Prediction of Traction and Microgeometry Effects on Rolling Contact Fatigue Life

1978 ◽  
Vol 100 (2) ◽  
pp. 156-165 ◽  
Author(s):  
T. E. Tallian ◽  
Y. P. Chiu ◽  
E. Van Amerongen
Keyword(s):  
Shear Stress ◽  
Film Thickness ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Deformation Bands ◽  
Hazard Functions ◽  
Stress Region ◽  
Surface Distress

A refined mathematical model for the prediction of rolling contact fatigue is presented. It analyzes the effect of frictional traction in the contact surface, and of surface asperity slope, on the failure hazard functions applicable to surface and subsurface originated spalls. Major effects of traction on life arise from three sources: (a) increased surface distress micropitting; (b) increased microscopic shear stresses beneath surface furrows; (c) greatly increased macroscopic shear stresses in the zone relatively free from shear-stress which exists, in the absence of traction, between the asperity stress region and the Hertzian shear stress region. The major effect of steeper asperity slopes is to increase surface distress micropitting. A strong effect of traction on the angular orientation of the Hertz stress field is used to correlate experimentally observed changes in the Martin angle of orientation of deformation bands. The correlation permits calculation of the variation in the effective traction coefficient as a function of film thickness/roughness ratio. The traction coefficients obtained are then used as input to numerical life prediction. Satisfactory agreement is obtained between theory and experiment in predicting the life of seven groups of fatigue tested ball bearings with different surface roughness, run at different film thickness/roughness ratios.

Effect of Roughness and Sliding Friction on Contact Stresses

1991 ◽  
Vol 113 (4) ◽  
pp. 729-738 ◽  
Author(s):  
D. M. Bailey ◽  
R. S. Sayles
Keyword(s):  
Sliding Friction ◽  
Numerical Technique ◽  
Contact Region ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Near Surface ◽  
Contact Fatigue Life ◽  
Surface Distress

The stress distributions associated with smooth surfaces in contact are rarely experienced in practice. Factors such as surface roughness, lubricant films, and third body particulates are known to influence the state of stress and the resulting rolling contact fatigue life. This paper describes a numerical technique for evaluating the complete subsurface field of stress resulting from the elastic contact of nonconforming rough bodies, based on measurements of their profile. The effect of sliding friction is included. The presence of asperities within the contact region gives rise to high shear stresses near the surface. Realistic coefficients of friction for lubricated sliding contacts (i.e., μ ≈ 0.1) causes the “smooth body” shear stresses to interact with the asperity stresses to produce a large, highly stressed region exposed to the surface. The significance of these near-surface stresses is discussed in relation to modes of surface distress which lead to eventual failure of the contacting surfaces.

A 3D Finite Element Study of Fatigue Life Dispersion in Rolling Line Contacts

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Nick Weinzapfel ◽  
Farshid Sadeghi ◽  
Vasilios Bakolas ◽  
Alexander Liebel
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Material Properties ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Critical Shear Stress ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Rolling Element Bearings ◽  
Rolling Element

Rolling contact fatigue of rolling element bearings is a statistical phenomenon that is strongly affected by the heterogeneous nature of the material microstructure. Heterogeneity in the microstructure is accompanied by randomly distributed weak points in the material that lead to scatter in the fatigue lives of an otherwise identical lot of rolling element bearings. Many life models for rolling contact fatigue are empirical and rely upon correlation with fatigue test data to characterize the dispersion of fatigue lives. Recently developed computational models of rolling contact fatigue bypass this requirement by explicitly considering the microstructure as a source of the variability. This work utilizes a similar approach but extends the analysis into a 3D framework. The bearing steel microstructure is modeled as randomly generated Voronoi tessellations wherein each cell represents a material grain and the boundaries between them constitute the weak planes in the material. Fatigue cracks initiate on the weak planes where oscillating shear stresses are the strongest. Finite element analysis is performed to determine the magnitude of the critical shear stress range and the depth where it occurs. These quantities exhibit random variation due to the microstructure topology which in turn results in scatter in the predicted fatigue lives. The model is used to assess the influence of (1) topological randomness in the microstructure, (2) heterogeneity in the distribution of material properties, and (3) the presence of inherent material flaws on relative fatigue lives. Neither topological randomness nor heterogeneous material properties alone account for the dispersion seen in actual bearing fatigue tests. However, a combination of both or the consideration of material flaws brings the model’s predictions within empirically observed bounds. Examination of the critical shear stress ranges with respect to the grain boundaries where they occur reveals the orientation of weak planes most prone to failure in a three-dimensional sense that was not possible with previous models.

Research on the Approach for the Assessment of Subsurface Rolling Contact Fatigue Damage

2013 ◽  
Vol 395-396 ◽  
pp. 845-851
Author(s):  
Xiao Feng Qin ◽  
Da Le Sun ◽  
Li Yang Xie
Keyword(s):  
Shear Stress ◽  
Friction Coefficient ◽  
Fatigue Damage ◽  
Stress Ratio ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Critical Stresses ◽  
Orthogonal Shear Stress

In this paper, the distribution of different critical stresses, which were used in previous correlation articles for the assessment of subsurface rolling contact fatigue damage, was analyzed. The rationality of orthogonal shear stress was selected as the key stress controlling the subsurface rolling contact fatigue damage was clarified. Base on the linear fatigue damage accumulative theory and the modification equation for the range of asymmetrical stress, the influence of friction on subsurface rolling contact fatigue damage was studied. The results show that the subsurface orthogonal shear stress is a completely symmetrical stress when the friction coefficient is zero, while it is an asymmetrical stress with considering the friction. The stress ratio of subsurface orthogonal shear stress and subsurface rolling contact fatigue damage is increased with the increasing of friction.

Acoustic Emission Monitoring for Rolling Contact Fatigue Damage of Machined Components by Hard Turning vs. Grinding

2007 ◽  
Author(s):  
A. W. Warren ◽  
Y. B. Guo
Keyword(s):  
Shear Stress ◽  
Acoustic Emission ◽  
Fatigue Damage ◽  
Surface Integrity ◽  
Rolling Contact Fatigue ◽  
Real Life ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Second Phase ◽  
Surface Cracks

The fundamental knowledge of fatigue damage mechanism is necessary for understanding manufacturing process effects. However, the artificial defects on the test samples in traditional fatigue tests will change the surface integrity and therefore may not reflect the nature of fatigue damage. This paper studies the fatigue damage resulting from real-life rolling contact tests and finite element analysis of AISI 52100 steel and identifies the possible mechanisms for fatigue failure in the presence of process induced surface integrity. Rolling contact fatigue damage was real-time monitored using an acoustic emission (AE) sensor. Surface and subsurface fatigue damage of the samples was then characterized using optical and scanning electron microscopy (SEM) and surface profiling. The results suggest that shear stress induced Mode II crack is the dominant fatigue mechanism. Two types of subsurface cracks were observed: main cracks that propagate parallel to the surface due to subsurface shear stress induced fracture/debonding of inclusions or second phase particles. Shear stress induced surface cracks propagate at shallow angles (∼35°) from the surface. Branching cracks eventually form and connect the main crack to surface. The formation of main cracks and surface cracks may be parallel processes, and spalling occurs as a combined effect of the main, surface, and branching cracks. The relationship between AE signals and fatigue damage was been established.

An Approach for the Gear Rolling Contact Fatigue Acceleration

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Sheng Li ◽  
Jeremy J. Wagner
Keyword(s):  
Film Thickness ◽  
Crack Formation ◽  
Crack Nucleation ◽  
Rotational Velocity ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Time Period ◽  
Gear Contact ◽  
Gear Rolling

This study proposes an approach for the acceleration of the experimental gear rolling contact fatigue (RCF) crack formation. By increasing the rotational velocity of a gear pair, the RCF experimental time period is reduced. However, the film thickness is increased to improve the fatigue performance, to counteract which it is proposed to raise the lubricant temperature to reduce the film thickness. A physics-based gear contact fatigue model is used to quantify and offset the effects of the rotational velocity and the lubricant temperature on the crack nucleation.

Occurrence of High Pressure Spike in Unidirectional Start–Stop–Start Point Contacts

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
P. Sperka ◽  
J. Wang ◽  
I. Krupka ◽  
M. Hartl ◽  
M. Kaneta
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Contact ◽  
Point Contacts ◽  
Pressure Distributions ◽  
Machine Element ◽  
Pressure Spike

The transient film thickness and pressure distributions in point elastohydrodynamic lubrication (EHL) contacts during start–stop–start motion are discussed based on experimental and numerical analyses. When the machine element starts to move after the stopping, where the oil is entrapped between two surfaces, the pressure at the exit area increases very much. The pressure increase depends markedly on the overall film thickness before the stopping of the motion, but is hardly controlled by the acceleration after the stopping. It can be considered that this phenomenon affects the rolling contact fatigue damage.

On Ratchetting-Based Models of Wear and Rolling Contact Fatigue (RCF)

2003 ◽  
Author(s):  
M. Ciavarella ◽  
L. Afferrante
Keyword(s):  
Shear Stress ◽  
Plastic Material ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Longitudinal Direction ◽  
Surface Flow ◽  
Rolling Contact ◽  
Stress Cycle ◽  
Shakedown Theory ◽  
Number Of Cycles

Recent efforts to develop simple unified models of both wear and RCF (Kapoor & Franklin, 2000, Franklin et al., 2001) are discussed, in view of previous theoretical and experimental results on ratchetting in rolling contact. At sufficiently high contact pressures, surfaces deform plastically with unidirectional cumulation of “ratchetting” strains (Johnson, 1985, Ch.9). However, the modelling of ratchetting strains as a function of plastic material properties has turned out more complicated than what originally suggested by the first attempts (Merwin & Johnson, 1963), as recently discussed by Ponter et al. (2003). Wear due to surface ratchetting occurs for sufficiently high friction, whereas RCF is mainly due to ratchetting subsurface. It appears that experimental data on ratchetting strains in the literature unfortunately do not show a clear and unique trend, and various proposed fitting equations differ significantly in quantitative and qualitative terms, particularly at large number of cycles. It is shown that ratchetting in rolling contact is a combination of “structural ratchetting” (that modelled with the perfect plasticity model) and “material ratchetting”, and the latter is very sensitive to the hardening behaviour of the material. Also, the surface and subsurface flow regimes are very different: in pure rolling, a simplified model of the stress cycle condition is a fully reversed cycle of shear superposed to an out-of-phase pulsating compression in a extended region below the surface (neglecting other two components also of pulsating compression); increasing the friction coefficient, a mean shear stress is induced as well as a tensile component in the direct stress, and for friction f > 0.3 the maximum moves at the surface, but the highly stressed zone becomes a thin surface layer which suffers uniquely of “material ratchetting”. In the limit of very high friction, we have the critical condition on the surface which obviously gives a pulsating shear stress cycle in phase with a pulsating compression, but in addition we have a nearly fully reversed cycle of tension-compression (although the tensile peak is very localized also in the longitudinal direction). Such multiaxial stress fields and their largely different features introduced cause a response of the material which has not been studied enough, perhaps both in terms of ratchetting rates and in terms of the failure condition. In particular, the ductility for ratchetting surface flow as used in wear models seems apparently much higher than that for RCF ratchetting models. Also, RCF at large number of cycles in the C&S experiments (Clayton & Su, 1996, Su & Clayton, 1997) seems not well correlated with shakedown theory, and accordingly, simple ratchetting equations based on excess of shakedown such as that of Tyfoor et al (1996), do not seem well suited a Wohler SN life curve. However, these conclusions are only very qualitative as the materials in the two tests are different, and at present empirical separate models for wear and RCF based on hardness of materials and a posteriori data fitting seem the only quantitative way forward for engineering purposes.

Internal Shear Stress Distribution and Subsurface Cracks of PPS Thrust Bearings under Rolling Contact Fatigue in Water

2020 ◽  
Vol 858 ◽  
pp. 101-105
Author(s):  
Syunsuke Mizozoe ◽  
Katsuyuki Kida
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Crack Propagation ◽  
Contact Stress ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Subsurface Crack ◽  
Thrust Bearings ◽  
Subsurface Cracks

In this study, crack propagation in PPS thrust bearings under rolling contact fatigue (RCF) in water was observed, and relation between subsurface crack and internal shear stress parallel to the surface was investigated. It was found the cause of flaking was subsurface crack. They were evaluated in terms of contact stress and friction between their faces. It was discovered that subsurface cracks distributed around shear stress peak, and flaking failure was dominated by subsurface shear stress.

scholarly journals Investigation of the asperity point load mechanism for thermal elastohydrodynamic conditions

2019 ◽  
Vol 300 ◽  
pp. 06001
Author(s):  
Carl-Magnus Everitt ◽  
Bo Alfredsson
Keyword(s):  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Leading Edge ◽  
Point Load ◽  
Rolling Contact ◽  
Shear Stresses ◽  
Asperity Contact ◽  
Trailing Edge ◽  
Tensile Stresses ◽  
Lubrication Film

The rolling contact fatigue damage called pitting or spalling develops more frequently in surfaces with negative than positive slip. Since normal line loads do not cause any tensile surface stresses this investigation considers the effects of small point shaped asperities. Shear traction causes tensile stresses at the trailing edge of asperities entering the contact at negative slip. At positive slip the tensile stresses appear at the leading edge when the asperities exit the contact. It was found that the trailing edge of the asperity breaks through the lubrication film at contact entry. This causes negative slip to be more detrimental than positive slip. At negative slip the location of large frictional shear stresses and tension stresses from normal asperity contact coincide.

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