scholarly journals Dynamic Capacity and Surface Fatigue Life for Spur and Helical Gears

1976 ◽  
Vol 98 (2) ◽  
pp. 267-274 ◽  
Author(s):  
J. J. Coy ◽  
D. P. Townsend ◽  
E. V. Zaretsky
Keyword(s):  
Fatigue Life ◽  
Gear Train ◽  
Rolling Element Bearing ◽  
Tangential Load ◽  
Dynamic Capacity ◽  
Probability Of Survival ◽  
Surface Fatigue ◽  
Rolling Element ◽  
Life Model ◽  
Life Predictions

A mathematical model for surface fatigue life of gear, pinion, or entire meshing gear train is given. The theory is based on the statistical approach used by Lundberg and Palmgren for rolling-element bearings. Also equations are presented which give the dynamic capacity of the gear set. The dynamic capacity is the transmitted tangential load which gives a 90 percent probability of survival of the gear set for one million pinion revolutions. The analytical results were compared with test data for a set of AISI 9310 spur gears operating at a maximum Hertz stress of 1.71 × 109 N/m2 (248,000 psi) and 10,000 rpm. The theoretical life predictions were very good when material constants obtained from rolling-element bearing tests were used in the gear life model.

A New Fatigue Life Model for Rolling Bearings

1985 ◽  
Vol 107 (3) ◽  
pp. 367-377 ◽  
Author(s):  
E. Ioannides ◽  
T. A. Harris
Keyword(s):  
Fatigue Life ◽  
Rolling Bearing ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Rolling Bearings ◽  
Structural Fatigue ◽  
Probability Of Survival ◽  
Life Model ◽  
Life Predictions ◽  
Fatigue Criterion

This paper describes a novel model for the prediction of fatigue life in rolling bearings. Central to this model is the postulation of a statistical relationship between the probability of survival, the fatigue life, and a stress-related fatigue criterion level above a fatigue limit for an elementary volume of material in the bearing. Using this concept, the stress volume to fatigue and the fatigue life of the bearing can be calculated for different loads, material and operating conditions. Comparisons between experimentally obtained rolling bearing fatigue lives and lives predicted using this theory indicate its ability to account for phenomena hitherto excluded from fatigue life predictions. Furthermore, comparisons between experimentally obtained fatigue lives for other specimens used in structural fatigue tests and fatigue lives predicted using the new model show good agreement.

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.

Ball Spalling in Rolling Element Bearings: Decrease in Rolling Contact Fatigue Life Due to Inferior Microstructure and Manufacturing Processes

2021 ◽  
Author(s):  
Graham Keep ◽  
Mark Wolka ◽  
Beth Brazitis
Keyword(s):  
Fatigue Life ◽  
Rolling Contact Fatigue ◽  
Microstructural Analysis ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Rolling Element Bearing ◽  
Bench Test ◽  
Bearing Life ◽  
Rolling Element ◽  
Contact Fatigue Life

Abstract Through hardened steel ball fatigue failure is an atypical mode of failure in a rolling element bearing. A recent full-scale bench test resulted in ball spalling well below calculated bearing life. Subsequent metallurgical analysis of the spalled balls found inferior microstructure and manufacturing methods. Microstructural analysis revealed significant carbide segregation and inclusions in the steel. These can result from substandard spheroidized annealing and steel making practices. In addition, the grain flow of the balls revealed a manufacturing anomaly which produced a stress riser in the material making it more susceptible to crack initiation. The inferior manufactured balls caused at least an 80% reduction in rolling contact fatigue life of the bearing.

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.

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.

Gear Pitting Life Prediction and Comparison With Experiments

2005 ◽  
Author(s):  
Dong Zhu ◽  
Michael Bujold ◽  
Leon M. Keer
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Life Prediction ◽  
Mixed Lubrication ◽  
Prediction Methods ◽  
Gear Design ◽  
Surface Fatigue ◽  
Life Model ◽  
Von Mises ◽  
Von Mises Stresses

Predicting gear surface fatigue life is vital to gear and transmission design. Although simplified approaches based on the smooth-surface Hertzian contact stress calculations are available, the trend of compact design of high-power gear systems requires the gear design calculation to consider severe operation and lubrication conditions and detailed surface topography. It is needed, therefore, to upgrade the life prediction methods. The research presented in this paper aims to develop a gear pitting life prediction approach based on the rough-surface mixed lubrication model developed by Hu and Zhu [1] and the fatigue life model developed by Zaretsky and modified by Epstein et al [2] with accurate surface-subsurface stress analyses. With this approach, gear design parameters, operating conditions, materials, lubricant, and real tooth surface topography are used as input data. When conducting surface fatigue life prediction, three modules are employed: the mixed lubrication module, the stress analysis module, and the fatigue life module. In the mixed lubrication module, machined gear surfaces are digitized and used for calculating the pressure distribution and lubricant film thickness in the mixed lubrication. The mixed-lubrication pressure distribution is inputted into the stress module to obtain surface and subsurface von Mises stresses. These stresses are then integrated in the fatigue life module for estimating the fatigue life corresponding to a certain failure probability (50% in the present study). In other words, the life prediction is now based on subsurface von Mises stresses in the lubricated rough surface contacts, instead of smooth contact Hertzian pressure. There are a few materials constants involved in the fatigue life module. They are calibrated by comparing the prediction results with available Eaton experimental data. Table 1 lists the experimental data for 15 gear sets (most of them are hobbed and shaved) under combined rolling and sliding. The Hertzian stress ranges from 0.8554 GPa to 2.9494 GPa. It has been found that most conventional pitting life prediction methods tend to give conservative life estimates. With optimized materials parameters in the present life model, predicted pitting life results well agree with available Eaton gear test data, and the correlation appears to be 96.3%. Figure 1 shows the comparison between experimental and prediction data. Obviously, the model prediction well represents the performance of this group of gear surfaces in contact and mixed lubrication.

scholarly journals The Series Hybrid Bearing—A New High Speed Bearing Concept

1972 ◽  
Vol 94 (2) ◽  
pp. 117-122 ◽  
Author(s):  
W. J. Anderson ◽  
D. P. Fleming ◽  
R. J. Parker
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Ball Bearing ◽  
Rolling Element Bearing ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Rolling Element ◽  
Element Bearing ◽  
Hybrid Bearing ◽  
Inner Race

The series-hybrid bearing couples a fluid-film bearing with a rolling-element bearing such that the rolling-element bearing inner race runs at a fraction of shaft speed. A series-hybrid bearing was analyzed and experiments were run at thrust loads from 100 to 300 lb and speeds from 4000 to 30,000 rpm. Agreement between theoretical and experimental speed sharing was good. The lowest speed ratio (ratio of ball bearing inner-race speed to shaft speed) obtained was 0.67. This corresponds to an approximate reduction in DN value of 1/3. For a ball bearing in a 3 million DN application, fatigue life would theoretically be improved by a factor as great as 8.

A Practical Method to Predict Total Fatigue Life of Welded Joints Structures

2015 ◽  
Author(s):  
Huiying Gao ◽  
Shun-Peng Zhu ◽  
Zhiqiang Lv ◽  
Fang-Jun Zuo ◽  
Hong-Zhong Huang
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Welded Joints ◽  
Practical Method ◽  
Crack Size ◽  
Initial Crack ◽  
Practical Procedure ◽  
Life Model ◽  
Crack Initiation Life ◽  
Life Predictions

Welded joints are usually the weakest link for welded structures due to the existence of stress concentration caused from welding. Fracture mechanics-based approach is a main method used to predict fatigue life for welded joints structures. In engineering, there are two main problems in fatigue life prediction, one is whether crack initiation life can be ignored or not, and the other one is to determine the crack size starting to propagate. Based on this research, a practical procedure is proposed to predict fatigue life of welded joints structures using an initial crack life model and Paris law. Emphasis is put on the discussion about crack initiation life and how to choose an appropriate method to determine the initial crack size. Noted that the proposed method in this paper does not need any tests to determine crack initiation life when crack size reaches a specified value, which depends on experience and is considered as crack size starting to propagate, thus human factors and uncertainty can be minished. Through comparison analysis, fatigue life predictions based on the proposed method are in a good agreement with experimental data.

Surface Roughness Effects on Fatigue in Partial EHD Lubrication

1976 ◽  
Vol 98 (4) ◽  
pp. 530-535 ◽  
Author(s):  
D. F. Li ◽  
J. J. Kauzlarich ◽  
W. E. Jamison
Keyword(s):  
Fatigue Life ◽  
Roughness Parameter ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Surface Model ◽  
Endurance Test ◽  
Roughness Effects ◽  
Surface Fatigue ◽  
Ehd Lubrication ◽  
Rolling Element

A simple surface originated fatigue theory has been developed to study the effects of surface topography on the fatigue life of rolling element bearings. The bearing surface fatigue life is assumed to relate to the magnitude of the average shearing stresses generated at the interacting asperities on the surfaces that are separated by an elastohydrodynamic lubricant film of some thickness. Utilizing a published rough surface model, it is possible to express the relative fatigue life of a bearing as a function of the lubricant film thickness to roughness ratio h/σ and a roughness parameter R. Comparison of the theory to sets of published endurance test data has been carried out. Possibilities of fatigue life prediction of both roller and ball bearings in the partial elastohydrodynamic lubrication regime are discussed.

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