Semi-Analytical Modeling of Crack Initiation Dominant Contact Fatigue Life for Roller Bearings

1997 ◽  
Vol 119 (2) ◽  
pp. 233-240 ◽  
Author(s):  
Wangquan (Winston) Cheng ◽  
Herbert S. Cheng
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Maximum Shear Stress ◽  
Equivalent Stress ◽  
Roller Bearing ◽  
Contact Fatigue ◽  
New Model ◽  
Roller Bearings ◽  
Contact Width

The fatigue test of a needle roller bearing suggests that the dominant failure mechanism is subsurface crack initiation and propagation. Therefore, a new semi-analytical contact fatigue model is derived from a micromechanics based crack initiation model. The analysis indicates that in the life calculation the selection of the critical stress, such as the maximum orthogonal shear stress, maximum shear stress, octahedral shear stress, or von Mises equivalent stress, becomes arbitrary under the nonfrictional Hertzian line contact condition. The fatigue life of roller bearings under the pure rolling condition can be predicted by simply knowing the Hertzian contact pressure and the contact width, which avoids complicated calculation of the subsurface stresses. The film thickness, roughness, and the material hardness effects on contact fatigue are also included in the new model. The comparisons with different models and the experimental data indicate that the new model makes similar life predictions as the Ioannides-Harris model, but the new model is much simpler to use. The Lundberg-Palmgren model does not fit with the experiment data.

Axial Load Effect on Contact Fatigue Life of Cylindrical Roller Bearings

2004 ◽  
Vol 126 (2) ◽  
pp. 242-247 ◽  
Author(s):  
Wangquan (Winston) Cheng ◽  
Shan Shih ◽  
John Grace ◽  
Wenke Tu
Keyword(s):  
Fatigue Life ◽  
Axial Load ◽  
Roller Bearing ◽  
Contact Fatigue ◽  
Limit Load ◽  
Load Effect ◽  
Roller Bearings ◽  
Contact Fatigue Life ◽  
Fatigue Life Analysis ◽  
Cylindrical Roller

Besides primarily carrying radial load, cylindrical roller bearings with flanges or lips on both inner and outer raceways need also carry axial load in some applications. Because of the axial load, the equivalent dynamic load of the bearing will be increased and the bearing contact fatigue life will be decreased accordingly. The axial load effect on the roller bearing fatigue life had been studied by researchers in the past. Because of different assumptions used in their models, quite different predictions were made in their analysis. This work combines the methods used in the Fernlund-Synek and Brandlein models and studies general contact conditions such as partial contact along the roller length, partial loading zone of the bearing race, manufacturing tolerance and running-in effects on roller length, etc. New formulas for equivalent dynamic loads of the rotating and stationary races are derived. A fatigue limit load is also included in the life calculation to reflect the latest development in contact fatigue life analysis.

Ship Performance Research Based on BP Neural Network

2014 ◽  
Vol 709 ◽  
pp. 176-179
Author(s):  
Han Liu ◽  
Fang Zhen Song ◽  
Ming Ming Li ◽  
Bo Song
Keyword(s):  
Neural Network ◽  
Shear Stress ◽  
Bp Neural Network ◽  
Optimization Design ◽  
Maximum Shear Stress ◽  
Equivalent Stress ◽  
Orthogonal Experimental Design ◽  
The Neural Network ◽  
Maximum Equivalent Stress ◽  
Ship Performance

The problem is solved that it is hard to provide analysis formulas about the maximum equivalent stress, the maximum shear stress and the structural geometric parameters for a ship. The finite element calculation is done with orthogonal experimental design under the most dangerous case. The data obtained are used as the training and test samples to establish BP neural network models of ship’s maximum equivalent stress and maximum shear stress. With the aid of Neural network toolbox in MATLAB, the topological structure of BP neural network mapping relationship between the whole ship performance indexes and design variables is established. The training and testing are completed with the data tested by the shipyard and the correctness of this network is verified. The neural network required for further optimization design is obtained. The neural network is helpful in reducing the ship mass without exceeding the allowable stress.

Micromechanics Modeling of Crack Initiation Under Contact Fatigue

1994 ◽  
Vol 116 (1) ◽  
pp. 2-8 ◽  
Author(s):  
W. Cheng ◽  
H. S. Cheng ◽  
T. Mura ◽  
L. M. Keer
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
Contact Fatigue ◽  
Contact Boundary ◽  
Dislocation Pileup ◽  
Near Surface ◽  
New Model ◽  
Crack Initiation Life ◽  
Micromechanics Modeling ◽  
Surface Crack Initiation

Using dislocation pileup theory, a model is given for the prediction of crack initiation life under contact fatigue. Near surface crack initiation is investigated by introducing the sliding contact boundary condition. Crack initiation originated at the surface and substrate are treated as extreme cases. The new model physically explains how a surface crack can be initiated and shows that the surface crack initiation life should be shorter than the subsurface crack initiation life under the same stress amplitude conditions. A discussion is given about the influence of residual stress, hardness, temperature, irreversibility of the plastic deformation, as well as other parameters that affect the crack initiation life. Preliminary comparisons show that the new model agrees well with the experimental observations of surface and near surface crack initiation.

Effect of Mean Stress on 2A12-T4 Aluminum Alloy under Tension-Torsion Constant Amplitude Loading

2016 ◽  
Vol 713 ◽  
pp. 334-337
Author(s):  
Tian Qing Liu ◽  
Xin Hong Shi ◽  
Jian Yu Zhang
Keyword(s):  
Shear Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Phase Angle ◽  
Stress Amplitude ◽  
Maximum Shear Stress ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Normal Mean ◽  
Fracture Appearance

Fatigue tests have been carried out to investigate the effects of mean-stress and phase-difference on the tension-torsion fatigue failure of 2A12-T4 aluminum alloy. The results show that for fully reversed tension-torsion loading, the fatigue life increases with the increase of phase angle, but the fatigue life decreases with the increase of phase angle, when mean-stress exists, both for shear mean-stress and normal mean-stress. Fracture appearance shows that the crack initiation is on the direction of maximum shear stress amplitude plane. Critical plane criteria based on the linear combination of the maximum shear stress amplitude and maximum normal stress are studied and further discussion on the drawbacks of this kind of criteria are performed.

Prediction of Equivalent Radial Loads for Tapered Roller Bearings

1996 ◽  
Vol 118 (3) ◽  
pp. 651-656
Author(s):  
Ted E. Bailey ◽  
Robert W. Frayer
Keyword(s):  
Fatigue Life ◽  
Rolling Contact Fatigue ◽  
Roller Bearing ◽  
Contact Fatigue ◽  
Subsequent Development ◽  
Rolling Contact ◽  
Tapered Roller Bearing ◽  
Applied Loading ◽  
Tapered Roller ◽  
Tapered Roller Bearings

Calculating the fatigue life of a tapered roller bearing has become a rather straightforward exercise thanks to the accumulation of rolling contact fatigue data and the subsequent development of formulation relating applied loading to bearing fatigue life. An integral part of the prediction process is to define an equivalent radial load (EQRL) by combining a bearing’s applied radial and thrust loading into a single entity. This paper reviews currently accepted formulation and offers a potentially more accurate alternative method for estimating the EQRL of a tapered roller bearing than does the current AFBMA standard.

ASME Sec VIII Div 3 Fatigue Life Predictions Using Critical Plane Approach

2015 ◽  
Author(s):  
Kumarswamy Karpanan ◽  
William Thomas
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Principal Stress ◽  
Stress Amplitude ◽  
Maximum Shear Stress ◽  
Fe Model ◽  
Critical Plane ◽  
Principal Stress Direction ◽  
Stress Direction ◽  
Surface Node

ASME VIII Div 3 fatigue evaluation is based on the theory that cracks tend to nucleate along the slip lines oriented in the maximum shear stress planes. This code provides methods to calculate the fatigue stresses when the principal stress direction does not change (proportional loading) and axes change (nonproportional loading). When principal stress direction does not change within a fatigue cycle, shear stress amplitude is calculated only on the three maximum shear stress planes. But when the principal stress directions do change within a loading cycle, the plane carrying the maximum shear stress amplitude (also known as critical plane) cannot be easily identified and all planes at a point needs to be searched for the maximum shear stress amplitude. This paper describes the development of an ANSYS-APDL macro to predict the critical plane at each surface node of an FE model using the FEA stress results. This macro searches through 325 planes (at 10° increments along two angles) at each surface node and for each load step to identify the maximum shear stress and the corresponding normal stress for each surface node. The fatigue life is calculated for each surface node and is plotted as a color contour on the FEA model. This macro can be extended to calculate the fatigue life using other critical plane approaches such as the Findley and Brown-Miller models.

An Analytical Dynamic Model of a Hollow Cylindrical Roller Bearing

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Jing Liu ◽  
Yimin Shao
Keyword(s):  
Fatigue Life ◽  
Dynamic Model ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
Great Influence ◽  
Radial Load ◽  
Shaft Speed ◽  
Roller Bearings ◽  
Cylindrical Roller ◽  
Analytical Dynamic

Hollow cylindrical roller bearings (HCRBs) have obtained much attention from design engineers in bearing industries since they can perform better than solid cylindrical roller bearings (SCRBs) in centrifugal forces, contact stiffness, cooling ability, fatigue life, etc. In this study, an analytical dynamic model of a lubricated HCRB is presented to analyze the influences of the radial load, the shaft speed, and the hollowness percentage of the roller on the bearing vibrations, which cannot be formulated by the methods in the reported literature. Both the support stiffness of the shaft and the roller mass are formulated in the presented dynamic model. The hollow hole in the roller is modeled as a uniform one. Numerical results show that the hollowness percentage of the roller has a great influence on the vibrations of the roller and the inner race of the HCRB. Moreover, the vibrations of the components of the HCRB are not only determined by the hollowness percentage of the roller, but also depended on the external radial load and shaft speed. Therefore, during the design process for the hollowness percentage of the roller, the influences of the radial load and the shaft speed on the vibrations of the bearing components should be considered, except for the fatigue life. The results show that this work can give a new dynamic method for analyzing the vibrations of the HCRBs. Moreover, it can give some guidance for the design method for the HCRBs.

A new model of multiaxial fatigue life prediction with the influence of different mean stresses

2019 ◽  
Vol 28 (9) ◽  
pp. 1323-1343 ◽  
Author(s):  
Bowen Liu ◽  
Xiangqiao Yan
Keyword(s):  
Fatigue Life ◽  
Equivalent Stress ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Stress Effect ◽  
Mean Stress ◽  
New Model ◽  
Von Mises ◽  
The Impact ◽  
Mean Stresses

In this paper, based on the thought of Modified Wöhler Curve Method (MWCM), a new general model for predicting multiaxial fatigue life with influence of mean stress is presented. Different from the MWCM, the expressions of multiaxiality effect and mean stress effect are located separately in the proposed fatigue equation, so that the new model can consider the impact of both axial and torsional mean stresses, and the equation form possesses excellent extendibility and variability. The wildly used von Mises equivalent stress is adopted as the fatigue parameter to improve computational efficiency. Finally, in conjunction with the Itoh criterion, the model can be trivially extended to perform non-proportional fatigue prediction with different mean stresses. Some representative fatigue tests published in the previous literature are used to verify this study.

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