Repeated Loading, Residual Stresses, Shakedown, and Tribology

Williams, John A.; Dyson, I. N.; Kapoor, Ajay

doi:10.1557/jmr.1999.0208

Cited by 33 publications

(15 citation statements)

References 32 publications

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“…A solution of this problem can also be useful for rough surfaces wear studies (Kapoor et al, 2002) and for contact shakedown in various rolling elements, see e.g. a review by Williams et al (1999). This review relates to problems where the elastic limit is not greatly exceeded, and hence the contact is assumed Hertzian.…”

Section: Introductionmentioning

confidence: 99%

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Multiple loading–unloading of an elastic–plastic spherical contact

Kadin

Kligerman

Etsion

2006

International Journal of Solids and Structures

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A model for multiple repeated loading and unloading of an elastic-plastic sphere and a rigid flat is presented to cover a wide range of loading conditions far beyond the elastic limit. The sphere material is modeled as elastic linear isotropic hardening and follows the von Mises yield criterion. It is shown that although most of the plastic deformation occurs during the first loading, secondary plastic flow may evolve during the first unloading. The occurrence of this secondary plastic flow depends on the level of first loading and is strongly affected by the Poisson's ratio and material hardening. The region of secondary plastic flow may propagate during the very first loading-unloading cycles, reaching a steady state after which the following loading-unloading cycles become fully elastic.

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Section: Introductionmentioning

confidence: 99%

“…A detailed review of repeated loading of an elastic-plastic half-space can be found in Williams et al (1999). Repeated loading, protective residual stresses and shakedown theory applied to tribology studies are presented.…”

Section: Introductionmentioning

confidence: 99%

Multiple loading–unloading of an elastic–plastic spherical contact

Kadin

Kligerman

Etsion

2006

International Journal of Solids and Structures

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“…Namely, according to the Hertz solution maximum effective stress and consequently strain are reached at the depth of 0.785 of half contact length b (e.g. see Williams et al, 1999), but in the experiments maximum hardness increment and hence maximum strain were observed at the depth of (1.5-2) b. This is apparently due to the descending nature of the distribution of material hardness in the transition zone of the hardened layer.…”

Section: Experimental Observationmentioning

confidence: 82%

Experimental observation and numerical modeling of formation of local plastic zones in hardened surface layers due to contact overloading

Vinogradov

Knyazhansky

Tsun

2015

Mechanics of Materials

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a b s t r a c tThe problem of formation of plastic zones in case-hardened metallic bodies due to contact overloading is studied both experimentally and numerically. Metallic materials exposed to surface hardening demonstrate spatial variation of the material hardness and yield strength with a decreasing profile with depth and belong to the class of so-called plastically graded materials. The presented experimental program employs micro-Vickers hardness tests to map the variation in material hardness and corresponding yield strength for both virgin and loaded case-hardened specimens made of a chromium tool steel. It is shown that, depending on the profile of the yield strength in the near-surface zones and contact parameters, a plastic deformation can originate underneath the hardened layer. The distribution of the effective plastic strain extracted from the micro-hardness increment measurements are found in good agreement with the results of finite element simulations of a plastically graded material subjected to similar loading conditions. Numerical analysis reveals significant perturbations in the stress field distribution within the hardened layer due to formation of a closed-shaped plastic zone in the gradient layers, including development of a tensile stress on the boundary between the elastic and plastic zones as well as an overall increase in the effective stress intensity. It is shown that the hardened layer behaves similar to an elastic beam on a compliant foundation. These stress field perturbations in the hardened layers with low deformation capacity can greatly affect the durability and serviceability of surface treated mechanical parts.

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“…By contrast, when shakedown is not possible, so that each load cycle is accompanied by an element of incremental plasticity, component lives are much curtailed. When shakedown does occur it may do so as rapidly as the second application of the load or it may take many cycles to become established -such variations depend on the effective hardening behaviour of the material in question [29,30].…”

Section: Shakedown and Shakedown Mapsmentioning

confidence: 99%

The Behaviour of Sliding Contacts Between Non-Conformal Rough Surfaces Protected by 'Smart' Films

Williams

2004

Tribology Letters

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Many tribological contacts involve two components, each exhibiting finite roughness, sliding over one another for many repeated cycles of operation. Although the initial contact may be plastic, if low wear rate conditions are to be achieved, the steady state situation should be one of predominantly elastic stresses in each surface. When lubrication is present, the stress fields in the components must be consistent with the presence of a low shear strength film separating the surfaces. Commercial lubricants invariably contain a chemically complex additive package with one of the aims of the formulation being the production of boundary layers, which beneficially influence both friction and wear when conditions are not conducive to the formation of either a hydrodynamic or an elasto-hydrodynamic film. These boundary layers must be physically robust enough to survive prolonged service but slippery enough to maintain acceptably low coefficients of friction. Reductions in friction are not necessarily synonymous with improvements in anti-wear behaviour. Recent experimental evidence from studies using both atomic force microscopy and micro-tribometry suggest that boundary films produced by the action of commercial anti-wear additives, such as ZDTP, can exhibit mechanical properties which are affected by local values of pressure -the film is tribologically 'smart' becoming more robust just where it is needed at the most heavily loaded points of the conjunction. These effects have been explored in a numerical model of rough surface contact and the implications for the mechanisms of wear of real devices is discussed.

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Repeated Loading, Residual Stresses, Shakedown, and Tribology

Cited by 33 publications

References 32 publications

Multiple loading–unloading of an elastic–plastic spherical contact

Multiple loading–unloading of an elastic–plastic spherical contact

Experimental observation and numerical modeling of formation of local plastic zones in hardened surface layers due to contact overloading

The Behaviour of Sliding Contacts Between Non-Conformal Rough Surfaces Protected by 'Smart' Films

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