scholarly journals Unbalance Response Prediction for Rotors on Ball Bearings Using Speed- and Load-Dependent Nonlinear Bearing Stiffness

2005 ◽  
Vol 2005 (1) ◽  
pp. 53-59 ◽  
Author(s):  
David P. Fleming ◽  
J. V. Poplawski
Keyword(s):  
Response Prediction ◽  
Rolling Element Bearing ◽  
Response Analysis ◽  
Ball Bearings ◽  
Moderate Amount ◽  
Constant Stiffness ◽  
Unbalance Response ◽  
Rolling Element ◽  
Bearing Stiffness ◽  
Element Bearing

Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus, an accurate rotordynamic analysis requires that bearing forces corresponding to the actual bearing deflection be utilized. For this work, bearing forces were calculated by COBRA-AHS, a recently developed rolling-element bearing analysis code. Bearing stiffness was found to be a strong function of bearing deflection, with higher deflection producing markedly higher stiffness. Curves fitted to the bearing data for a range of speeds and loads were supplied to a flexible rotor unbalance response analysis. The rotordynamic analysis showed that vibration response varied nonlinearly with the amount of rotor imbalance. Moreover, the increase in stiffness as critical speeds were approached caused a large increase in rotor and bearing vibration amplitude over part of the speed range compared to the case of constant-stiffness bearings. Regions of bistable operation were possible, in which the amplitude at a given speed was much larger during rotor acceleration than during deceleration. A moderate amount of damping will eliminate the bistable region, but this damping is not inherent in ball bearings.

scholarly journals Transient Vibration Prediction for Rotors on Ball Bearings Using Load-Dependent Nonlinear Bearing Stiffness

2004 ◽  
Vol 10 (6) ◽  
pp. 489-494 ◽  
Author(s):  
David P. Fleming ◽  
J. V. Poplawski
Keyword(s):  
High Speed ◽  
Roller Bearing ◽  
Transient Behavior ◽  
Rolling Element Bearing ◽  
Ball Bearings ◽  
Transient Vibration ◽  
Vibration Prediction ◽  
Rolling Element ◽  
Bearing Stiffness ◽  
Element Bearing

Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for nonlinear speed and load-dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis—Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running five degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller bearings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.

The importance of bearing stiffness and load when estimating the size of a defect in a rolling element bearing

2018 ◽  
Vol 18 (5-6) ◽  
pp. 1527-1542 ◽  
Author(s):  
Francesco Larizza ◽  
Alireza Moazen-Ahmadi ◽  
Carl Q Howard ◽  
Steven Grainger
Keyword(s):  
Large Data ◽  
Rolling Element Bearing ◽  
Static Stiffness ◽  
Data Set ◽  
Rolling Element ◽  
Bearing Stiffness ◽  
Bearing Assembly ◽  
Element Bearing ◽  
Vibration Signatures ◽  
Force Displacement

The change in the static stiffness of a bearing assembly is an important discriminator when determining the size of a defect in a rolling element bearing. In this article, the force–displacement relationships for defective bearings under various static radial loadings at various cage angular positions are analytically estimated and experimentally measured and analyzed. The study shows that the applied load has a significant effect on the static stiffness variations in defective rolling element bearings. The experimental measurements of the effect of the defect size on the varying stiffness of the bearing assembly, which has not been shown previously, provides valuable knowledge for developing methods to distinguish between defective bearings with defects that are smaller or larger than one angular ball spacing. The methods and results presented here contribute to the wider experimental investigation of the effects of loadings on the varying static stiffness of defective bearings and its effects on the measured vibration signatures. A large data set was obtained and has been made publicly available.

scholarly journals Fatigue Life of High-Speed Ball Bearings With Silicon Nitride Balls

1975 ◽  
Vol 97 (3) ◽  
pp. 350-355 ◽  
Author(s):  
R. J. Parker ◽  
E. V. Zaretsky
Keyword(s):  
Fatigue Life ◽  
Silicon Nitride ◽  
High Speed ◽  
Bearing Steel ◽  
Rolling Element Bearing ◽  
Ball Bearings ◽  
Rolling Element ◽  
Low Mass ◽  
Element Bearing ◽  
Steel Balls

Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. This material has a low specific gravity (41 percent that of bearing steel) and has a potential application as low mass balls for very high-speed ball bearings. The five-ball fatigue tester was used to test 12.7-mm- (0.500-in-) dia silicon nitride balls at maximum Hertz stresses ranging from 4.27 × 109 N/m2 (620,000 psi) to 6.21 × 109 N/m2 (900,000 psi) at a race temperature of 328K (130 deg F). The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.

Load-Displacement Relationships for Ball and Spherical Roller Bearings

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
L. Houpert
Keyword(s):  
Contact Angle ◽  
Roller Bearing ◽  
Point Contact ◽  
Rolling Element Bearing ◽  
Smooth Transition ◽  
Ball Bearings ◽  
Roller Bearings ◽  
Deep Groove ◽  
Rolling Element ◽  
Element Bearing

Analytical relationships for calculating three rolling element bearing loads (Fx, Fy, and Fz) and two tilting moments (My and Mz) as a function of three relative race translations (dx, dy, and dz) and two relative race tilting angles (dθy and dθz) have been given in a previous paper. The previous approach was suggested for any rolling element bearing type, although it has been recognized that the assumption of a constant rolling element-race contact angle is not well supported by deep groove ball bearings (DGBB) or angular contact ball bearings (ACBB). The new approach described in this paper addresses the latter weaknesses by accounting for the variation of the contact angle on the most loaded ball and also shows that misalignment effects on spherical roller bearing (SRB) loads are negligible. Comparisons between the simplified approach (option 1) and the “enhanced” numerical approach (option 2, which requires a summation of the load components on each ball with the appropriate contact angle included) is made, showing a good correlation as long as the relative misalignment remains reasonable or occurs in the plane corresponding to maximum radial displacement. Option 2 can, however, be recommended since it is easy to program and quite accurate at any misalignment level. Other pros and cons of both options are described. As in the previous paper, a full coupling between all displacements and forces, as well as roller and raceway crown radii, are considered, meaning that Hertzian point contact stiffness is used in roller bearings at low load with a smooth transition toward Hertzian line contact as the load increases. This approach is particularly recommended for programming the rolling element bearing behavior in any finite element analysis or multibody system dynamic tool, since only two nodes are considered: one for the inner race (IR) center, usually connected to a shaft, and another node for the outer race (OR) center, connected to the housing.

An Enhanced Study of the Load–Displacement Relationships for Rolling Element Bearings

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
L. Houpert
Keyword(s):  
Contact Angle ◽  
Roller Bearing ◽  
Rolling Element Bearing ◽  
Smooth Transition ◽  
Ball Bearings ◽  
Element Analysis ◽  
Outer Race ◽  
Deep Groove ◽  
Rolling Element ◽  
Element Bearing

An enhanced analytical approach is suggested for calculating three rolling element bearing loads Fx, Fy, and Fz as well as the two tilting moments My and Mz as a function of five relative race displacements: three translations dx, dy, and dz, and two tilting angles dθy and dθz. A full coupling between all these displacements and forces is considered. This approach is particularly recommended for programming the rolling element bearing behavior in any finite element analysis or multibody system dynamic tool, since only two nodes are considered: one for the inner race center, usually connected to a shaft, and another node for the outer race center, connected to the housing. Also, roller and raceway crown radii are considered, meaning that Hertzian point contacts stiffness can be used at low load with a smooth transition toward Hertzian line contact as the load increases. This approach can be used for describing any rolling element bearing type when neglecting centrifugal and gyroscopic effects and applying the approximation of a constant ball–race contact angle. Deep groove ball bearings (whose contact angle sign follows the sign of the applied bearing axial force) or other ball bearings or spherical roller bearing operating under large misalignment may not support such approximations.

Contact characteristic and vibration mechanism of rolling element bearing in the process of fault evolution

2021 ◽  
Vol 235 (1) ◽  
pp. 19-36 ◽  
Author(s):  
Wenbing Tu ◽  
Jinwen Yang ◽  
Wennian Yu ◽  
Ya Luo
Keyword(s):  
Fault Diagnosis ◽  
Vibration Response ◽  
Rolling Element Bearing ◽  
Bearing Fault Diagnosis ◽  
Rolling Element ◽  
Vibration Mechanism ◽  
Contact Characteristic ◽  
Element Bearing ◽  
Bearing Vibration ◽  
Fault Evolution

The vibration response of rolling element bearing has a close relation with its fault. An accurate evaluation of the bearing vibration response is essential to the bearing fault diagnosis. At present, most bearing dynamics models are built based on rigid assumptions, which may not faithfully reveal the dynamic characteristics of bearing in the presence of fault. Moreover, previous similar works mainly focus on the fault with a specified size without considering the varying contact characteristics as the fault evolves. This paper developed an explicit dynamics finite element model for the bearing with three types of raceway faults considering the flexibility of each bearing component in order to accurately study the contact characteristic and vibration mechanism of defective bearings in the process of fault evolution. The developed model is validated by comparing its simulation results with both analytical and experimental results. The dynamic contact patterns between the rolling elements and the fault, the additional displacement due to the fault and the faulty characteristics within the bearing vibration signal during the fault evolution process are investigated. The analysis results from this work can provide practitioners an in-depth understanding towards the internal contact characteristics with the existence of raceway fault and theoretical basis for rolling bearing fault diagnosis.

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