Cage Pocket Research Articles

Experimental Investigation of Cage Dynamics and Ball-Cage Contact Forces in an Angular Contact Ball Bearing

The objectives of this investigation were to experimentally examine the cage motion and ball-cage contact forces for an angular contact ball bearing (ACBB) operating under various load and speed combinations. In order to achieve the objectives, a Counter Rotating Angular Contact Ball Bearing Test Rig (CRACTR) was designed and developed such that both the races of an ACBB can be rotated simultaneously in opposite directions, providing valuable insights into the ball-cage interaction. Five proximity probes were used concurrently to measure the in-plane (radial) and out-of-plane (axial) motion for three commercially available cage designs. Two load cells were used to measure the contact forces between the balls and cage pocket. The experimental results demonstrate that high inner race speeds and high axial loads develop the smallest and most circular cage whirl motions. Additionally, cage radius, cage pocket clearance, cage pocket area and cage inertia were the prominent factors affecting the magnitude of cage whirl. Experimental results also indicate that contact forces between the ball and cage pocket increase linearly with the increased race speeds. Ball-cage contact force was shown to be different for the three cages and was primarily governed by the cage pocket area and the cage radius. Results from this investigation can be utilized to predict the correlation between the ball-cage contact forces and the race speeds, and identify the key parameters governing the stable cage motion during bearing operation.

A Study on Bearing Dynamic Features under the Condition of Multiball–Cage Collision

Cage stability directly affects the dynamic performance of rolling bearing, which, in turn, affects the operating state of rotating equipment. The random collision between the rolling elements and the cage pocket is the main reason for cage instability. In this paper, from the perspective of the relative sliding velocity between the rolling elements and the bearing raceway, the interactions of the rolling elements and the cage pockets were analyzed, and the four zones with different collision features were defined. On this basis, and on the basis of the bearing dynamics model, the interaction of two adjacent rolling elements and the cage pockets in the a’–b’ area is discussed, and the peak impact force of the adjacent two balls and the cage pockets was investigated in terms of the rotation speed, radial load, acceleration/deceleration, and materials. When the ball runs close to the loaded zone, the probability of multiball random collision increases, which leads to an increase in the cage instability. At the entrance of the loaded zone, the peak impact force has the greatest impact on the cage stability during the acceleration process. Compared to the radial load applied to the bearing, the peak impact force is more sensitive to the bearing speed changes. The multiball collision analysis method provides a new idea for the research of cage stability.

Contact forces between roller and cage pocket in cylindrical roller bearings (Consideration based on dynamic behavior between roller and cage)

Contact forces between roller and cage pocket in cylindrical roller bearings (Consideration based on dynamic behavior between roller and cage)

Experimental Investigation of Clearance Influences on Cage Motion and Wear in Ball Bearings

Clearances of cages in ball bearings, including pocket and guiding clearances, play a vital role in the stability and reliability of bearings. In this paper, experiments on the cage motion and wear were carried out to investigate the influence of clearances in ball bearings. Firstly, the cages with a series of pocket and guiding clearances were specially designed and tested for prescribed operating conditions on a bearing test rig in which the cage motions were measured, and corresponding wear was also observed. Then, the normalized trajectory, waveform, and spectra of cage motion were constructed and compared to illustrate the effects of clearances on the cage motion and then to establish the relationship between cage motion and wear. Results reveal that the cage motion and wear are both significantly affected by its clearances. The increment of cage guiding clearance makes the whirl trajectories of the cage regular and the motion frequency of cage motion significantly change. However, the increment of cage pocket clearance make the whirl trajectories change from well-defined patterns to complicated ones, and the frequency of cage motion apparently changes. Additionally, the bearing wear is closely related to the cage motion. If the inner ring frequency is of domination for the cage motion, the cage guiding surface will wear seriously. While cage motion is dominated by two times cage frequency in spectrum domain, the cage pocket will wear more seriously.

Helicity induction by innocent anion in a quadruple stranded cage

Anion induced twisted disposition of four units of a bidentate ligand around two palladium(II) centers in the cage of [Pd2L4](ClO4)4 formulation resulted in a helical structure. The crystal structure reveals the existence of both M and P enantiomers. The disposition of one of the arms is noticeably different from the other three, hence the molecular symmetry of the helicate is lowered. The encapsulation of perchlorate anion within the cage pocket with H-bonding interactions provided the driving force for the helicity. However, the analogues complex [Pd2L4](NO3)4 with nitrate as counter anion is nonhelical. Formation of helical and nonhelical Pd2L4 arrangement by mere change of counter anion was not reported hence it is a new finding.

Dynamic behaviors of angular contact ball bearing with a localized surface defect considering the influence of cage and oil lubrication

Angular contact ball bearing plays a significant role in guaranteeing the service performance of the mechanical equipment. However, the occurrence of localized defect dramatically affects the tribo-dynamic performance of the bearing, which can further result in serious accidents. Considering the influence of cage and oil lubrication, this paper proposes a complete multi-degree-of-freedom (DOF) dynamic model for defective angular contact ball bearing by analyzing the full multi-body interactions. The defect is modeled in the geometrical constraint relationships to replace the excitation functions proposed in previous studies. Based on the analysis of high-speed conditions, the effects of outer raceway defects with different sizes and position angles on the dynamic behaviors of the bearing are revealed. It is found that the defect significantly influences the load characteristics and the angular misalignments, and the traction in the ball-raceway contact shows an abrupt change around the defect exit event. The results also show that the reciprocating collisions between the ball and the cage pocket occur in the defective case which are affected by the defect scale and the bearing speed.

Effects of Cage Pocket Shapes on Dynamics of Angular Contact Ball Bearings

Effects of Cage Pocket Shapes on Dynamics of Angular Contact Ball Bearings

Dynamic characteristics of ball bearing with flexible cage lintel and wear

In view of the practical problem of wear on the cage pocket, which is unavoidable during the operation of high-speed ball bearing, a dynamic model of high-speed ball bearing with flexible cage lintel was established considering the cage-pocket wear loss (BPWL), the gravity, drag force from the oil, and the hydrodynamic effect on the cage, and then, the dynamic simulations with different amounts of BPWL were obtained by solving the ball bearing dynamic equations using varying steps Runge-Kutta integration. The effect of the BPWL on the trajectory of the cage’s centroid and cage skidding ratio were obtained. The computational results show that the trajectory of the cage’s centroid presents two vibration modes with different amplitudes. And the two different forms of trajectories of different amplitudes emerge alternatively with BPWL increase. Moreover, the diameter of the trajectory decreases significantly with the BPWL increasing which is consistent with the experimental result. The change of the BPWL has little effect on the average skidding ratio of the cage; however, the fluctuation amplitude would become larger as BPWL increase. This study can provide important ideas for the design of bearing cage pocket size and the fault identification of the ball bearing.

Skidding research of a high-speed cylindrical roller bearing with beveled cage pockets

PurposeThis study aims to uncover the influencing mechanism of the tilt angles of the cage pocket walls of the high-speed cylindrical roller bearing on the bearing skidding.Design/methodology/approachA novel cylindrical roller bearing with the beveled cage pockets was proposed. Using the Hertz contact theory and the elastohydrodynamic and hydrodynamic lubrication formulas, the contact models of the bearing were built. Using the multibody kinematics and the Newton–Euler dynamics theory, a dynamics model of the bearing was established. Using the Runge–Kutta integration method, the dynamics simulations and analysis of the bearing were performed.FindingsThe simulation results show that the effects of the tilt angles of the front and rear walls of the pocket on the bearing skidding are remarkable. Under a 5° tilt angle of the front wall of the pocket and a 10° tilt angle of the rear wall, the bearing skidding can be effectively decreased in the rotational speed range of 10,000-70,000 r/min.Originality/valueIn this paper, a novel cylindrical roller bearing with the beveled cage pockets was proposed; a dynamics model of the bearing was established; the influence mechanism of the tilt angles of the front and rear walls of the pocket on the bearing skidding was investigated, which can provide fundamental theory basis for optimizing the pocket.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0035/

Genome-wide identification and expression analysis of YTH domain-containing RNA-binding protein family in common wheat

BackgroundN6-Methyladenosine (m6A) is the most widespread RNA modification that plays roles in the regulation of genes and genome stability. YT521-B homology (YTH) domain-containing RNA-binding proteins are important RNA binding proteins that affect the fate of m6A-containing RNA by binding m6A. Little is known about the YTH genes in common wheat (Triticum aestivum L.), one of the most important crops for humans.ResultsA total of 39 TaYTH genes were identified in common wheat, which are comprised of 13 homologous triads, and could be mapped in 18 out of the 21 chromosomes. A phylogenetic analysis revealed that the TaYTHs could be divided into two groups: YTHDF (TaDF) and YTHDC (TaDC). The TaYTHs in the same group share similar motif distributions and domain organizations, which indicates functional similarity between the closely related TaYTHs. The TaDF proteins share only one domain, which is the YTH domain. In contrast, the TaDCs possess three C3H1-type zinc finger repeats at their N-termini in addition to their central YTH domain. In TaDFs, the predicated aromatic cage pocket that binds the methylysine residue of m6A is composed of tryptophan, tryptophan, and tryptophan (WWW). In contrast, the aromatic cage pocket in the TaDCs is composed of tryptophan, tryptophan, and tyrosine (WWY). In addition to the general aspartic acid or asparagine residue used to form a hydrogen bond with N1 of m6A, histidine might be utilized in some TaDFb proteins. An analysis of the expression using both online RNA-Seq data and quantitative real-time PCR verification revealed that the TaDFa and TaDFb genes are highly expressed in various tissues/organs compared with that of TaDFcs and TaDCs. In addition, the expression of the TaYTH genes is changed in response to various abiotic stresses.ConclusionsIn this study, we identified 39 TaYTH genes from common wheat. The phylogenetic structure, chromosome distribution, and patterns of expression of these genes and their protein structures were analyzed. Our results provide a foundation for the functional analysis of TaYTHs in the future.

Validation of combined analytical methods to predict slip in cylindrical roller bearings

This paper presents a combination of models that together calculate the cage and roller speeds of a cylindrical roller bearing. The models consider elastohydrodynamic lubrication and contact elasticity between the roller and raceway, roller centrifugal forces, hydrodynamic lubrication at the cage pocket, and frictional forces. Using these models, the predicted cage and roller speeds and the extent of slip are compared to measurements acquired on cylindrical roller bearings in a commercial gearbox in steady-state and transient operating conditions of a wind turbine. In steady-state conditions at low wind speeds and low lubricant temperatures, cage and roller slip up to 60% occur in the loaded zone of the bearing. In the unloaded zone, up to 80% roller slip occurs. Cage and roller slip then decrease as the lubricant temperature and wind speed increases. In general, the analytical model results match experimental measurements within 10% for lubricant temperatures above 40°C and wind speeds over 10 meters per second. The analytical model is further evaluated during a transient start-up event and highly dynamic emergency stop event and also used to examine changes in the bearing design or lubricant properties. Roller and cage slip in cylindrical bearings is a combined effect of the bearing design, applied load, shaft speed, and lubricant properties and temperature, and can be quickly evaluated with the combined analytical models.

Modeling and Simulation of Cage Wear in Solid-Lubricated Rolling Bearings

Cage not only separates the rolling elements but play an essential role of lubricant supplier in solid lubricated rolling bearings, thereby lubricating the rolling contacts. In such bearings, whose service life can be significantly extended by targeted cage wear, a better understanding and a reliable prediction of the wear is necessary in order to achieve a further increase in the service life. In order to predict wear and eventually their life-time is a complex phenomenon as it involves several transfer processes taking place in the rolling and sliding contacts. The lifespan of such bearings can be determined by performing numerous lifetime experiments. Global lifetime model for solid-lubricated rolling bearings does not exist so far like a conventional bearing life model. Therefore, a dynamic simulation strategy based on Adams multibody simulation environment to predict and model wear at cage pocket interface have been proposed. An incremental wear simulation approach based on Fleischer wear law is introduced. Uniform global wear of the cage pocket depending on the recalculation of cage geometry and converted frictional energy for each wear increment is calculated. Simulation results show good accordance with the experimental results. The importance and suitability of such a wear simulation approach will be enunciated in this paper.

An Approach to Determine and Analyze the Wear Rates at Cage Pocket Contacts in Solid-Lubricated Rolling Bearings

Solid-lubricated rolling bearings are widely known in many technical systems where conventional lubrication, such as oil or grease, fails due to critical conditions like vacuum or high temperatures. Polymeric cages (e.g., polyimide) endowed with molybdenum disulfide (MoS2) particles and silver (Ag) coating on the bearing components have proven themselves as dry lubricants that could significantly increase the service life of solid-lubricated rolling bearings. It has been demonstrated that during the bearing operation, material particles of the cage are transferred onto the raceways and lubricate the bearing. Thereby, the energy dissipates due to the momentary sliding at the ball–cage pocket interface. As a result of this behavior, the cage experiences wear apart from serving as a lubrication reservoir. In order to describe the lubrication transfer amount or the wear volume at the cage pocket, it is essential to estimate the material-specific wear rate. This contribution introduces an approach to determine and analyze the wear rates at the ball–cage pocket interface. In this article, only one example of lubrication coatings with specific operating conditions are shown, but the approach applies to other cases as well. This analysis has been achieved by performing bearing experiments under high vacuum conditions together with the combination of computational modeling. As an outcome, there are two aspects considered. The present contribution provides insight into the procedure to estimate material-specific wear rates. Additionally, it shows how wear rate data distribution can be analyzed. The future scope of this work is the input for the development of the model to predict and optimize the service life of such bearings to some extent.

Dynamic Interactions Between the Rolling Element and the Cage in Rolling Bearing Under Rotational Speed Fluctuation Conditions

Abstract A nonlinear dynamic model is proposed to investigate the dynamic interactions between the rolling element and cage under rotational speed fluctuation conditions. Discontinuous Hertz contact between the rolling element and the cage and lubrication and interactions between rolling elements and raceways are considered. The dynamic model is verified by comparing simulation result with the published experimental data. Based on this model, the interaction forces and the contact positions between the rolling element and the cage with and without the rotational speed fluctuation are analyzed. The effects of fluctuation amplitude, fluctuation frequency, and cage pocket clearance on the interaction forces between the rolling element and the cage are also investigated. The results show that the fluctuation of the rotational speed and the cage pocket clearance significantly affects the interaction forces between the rolling element and the cage.

Investigation of the dynamic local skidding behaviour of rollers in cylindrical roller bearings

Skidding has a great influence on the reliability and the life of rolling element bearings. The previous research of bearing skidding mainly focussed on the gross skidding of bearings under severe conditions. However, the local skidding of rolling element also exists and cannot be ignored when bearing normally runs at steady state. In this paper, considering the discontinuous contact between the roller and the cage, the Hertz contact between the roller and races, lubrication, centrifugal effects and the cage pocket clearance, a nonlinear dynamic model is established to investigate the local skidding behaviour of a roller in cylindrical roller bearings. The equations of the dynamic model are solved by the fourth-order Runge–Kutta algorithm and verified by comparing simulation results with the published experimental data. The results show that the local skidding of the roller still noticeably exists in bearings even when the gross skidding can be ignored, especially on the inner raceway. The local skidding at the entry of the loaded zone may cause the smearing on the raceway surface. However, it can be found that the probability of the local skidding of the roller will be decreased by increasing radial load and reducing the bearing rotational speed. The cage pocket clearance would induce violent fluctuations on the roller rotational angular velocity as well as on the sliding velocity. Furthermore, it can generate extraordinary impact forces between the rollers and the cage. Thus, the cage pocket clearance should be carefully considered in the design of bearings.

Dynamic Parameter Analysis of Spindle Bearing Using 3-Dimension Quasi-Dynamic Model

Spindle bearing with high rotational speed is the kernel of many rotating machines which plays massive important role in the performance of the whole machine. There are also some deficiencies of the present quasi-dynamic mathematical models of the rolling bearing in analyzing the bearing dynamic parameters. This paper develops the 3D quasi-dynamic model with ball’s 6-DOF, cage’s 6-DOF, and driving ring’s 5-DOF under steady working stage, based on the analysis of the relative position of each component to determine the normal forces between each component and the analysis of the relative velocity of the contacting point to determine the tangential force between each component. This model can analyze the dynamic parameters, such as the spin-to-roll ratio of inner and outer rings, the angular velocity of rolling elements in y-axis of the location coordinate, the normal contact force of cage pocket and ball, the cage angular velocity and ball revolution velocity, and the gyroscopic moment under different working condition. Compared with the numerical calculation results of ADORE program, the results of the proposed model are able to accurately describe the change laws of the spindle bearing parameters.

Modeling the frictional torque of a dry-lubricated tapered roller bearing considering the roller skewing

In this paper, an equation for the calculation of the frictional torque of a dry-lubricated tapered roller bearing (TRB) is provided in which the effect of the roller skewing is emphasized. Calculations were performed to investigate the effect of the roller skewing on the torque of dry-lubricated TRB for two representative preload methods, that is, axial force preload and axial displacement preload. The results show that a proper roller skewing angle under axial force preload benefits the reduction of the TRB torque. However, the roller skewing angle should not exceed a certain critical value; otherwise, it will cause a steep rise in the TRB torque. Finally, the critical value of the roller skewing angle as a function of the friction coefficient and cage pocket clearance is presented. The developed torque model provides a tool for the internal design and torque optimization of dry-lubricated TRBs.

Effect of roller dynamic unbalance on cage stress of high-speed cylindrical roller bearing

PurposeThe purpose of this study is to investigate the effect of roller dynamic unbalance on cage stress.Design/methodology/approachConsidering the impact of roller dynamic unbalance, the dynamic analysis model of high-speed cylindrical roller bearing is established. And then the results of dynamic model are used as the boundary conditions for the finite element analysis model of roller and cage to obtain the cage stress.FindingsRoller dynamic unbalance affects the contact status between roller and cage pocket and causes the overall increase in cage stress. The most significant impact on cage stress is roller dynamic unbalance in angular direction of roller axis, followed by radial and axial directions. Smaller radial clearance of bearing and a reasonable range of pocket clearance are beneficial to reduce the impact of roller dynamic unbalance on cage stress; the larger cage guide clearance is a disadvantage to decrease cage stress. The impact of roller dynamic unbalance on cage stress under high-speed condition is greater than that in low-speed conditions.Originality/valueThe research can provide some theoretical guidance for the design and manufacture of bearing in high-speed cylindrical roller bearing.

Experimental study on dynamic behavior of ball bearing cage in cryogenic environments, Part I: Effects of cage guidance and pocket clearances

Abstract In cryogenic environments, it is not possible to apply oil or grease to ball bearings, owing to the extreme temperature conditions. Thus, polytetrafluoroethylene (PTFE) cages are used as solid lubricants in such environments, because PTFE has a low coefficient of friction. PTFE cages increase the rotational stability of the ball bearings by reducing the frictional force of the rolling elements. In addition, design parameters such as the cage guidance and ball-pocket clearances significantly affect the stability of the ball bearings. In this study, the dynamic behavior of a ball bearing cage submerged in a cryogenic fluid was investigated for different cage clearances and rotation speeds. For experimental verification, a test rig was designed to realize a cryogenic environment. The test rig could be driven to 11,000 rpm using a DC motor and provided loads of up to 20 kN using a pneumatic cylinder. A metal ring was employed to measure the cage whirling amplitude using a fiber optic displacement sensor. The parameters considered included the cage whirling amplitude, ball bearing torque, and cage wear. The effects of the clearances and rotation speed on the cage stability and performance were analyzed using the probability density function of the cage whirling frequency, and the standard deviation of this function decreased as the outer guidance clearance decreased. In addition, the cage wear loss increased with decreasing cage ball-pocket clearance, owing to the collisions between the balls and cage pocket. The experimental results agreed partially with the existing theory and demonstrated that the cage instability increased as the cage guidance clearance increased.

Dynamic analysis of a tapered roller bearing

PurposeThis study aims to analyze the roller dynamic characteristics and cage whirling of tapered roller bearing considering roller tilt and skew which provide a theoretical basis for the design and application of tapered roller bearing.Design/methodology/approachBased on rolling bearing dynamic analysis, the dynamic differential equations of tapered roller bearing are established. Fine integral method and predict correct Adams–Bashforth–Moulton multi-step method are used to solve the dynamic differential equations of tapered roller bearings.FindingsFriction at the flange contact between roller and large flange is the chief factor of roller skew. In comparison to cone speed, axial loads have more visible effect on roller skew, and proper speed or axial load is beneficial to sustain cage motion and decrease cage instability. Under the combined effort of axial load and radial load, the distribution of roller skew is correlated to the roller-flange contact load. In addition, roller skew angle in loaded zone is larger than that in unloaded zone; hence, it is helpful for cage stability if an extent radial load is applied. The pocket clearance of cage has very small influence on roller skew; therefore, a reasonable pocket clearance is suggested to assure minimum instability of cage. Friction coefficient of flange contact has a large effect on roller skew, and cage whirl is found to demonstrate a circular orbit with increasing friction coefficient.Originality/valueThe dynamic differential equations of tapered roller bearing considering roller large end/inner ring back face rib contact under various lubrication states were established. The impact of flange friction working conditions and cage pocket clearance on cage instability and roller skew were focused on. It is the first time that the ratio of the standard deviation of the cage-center translational speed to its mean value is used to access the instability of cage in tapered roller bearing.