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Load distribution is a very important indicator that has a great effect on bearing service performance. Unreasonable load distribution is likely to accelerate the bearing failures. The dynamic effects of the moving parts of the rolling bearing have significant influence on the load distribution. In order to study the load distribution of rolling bearings, the dynamic interaction between raceways and balls is considered in detail and a dynamic model of ball bearings subjected to radial loads is presented. The results of the proposed model are compared with those of the traditional static model and the quasi‐static model. The dynamic load coefficient and the dynamic angular extent coefficient are defined to show the characteristics of the dynamic load distribution. The effects of radial clearance, the radial load, and the rotational speed on the dynamic load distribution are studied. Through the above research, this paper concludes that the load distribution is greatly influenced by the dynamic effects of moving parts, especially under the conditions of large clearance, light load, or high speed. [ABSTRACT FROM AUTHOR]

ABSTRACT Full‐ceramic bearings possess numerous exceptional attributes, such as enhanced rigidity and superior resistance to wear. Nevertheless, full‐ceramic bearings consistently encounter elevated temperatures for extended periods of high‐speed operation, which easily affect the processing performance of the equipment. Lubrication viscosity has a significant effect on bearing heat generation, so it is meaningful to approach the effect of lubrication viscosity with respect to the dynamics of full‐ceramic bearings. Full‐ceramic angular contact ball bearings are treated as research objects to analyse their optimal working condition in this article. A coupled fluid–solid simulation model is constructed for analysis of the fluid and solid in the bearing cavity. First, at the conditions of different lubricant viscosity, the oil volume distribution, temperature field distribution in the bearing cavity is analysed. Then, the vibration characteristics of the inner ring is examined by constructing a dynamic model of the inner ring. Meanwhile, temperature and vibration variation of full‐ceramic bearings are verified through experiments under different rotational speeds. The results show that the lubricant volume distribution inside the bearing cavity is nonuniformly distributed, which the lubricant is mainly located in the outer ring groove position. Moreover, elevating the lubricant viscosity within a certain range promotes the enhancement of bearing lubrication properties. The maximum error of the bearing temperature between the simulation results and the experiment is 7.592%. Ultimately, the simulation analysis is validated through experiments, and it provides a theoretical foundation for selecting optimal parameters for the oil–air lubrication of full‐ceramic bearing. [ABSTRACT FROM AUTHOR]

Copyright of Automotive Engineer (1674-6546) is the property of Auto 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.)

The problem of estimation the friction torque in operating miniature ball bearings lubricated with oil or grease is a complex one. Generally, in an angular contact ball bearing (ACBB), various types of losses can appear including losses caused by kinematics in ball-race contacts (rolling, sliding and pivoting), losses between the cage and the balls and between the cage and the guiding race and losses generated by lubricant, especially at high speeds. In the miniature ACBB, the applied loads have generally low values, and some losses can be ignored. In these circumstances, the most important contribution to the increase in the losses in miniature ACBB is the presence of the lubricant. In normal rolling bearings, the lubricant has an important contribution to decrease the losses and increase the reliability in miniature ball bearing; the lubricant (oil or grease) leads to the increase in the losses compared to the dry or limit lubrication conditions. The catalogues of various rolling bearing companies have not provided more details referring to the friction losses in miniature ball bearings. In order to evaluate the total friction torque in the rolling bearings, some empirical complex relations are presented via the SKF methodology, which can be applied only to moderate and high loads applied to the rolling bearings. Other empirical relations are presented by the Schaeffler catalogue. Based on previous experiments, the authors determined the friction torque in a 7000C ACBB with the spin-down method. The experimental results were correlated with the results obtained via the theoretical model developed by Houpert for IVR lubrication conditions. The theoretical results evidenced that the hydrodynamic rolling resistance generated by the lubricant is the most important component of the friction torque for 7000C ACBB. The experimental and theoretical results were compared to the results obtained according to the SKF and Schaeffler relations. The experimental results and the results obtained with the Houpert model generally had higher values compared to the results obtained with the SKF and Schaeffler relations. [ABSTRACT FROM AUTHOR]

During the heat treatment process, bearing rings are subjected to drastic temperature variability and complex microstructural evolution, which result in deformation, high residual stresses, operational instability and a limited operating life. However, the underlying relationship between temperature, phase transformation, and deformation has not been fully revealed in previous research. As a result, it is difficult to accurately control the roundness of bearing rings during the heat treatment process. Therefore, a combination of numerical simulations and experimental methods was employed to analyze the heat treatment process of the rings of angular-contact ball bearings (ACBB) (7008C). Firstly, according to the multiple coupling theory of thermal, phase-transition, and stress–strain fields, a model for the numerical simulation of the quenching and tempering process was established. Secondly, the thermal–physical properties of the material were calculated using the Jmatpro 7.0 software, and the quenching and tempering processes were numerically simulated using the Deform software. Subsequently, the evolution of the stress, phase-transformation, and deformation behaviors of bearing rings during the quenching and tempering were studied in detail. Finally, the roundness errors of the bearing rings were obtained by a coordinate-measuring machine (CMM). The results showed that the axial and radial stress distributions at the surface and center of the bearing rings were significantly different. The bearing rings experienced uneven expansion and deformation. The roundness errors of the inner diameter and outer diameter of the inner ring were 0.0386 mm and 0.0423 mm, respectively. The roundness errors of the inner diameter and outer diameter of the outer ring were 0.0202 mm and 0.0180 mm, respectively. In this study, the mechanism of the effect of the temperature variation and phase transformation on deformation during the quenching and tempering process was revealed in detail. This provides a reference for controlling the roundness of bearing rings in actual production processes. [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.)

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.)

Bearing is the core component of high‐speed rotating machinery. However, the lubricating oil plays an important role in reducing the temperature and the collision between components. It can improve the performance of the bearing under high‐speed rotation. Therefore, based on the theory of oil‐air two‐phase flow, this paper establishes a numerical analysis flow‐heat model of ball bearing under different oil supply. At the same time, the vibration is calculated. The influence of internal oil‐air field and thermal characteristics on vibration is analyzed. The results show that the volume of oil is not uniformly distributed in the bearing chamber. The oil gradually decreases from the outer ring to the inner ring. It is mainly concentrated on the oil‐air inlet. With the increasing of oil supply speed, the temperature of the bearing decreases firstly and then increases, and there is an optimal oil supply speed. The inner ring vibration velocity is basically similar to the temperature trend. Meanwhile, the lowest temperature is mainly concentrated near the oil‐air inlet. The maximum error between simulation results and experimental results is 11.37%. Finally, the reliability of the simulation analysis is verified by the temperature and vibration experiment. It provides some theoretical support for the optimization of oil‐air lubrication parameters of angular contact ball bearings. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this research work is to find an onboard, non-destructive technique which can be correlated directly with the level of wear resistance using vibration signature analysis. Method: Five ball bearings (Model: 6205) and standard specimens were electroplated with five different coatings with unique level of wear resistance. The wear resistance of the standard specimens was measured using Pin-on-disk apparatus and presented in ascending order: Black oxide, Silver, Copper, Zinc phosphate (ZnP) and Nickel respectively. The coated bearings were made to run in customised bearing test rig at five different speeds ranging between 300 rpm to 1500 rpm and vibration signatures were recorded. The acquired signals were decomposed into six modes using Variational mode decomposition (VMD) for band wise statistical analysis by calculating RMS, Crest factor, Variance, Skewness, Kurtosis, Shannon entropy and Log energy, to develop correlation with the level of wear resistance. Results: All the six bands were analysed by calculating the statistical parameters in reference to different level of wear resistance. Significant variation in variance, log energy and Shannon entropy was found at one of the six bands at all speeds except 900 RPM. With the variation in wear resistance, the corresponding change in responded statistical parameters was found in low energy bands generated by the VMD, which signifies low impact of wear resistance variation on signal's energy. On further analysis using chain indexing, Shannon entropy and log energy were found to be most relevant parameters at low and high rpm respectively. Conclusion: The given technique found to be useful to monitor the wear resistance level of bearing surface, while bearing is in running condition. Therefore, surface defects due to variation in wear resistance can be notified at very incipient stage by carrying out statistical analysis of vibration signature after decomposing the signal up to sixth level using Variational mode decomposition method. [ABSTRACT FROM AUTHOR]

The rolling bearing is a vital part used in different rotating electrical devices. Detecting defects in bearings is crucial for the safe operation of these machines. However, it is challenging to use Deep Learning techniques to identify bearing defects when the machine is not under load. To resolve this issue, this paper presents the Constant-Q Non-stationary Gabor Transform with enhanced Inception ResNet-V2, proposed for the early-stage classification of ball bearing faults in induction motors. The proposed model obtained the vibration images, i.e. time-frequency images of unfiltered vibration signals from the laboratory experimental setup. These images are applied to the proposed model, which classifies the ball bearing faults under various load conditions while adjusting its hyperparameter values instead of employing default ones. Furthermore, the model underwent training using k-fold method to assess its resilience with the use of optimal values obtained from hyperparameter tuning. The model is evaluated by performance metrics like F1-score, Recall, Precision, Confusion Matrix and Training time. The proposed model accomplished an average classification accuracy of 99.84% in low load and full load conditions within a few epochs. Ultimately, when compared to Inception-V4 and ResNet-50, which achieved 91.41% and 91.65%, respectively, the experimental findings unambiguously demonstrate the superior performance of the proposed model over both models. [ABSTRACT FROM AUTHOR]

The starved lubrication caused by long-term operation of deep groove ball bearing (DGBB) will change the interaction between components, causing changes in the vibration characteristics of bearing with local defect in rolling element (RE), which is not conducive to accurate identification of bearing fault. In this paper, starved lubrication condition was quantified by relying on lubricant flow rate, and the bearing motion equation by introducing the RE local defect model was established. The results indicated that the degree of starved lubrication increased, the thickness of the oil film decreased, and the lubrication condition of the bearing deteriorated. The contact force and friction between RE and the raceway increased, and the increased friction suppressed the sliding effect of the bearing, manifested as a decrease in the sliding speed between RE and the raceway and an increase in the speed of the cage. Meanwhile, the vibration characteristic frequency of bearing with RE defect increased and approached the theoretical value, but still differed from the theoretical value. The research results provide reference for the fault identification technology of DGBB, which requires identifying bearing fault characteristics based on actual lubrication conditions. [ABSTRACT FROM AUTHOR]

Understanding the contact behaviour of slewing-ring thrust ball bearings is essential for accurate predictions of load distribution and evaluations of static and dynamic load capacity. Applying Hertz's theory to non-standard slewing ring bearings presents unique challenges due to their complex geometries and difficulties in achieving uniform surface finishes, leading to significant deviations from actual stress. This study addresses these limitations by comparing experimental results, numerical results, and the Hertz theory. The analysis considers three Hertz contact configurations between the bearing ball and the raceway. The results reveal significant deviations from the experimental values. To determine the cause of these variations, the friction coefficient between the ball and the raceway is determined using the gravitational method by varying the number of balls. Uneven load distribution across balls in slewing ring bearings under mechanical loads is exposed by friction coefficient measurement. To further explore, load-deformation experiments are conducted on the LMMB by placing varying numbers of balls and their positions. Results expose variations in load-taking behaviour among the balls, emphasizing the critical influence of contact area load distribution. [ABSTRACT FROM AUTHOR]

Bearing failures in electrical machines pose significant challenges, attracting attention in diagnostic research. The widespread adoption of variable-speed drives across various motor applications has increased the effects of bearing currents, necessitating thorough exploration in both academic and industrial contexts. The paper contributes valuable insights into identifying and addressing bearing-related issues in electrical machines. It comprehensively investigates the matter, investigating damage types and diagnostic techniques specific to bearing currents in induction machines. Moreover, it provides insights from experiments conducted in controlled laboratory settings to replicate bearing current faults. As the industry integrates advanced technologies into manufacturing processes and gains traction, preventive maintenance is increasingly emphasized. Consequently, the paper expands its investigation into signal pre-processing to enhance fault prediction accuracy by optimizing machine signals. Given the dynamic nature of industrial standards and the growing demand for predictive maintenance strategies, this research presents a predictive method for early fault detection. Aiming for heightened efficiency, reduced downtime, and enhanced reliability, the perspectives outlined in this paper make a meaningful contribution to the evolving field of predictive maintenance. [ABSTRACT FROM AUTHOR]

A nonlinear dynamic model of angular contact ball bearing under combined external loads is established based on the nonlinear elastic Hertz contact theory and raceless control theory. The established dynamic model is solved by employing variable step size Newton Raphson iteration method and the validation of model is verified by comparing the proposed results with the corresponding results come from the existing literatures. The solution of the presented model has high accuracy compared with the existing experimental results. In addition, the computational efficiency of the proposed model is improved significantly by introducing iteration step size adjustment factor. According to the proposed model, the dynamic contact and stiffness characteristics of angular contact ball are studied systematically by investigating the effects of combined external load working conditions on the contact parameters including contact angle and contact force and the stiffness parameters including diagonal stiffness and off-diagonal stiffness. This research can provide the theoretical basis and technique guidance for the designation and manufacture of angular contact ball bearing under combined external loads. [ABSTRACT FROM AUTHOR]

The effect of particle shape on micro and macroscopic behaviour is investigated experimentally through a series of biaxial compression tests on round and angular rods. Dual-size assemblies of thousands of circular (round) or hexagonal (angular) particles were sheared under three confining pressures. The displacement, rotation and evolution of coordination number of all the particles during the shearing process were identified through image analysis. The macroscopic results show that the angular assemblies exhibit higher strengths and dilations. Angular particles tend to be more dilative and have higher critical state strengths. The microscale features show that the magnitude of particles' rotation is higher in circular assemblies. Particle rotations are normally distributed within both samples. However, rotating clusters are observed in angular samples. Angular particles are more resistant to rotations due to interlocking and clustering, causing higher strength at the macroscale. The absolute mean cumulative rotation for the circular assemblies at the end of shearing was approximately twice that of the angular assemblies. In circular assemblies, small particles rotate almost twice as much as big particles, which initiates a ball-bearing effect that further contributes to strength reduction. Particle rotation further governs the average coordination number, with hexagonal aggregates having higher coordination numbers. [ABSTRACT FROM AUTHOR]

Deep groove ball bearings (DGBBs) are extensively utilized in industrial machinery, mechanical systems, and household appliances due to their simple design, low maintenance, and ability to operate at high speeds. A critical issue in the performance of these bearings is the power loss by internal friction torque, which adversely affects system efficiency, longevity, and reliability, particularly in demanding applications such as aviation and marine systems. The friction torque in DGBBs is influenced by factors such as load, speed, surface roughness, and lubricant viscosity, making the precise understanding of these elements essential for optimizing system efficiency. Despite its significance, the effect of surface roughness on friction torque in DGBBs remains underexplored. This paper presents an analytical model to evaluate the frictional moments resulting from interactions between the ball–race and ball–cage in lubricated, low-speed DGBBs. This model employs a mixed elastohydrodynamic lubrication approach to determine the friction coefficient at the contact interfaces. This study explores how surface roughness and speed affect both ball–race and ball–cage friction torque, offering a comprehensive analysis of their influence on overall frictional torque. Additionally, the effect of surface roughness on ball–cage contact forces is investigated, enhancing the understanding of its contribution to friction torque. These insights aim to improve DGBB design and operation, maximizing performance and energy efficiency. [ABSTRACT FROM AUTHOR]

This article presents a general numerical method to establish a mathematical model of a bearing–rotor–disk system. This mathematical model consists of two double-row angular contact ball bearings (DRACBBs), a rotor and a rigid disk. The mathematical model of the DRACBB is built on the basis of elastic Hertz contact by adopting the Newton Raphson iteration method, and three different structure forms are taken into account. The rotor is modeled by employing a finite element method in conjunction with Timoshenko beam theory, and the rigid disk is modeled by applying the lumped parameter method. The mathematical model of the bearing–rotor–disk system is constructed by the coupling of the bearing, rotor and disk, and the dynamic response of the bearing–rotor–disk system can be solved by employing the Newmark-β method. The validation of the above mathematical model is demonstrated by comparing the proposed results with the results from the existing literature and finite element software. The dynamic characteristics of the DRACBBs and the dynamic response of the bearing–rotor–disk system are investigated by parametric study. A dynamic characteristic analysis of the DRACBB is conducted to ensure the optimal structure form of the DRACBB under complex external loads, and it can provide a reference for the selection of the structural forms of DRACBBs. [ABSTRACT FROM AUTHOR]

In this paper, the lubrication flow field model for an angular contact ball bearing considering the characteristics of the nozzle position was constructed with CFD methods, and the simulation results were compared and validated with the test results. The research was carried out on the lubricant distribution characteristics in the bearing cavity under different nozzle angles and heights, and the nozzle position was optimized with the response surface methodology. The results show that the lubrication distribution characteristics in the bearing cavity are closely related to the nozzle angle and height. The weighted average of the oil phase volume fraction on the cage guiding surface decreases first and then increases with the increase of the nozzle height and decreases with the increase of the nozzle angle on the ball surface. The optimal nozzle position was determined by finding the maximum value of the regression function in the specified area. [ABSTRACT FROM AUTHOR]

In response to vibration problems caused by unbalanced faults in multi-disk rotor systems of compressors, this research study proposes a new type of integral damping bearing (IDB) with an integral structure and better damping performance. The IDB's stiffness and damping coefficients were acquired through computational fluid dynamics (CFD) analysis. When the IDB was applied to a multi-disk rotor system, the analysis results show that it effectively lowered the bending stress and strain energy of the shaft and enhanced the stability of the system. The bending stress was reduced from 45 MPa (with traditional ball bearings) to 8.63 MPa (with the IDB). By using the IDB, the strain energy borne by the shaft and bearing was only 10.44%. Subsequently, experimental research was conducted on the suppression of unbalanced vibration by using the IDB under various working conditions. The peak amplitude of the rotor system with the IDB was reduced by 19.94%, and the amplitude at the 1X frequency was reduced by 32.73% compared with ball bearings. The experimental results indicate that the IDB can efficiently dampen the vibration of the rotor system. And it was found that the IDB has stable vibration reduction performance under various working conditions. [ABSTRACT FROM AUTHOR]

Bearings are vital components in machinery, and their malfunction can result in equipment damage and reduced productivity. As a result, considerable research attention has been directed toward the early detection of bearing faults. With recent rapid advancements in machine learning algorithms, there is increasing interest in proactively diagnosing bearing faults by analyzing signals obtained from bearings. Although numerous studies have introduced machine learning methods for bearing fault diagnosis, the high costs associated with sensors and data acquisition devices limit their practical application in industrial environments. Additionally, research aimed at identifying the root causes of faults through diagnostic algorithms has progressed relatively slowly. This study proposes a cost-effective monitoring system to improve economic feasibility. Its primary benefits include significant cost savings compared to traditional high-priced equipment, along with versatility and ease of installation, enabling straightforward attachment and removal. The system collects data by measuring the vibrations of both normal and faulty bearings under various operating conditions on a test bed. Using these data, a deep neural network is trained to enable real-time feature extraction and classification of bearing conditions. Furthermore, an explainable AI technique is applied to extract key feature values identified by the fault classification algorithm, providing a method to support the analysis of fault causes. [ABSTRACT FROM AUTHOR]

The aim of this paper is to develop a mathematical model for an unconventional worm gear consisting of a globoid worm and a worm wheel where the teeth are bearings. Using rolling elements such the teeth of the worm wheel (ball bearings) transforms the sliding friction to rolling friction during the process of worm gear meshing, improving power. The geometry of the component elements of the gear is analyzed in correlation with its kinematics. After the creation of the mathematical model, it is validated both analytically (through complex graphic representations) and experimentally (by creating, for a particular case, the 3D model and the concrete physical model (prototype) of the gear through 3D printing). [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION 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.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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: This paper aims to study the problem of starvation lubrication of high-speed ball bearings due to temperature rise during operation and to avoid thermal failure of bearing lubrication. Design/methodology/approach: Under the quasi-statics model of grease lubrication, both the oil film dragging force and the rolling friction between the balls and raceways collectively counteract the gyroscopic torque. Initially, the static model for grease lubrication is solved, followed by calculating the generated heat using the local heat generation method and ultimately the multinodal thermal network model is solved, and the solved results of the quasi-statics are updated by the temperatures of the grease nodes based on the relationship of the grease temperature and viscosity, as well as the relationship of the viscosity and the film thickness. Findings: By comparing the numerical calculation results of bearings under different working conditions, the influence of starvation lubrication on the oil film thickness, oil film drag force and rolling friction of bearings is discussed, and it is found that the numerical calculation results of the outer ring temperature of bearings under the starvation lubrication due to the consideration of temperature rise are closer to the experimental values. Originality/value: This study reveals the dynamic characteristics of bearings under starvation lubrication, which is more practical and engineering guiding significance for the design of bearings, and introduces a new method and basis for the calculation of temperature rise of rolling bearings. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0208/ [ABSTRACT FROM AUTHOR]

This study investigates the power losses of rolling element bearings (REBs) lubricated using an oil bath. Experimental tests conducted on two different deep-groove ball bearings (DGBBs) provide valuable insights into the behaviour of DGBBs under different oil levels, generating essential data for developing accurate models of power losses. Observations of the oil bath dynamics reveal the formation of an oil ring at high oil levels, as observed for planetary gear trains, leading to modifications in the oil flow behaviour. The experiments demonstrate that oil bath lubrication generates power losses comparable to injection lubrication when the oil level is low. However, as the oil level increases, so do the power losses due to increased drag within the bearing. This study presents a comprehensive model for calculating drag losses. The proposed drag power loss model accounts for variations in oil level and significantly improves loss predictions. A comparison of existing models with the experimental results shows good agreement for both bearings, demonstrating the effectiveness of the developed model in accounting for oil bath height in loss calculations. [ABSTRACT FROM AUTHOR]

When a high-speed rolling bearing cage comes into contact with rollers, it experiences random movement due to friction and collision, which significantly impacts the overall performance of the bearing. To further investigate the motion law of cages, a test bench for a 7010C angular-contact bearing cage was constructed. This setup utilized laser sensors to obtain changes in attitude and displacement during operation. After analyzing how cage deflection errors influenced trajectory measurements, corrections were applied to the measurement results. Additionally, an investigation was conducted into the effects of varying rotational speeds on the dynamic performance of the cage. Simulations were performed using ADAMS software, which verified both the effectiveness of the measuring method and the testing results. The findings indicated that within the tested range of rotational speeds, the centroid trajectory stability of the cage gradually improved as rotational speed increased and then began to show a tendency to deteriorate. Furthermore, there existed a negative correlation between the deflection error of the cage and the centroid trajectory stability. [ABSTRACT FROM AUTHOR]

To investigate four-point contact ball slewing bearings, a bearing support bolt-integrated model was created with HyperMesh and ANSYS software, and its accuracy was theoretically confirmed. This study examines how the rolling element number Z, contact angle α, bolt number N, bolt pre-tightening force coefficient P, and radial load-overturning moment angle θ affect the comprehensive performance of four-point contact ball slewing bearings and connecting bolts. The study found that increasing Z, α, N, P, and θ reduces overall bearing, ring, rolling element, and contact load deformations. The maximum deformation and stress of bolts rise with P but decrease with Z, α, N, and θ. The degree of influence of each parameter on the deformation of the inner and outer rings, the deformation of the rolling element, and the contact load of the rolling body from large to small is ranked as follows: α, N, Z, θ, and P; the degree of influence on bolt deformation and bolt stress distribution uniformity from large to small is ranked as follows: N, α, Z, θ, and P; the degree of influence on the overall deformation of the bearing from large to small is ranked as follows: N, θ, α, Z and P; the degree of impact on the maximum stress of the bolt from large to small is ranked as follows: P, N, Z, α, θ. To improve the overall performance of a four-point contact ball slewing bearing, increase α, N, Z, and θ. [ABSTRACT FROM AUTHOR]

Estimation of fault severity throughout bearing life is required for bearing prognostics and remaining useful life estimation. The useful life limit varies based on the function and criticality of the bearing and the machine. Most research has focused on the initial stages when faults are small. This paper presents novel severity categories of a spall-like fault located on a deep groove bearing outer race by investigating the dynamic behavior. Different stages of fault severity, classified as small, medium, and large faults, are characterized from fault initiation to faults extending to angles corresponding to several balls interacting simultaneously with the fault. This research combines dynamic modeling and experiments. The dynamic model is used to understand dynamic behavior, and the experiments are used to validate the results. The dynamic behavior is used to analyze and explain new unique patterns in the vibration signatures of different fault severities. This study enhances the capabilities for estimating fault severity in ball bearings, providing valuable insights that contribute to the development of more accurate and effective maintenance strategies. This is particularly relevant in scenarios where the system can operate efficiently even with large faults exceeding the "small" category. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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 rotational speed vectors of the bearing balls affect their service life and running performance. Observing the actual rotational speed of the ball is a prerequisite for revealing its true motion law and conducting sliding behavior simulation analysis. To address the need for accuracy and real-time measurement of spin angular velocity, which is also under high-frequency and high-speed ball motion conditions, a new measurement method of ball rotation vectors based on a binocular vision system is proposed. Firstly, marker points are laid on the balls, and their three-dimensional (3D) coordinates in the camera coordinate system are calculated in real time using the triangulation principle. Secondly, based on the 3D coordinates before and after the movement of the marker point and the trajectory of the ball, the mathematical model of the spin motion of the ball was established. Finally, based on the ball spin motion model, the three-dimensional vision measurement technology was first applied to the measurement of the bearing ball rotation vector through formula derivation, achieving the analysis of bearing ball rolling and sliding characteristics. Experimental results demonstrate that the visual measurement system with the frame rate of 100 FPS (frames per second) yields a measurement error within ±0.2% over a speed range from 5 to 50 RPM (revolutions per minute), and the maximum measurement errors of spin angular velocity and linear velocity are 0.25 °/s and 0.028 mm/s, respectively. The experimental results show that this method has good accuracy and stability in measuring the rotation vector of the ball, providing a reference for bearing balls' rotational speed monitoring and the analysis of the sliding behavior of bearing balls. [ABSTRACT FROM AUTHOR]

The use of thermite to aid spacecraft demise during atmospheric re-entry has been investigated in the ESA-TRP SPADEXO project. An experimental campaign in DLR's L2K arc-heated wind tunnel facility was dedicated to explore the Thermite-for-Demise concept. Steel mock-ups of a ball bearing unit, partially filled with thermite, were placed in L2K. The breadboards were then exposed to an air flux simulating the typical conditions that characterize spacecraft re-entry. In this paper, the key results of the tests are presented. The dispersion of a mechanically activated fraction of thermite proved to be effective in controlling the overall charge ignition temperature. Thermite-induced demise was experimentally verified in the wind tunnel. The SCARAB software was extended and used to rebuild the retrieved thermal data. The results of the simulations were in good agreement in both predicting the ignition timing and the effects of the thermite charge on the sample. • Thermite-induced demise was verified in hypersonic wind tunnel conditions. • Mechanical activation can tune thermite passive ignition in space-like environment. • Numerical models can describe and foresee thermite-induced demise. [ABSTRACT FROM AUTHOR]

The atomization mechanism of lubrication fluid in rolling bearings under high-speed airflow between the rings was investigated. A simulation model of gas–liquid two-phase flow in angular contact ball bearings was developed, and the jet lubrication process between the bearing rings was simulated using FLUENT computational fluid dynamics software (Ansys 19.2). The complex motion boundary conditions of the rolling elements were addressed through a layered approach. We can obtain more accurate boundary layer flow field changes and statistics of the diameter of oil particles in lubricating oil atomization, which lays the foundation for analyzing the law of influence on lubricating oil atomization. The results show that as the number of boundary layer layers increases, the influence of the boundary layer flow field on the lubricating oil is more obvious. The oil particle size is excessively flat, and the concentration of large particles of oil appears to decrease. As the speed increases, the amount of oil in the cavity decreases, but the oil droplets are also fragmented, which intensifies the atomization and reduces the particle diameter. This reduces the Sauter Mean Diameter (SMD), which is not conducive to the lubrication of the bearing. Under different injection pressures, when the injection pressure is large, it is beneficial to the lubrication of the bearing. [ABSTRACT FROM AUTHOR]

Research on White Etching Cracks (WEC) in multiple bearing applications has identified various drivers that cause them. Lubricants and electricity combined with contact mechanics have been proven to catalyze WEC significantly. However, none of these factors solely cause WEC on its own; instead, combinations of factors discretize whether WEC appears or not. Hence, the WEC phenomenon appears to be multidimensional, making WEC still unpredictable. The current paper is about a systematic study using a Deep Grove Ball Bearing test rig to investigate how lubricant chemicals, combined with electricity and variations in oil flow and pressure, lead to WEC formation. It becomes evident that even under critical conditions for WEC formation, increasing oil flow and decreasing contact pressure can prevent WEC. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of monitoring the ratio involving three variables, jointly distributed as trivariate normal. The Shewhart-type and two exponentially weighted moving average (EWMA) type schemes for monitoring depth ratio are proposed. The ratio of a normal variable to the average of two other normal variables has wide applications in natural science, production, and engineering. It is defined with slightly different terminology in various contexts, such as depth or aspect ratios. In modern bearing manufacturing, the aspect ratio of width to the average of inner and outer diameters can be an essential indicator of product quality and process stability. While there are many helpful existing charts for monitoring the three components separately or jointly when these characteristics follow a normal distribution, the ratio aspect is often ignored. The Shewhart-type schemes' exact and approximated control limits are considered and analyzed. Numerical results based on Monte-Carlo are conducted using the average run length as a metric with different values of in-control ratio and correlation between the three variables. An application based on the parts manufacturing data illustrates the implementation design of the two control charts. The real-life data analysis shows the efficacy of the proposed monitoring schemes in practice. [ABSTRACT FROM AUTHOR]

Bearings are common components used in the transmission system of tool machinery and linear drive equipment. With increasing demand for higher efficiency and faster production under the required accuracy, the control of bearing temperature rise under high operational speed becomes a critical issue. The improper control of temperature rise can lead to the thermal deformation and life reduction of the machinery. Conventionally, a circulating oil lubrication system is utilized with journal bearings. In this study, a similar lubrication system was adopted for the ball bearing with a retrofit design. Three control factors, i.e., rotational speed, bearing preload, and the viscosity of the lubricant used, were chosen to study their effects on the temperature performance of the proposed lubrication system. Experimental measurements showed that the lubrication system was able to lower the temperature rise of the bearing considerably compared with its unlubricated counterpart, especially at high rotational speeds. Even with the enhanced cooling from the oil circulation system, temperature rise still increased with rotational speed. However, with increased preload, the temperature rise first dropped and then increased owing to the different contact characteristics of the balls and rings of the bearing. A fitted function for the temperature rise of the bearing under different operational conditions was demonstrated to have a prediction accuracy within 3%. Therefore, the retrofitted bearing oil cooling system should be applicable in the design of high-speed machinery for industry. [ABSTRACT FROM AUTHOR]

AbstractAs an important component of rotating machinery, the rotor system (RSM) has a decisive effect on the system dynamics. Most previous works established the RSM dynamic model without the bearing slip, ball dynamics, and cage dynamics. This work proposes a flexible rotor system (FRSM) dynamic model with the bearing slip, ball dynamics, and cage dynamics. The effect of the bearing slip on the FRSM dynamic is analyzed. The FRSM consists of the rotor, rigid disk, and ball bearings. The rotor is modeled using the Timoshenko beam elements. The dynamic models of the rigid disk and ball bearing are established by using the lumped parameter method. The bearing clearance and installation method effects are considered. An experimental verification is developed to demonstrate the validity of the proposed dynamic model. The results obtained by the proposed model and the previous model without the bearing slip are compared. Moreover, the effects of the rotor rotational speed and rigid disk unbalance eccentric distance on the FRSM dynamics and bearing slip are analyzed. The results shows that rotor rotation frequency (fs) is not obvious for health FRSM and the amplitudes of fs and nfs increase with rotation speed and unbalance eccentric distance, which can provide guidance for fault diagnosis. [ABSTRACT FROM AUTHOR]

An unconventional and innovative mechanical transmission component, the curved groove ball bearing without retainer (CGBBR), is introduced in this article to facilitate the conversion between rotational and reciprocating motion. The CGBBR boasts several advantages over conventional motion conversion mechanisms, including a streamlined and compact structure, as well as the mitigation of high-order vibrations. This article delves into the design methodology, structural attributes, kinematic principles, and dynamic response properties of the CGBBR. A novel design method named closed curve envelopment theory is proposed to generate the distinctive spatial surface structure of the CGBBR. Moreover, a design scheme is presented that employs the concept of diameter-stroke ratio for CGBBR implementation. A calculation methodology is also introduced for determining the number of rolling elements within the CGBBR, which serves as the foundation for subsequent optimization design. This article deeply analyzes the kinematics principle of CGBBR and provides a new insight of motion conversion in mechanism. [ABSTRACT FROM AUTHOR]

To enhance the static and dynamic performance of the grinding wheel spindle system, with the gear grinding machine (YKF2060) as the research object, a static mechanics model of the spindle system was established based on Castigliano's theorem, taking into account the equivalent effect of the triple-point contact ball bearing at the front end of the spindle. Meanwhile, based on the overall transfer matrix method, a dynamic model of the main spindle–eccentric shaft dual-rotor system was established, taking into account the effects of shear deformation and gyroscopic moments. On this basis, the effect of the spindle span, the front and rear overhang of the eccentric shaft, and the bearing stiffness on the static stiffness and first-order critical speed of the system was analyzed. Finally, static stiffness experiments, modal tests, and finite element simulation models were conducted to verify the static and dynamic models. The results show that the stiffness of the front outer bearing has the greatest influence on the static and dynamic performance of the system, while the stiffness of the rear inner bearing has the least influence. The relative errors of the static stiffness and the first two natural frequencies between static stiffness experiments, modal tests, and finite element simulation models are less than 10%, and the mode shapes match well. The established static and dynamic model can effectively reflect both the static and dynamic characteristics of the spindle system. [ABSTRACT FROM AUTHOR]

Test methods that use pushing forces to evaluate the maximal load capacities of carts in design standards require a flat, smooth and horizontal steel plate and thus do not take into account the real conditions of work. Resistive forces of a single wheel of a cart in a uniform rectilinear motion were measured using a unique test bench with five loads. Forty-four wheels were tested (varying diameters, treads and bearings) with one steel plate and four resilient floor coverings. Based on a linear mixed model, all the following results were significant (p < 0.05). Resistive forces were increased linearly with the load and depended on the characteristics of both the wheel and floor. These forces decreased as the diameter increased. They were important for wheels with sleeve bearings but decreased for cone ball bearings and precision ball bearings. Resistive forces depended on the material of the tread and were higher for solid rubber treads. In contrast, the hardness of the tread had little effect. Resistive forces strongly depended on the hardness of the base foam of resilient floor coverings: the softer the base foam, the higher the resistive forces. Test methods in design standards should be reviewed, using corrective forces based on these present results, to prevent musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

This work proposes a new dynamic model for evaluating the nonlinear characteristics of deep groove ball bearing considering the contact–impact characteristics. With clearance taken into account, the elements of the deep groove ball bearing are modeled as the contact bodies. The normal force in the contact bodies is established by the dissipative contact force model, which includes elastic deformation and energy loss. Based on the modified Coulomb friction model, the tangential force can be established. The dynamic analysis model of deep groove ball bearing with contact–impact characteristics is obtained. Moreover, the experimental platform is established and the dynamic performance experiment is conducted. Finally, the influence of structure features on the dynamic behavior of deep groove ball bearing is discussed in detail. The simulation results could represent that clearance plays an important element in evaluating accurately the dynamic behavior of deep groove ball bearing, which would cause strong nonlinear mechanical systems. [ABSTRACT FROM AUTHOR]

Standard ML relies on ample data, but limited availability poses challenges. Transfer learning offers a solution by leveraging pre-existing knowledge. Yet many methods require access to the model's internal aspects, limiting applicability to white box models. To address this, Tsai, Chen and Ho introduced Black Box Adversarial Reprogramming for transfer learning with black box models. While tested primarily in image classification, this paper explores its potential in time series classification, particularly predictive maintenance. We develop an adversarial reprogramming concept tailored to black box time series classifiers. Our study focuses on predicting the Remaining Useful Life of rolling bearings. We construct a comprehensive ML pipeline, encompassing feature engineering and model fine-tuning, and compare results with traditional transfer learning. We investigate the impact of hyperparameters and training parameters on model performance, demonstrating the successful application of Black Box Adversarial Reprogramming to time series data. The method achieved a weighted F1-score of 0.77, although it exhibited significant stochastic fluctuations, with scores ranging from 0.3 to 0.77 due to randomness in gradient estimation. [ABSTRACT FROM AUTHOR]

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. This paper presents the process of the optimization of linear ball bearings with four-point connection using a genetic algorithm and the finite element method. Currently, modern steering systems without an intermediate shaft—steer-by-wire systems—are being developed. The focus of this paper was on the optimization of linear ball bearings with four-point connection, embedded between the outer and inner columns tube in terms of the number of balls in the bearing and the clearance between balls. The aim of the research was to maximize the first two natural frequencies in the steering system, which is crucial for improving the stability and efficiency of the system. Various factors influencing natural vibration such as bearing geometry, raceway and ball materials, and operating conditions (preload) were taken into account in the research. Preload is a major factor affecting not only linear motion but also natural frequency. In order to speed up the calculations, the author's simplified model of a linear bearing with the use of a system of springs was proposed. The nonlinear properties of the spring were determined on the basis of Hertz's theory. A genetic optimization process resulted in a linear bearing structure that meets the natural frequency criteria. In addition, the full reference model was numerically compared with the simplified one, which showed convergent results of natural frequencies. [ABSTRACT FROM AUTHOR]

The distribution of oil and gas phases around ball–raceway local regions is an important basis and foundation for determining whether a bearing is sufficiently lubricated. To obtain the oil phase distribution law in the inner raceway–ball contact local region (IBCR) and outer raceway–ball contact local region (OBCR) of the ball bearing with under-race lubrication, the numerical simulation method is used. The effects of bearing rotation speed, oil flow rate, oil viscosity, and oil density on these two regions are studied. The results indicate that the oil phase exhibited significant periodic changes in both time and space. Compared with that in the IBCR, the oil phase distribution in the OBCR is more uniform. Increasing the bearing rotation speed and reducing the oil flow rate made the IBCR and OBCR more uniform. Changing the oil viscosity only alters the distribution pattern of the OBCR. The oil density may not affect the fluid flow state or the oil phase distribution in the bearing. [ABSTRACT FROM AUTHOR]

Improved lognormal reliability test plans are proposed for lot sentencing. A mixed integer nonlinear programming problem is stated and solved in order to find the duration of the reliability test based on lognormal failure count data that minimises the inspection effort. The maximum number of failures tolerated by the decision maker and the necessary number of devices to be tested are also determined. The producer and consumer risks are limited in advanced, whereas the cost function is essentially a linear combination of the required sample size and test time. The minimum-cost test for device reliability demonstration provides the best criterion to decide the acceptability of manufacturing processes and submitted lots. A quick and effective iterative algorithm is suggested to obtain the optimal reliability demonstration test plan. The developed methodology is applied to the production of microelectronic chips, semiconductor lasers and ball bearings for illustrative purposes. [ABSTRACT FROM AUTHOR]

Abstract Despite being a well‐known problem, bearing faults are still one of the major challenges that the industry face. The growing use of voltage source inverters imposed the alertness of possible bearing damage due to their high‐frequency signals. The aim of this paper is to investigate the effect of capacitive discharges on a rolling element bearing to obtain a series of faulty bearings with different deterioration levels. An ageing test bench is built to generate bearing roughness using Electric Discharge Machining. The purpose is to study the effect of operation conditions, such as frequency of drive, amplitude of shaft voltage, radial load level as well as rotational speed, on the capacitive discharge occurrence within the bearing. Having the desire to further understand this phenomenon, the influence of each parameter on the discharge activity and the discharge waveform is analysed. A worst‐case scenario is conducted and applied to a series of bearings. Finally, the bearing damage is examined, and a quantitative fault detection method is presented based on a microscopic inspection of the bearing's surface.

Standard ML relies on ample data, but limited availability poses challenges. Transfer learning offers a solution by leveraging pre-existing knowledge. Yet many methods require access to the model’s internal aspects, limiting applicability to white box models. To address this, Tsai, Chen and Ho introduced Black Box Adversarial Reprogramming for transfer learning with black box models. While tested primarily in image classification, this paper explores its potential in time series classification, particularly predictive maintenance. We develop an adversarial reprogramming concept tailored to black box time series classifiers. Our study focuses on predicting the Remaining Useful Life of rolling bearings. We construct a comprehensive ML pipeline, encompassing feature engineering and model fine-tuning, and compare results with traditional transfer learning. We investigate the impact of hyperparameters and training parameters on model performance, demonstrating the successful application of Black Box Adversarial Reprogramming to time series data. The method achieved a weighted F1-score of 0.77, although it exhibited significant stochastic fluctuations, with scores ranging from 0.3 to 0.77 due to randomness in gradient estimation.