Modeling Solid Contact between Rough Surfaces with Various Roughness Parameters

Tomota, Tatsunori; Masuda, Ryo; Kondoh, Yasuhiro; Ohmori, Takao; Yagi, Kazuichi

doi:10.1080/10402004.2020.1820123

Cited by 8 publications

(4 citation statements)

References 46 publications

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“…In addition, because the nominal contact area is an index that can be compared with theoretical predictions, such as from Hertzian contact analysis, we conducted a quantitative evaluation. As for the definition of the nominal contact area, the contact theory based on statistical theory 11 , 12 , 36 – 40 is often used. According to reference 38 , if the mean film thickness in a certain area is less than three times the root mean square roughness, it is highly likely that some of the asperities are in contact with the surface; and that the area can be regarded as the nominal contact area (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In reality, a large friction coefficient may be obtained on a rough surface with a considerably low roughness 9 . Currently, it is clear that the real contact area changes owing to the difference in the profile of the surface roughness, even if the surface roughness has the same size 10 – 12 . Although the influence of the surface profile can be measured by scalar values, such as the “real contact area” and “friction coefficient,” it is difficult to measure the actual contact state.…”

Section: Introductionmentioning

confidence: 99%

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Elucidation of contact state on various rough surfaces via highly robust colorimetric optical interferometry

Tomota

Tohyama

Yagi

2022

Sci Rep

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In this study, we developed and practiced colorimetric optical interferometry for the direct observation of contact states to clarify contact phenomena. We theoretically demonstrated that the effect of roughness diffuse reflection could be neglected using interferometric light intensity according to the relationship between the optical film thickness and hue. Then, we measured the static contact surfaces of spherical test pieces of different root mean square roughnesses. Results indicate that the nominal contact area is significantly larger than that obtained from the Hertzian theory of smooth contact as the surface roughness increases. The contact film thickness on the nominal contact area increases almost in proportion to the root mean square roughness. Our experiment supports the validity of the contact theory and contact simulation with very small roughnesses, which have been difficult to verify experimentally. The advantage of this measurement is that it can simultaneously capture the macroscopic contact area and microscopic film thickness distribution, which is expected to further expand the range of application.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Elucidation of contact state on various rough surfaces via highly robust colorimetric optical interferometry

Tomota

Tohyama

Yagi

2022

Sci Rep

Self Cite

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“…From equations. (6), ( 7) and ( 9)-( 11), the following applies to the equivalent standard deviation, radius of curvature and asperity density: According to Tomota [68], the skewness and kurtosis of the equivalent rough surface are obtained by…”

Section: Stochastic Approachesmentioning

confidence: 99%

“…Thereby, a rough surface was represented by a population of hemispherical asperities following a Gaussian distribution. Since the model was subjected to certain assumptions (isotropic surfaces, spherical asperities with constant radius, no interaction between asperities, no bulk deformation), it has been further extended to account for two rough surfaces with misaligned asperities [56], elliptically-shaped asperities [57][58][59], non-uniform radii of curvature of asperity peaks [60,61], interaction between asperities [62,63], non-Gaussian surfaces [64][65][66][67][68], elastic-plastic material behavior [69][70][71] and surface tension [72]. Beyond asperity-based contact models, other stochastic contact models have been developed which can be applied to fractal surfaces.…”

Section: Introductionmentioning

confidence: 99%

Micro-scale deterministic asperity contact FEM simulation

Kolli¹,

Winkler²,

Wartzack³

et al. 2022

Surf. Topogr.: Metrol. Prop.

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There are numerous stochastic approaches to indirectly couple solid asperity contact with the fluid hydrodynamics in the region of boundary or mixed lubrication. In contrast, deterministic approaches for calculating solid contact pressure curves offer advantages in terms of flexibility and accuracy. This contribution aims at providing a publicly available, automated method to derive solid asperity contact pressure curves for given surfaces, implemented in commercial software based upon Finite Element Method (FEM). Solid asperity pressure curves were calculated and compared to various established stochastic models for artificially generated surfaces and surfaces measured via laser scanning microscopy. Thereby, it was shown that the usage of artificially generated surfaces based on stochastic parameters only allowed an approximate representation of real measured surfaces as well as to lower calculated pressures, so that 3D measurement data is preferred to calculate the contact pressure. Moreover, the values of the FEM model were in a similar region but slightly below the stochastic models over a wide range of gap distances and the asperity pressure graphs were more curved/convex. At very small gap height values, the pressure in the FEM model reached values similar to the stochastic models. This was attributed to the fact that real surface topographies were considered, also allowing for peak-to-valley pairings instead of merely asperity-to-asperity contacts, as well as to the fact that the roughness and mean planes were re-calculated in each simulation step, while most stochastic approaches neglect the elastic deformation of asperities when determining the distances between the rough surfaces.

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