Fatigue Life Of Roller Bearings Research Articles

Fatigue life prediction of rolling bearings based on damage accumulation considering residual stresses

The determination of the fatigue life of rolling bearings is recommended to be conducted using the standard calculation models defined in ISO 281. These models yield reliable results for rotating applications. The standard models are continuously refined to align with advancements in bearing production processes and material improvements. However, when dealing with rolling bearings exposed to complex load conditions including oscillatory movements, as seen in rotor blade bearings in wind turbines, a validated calculation model has yet to be established. In the domain of structural mechanics, fatigue life evaluation for steel components is based on S-N curves. Variable operational loads are treated as load collective, and the load cycle to failure N under given operational conditions is determined through the application of the linear damage rule. This paper introduces a novel model that integrates the linear damage rule with established conventional bearing theories. Within one internal stress cycle, all rolling contacts are regarded as an internal load collective. To evaluate the internal load collective, the stress state at each rolling contact is assessed based on the S-N curve determined in alternating torsional loads. The core rationale behind the selection of an S-N curve lies in the stress criterion τo based on Lundberg-Palmgren theory, which is incorporated in the new model. This paper includes a comprehensive step-by-step procedure for applying the new model, utilizing the cylindrical roller bearing NU 1006 as a reference. The results of this study indicate a favorable agreement between the fatigue life obtained using the new model and those determined according to ISO 281. Furthermore, a new approach is introduced to analytically account for residual stress - es when measured values are available. In this study, by applying this new approach, the results were observed to be in close agreement with the test results. Based on this investigation, it can be confirmed that the new model has the potential to provide reliable results without necessitating the bearing life exponent as well as the correction factors often required in conventional calculation models.

Effects of Axial Clearance on Surface Initiated Flaking in Tapered Roller Bearings

Abstract The calculating method for fatigue life of rolling bearings is based on the theory of Lundberg and Palmgren. The rated life is determined from the ratio of the dynamic load rating of the bearing to the dynamic equivalent load. However, in actual applications, flaking damage may occur earlier than this rated life. For example, surface initiated flaking may occur due to contamination in the lubricant. In addition, differences in the internal clearance of bearings are also thought to influence the occurrence of surface initiated flaking. This study aims to investigate the effect of different internal clearance on surface initiated flaking in tapered roller bearings. First, rotating tests were conducted on combination tapered roller bearings with dented raceways under several axial clearances different from the standard condition. Second, the surface profiles of the bearings before and after the tests were compared to investigate the relationship between the distribution of flaking area and the axial clearance. Furthermore, the effect of axial clearance on the surface initiated flaking life was clarified from the comparison between the results of the rotating tests. Finally, the theoretical and experimental lives were compared. As a result, it has been found that when the axial clearance is excessively large, the distribution of flaking is biased toward the large diameter side of the outer raceway. In addition, it has been demonstrated that the bearing life is substantially affected by the axial clearance, and that the bearing life shortens as the axial clearance increases.

Sensitivity analysis of rolling bearing fatigue life under cyclic loading

Sensitivity analysis of rolling bearing fatigue life under cyclic loading

A new approach for the prediction of fatigue life in rolling bearings based on damage accumulation theory considering residual stresses

Today, the service life calculation of rolling bearings is standardized in ISO 281, based on the theory of Lundberg and Palmgren. In the standard calculation method, material properties such as fatigue limit stress were taken into account by introducing the fatigue limit stress proposed by Ioannides and Harris. This standard calculation method provides a reasonable range of fatigue life in good agreement with experimental results under ideal test conditions such as constant external load. However, complex operating conditions of bearings such as varying loads and oscillating motion are not considered. Therefore, there is a need for a new analytical calculation model that can predict the fatigue life of rolling bearings operating under these complex conditions. This makes it possible to advance the application of rolling bearings and optimize their use in machines such as wind turbines. In the proposed approach, the fatigue life is determined based on the Palmgren-Miner linear damage rule, evaluating the subsurface stresses below the rolling contact using the S-N curve according to the fatigue criterion proposed by Lundberg and Palmgren. All rolling contacts that occur in an internal stress cycle due to the internal dynamic behavior during rotating operations are evaluated individually and referred to as partial damage risks. The partial damage risks are accumulated linearly according to the Palmgren-Miner theory to obtain the load cycle to failure. At this time, the loaded volume is assessed along the depth from the contact area to the core of the bearing ring, which makes it possible to indicate the depth position of fatigue occurrence in terms of crack initiation. The material properties such as the fatigue limit stress and the probability of failure are taken from the S-N curve itself. To consider the residual stress, a simple link concept is suggested by using the ratio of the maximum contact pressure to the yield criteria. The proposed approach can be extended to calculate oscillating fatigue life regarding the number of rolling contacts at a given oscillation amplitude. In this study, it can be confirmed that the analytically determined fatigue lifetime according to ISO 281 is still close to the bearing life test result. In addition, it shows that the results obtained using the proposed approach agree well with the calculation results obtained using ISO 281.

Investigation on the oil transfer behaviors and the air-oil interfacial flow patterns in a ball bearing under different capillary conditions

Lubricant oil is crucial to the rolling bearings as the main medium of lubricating, cooling, cleaning, and so on. The oil starvation in and around the contacts is harmful to the performance and fatigue life of rolling bearings. Therefore, it is of necessity to understand the behaviors of oil transfer and the patterns of air-oil two-phase flow in bearings, especially with the influence of different capillary properties. This work established a transient air-oil two-phase flow model in a ball bearing based on computational fluid dynamics (CFD). Groups of cases are implemented to investigate the behaviors of oil transfer and air-oil flow under different capillary conditions with speed, surface tension, and viscosity. Flow patterns are classified by the morphological features of the air-oil flow. Staged phenomena are analyzed with flow patterns and reach good agreements with the observations from experiments. It is found that the oil distribution and air-oil flow behaviors in a ball bearing are strongly related to the speed and the ratio of oil viscosity and air-oil surface tension (μoil/σ). The flow maps imply that the levels of capillary number (Ca) may be the boundaries and the critical points of flow pattern transition between the different flow patterns in bearing.

Local grid refinement in multigrid method for point contact problems of polycrystalline anisotropic material under dry and lubricated conditions

Predicting rolling bearing fatigue life requires knowledge of the three-dimensional (3D) stress fields in the roller and raceway near the lubricated contact. Owing to the increasingly severe operating conditions, the effect of localized features such as surface roughness, subsurface inclusions, and even the crystallographic structure of the material becomes important. Achieving such detail requires (locally) extremely dense gridding in simulations, which in 3D is a major challenge. Multigrid techniques have been demonstrated to be capable of solving such problems. In this study, multigrid techniques are shown to further increase the efficiency of the solution by exploiting local grid refinement while maintaining the simplicity of a uniform discretization. This is achieved by employing increasingly finer grids only locally, where the highest resolution is required. Results are presented for dry contact and elastohydrodynamically lubricated contact cases, circular as well as elliptic, with varying crystallographic structure, and with surface roughness. The results show that the developed algorithm is very well suited for detailed analysis, with also excellent prospects for computational diagnostics involving actual material crystallographic structure from electron backscatter diffraction measurements.

A modified nonlinear fatigue damage accumulation model for life prediction of rolling bearing under variable loading conditions

AbstractDuring the use of rolling bearings in wind turbines, aero engines, and other equipment, they often operate under variable operating and loading conditions. The practice has shown that the sequence of these loads and their interaction has a significant impact on the fatigue life of rolling bearings. In order to better understand this issue, a modified nonlinear fatigue damage accumulation model, which considers the influences of both load sequence and load interaction, is proposed in this paper and verified using the fatigue testing data for six materials. Then, the verified model was applied to evaluate the fatigue damage accumulation and fatigue life of a rolling bearing. The results have shown that, compared with the existing models, the proposed model can more accurately predict the damage accumulation and fatigue life of the rolling bearing under variable loading conditions.

Relative contact width evaluation of end hemispherical cavities rollers as an indication of Hertzian contact pressure

In a recent investigation, the end hemispherical cavities (EHC) rollers exhibited better strength against fracture than hollow rollers. Furthermore, EHC rollers looked promising from a higher fatigue life aspect than conventional solid rollers in a simulation study. Therefore, it necessitated further exploration of the EHC roller concept and to this end, in the present investigation, the contact widths of EHC rollers were relatively evaluated to judge its contact stresses' behavior with respect to the solid roller because the contact stresses are responsible for the fatigue life of rolling bearings. In the experiments, the contact footprints were obtained by forcing specimens of rollers against chemically etched surfaces and were examined by a microscope for measurement of contact widths. The experimental trials were performed with individual roller-on-plate tests and also with full-bearing samples. The etch correction factor was used to correct anomalies of real and observed contact widths due to etching film thickness. The parabolic relationships were established for roller variants which yielded constants signifying their relative ranks. The contact semi-widths, thus derived from corrected experimental results of individual roller-on-plate tests, demonstrated good agreement (<5%) with those derived from simulation results. The results of full-bearing sample tests for roller variants also ranked same as individual roller-on-plate tests. The encouraging results of contact semi-width assuredly favor the prospects of relatively higher fatigue life in case of EHC rollers.

Fatigue Life Prediction of Rolling Bearings Based on Modified SWT Mean Stress Correction

The existing engineering empirical life analysis models are not capable of considering the constitutive behavior of materials under contact loads; as a consequence, these methods may not be accurate to predict fatigue lives of rolling bearings. In addition, the contact stress of bearing in operation is cyclically pulsating, it also means that the bearing undergo non-symmetrical fatigue loadings. Since the mean stress has great effects on fatigue life, in this work, a novel fatigue life prediction model based on the modified SWT mean stress correction is proposed as a basis of which to estimate the fatigue life of rolling bearings, in which, takes sensitivity of materials and mean stress into account. A compensation factor is introduced to overcome the inaccurate predictions resulted from the Smith, Watson, and Topper (SWT) model that considers the mean stress effect and sensitivity while assuming the sensitivity coefficient of all materials to be 0.5. Moreover, the validation of the model is finalized by several practical experimental data and the comparison to the conventional SWT model. The results show the better performance of the proposed model, especially in the accuracy than the existing SWT model. This research will shed light on a new direction for predicting the fatigue life of rolling bearings.

A method for predicting subsurface fatigue life of rolling bearings based on macro–micro coupling model

The fatigue life of the bearing can be predicted effectively by combining the multifield coupling condition of the working process with the internal microstructure. In this paper, a bearing fluid lubrication model is established based on the computational fluid dynamics method, and the calculation result is coupled to the thermal-solid model by the grid mapping method. Through this method, a bearing thermal-fluid-solid multifield coupling dynamics model is established to obtain the evolution information of bearings. Simultaneously, the micro-characterization experiments of SKF6406 bearing (M50 bearing steel) were carried out by electron backscatter diffraction, scanning electron microscope and nano-indentation. The microstructure model of bearing containing micro-inclusions was established by the Voronoi method. On this basis, the microscopic stress distribution characteristics and the motion law of bearing microstructure under the multifield coupling action are solved. In the end, the fatigue life prediction method of rolling bearing was established.

Bearing roller smearing testing machine and its simulation analysis

Rolling bearings are the most common rotating mechanical parts in actual work, with the rapid development of industrial technology, the performance requirements of rolling bearings in actual work are getting widely used, but under the actual working conditions, some large bearings with low speed and heavy load are easy to be smeared and lead to the extension of bearing life. In order to study the effect of early surface smearing on the fatigue life of rolling bearings, a self-designed bearing roller early smearing tester was designed, the test machine can simulate the movement process of roller in the bearing and make different degree of smearing on the surface of roller. According to the function, the smearing testing machine is divided into four parts: driving system, loading system, signal acquisition system and test system. The smearing testing machine can set the test conditions according to relevant theories to fabricate different degree of early smearing on the bearing roller surface, the transient dynamics simulation can simulate the smearing test of the testing machine, by comparing the results of the simulation analysis with the actual experimental circumstances, the stability and reliability of the testing machine can be proved, and it can also be testified that the test results of the testing machine are researchable.

Lubrication and Fatigue Life Evaluation of High-Speed Cylindrical Roller Bearing under Misalignment

This paper developed a coupled model, incorporating the quasistatic model, fatigue life model, and mixed lubrication model, to investigate the effect of misalignment angle on high-speed cylindrical roller bearings. The model is verified by comparing with the published literature results. Then, a parametric analysis is carried out. The results show that as the misalignment increases, the load distribution is basically unchanged, but the fatigue life of the roller bearing decreases due to the variation of contact pressure, and the skewing moment of single roller contact pair increases. Furthermore, the optimal design of roller profile needs to consider the effect of lubrication in order to improve the fatigue life of roller bearings. In general, the optimal crown drop is too small according to the design from the slicing technique.

Studies on the Influence of Residual Stresses on the Fatigue Life of Rolling Bearings in Dependence on the Production Processes

The production process significantly influences the surface properties of rolling element bearings raceways. Deep rolling can induce a depth dependent residual stress state. Previous numerical and experimental studies have shown that rolling bearings fatigue life can be positively influenced by high compressive residual stress to a depth of around 300 µm from the surface. By extending the components life, the resource efficiency of machine components can be increased. In order to determine the influence of the residual stress state in bearing fatigue life, a calculation method was developed for predicting the bearing fatigue life. This method was validated for hard-turning and subsequent deep rolling by experiments on a test rig in four-bearing configuration under radial load. An increase of the L10 bearing life by a factor of 2.5 has been achieved by inducing residual stresses on the bearing’s inner ring. Due to similar process control, the manufacturing steps turning and deep rolling were combined. Bearings were manufactured combining the processes hard-turning and deep rolling (called turn-rolling). The heat from the hard machining has an effect on the residual stresses in the bearing subsurface, thus further altering the magnitude and maximum depth of the residual stress influencing the microstructure. With these bearings, the additional fatigue life was determined experimentally and compared to the results of the bearings produced by hard-turning and subsequent deep rolling. It could be shown, that the process of hard turning and subsequent deep rolling has highest potential to achieve improved bearing fatigue life. These findings were transferred to a “Tailored Forming” shaft with integrated raceway in a second step. In this case, a shaft made of mild steel is combined with a cladding layer of high strength bearing steel to be used as a bearing raceway.

Method for Calculating the Fatigue Life of Bearings Taking into Account Wearing of Rolling Elements

Experimental data on the wear of rolling elements are used to develop a method developed for determining the fatigue life of rolling bearings taking into account their wear. The results of calculating the fatigue life of a bearing taking into account the wear of rolling elements are given. It is shown that wear of rolling elements reduces the fatigue life of bearings.

A variational simulation framework for the analysis of load distribution and radial displacement of cylindrical roller bearings

In many technical systems, rolling bearings are critical machine elements concerning accuracy and lifetime. Their load distribution and radial displacement are directly linked to the accuracy and the fatigue life of rolling bearings. However, load distribution and radial displacement form a complex interdependency. Geometric deviations further influence this mutual connection. Although there are several approaches to determine the load distribution and the radial displacement, most of them are either too simplistic, allowing only the consideration of dimensional deviations, or too sophisticated and therefore unsuitable for a statistical evaluation of geometric deviations. Hence, the main purpose of this contribution is to provide a method for the determination of load distribution and radial displacement of cylindrical roller bearings that allows the consideration of geometric deviations as well as statistical evaluation of these deviations. Moreover, applying the method to a use case shows, whether the consideration of geometric deviations in the determination of load distribution and radial displacement is reasonable. The novelty of the contribution is, therefore, the provision of a statistical variational simulation framework for the analysis of load distribution and radial displacement of rolling bearings.

Enhancement of roller bearing fatigue life by innovative production processes

Purpose The efficient and economical use of natural resources is a big issue. Machine elements with a rolling contact are highly relevant because of their wide application in technical systems and a large production quantity. Innovative hard machining can reduce the friction and increase the fatigue strength of rolling element bearings. The purpose of this study is to focus on the surface properties of such parts. Design/methodology/approach A new model to predict bearing fatigue life is presented which takes compressive residual stresses in the bearing subsurface area into consideration. The investigated bearings were machined by the processes of hard turning, hard turning with subsequent deep rolling and a combination of hard turning and deep rolling (turn-rolling) in one process step. Changes in the residual stress state during bearing fatigue tests were investigated and the influence of residual stresses on the bearings fatigue life was researched. Findings Both combinations including the deep rolling process decrease the surface roughness and induce compressive residual stresses. As a result, the L10 fatigue life of roller bearings was increased by the factor of 2.5. Owing to the developed models, this effect can be considered within the design process. Originality/value In the context of the research program “Resource efficient Machine Elements (SPP1551),” machining processes of bearings were investigated regarding the bearing fatigue life. By inducing beneficial residual stresses on the bearings’ subsurface area, the fatigue life could be increased. Thus higher resource efficiency was achieved. To increase the productivity, a combination of hard turning and deep rolling was evaluated.

Research on Bearing Stress Characteristics of Stacking Robot Base under New Engineering Background

Under the background of the continuous development of new engineering, more and more researches are aiming at new cutting-edge technologies, among which industrial robots have attracted much attention. Based on typical trajectory and a given load condition of the palletizing robot, the dynamics analysis and calculation was accomplished by using the dynamics analysis and calculation module of Adams software under the condition that the palletizing robot was working normally, then obtained the dynamic load variation when rolling bearing was running, furthermore, the contact stress change rule was obtained by using the finite element analysis calculation method, and the rule was regard as the basis of rolling bearing fatigue life analysis and evaluation. Judging from the results of analysis and calculation, the contact stress distribution of rolling bearing under the combined effect of both external load and dynamic load, which was similar to the phenomenon of commonly used rolling bearing stress fatigue destruction, this method can effectively overcome the deficiencies of traditional rolling bearing fatigue life calculation method that only consider static load, and reference for relevant engineering and technical personnel.

From the grain/workpiece interaction to the coupled thermal-mechanical residual stresses: an integrated modeling for controlled stress grinding of bearing ring raceway

The residual stress distribution in the surface layer of bearing ring raceway has a significant impact on the fatigue life of rolling bearings. Grinding is the critical manufacturing process for bearing rings, and directly determines the residual stress distribution. However, the residual stress distribution is generally not detected in the manufacturing procedure of rolling bearings, and there are no corresponding control standards or measures. This research intensively investigated the grinding mechanism of bearing ring raceway, and performed an integrated modeling to achieve controlled stress grinding. The integrated modeling starts from the grain/workpiece interaction, through modeling of the distributions of interaction stresses and heat flux, and ends up with the numerical model for coupled thermal-mechanical residual stress analysis. The integrated modeling was validated experimentally through the comparisons between the measured and simulated temperatures and residual stresses. With the integrated model, the generating mechanism of the residual stress distribution was revealed, the influences of grinding parameters and cooling conditions were investigated, and the control strategy was finally put forward. The investigations show that grinding can produce compressive residual stresses in the surface layer of bearing ring raceway. Heat flux is still detrimental to the formation of compressive residual stresses, although thermally induced tensile residual stresses are prevented. To produce compressive residual stresses in the surface layer of bearing ring raceway, the rotational speed of bearing ring should be increased, the rotational speed of grinding wheel and the transverse feed speed should be reduced, and increasing convective heat transfer coefficient is more effective than reducing the initial temperature of grinding fluid.

Working Performance Analysis of Rolling Bearings Used in Mining Electric Excavator Crowd Reducer

Refer to the statistical load data of digging process, on the basis of simulation analysis of crowd reducer system dynamics, the working performance simulation analysis of rolling bearings used in crowd reducer of large mining electric excavator is completed. The contents of simulation analysis include analysis of internal load distribution, rolling elements contact stresses and rolling bearing fatigue life. The internal load characteristics of rolling elements in cylindrical roller bearings are obtained. The results of this study identified that all rolling bearings satisfy the requirements of contact strength and fatigue life. The rationality of bearings selection and arrangement is also verified.

Rolling bearing performance degradation condition recognition based on mathematical morphological fractal dimension and fuzzy C-means

In allusion to performance degradation condition recognition issue for rolling bearing, a method based on mathematical morphological fractal dimension (MMFD as abbreviation) and fuzzy C-means algorithm (FCM as abbreviation) is proposed in this paper. MMFD of vibrating signal is able to describe the complexity and irregularity from the perspective of fractal, its effectiveness and stability is justified by means of signal simulation. On this basis, considering fuzzy character of performance degradation condition boundary, FCM is introduced in degradation condition recognition. Rolling bearing fatigue life enhancement testing was carried out in Hangzhou Bearing Test & Research Center, the whole life data was gathered and applied in this paper, the result shows that the proposed technique of MMFD-FCM has an excellent effect.