Load Distribution Of Bearing Research Articles

A novel method to model effects of natural defect on roller bearing

Abstract The assumption that the defects extend axially throughout rollers or raceways was widely adopted in previous studies, however, this is hardly the situation in natural defects. A contact model that considered the geometric feature of natural defect was developed to analyze effects of defect on roller-raceway contact. The contact stiffness expression for defected roller-raceway was derived by numerical fitting. The contact stiffness expression was introduced into the quasi-static model of roller bearing to model defected roller bearing. The contact load distribution and stiffness of roller bearing were simulated under different defect sizes and operating conditions. Results demonstrate that roller bearing was insensitive to natural defects and the prevailing fatigue criteria is not applicable to roller bearing.

Movement of a Solid Body across a Horizontal Plane with a Circular Area of the Bearing and Uniform Load Distribution under Asymmetric Orthotropic Friction

The motion of a solid body across a horizontal plane with asymmetric orthotropic friction has been studied. The direction of the velocity of the center of mass and its distance to the instantaneous velocity center have been determined for the moment of time immediately before the body stops. It has been shown that, upon the initial pure rotation, the instantaneous acceleration of the center of mass begins the in-plane parallel motion. In the case of initial forward movement, its character does not change.

Effect of preload on ball-raceway contact state and fatigue life of angular contact ball bearing

The performance of angular contact ball bearing is greatly affected by the preload. In the present research, by analyzing the state of ball-raceway contact, a quasi-dynamic model is proposed to study the load distribution of ball bearing under arbitrary preloads. The new model is then used to study the influences of external loads, rotating speed and preload on ball-raceway contact state. Based on this, the fatigue life of ball bearing under running condition is calculated. The results show that a proper preload improves the load distribution and extends the fatigue life of ball bearings. For any given load and rotating speed, an optimum preload, estimated through the bearing life, can be obtained.

Influence of cutterhead system structure on load distribution and life of main bearing

Service life of main bearing represents the life of tunnel boring machine (TBM) system. It is affected by the raceway load distribution which is related to the stiffness of supporting structure, as the main bearing is not rigid. To improve the service life of main bearing, the influences of key parameters of cutterhead system structure on the uniformity of load distribution are revealed, and the structure is optimized based on that. A finite element method (FEM) model of main structure is constructed to get the accurate load distribution in the main bearing for service life calculation, and the springs with nonlinear stiffness are employed to simulate the relationships between rock and cutters on the basis of Colorado School of Mines (CSM) method. Compared with the original structure, it shows that the uniformity of axial force distribution on thrust raceway increases obviously, and the service life of the main bearing is extended.

Theoretical and experimental research on turbo-generator shaft alignment using strain gauge method

Shaft alignment is a key factor for the safe and reliable operation of a turbine unit. This paper presents an approach to estimate the turbo-generator shaft alignment using strain gauge technique with two measuring sections nearby each coupling. The change of shaft bending moment is linearly proportional to the change of bearing elevation and reaction force. So the bearing load distribution can be identified from the strain values and bending moments which are measured using strain gauge. The transfer matrix method is used to calculate the detailed shaft alignment data including deflection, slopes, bearing reaction forces, influence coefficients, sag/gap values. Experiments were carried out on a test rig with 3 rotors, 2 couplings and 6 bearings. It was shown that the strain gauge identification results agree well with the results using the jack-up method. The maximum relative error of each bearing loads is almost 8.7%. The sag/gap values using the strain gauge method are close to those using the laser alignment method. The maximum relative error is less than 7.5%. Results also show that the strain gauge method is sensitive to possible disturbances in the bearing elevation. In the end, strain gauge alignment technique with two measuring sections nearby each coupling was applied on the shaft alignment estimation of a 600 MW turbine unit successfully. The bearing loads and shaft deflection were obtained accurately.

Analyzing the load distribution of four-row tapered roller bearing with Boundary Element Method

A Boundary Element Method (BEM) is used to study the roller bearing contact problem due to its high non-linearity. The plate units are used to simulate the rollers, the bearing boundary elements are used to realize the discontinuous nature of the traction on the contact area, and the Hertz contact theory is used to revise contact widths between rollers and the inner and outer races. According to assembly and fit characteristics of rolling mill tapered roller bearings, in which both clearance fits are adopted to the inner race with the mill roll and the outer race with the shaft block, the four-objects elastic frictional contact program of bearing BEM is compiled, with which a rolling mill four-row tapered roller bearing is simulated. The shaft block direct measure method is used to measure the load distribution of the four-row tapered roller bearing. The experimental data and the result of simulation are compared, and the load distribution laws of simulation identify with the test result, which proves the validity and effectiveness of using elastic frictional contact BEM to analyze the load distribution of bearing.

Adjustment of Blank Holding Force Distribution Utilizing a Multi-Point Die Support System

In this study, the authors employ a multi-point die-support structure to hold the upper die for deep drawings in order to adjust the distribution of the blank holding force (BHF) so as to eliminate wrinkles. The developed multi-point support structure has 12 support cells (support units) between the upper die and the outer slide of a double-action press; the cells are metal cylinders working as springs. The support unit has a ball contact at the interface with the upper die, and the interface freely rotates and slides horizontally. The support unit has strain gauges on the side surface, and the bearing load at each unit can be determined, as well as the elastic deformation. The bearing load distribution is observed through a trial blow, and then the support units are manually relocated to better distribute the supporting points to create the appropriate BHF distribution. To demonstrate the efficiency of the suggested structure, the authors perform deep drawing with off-centered setting of a blank to create wrinkles intentionally. They then employ the multi-point die-support system, relocate the support units, and eliminate wrinkles.

Long‐term contact fatigue analysis of a planetary bearing in a land‐based wind turbine drivetrain

AbstractThis paper presents an approach for performing a long‐term fatigue analysis of rolling element bearings in wind turbine gearboxes. Multilevel integrated analyses were performed using the aeroservoelastic code HAWC2, the multibody dynamics code SIMPACK, the three‐dimensional finite element code Calyx and a simplified lifetime prediction model for rolling contact fatigue. The National Renewable Energy Laboratory's 750 kW wind turbine and its planetary bearing were studied. Design load cases, including normal production, parked and transient load cases, were considered. To obtain the internal bearing load distribution, an advanced approach combining a finite element/contact mechanics model and a response surface model were used. In addition, a traditional approach, the Harris model, was also applied for comparison. The long‐term probability distribution of the bearing raceway contact pressure range was then obtained using Weibull and generalized Gamma distribution functions. Finally, we estimated the fatigue life of the bearing, discussed the differences of the methods used to obtain the bearing internal loads and analyzed the effects of the environmental conditions and load cases on the results. The Harris model may underestimate the inner raceway life by 55.7%, which can cause large load fluctuations along the raceways. The bearing fatigue life is very sensitive to the wind distribution and less affected by the transient and parked load cases. Copyright © 2014 John Wiley & Sons, Ltd.

Contact Force Distribution and Static Load-carrying Capacity of Large Size Double Row Four-point Contact Ball Bearing

Abstract Clearance not only affects the startup torque, rotation precision and stiffness of bearing, but also affects the load distribution, load-carrying capacity and life of bearing. A computational model in which the clearance of bearing is first included is presented for determining the contact force distribution and static load-carrying capacity of a double row four-point contact ball bearing which is subjected to the combined radial, axial and overturning moment loadings. The relation between the negative axial clearance and the contact force distribution is analyzed. The static load-carrying capacity curves are established, and the effects of the changes in negative axial clearance, curvature radius coefficient of raceway groove and initial contact angle on the static load-carrying capacity are analyzed. The results show that, with the increase in the absolute value of negative clearance, the maximum contact load decreases first and then increases. The clearance values in the range of −0.2 mm–0 mm have little effect on the static load-carrying capacity of bearing. With the increase in the curvature radius coefficient of raceway groove and the decrease in the initial contact angle, the static load capacity of bearing decreases.

Prediction of Mechanical Power Loss of Planet Gear Roller Bearings Under Combined Radial and Moment Loading

A modeling methodology is proposed to predict load-dependent (mechanical) power loss of cylindrical roller bearings under combined radial and moment loading with focus on planetary gear set planet bearings. This methodology relies on two models. The first model is a bearing load distribution model to predict load intensities along rolling element contacts due to combined force–moment loading. This model takes into account planet bearing macrogeometry as well as micromodifications to the roller and race surfaces. The second model is an elastohydrodynamic lubrication (EHL) model employed to predict rolling power losses of bearing contacts with load intensities predicted by the load distribution model. The bearing mechanical power loss methodology is applied to bearings of an automotive planetary gear set to quantify the sensitivity of mechanical power loss to key bearing, lubrication and surface parameters as well as operating speed, load and temperature conditions.

Identification of bearing load by three section strain gauge method: Theoretical and experimental research

Reasonable bearing load distribution is important for the safe and reliable operation of rotating machinery. However, it is difficult to measure bearing load in field. This paper puts forward a bearing load identification method based on the measured three section strain values. Shaft is divided into several sections at strain gauge locations. The force and moment equilibrium equations are set up and assembled to form bearing load solving equations. This method can reduce the modeling error, especially for the machines with irregular rotating parts. It can also be applied for the entire shaft system bearing load distribution study with high accuracy and fault tolerant. Test was done on a rotor-bearing system rig. Bearing load distribution in different shaft alignment states is identified and analyzed. Test results show that the bearing load distribution varies sensitively and linearity to the change of bearing elevation. Further research shows that the accuracy of the method depends on the strain gauge locations. It would be best to place the strain gauge at location where the bending moment is sensitive to the change of bearing load. Moreover, mounting the strain gauge further from the bearing reduces the relative error due to the exact reaction point location is not known, which influences the accuracy of beading moment arm from the strain gauge location to the reaction point.

풍력발전기용 피치베어링의 하중분배, 접촉 및 피로수명 해석

This study is aimed to predict the fatigue life for pitch bearings under combined radial, thrust load and moment. In order to do this, a series of simulation such as bearing load distribution, initial surface stress, subsurface stress and fatigue analysis is needd. Fatigue life for pitch bearing can be predicted by using a bearing's material fatigue property.

Analysis on Load Distribution of Needle Bearing Considering Misalignment

A quasi-static analytical model for needle bearing was established base on the rolling contact theory and the force analysis of needle bearing,and the model was caculated by computer program.Conclusions are drawn as follows by analysis of needle bearing load distribution in different misalignment,different load,different clearance,different speed,different crown drop of needle:work of bearing would be influenced if misalignment so big,the influence of misalignment must be considered when the engineer determine the clearance of beearing, it’s rotational speed has small influence on the load distribution of bearing ,reasonable choise of crowning of needle could be enhanced the lifetime of needle bearings.

Load Distribution of Cross-Roller Slewing Bearing

Because of cross roller-slewing bearing structure have a certain degree of particularity, and two sets of cross rollers is equivalent to two columns roller stack situation, therefore it should deduce roller calculation formula for two sets of roller respectively. According to the stress of the slewing bearings, we proceed load distribution calculation synthetically under the center of bearing axial force, overturning moment and radial force. Finally, based on the above formula for calculating the bearing load distribution and through the Matlab software, we analyze the influence of some parameters on the bearing load distribution. For ensuring bearing design parameter, it has the certain reference value.

Optimum Design for Improvement of Roller Bearing Load Distribution in a Medium Scale Mill

In roller bearing reformation of a medium scale mill, the micro-dimensional theory of mill is adopted. A new space self-alignment roll system is developed, including a divided base. This ensures the statically determinate of the mill under both light duty and heavy duty conditions. So the load distribution of roller bearing can be improved, and the bearing will have a long life. Since the new roll system began to run, it is in a fine motion until now. The roller bearing has exceeded its specified life. The design aim of service longevity is realized.

Optimal Bearing Housing Designing Using Topology Optimization

The internal load distribution in rolling bearings has a high impact on the bearing fatigue life. This study presents a method to optimize roller bearing housing design in order to maximize the bearing fatigue life by ensuring an optimal internal load distribution. An FE-model of a cylindrical roller bearing utilizing nonlinear springs in the roller modeling is presented, which is capable of simulating the bearing load distribution efficiently. The optimal load distribution is achieved by specifying the desired internal load distribution as design constraints in a topology optimization of the bearing housing design. The superiority of the method is clearly demonstrated through case studies involving a cylindrical roller bearing, where it is shown that the fatigue life is increased and the bearing housing mass and roller contact misalignment is reduced.

Effect of Internal Clearance on Load Distribution and Life of Radially Loaded Ball and Roller Bearings

The effect of internal clearance on radially loaded deep-groove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearance (interference) conditions to produce a curve of life factor versus internal clearance. Rolling element loads can be optimized and bearing life maximized for a small negative operating clearance. Life declines gradually with positive clearance and rapidly with increasing negative clearance. Relationships were found between bearing life and internal clearance as a function of ball or roller diameter adjusted for load. Results are presented as life factors for radially loaded bearings independent of bearing size or applied load. In addition, a modified Stribeck equation is presented that relates the maximum rolling element load to internal bearing clearance.

모멘트 하중을 고려한 볼베어링의 하중분배, 접촉 및 피로수명 해석

This study is aimed to predict the fatigue life for bearings under combined radial, thrust and moment load. In order to do this, a series of simulation such as bearing load distribution, initial surface stress, subsurface stress and fatigue analysis is needed. And using the bearing's material fatigue property we can predict fatigue life for ball bearing.

Study on Precise Stamping under Eccentric Load Using a Multi-Point Die-Support Structure

In this study, the authors employ a multi-point die-support structure to hold the punch plate of a stamping die in order to intercept useless force from the slide of a press machine. The developed multi-point support structure has 12 support cells (support units) between the punch plate and the slide of the press machine; the cells are metal cylinders working as springs. The support unit has a ball contact at the interface of the punch plate, and the interface freely for rotates and slides horizontally. The support unit has strain gauges on the side surface, and we can determine the bearing load at each unit, as well as elastic deformation. We can observe the bearing load distribution and then relocate the support units to better distribute the supporting points. The authors discuss the relocation of support units and demonstrate the efficiency of the proposed structure for reducing the jolt of a stamping die set. The range of jolt between the punch plate and the die plate of the experimental die is 0.711mm with normal support for piercing a 30mm-diameter hole on a 1.2mm-thick JSC980Y sheet. However, it is 0.355mm with the proposed die-support structure after several relocations of the support units.

Effect of load transfer on the cracking behavior at a countersunk fastener hole

The objective of this paper is to describe the effect of fastener load transfer on the cracking behavior at countersunk fastener holes. Both experimental and computational studies are described and compared when possible. Fatigue failures at previously tested mechanical joint specimens were investigated and characterized. Qualitative three-dimensional finite element analyses revealed that the degree of load transfer through the fastener could influence the cracking behavior at the countersunk fastener hole. This finding from the qualitative analysis provides one good explanation to the experimental results of the mechanical joint specimens. The cracking location’s dependence on the load transfer can be attributed to the non-uniform bearing load distribution along the straight bore caused by the load transfer.