Indentation of a plastically deforming metal crystal with a self-affine rigid surface: A dislocation dynamics study

Venugopalan, Syam Parayil; Nicola, Lucia

doi:10.1016/j.actamat.2018.10.020

Cited by 18 publications

(11 citation statements)

References 58 publications

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“…Additionally, glasses plastically deform by shear banding [38][39][40][41], which is known to have a well-defined yield strength that does not vary significantly in the presence of (flat) surfaces [42,43]. Dislocation nucleation, on the other hand, is very sensitive to the nature of interfaces and to size effects [36], making an exact yield strength less accessible for the complex geometry of asperities [25].…”

Section: A Methods and Atomistic Modelmentioning

confidence: 99%

“…1(a) left], by formulating a critical length scale in terms of a competition between plastic deformation of an asperity under load and its breaking off [16]. In addition to predicting a minimum size of wear particles, it also provides a way to understand surface roughness evolution [17]: Purely plastic deformation of asperities has been found to mostly flatten the surfaces or lead to welding [18][19][20][21][22][23][24], while the breaking off of wear particles seems to be the ingredient to reroughen worked surfaces [17], although surface kinks due to dislocation plasticity have also been suggested as sources of roughness [25]. The critical length scale is most generally defined as…”

Section: Introductionmentioning

confidence: 99%

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Adhesive wear mechanisms in the presence of weak interfaces: Insights from an amorphous model system

Brink

Molinari

2019

Phys. Rev. Materials

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Engineering wear models are generally empirical and lack connections to the physical processes of debris generation at the nanoscale to microscale. Here, we thus analyze wear particle formation for sliding interfaces in dry contact with full and reduced adhesion. Depending on the material and interface properties and the local slopes of the surfaces, we find that colliding surface asperities can either deform plastically, form wear particles, or slip along the contact junction surface without significant damage. We propose a mechanism map as a function of material properties and local geometry, and confirm it using quasi-two-dimensional and three-dimensional molecular dynamics and finite-element simulations on an amorphous, siliconlike model material. The framework developed in the present paper conceptually ties the regimes of weak and strong interfacial adhesion together and can explain that even unlubricated sliding contacts do not necessarily lead to catastrophic wear rates. A salient result of the present paper is an analytical expression of a critical length scale, which incorporates interface properties and roughness parameters. Therefore, our findings provide a theoretical framework and a quantitative map to predict deformation mechanisms at individual contacts. In particular, contact junctions of sizes above the critical length scale contribute to the debris formation.

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Section: A Methods and Atomistic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Adhesive wear mechanisms in the presence of weak interfaces: Insights from an amorphous model system

Brink

Molinari

2019

Phys. Rev. Materials

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“…[27,28]. Several studies of surface roughness and plastic flow have been reported using microscopic (atomistic) models [29], or models inspired by atomic scale phenomena that control the nucleation and glide of the dislocations [30][31][32][33]. These models supply fundamental insight into the complex process of plastic flow, but are not easy to apply to practical systems involving inhomogeneous polycrystalline metals and alloys exhibiting surface roughness of many length scales.…”

Section: Introductionmentioning

confidence: 99%

Fluid Leakage in Metallic Seals

Fischer¹,

Schmitz²,

Tiwari³

et al. 2020

Tribol Lett

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Metallic seals are crucial machine elements in many important applications, e.g., in ultrahigh vacuum systems. Due to the high elastic modulus of metals, and the surface roughness which exists on all solid surfaces, if no plastic deformation would occur one expects in most cases large fluid flow channels between the contacting metallic bodies, and large fluid leakage. However, in most applications plastic deformation occurs, at least at the asperity level, which allows the surfaces to approach each other to such an extent that fluid leakage often can be neglected. In this study, we present an experimental set-up for studying the fluid leakage in metallic seals. We study the water leakage between a steel sphere and a steel body (seat) with a conical surface. The experimental results are found to be in good quantitative agreement with a (fitting-parameter-free) theoretical model. The theory predicts that the plastic deformations reduce the leak-rate by a factor $$\approx 8$$ ≈ 8 .

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“…Recently, several studies of surface roughness and plastic flow have been reported using microscopic (atomistic) models [32], or models inspired by atomic scale phenomena that control the nucleation and glide of the dislocations [33][34][35]. These models supply fundamental insight into the complex process of plastic flow, but are not easy to apply to practical systems involving inhomogeneous polycrystalline metals and alloys exhibiting surface roughness on many length scales.…”

Section: Introductionmentioning

confidence: 99%

Plastic Deformation of Rough Metallic Surfaces

2020

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The contact between rough metallic bodies almost always involves plastic flow in the area of real contact. We performed indentation experiments on sandblasted aluminum surfaces to explore the plastic deformation of asperities and modeled the contact mechanics using the boundary element method, combined with a simple numerical procedure to take into account the plastic flow. The theory can quantitatively describe the modification of the roughness by the plastic flow. Since the long-wavelength roughness determines the fluid leakage of metallic seals in most cases, we predict that the leakage can be estimated based on the elastoplastic contact mechanics model employed here.

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Indentation of a plastically deforming metal crystal with a self-affine rigid surface: A dislocation dynamics study

Cited by 18 publications

References 58 publications

Adhesive wear mechanisms in the presence of weak interfaces: Insights from an amorphous model system

Adhesive wear mechanisms in the presence of weak interfaces: Insights from an amorphous model system

Fluid Leakage in Metallic Seals

Plastic Deformation of Rough Metallic Surfaces

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