient of the yaw damper and the lateral damper damping. However, the requirement of suspension parameters for stability can conflict in carbody hunting and bogie hunting cases. [ABSTRACT FROM AUTHOR]

This research paper reviews the recent works on the rolling contact fatigue of rail wheels. The topic covered includes the mathematics equations of rail-wheel contact stress and fatigue, RCF defects in the rail, the development of cracks, and the strategies used to reduce the rate of RCF defects. Therefore, the main understandings of RCF as they currently stand are crucial for the improvement and mitigation on rail fatigue failures in the future. This research paper has not been published yet and has not been discussed yet by the Malaysia Railway Network. [ABSTRACT FROM AUTHOR]