Stiffness Optimization of Hollow Cylindrical Rolling Element Bearing

2008 ◽  
Author(s):  
P. H. Darji ◽  
D. P. Vakharia
Keyword(s):  
Load Capacity ◽  
Contact Problems ◽  
Contact Stresses ◽  
Rolling Element Bearing ◽  
Thin Wall ◽  
Element Analysis ◽  
Normal Loading ◽  
Rolling Element ◽  
Rolling Elements ◽  
Minimum Stress

Since being originally introduced, cylindrical rolling element bearings have been significantly improved, in terms of their performance and working life. A major objective has been to decrease the Hertz contact stresses at the roller–raceway interfaces, because these are the most heavily stressed areas in a bearing. It has been shown that bearing life is inversely proportional to the stress raised to the ninth power (even higher). Investigators have proposed that under large normal loads a hollow element with a sufficiently thin wall thickness will deflect appreciably more than a solid element of the same size. An improvement in load distribution and thus load capacity may be realized, as well as contact stress is also reduced considerably by using a bearing with hollow rolling elements. Since for hollow rolling element no method is available for the calculation of contact stresses and deformation. The contact stresses in hollow members are often calculated by using the same equations and procedures as for solid specimens. This approach seems to be incorrect. Recently, the Finite Element Analysis (FEA) has been successfully used to evaluate contact problems for the roller bearings. Investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages ranging from 0% to 90% have been analysed in FEA software to find the optimum percentage hollowness which gives minimum stress and finally longest fatigue life.

Determination of Optimum Hollowness for Hollow Cylindrical Rolling Element Bearing

2008 ◽  
Author(s):  
P. H. Darji ◽  
D. P. Vakharia
Keyword(s):  
Load Capacity ◽  
Contact Problems ◽  
Contact Stresses ◽  
Rolling Element Bearing ◽  
Thin Wall ◽  
Element Analysis ◽  
Normal Loading ◽  
Roller Bearings ◽  
Light Load ◽  
Rolling Element

Hollow-cylindrical-roller bearings are intended for light load applications, including all types of grinding, machining, and milling spindles. They use hollow cylindrical rollers instead of solid rollers. These provide significant advantages over standard bearings, such as reduced vibration, low-radial runout, better radial stiffness, higher operating speeds, and lower operating temperatures. Investigators have proposed that under large normal loads a hollow element with a sufficiently thin wall thickness will deflect appreciably more than a solid element of the same size. An improvement in load distribution and thus load capacity may be realized, as well as contact stress is also reduced considerably by using a bearing with hollow rolling elements. Since for hollow rolling element no method is available for the calculation of contact stresses and deformation. The contact stresses in hollow members are often calculated by using the same equations and procedures as for solid specimens. This approach seems to be incorrect. Recently, the Finite Element Analysis (FEA) has been successfully used to evaluate contact problems for the roller bearings. Investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages ranging from 0% and 30% to 80% have been analysed in FEA software to find the optimum percentage hollowness which gives minimum stress and finally longest fatigue life.

Rolling Element Bearing Non-Linearity Effects

2000 ◽  
Author(s):  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Equations Of Motion ◽  
Rolling Element Bearing ◽  
Radial Clearance ◽  
Rotor Systems ◽  
Bearing Life ◽  
Rolling Element ◽  
Bearing Load ◽  
Rolling Elements ◽  
Element Bearing ◽  
Negative Clearance

Non-linearity effects in rolling element bearings arise from two sources, viz. the Hertzian force deformation relationship and the presence of clearance between the rolling elements and the bearing races. Assuming that centrifugal effects may be neglected and that the presence of axial preload is appropriately reflected in a corresponding change in the radial clearance, this paper analyses a simple test rig to illustrate that non-linear phenomena such as synchronous multistable and nonsynchronous motions are possible in simple rigid and flexible rotor systems subjected to unbalance excitation. The equations of motion of the rotor bearing system were solved by transient analysis using fourth order Runge Kutta. Of particular interest is the effect of clearance, governed in practice by bearing specification and the amount of preload, on the vibration behaviour of rotors supported by ball bearings and on the bearing load. It is shown that in the presence of positive clearance, there exists an unbalance excitation range during which the bearing is momentarily not transmitting force owing to contact loss, resulting in rolling element raceway impact with potentially relatively high bearing forces; and indicating that for long bearing life, operation with positive clearance should be avoided in the presence of such unbalance loading. Once the unbalance excitation is high enough to avoid such contact loss, it is the bearings with zero or negative clearance which produce maximum bearing forces.

Traction Characteristics of a Rolling Element Bearing Under Rapid Acceleration and Implications for Auxiliary Operation in Magnetic Bearing Systems

2006 ◽  
Author(s):  
Matthew O. T. Cole ◽  
Theeraphong Wongratanaphisan
Keyword(s):  
Dynamic Behavior ◽  
Magnetic Bearing ◽  
Rolling Element Bearing ◽  
Elastic Behavior ◽  
Friction Forces ◽  
Auxiliary Operation ◽  
Rolling Element ◽  
Rolling Elements ◽  
Auxiliary Bearing ◽  
Bearing Assembly

The application of rolling element bearings for auxiliary operation in magnetic bearing systems is quite common, yet such operation is very different to that for which standard bearings are designed. During initial touchdown of a spinning rotor with an auxiliary bearing, rapid acceleration of the bearing inner race results in large inertial and friction forces acting on the rolling elements. Complex dynamic behavior of the bearing assembly and resulting traction forces are difficult to predict but, nonetheless, have important implications for both rotor dynamic behavior and thermo-elastic behavior of the bearing components. The aim of this work is to obtain an insight into bearing behavior by analyzing component interaction forces that would arise based on the assumption that the overall bearing traction torque is dependent only on instantaneous load, speed and acceleration. How such an analysis can be verified by experimental measurements of traction during rapid acceleration is discussed and some initial experimental results are presented. The implications for modeling and prediction of rotor-magnetic bearing system behavior during touchdown are also discussed.

scholarly journals Component Hardness Differences and Their Effect on Bearing Fatigue

1967 ◽  
Vol 89 (1) ◽  
pp. 47-54 ◽  
Author(s):  
E. V. Zaretsky ◽  
R. J. Parker ◽  
W. J. Anderson
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Load Capacity ◽  
Full Scale ◽  
Contact Temperature ◽  
Rolling Element Bearings ◽  
Rolling Element ◽  
Rolling Elements ◽  
Compressive Residual Stresses

The five-ball fatigue tester and full-scale rolling-element bearings were used to determine the effect of component hardness differences of SAE 52100 steel on bearing fatigue and load capacity. Maximum fatigue life and load capacity are achieved when the rolling elements of a bearing are one to two points (Rockwell C) harder than the races. There appears to be an interrelation among compressive residual stresses induced in the races during operation, differences in component hardness, and fatigue life. Differences in contact temperature and plastically deformed profile radii could not account for differences in fatigue life.

Diagnosis of Rolling-Element Bearings Failure by Localized Electrical Current Between Track Surfaces of Races and Rolling-Elements

2002 ◽  
Vol 124 (3) ◽  
pp. 468-473 ◽  
Author(s):  
Har Prashad
Keyword(s):  
Theoretical Model ◽  
Electrical Current ◽  
Rolling Element Bearing ◽  
Rolling Element Bearings ◽  
Bearing Failure ◽  
Cause Analysis ◽  
Rolling Element ◽  
Rolling Elements ◽  
Dimensional Parameters ◽  
Element Bearing

The diagnosis and cause analysis of rolling-element bearing failure have been well studied and established in literature. Failure of bearings due to unforeseen causes were reported as: puncturing of bearings insulation; grease deterioration; grease pipe contacting the motor base frame; unshielded instrumentation cable; the bearing operating under the influence of magnetic flux, etc. These causes lead to the passage of electric current through the bearings of motors and alternators and deteriorate them in due course. But, bearing failure due to localized electrical current between track surfaces of races and rolling-elements has not been hitherto diagnosed and analyzed. This paper reports the cause of generation of localized current in presence of shaft voltage. Also, it brings out the developed theoretical model to determine the value of localized current density depending on dimensional parameters, shaft voltage, contact resistance, frequency of rotation of shaft and rolling-elements of a bearing. Furthermore, failure caused by flow of localized current has been experimentally investigated.

Transient Rotordynamic Modeling of Rolling Element Bearing Systems

2001 ◽  
Author(s):  
A. Liew ◽  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Rolling Element Bearing ◽  
Hertzian Contact ◽  
Centrifugal Load ◽  
Linear Behavior ◽  
Deep Groove ◽  
Rolling Element ◽  
Rolling Elements ◽  
Load Effects ◽  
Element Bearing ◽  
Bearing Preload

Non-linearity effects in rolling element bearings may arise from the Hertzian contact force deformation relationship, the presence of clearance between the rolling elements and the bearing races, and the bearing to housing clearance. Assuming zero bearing to housing clearance and ignoring rolling element centrifugal load effects, it has been shown in earlier work that Rotor Bearing Systems (RBSs) with deep groove ball bearings can give rise to non-linear behavior such as chaotic motion and jump. This paper extends the bearing model to include rolling element centrifugal load, angular contacts and axial dynamics. The effect of more sophisticated bearing models is illustrated in both a rigidly supported rigid RBS and a flexibly supported flexible RBS, the latter being a model of a test rig designed to simulate an aircraft mounted accessory drive unit. Results are presented on the effect of bearing preload on the unbalance response up to a speed of 18,000 rpm.

Strength Against Fracture of End Hemispherical Cavity Roller Under Static Loading: Experimental and Simulation Investigation

2020 ◽  
Vol 143 (7) ◽  
Author(s):  
Paresh C. Chhotani ◽  
Dipak P. Vakharia
Keyword(s):  
Fatigue Life ◽  
Maximum Shear Stress ◽  
Contact Stresses ◽  
Fracture Load ◽  
Experimental Results ◽  
Rolling Element Bearing ◽  
Catastrophic Failure ◽  
Rolling Element ◽  
Fracture Tests ◽  
Novel Concept

Abstract Enhancement in fatigue life of the rolling-element bearing has been captivating since years. The hollow concept had been triggered years back; however, it could not catch widespread applications due to catastrophic failure. Thus, any novel concept of the rolling element must be assessed for its strength against catastrophic failure before competing for better fatigue life on field with other alternatives. This paper commences with the outcomes of the comparative assessment of the experimental evaluation of strength against fracture under static loads for layered and hollow rollers with solid rollers, which devise the requirements for new concepts. The end hemispherical cavity (EHC) roller concept, being a proper geometrical blending of solidity and hollowness, prospects to overcome the strength concern along with a considerable reduction in contact stresses. Thus, experimental investigation was conducted with full-bearing fracture tests and individual roller specimens fracture tests for five variants: EHC, solid, layered, 61H, and 37H (hollow rollers with 61% and 37% hollowness, respectively). The simulations were carried out to support the outcomes of experimental trials. The experimental results with full-bearing samples and individual roller specimens demonstrated ranking as follows: EHC, 37H, layered, and 61H. The EHC roller concept was substantiated to be stronger than hollow and layered rollers besides prompting appreciable reduction in contact stresses compared with the solid roller. The simulation results agreed well with experimental results of fracture tests, and the recommendations from findings of failure theories (maximum normal stress, distortion energy, and maximum shear stress) adopted for estimating fracture load for rollers have been discussed.

Effect of Differential Hardness on Static Load Capacity of AISI 52100 Bearing Steel

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
Iqbal Shareef ◽  
Joshua A. Brandes ◽  
Erwin V. Zaretsky
Keyword(s):  
Static Load ◽  
Load Capacity ◽  
Bearing Steel ◽  
Ball Bearings ◽  
Element Analysis ◽  
Heat Treated ◽  
Aisi 52100 ◽  
The Finite Element Analysis ◽  
Rolling Element ◽  
Steel Heat

Abstract Static Load Capacity as defined by Palmgren is the load (stress) applied to a bearing that results in an indentation greater than 0.0001 times the diameter of the rolling element. The effect of hardness on the Static Load Capacity of AISI 52100 bearing steel heat treated to six different hardnesses was investigated. Indentation, depth, diameter, volume, and surface area were measured by the white light interferometer. A total of 468 hardness ball–plate combination tests were conducted. For a given plate (race) hardness, the Static Load Capacity was dependent on plate (race) hardness and independent of mating ball hardness from Rockwell C 56 to 66. For plate (race) hardness between Rockwell C 56 and 60, the Static Load Capacity was relatively constant. At Rockwell C hardness between 60 and 61, the Static Load Capacity increased and then rapidly decreased at a plate hardness of Rockwell C 66, below that value obtained at Rockwell C 56. Experimental results obtained for Static Load Capacity using the Palmgren criteria correlated with the finite element analysis for ball-on-plate indentation but not with Hertz theory. The Static Load Capacity based on Yhland for ball bearings was equal to a maximum Hertz stress of 3.71 GPa (538 ksi) at a ball-race conformity of 52%. This value is 12% lower than that specified in the ISO and ANSI/ABMA Bearing Standards. The manufacturers’ Static Load Rating can be reduced from 4% to 7% for ball bearings and from 8% to 25% for roller bearings.

Analysis of a Rolling-Element Idler Gear Bearing Having a Deformable Outer-Race Structure

1963 ◽  
Vol 85 (2) ◽  
pp. 273-278 ◽  
Author(s):  
A. B. Jones ◽  
T. A. Harris
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Roller Bearing ◽  
Rolling Element Bearing ◽  
Outer Ring ◽  
Outer Race ◽  
Rolling Element ◽  
Rolling Elements ◽  
Planet Gear ◽  
Bearing Rings

Conventional calculations of ball and roller bearing carrying capacity and fatigue life assume that the raceway bodies are rigid structures and that all elastic deformation occurs at the rolling elements’ contact with the raceways. In many instances, and particularly with aircraft applications, the bearing rings and their supports cannot be considered rigid. One such application is the planet gear in a transmission. This report develops a theory whereby the effects of the elastic distortions of the outer race of a rolling-element bearing on the internal load distribution and fatigue life of the bearing can be considered. The theory has been programmed for a high-speed, digital computer. An example of calculation for a planet gear roller bearing whose outer race is integral with the gear and of relatively thin section is given. The distortions of the flexible outer ring cause a significantly lower bearing fatigue life (L10) than would occur if the outer ring were rigid and considering a practical range of bearing diametral clearances. Mr. Jones developed the theoretical analysis for this paper and Mr. Harris provided the programming and the experimental data.

Spalling Size Evaluation of Rolling Element Bearing Using Acoustic Emission

2013 ◽  
Vol 569-570 ◽  
pp. 497-504 ◽  
Author(s):  
An Bo Ming ◽  
Zhao Ye Qin ◽  
Wei Zhang ◽  
Fu Lei Chu
Keyword(s):  
Acoustic Emission ◽  
Rolling Element Bearing ◽  
Rolling Element Bearings ◽  
Outer Race ◽  
Cepstrum Analysis ◽  
Rolling Element ◽  
Rolling Elements ◽  
Element Bearing ◽  
Envelope Spectrum ◽  
Size Evaluation

Spalling of the races or rolling elements is one of the most common faults in rolling element bearings. Exact estimation of the spall size is helpful to the life prediction for rolling element bearings. In this paper, the dual-impulsive phenomenon in the response of a spalled rolling element bearing is investigated experimentally, where the acoustic emission signals are utilized. A new method is proposed to estimate the spall size by extracting the envelope of harmonics of the ball passing frequency on the outer race from the squared envelope spectrum. Compared with the cepstrum analysis, the proposed procedure shows more powerful anti-noise ability in the fault size evaluation.

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