Martensite decay in micropitted gears

Oila, Adrian; Shaw, Brian; Aylott, Chris; Bull, Steve

doi:10.1243/135065005x9790

Cited by 37 publications

(18 citation statements)

References 40 publications

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“…Oila and Bull [18] and Febre et al [19] describe the relative influence of a range of factors affecting micropitting. Metalographical and morphological aspects of micropitting are described in [20][21][22]. Olver and co-workers [5][6][7][8] focus on the influence of lubricant additives and lambda ratio on the progression of micropitting using a triple-disc contact fatigue rig, while Rycerz and Kadiric [23] utilise the same rig to study the influence of slide-roll-ratio on micropitting.…”

Section: Introductionmentioning

confidence: 99%

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Morales-Espejel

Rycerz

Kadiric

2018

Wear

135

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A B S T R A C TThe present paper studies the occurrence of micropitting damage in gear teeth contacts. An existing general micropitting model, which accounts for mixed lubrication conditions, stress history, and fatigue damage accumulation, is adapted here to deal with transient contact conditions that exist during meshing of gear teeth. The model considers the concurrent effects of surface fatigue and mild wear on the evolution of tooth surface roughness and therefore captures the complexities of damage accumulation on tooth flanks in a more realistic manner than hitherto possible. Applicability of the model to gear contact conditions is first confirmed by comparing its predictions to relevant experiments carried out on a triple-disc contact fatigue rig. Application of the model to a pair of meshing spur gears shows that under low specific oil film thickness conditions, the continuous competition between surface fatigue and mild wear determines the overall level as well as the distribution of micropitting damage along the tooth flanks. The outcome of this competition in terms of the final damage level is dependent on contact sliding speed, pressure and specific film thickness. In general, with no surface wear, micropitting damage increases with decreasing film thickness as may be expected, but when some wear is present micropitting damage may reduce as film thickness is lowered to the point where wear takes over and removes the asperity peaks and hence reduces asperity interactions. Similarly, when wear is negligible, increased sliding can increase the level of micropitting by increasing the number of asperity stress cycles, but when wear is present, an increase in sliding may lead to a reduction in micropitting due to faster removal of asperity peaks. The results suggest that an ideal situation in terms of surface damage prevention is that in which some mild wear at the start of gear pair operation adequately wears-in the tooth surfaces, thus reducing subsequent micropitting, followed by zero or negligible wear for the rest of the gear pair life. The complexities of the interaction between the contact conditions, wear and surface fatigue, as evident in the present results, mean that a full treatment of gear micropitting requires a numerical model along the lines of that applied here, and that use of overly simplified criteria may lead to misleading predictions.

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Section: Introductionmentioning

confidence: 99%

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Morales-Espejel

Rycerz

Kadiric

2018

Wear

135

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“…Each spall of micropitting is typically 10 μm or more in width and a few microns in depth. It is also known that micropitting is often associated with the plastic deformation near the surface [2][3][4][5]. These features suggest that stresses acting in the region affected by surface asperities (hereinafter called 'near-surface stress') correlate with the occurrence of micropitting.…”

Section: Introductionmentioning

confidence: 99%

Estimation Method of Micropitting Life from <i>S</i>-<i>N</i> Curve Established by Residual Stress Measurements and Numerical Contact Analysis

et al. 2019

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Micropitting is a type of rolling contact fatigue (RCF) associated with rough surfaces and severe lubrication conditions. In the present study, we developed an estimation method for micropitting life. An S-N curve, which is a relationship between micropitting life and stresses acting in the region affected by surface asperities (near-surface stress), is established by using data from RCF tests and estimated histories of near-surface stresses (stress history). Changes in the surface topography and residual stresses including the initial condition are measured in order to estimate the stress history. This enables us to consider the influences of surface topography and residual stresses on micropitting. Micropitting life under an arbitrary operating condition is estimated from the established S-N curve and the estimated stress history up to a finite cycle. It is revealed that micropitting life can be accurately estimated from the established S-N curve within the range of our experiment. The median, minimum, and maximum of the relative life ratio (ratio of actual micropitting life to the estimated life) were 0.89, 0.49, and 1.82, respectively. Further analysis confirms that the accuracy is improved by considering residual stresses.

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“…Oila [16,17] investigated micropitting in gears associated with microstructural changes. He observed martensite decay i.e.…”

Section: Introductionmentioning

confidence: 99%

Influence of running-in on surface characteristics of efficiency tested ground gears

Mallipeddi

Norell

Sosa

et al. 2017

Tribology International

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The effect of running-in load (0.9 or 1.7 GPa) on surface characteristics of ground spur gears, and on their development during subsequent efficiency testing (FZG rig), is examined. The effect was confined to less than 10 μm depth. Micropitting was associated with surface asperities and their plastic deformation; higher running-in load gave more micropitting, also after identical efficiency tests. Running-in increased unequal compressive residual stresses in both profile and axial directions, while after efficiency testing they approached equal levels. Deformation induced martensite is considered to form during running-in only at high load, still the amount after efficiency testing increased with running-in load. Higher surface content of phosphorous from extreme pressure additive (EP) occurred only after efficiency test following running-in at high load.

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Martensite decay in micropitted gears

Cited by 37 publications

References 40 publications

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Estimation Method of Micropitting Life from <i>S</i>-<i>N</i> Curve Established by Residual Stress Measurements and Numerical Contact Analysis

Influence of running-in on surface characteristics of efficiency tested ground gears

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