The Experts below are selected from a list of 19539 Experts worldwide ranked by ideXlab platform
K Komvopoulos - One of the best experts on this subject based on the ideXlab platform.
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contact mechanics analysis of oscillatory sliding of a rigid Fractal Surface against an elastic plastic half space
Philosophical Magazine, 2014Co-Authors: Z Song, K KomvopoulosAbstract:Oscillatory sliding contact between a rigid rough Surface and an elastic–plastic half-space is examined in the context of numerical simulations. Stick-slip at asperity contacts is included in the analysis in the form of a modified Mindlin theory. Two friction force components are considered – adhesion (depending on the real area of contact, shear strength and interfacial adhesive strength) and plowing (accounting for the deformation resistance of the plastically deformed half-space). Multi-scale Surface roughness is described by Fractal geometry, whereas the interfacial adhesive strength is represented by a floating parameter that varies between zero (adhesionless Surfaces) and one (perfectly adhered Surfaces). The effects of Surface roughness, apparent contact pressure, oscillation amplitude, elastic–plastic properties of the half-space and interfacial adhesion on contact deformation are interpreted in the light of numerical results of the energy dissipation, maximum tangential (friction) force and slip ...
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a discrete dislocation plasticity analysis of plane strain indentation of a single crystal half space by a smooth and a rough rigid asperity
STLE ASME 2010 International Joint Tribology Conference, 2010Co-Authors: X Yin, K KomvopoulosAbstract:A discrete dislocation plasticity analysis of plane-strain indentation of a single-crystal half-space by a smooth or rough (Fractal) rigid asperity is presented. The emission, movement, and annihilation of edge dislocations are incorporated in the analysis through a set of constitutive rules [1,2]. It is shown that the initiation of the first dislocation is controlled by the subSurface Hertzian stress field and occurs in the ±45° direction with respect to the normal of the crystal Surface, in agreement with the macroscopic yielding behavior of the indented halfspace. For fixed slip-plane direction, the dislocation density increases with the applied normal load and dislocation source density. The dislocation multiplication behavior at a given load is compared with that generated by a rough indenter with a Fractal Surface profile. The results of the analysis provide insight into yielding and plastic deformation phenomena in indented single-crystal materials.© 2010 ASME
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stress analysis of a layered elastic solid in contact with a rough Surface exhibiting Fractal behavior
International Journal of Solids and Structures, 2007Co-Authors: K Komvopoulos, Z Q GongAbstract:A contact stress analysis is presented for a layered elastic half-space in contact with a rough Surface exhibiting self-affine (Fractal) behavior. Relationships for the mean contact pressure versus representative strain and the real half-contact width versus elastic properties of the layer and the substrate, asperity radius, layer thickness, and truncated half-contact width were derived from finite element simulations of a layered medium compressed elastically by a rigid cylindrical asperity. These relationships were incorporated in a numerical algorithm that was used to obtain the contact pressure distributions and stresses generated by the asperity contacts formed at the interface of the layered medium and the Fractal Surface. Analytical solutions illustrate the significance of the elastic material properties, layer thickness, and Surface topography (roughness) on global parameters such as normal load and real contact area. Results for the contact pressure distribution and the Surface and subSurface stresses provide insight into the initiation of yielding and the tendency for cracking in the layered medium. It is shown that cracking at the Surface and the layer/substrate interface is more likely to occur in the case of a stiff layer, whereas Surface cracking is more prominent for a relatively compliant layer.
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thermomechanical analysis of semi infinite solid in sliding contact with a Fractal Surface
Journal of Tribology-transactions of The Asme, 2005Co-Authors: Z Q Gong, K KomvopoulosAbstract:A thermomechanical analysis is presented for a semi-infinite elastic solid sliding against a rigid, rough Surface characterized by Fractal geometry. A piecewise-linear distribution of the contact pressure was obtained by superposition of overlapping triangular pressure elements. The normal Surface displacements due to the effects of contact pressure, shear traction, and thermoelastic distortion caused by frictional heating are incorporated in the influence coefficients of the matrix-inversion method. Results for a smooth, cylindrical Surface sliding over a semi-infinite elastic solid demonstrate the accuracy of the analysis and provide reference for comparison with results obtained with the rough (Fractal) Surface. The effects of Surface topography and interaction between neighboring asperity microcontacts on the Surface and subSurface temperature rise and stress field of the elastic semi-infinite solid are discussed in the context of numerical results. The significance of frictional heating on the contact pressure, temperature rise, and stresses is interpreted in terms of the Peclet number and topography (Fractal) parameters. The results provide insight into the likelihood for cracking and plastic flow at the Surface due to the combined effects of mechanical and thermal Surface tractions.
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thermomechanical analysis of semi infinite solid in sliding contact with a Fractal Surface
ASME STLE 2004 International Joint Tribology Conference Parts A and B, 2004Co-Authors: Z Q Gong, K KomvopoulosAbstract:A thermomechanical analysis is presented for semi-infinite elastic solid sliding against a rigid rough Surface characterized by Fractal geometry. A piecewise-linear distribution of the contact pressure was obtained by superposition of overlapping triangular pressure elements. The normal Surface displacements due to the effects of contact pressure, shear traction, and thermoelastic distortion caused by frictional heating are incorporated in the influence coefficients of the matrix inversion method. Results for a smooth cylindrical Surface sliding over a semi-infinite elastic solid demonstrate the accuracy of the analysis and provide reference for comparison with results obtained with the rough (Fractal) Surface. The effects of Surface topography and interaction between neighboring asperity microcontacts on the Surface and subSurface temperature rise and stress field of the elastic semi-infinite solid are discussed in the context of numerical results. The significance of frictional heating on the contact pressure, temperature rise, and stresses in interpreted in terms of the Peclet number and topography (Fractal) parameters. The results provide insight into the likelihood for cracking and plastic flow at the Surface due to the combined effects of mechanical and thermal Surface tractions.Copyright © 2004 by ASME
Itai Einav - One of the best experts on this subject based on the ideXlab platform.
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Static friction at Fractal interfaces
Tribology International, 2016Co-Authors: Dorian A.h. Hanaor, Yixiang Gan, Itai EinavAbstract:Tribological phenomena are governed by combined effects of material properties, topology and Surface-chemistry. We study the interplay of multiscale-Surface-structures with molecular-scale interactions towards interpreting static frictional interactions at Fractal interfaces. By spline-assisted-discretization we analyse asperity interactions in pairs of contacting Fractal Surface profiles. For elastically deforming asperities, force analysis reveals greater friction at Surfaces exhibiting higher Fractality, with increasing molecular-scale friction amplifying this trend. Increasing adhesive strength yields higher overall friction at Surfaces of lower Fractality owing to greater true-contact-area. In systems where adhesive-type interactions play an important role, such as those where cold-welded junctions form, friction is minimised at an intermediate value of Surface profile Fractality found here to be in the regime 1.3-1.5. Our results have implications for systems exhibiting evolving Surface structures. https://doi.org/10.1016/j.triboint.2015.09.016
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effects of Surface structure deformation on static friction at Fractal interfaces
Geotechnique Letters, 2013Co-Authors: Dorian A.h. Hanaor, Yixiang Gan, Itai EinavAbstract:The evolution of Fractal Surface structures with flattening of asperities was investigated using isotropically roughened aluminium Surfaces loaded in compression. It was found that asperity amplitude, mean roughness and Fractal dimension decrease through increased compressive stress and number of loading events. Of the samples tested, Surfaces subjected to an increased number of loading events exhibited the most significant Surface deformation and were observed to exhibit higher levels of static friction at an interface with a single-crystal flat quartz substrate. This suggests that the frequency of grain reorganisation events in geomaterials plays an important role in the development of intergranular friction. Fractal Surfaces were numerically modelled using Weierstrass– Mandelbrot-based functions. From the study of frictional interactions with rigid flat opposing Surfaces it was apparent that the effect of Surface Fractal dimension is more significant with increasing dominance of adhesive mechanisms.
Albrecht Wiedenmann - One of the best experts on this subject based on the ideXlab platform.
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the Surface geometry of vycor
Journal of Colloid and Interface Science, 1997Co-Authors: Ch A Mitropoulos, P.k. Makri, Nick K. Kanellopoulos, U. Keiderling, Albrecht WiedenmannAbstract:The interface geometry of Vycor porous glass was examined by adsorption of water in conjunction with small-angle scattering of X rays and neutrons. When the sample is dry, a Fractal Surface with a Fractal dimensionD∼ 2.5 was detected. When wet, a soft hydrogel is formed, resulting in a diffuse boundary. To observe a Fractal Surface, thorough drying of the sample is necessary, however. It was shown that a small amount of water, 3% w/w, is sufficient to render the Surface smooth.
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On the morphology and Surface geometry of Vycor
Physica B-condensed Matter, 1997Co-Authors: Fotios K. Katsaros, P.k. Makri, Nick K. Kanellopoulos, U. Keiderling, Athanasios C Mitropoulos, Albrecht WiedenmannAbstract:A Vycor porous glass is examined by adsorption of H2O/D2O as well as CH2Br2 in conjunction with small-angle scattering of neutrons and X-rays, respectively. For dry samples, the data indicates a Fractal Surface with a Fractal dimension D ∼ 2.6. After the deposition of an adsorbed film, deFractalization is observed. However, this procedure is different for H2O and CH2Br2. It is suggested that H2O yields a soft hydrogel on the Vycor Surface. Theoretical considerations on the morphology of the pore structure as well as the Surface geometry are given in terms of two-dimensional Fractal configurations.
Z Q Gong - One of the best experts on this subject based on the ideXlab platform.
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stress analysis of a layered elastic solid in contact with a rough Surface exhibiting Fractal behavior
International Journal of Solids and Structures, 2007Co-Authors: K Komvopoulos, Z Q GongAbstract:A contact stress analysis is presented for a layered elastic half-space in contact with a rough Surface exhibiting self-affine (Fractal) behavior. Relationships for the mean contact pressure versus representative strain and the real half-contact width versus elastic properties of the layer and the substrate, asperity radius, layer thickness, and truncated half-contact width were derived from finite element simulations of a layered medium compressed elastically by a rigid cylindrical asperity. These relationships were incorporated in a numerical algorithm that was used to obtain the contact pressure distributions and stresses generated by the asperity contacts formed at the interface of the layered medium and the Fractal Surface. Analytical solutions illustrate the significance of the elastic material properties, layer thickness, and Surface topography (roughness) on global parameters such as normal load and real contact area. Results for the contact pressure distribution and the Surface and subSurface stresses provide insight into the initiation of yielding and the tendency for cracking in the layered medium. It is shown that cracking at the Surface and the layer/substrate interface is more likely to occur in the case of a stiff layer, whereas Surface cracking is more prominent for a relatively compliant layer.
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thermomechanical analysis of semi infinite solid in sliding contact with a Fractal Surface
Journal of Tribology-transactions of The Asme, 2005Co-Authors: Z Q Gong, K KomvopoulosAbstract:A thermomechanical analysis is presented for a semi-infinite elastic solid sliding against a rigid, rough Surface characterized by Fractal geometry. A piecewise-linear distribution of the contact pressure was obtained by superposition of overlapping triangular pressure elements. The normal Surface displacements due to the effects of contact pressure, shear traction, and thermoelastic distortion caused by frictional heating are incorporated in the influence coefficients of the matrix-inversion method. Results for a smooth, cylindrical Surface sliding over a semi-infinite elastic solid demonstrate the accuracy of the analysis and provide reference for comparison with results obtained with the rough (Fractal) Surface. The effects of Surface topography and interaction between neighboring asperity microcontacts on the Surface and subSurface temperature rise and stress field of the elastic semi-infinite solid are discussed in the context of numerical results. The significance of frictional heating on the contact pressure, temperature rise, and stresses is interpreted in terms of the Peclet number and topography (Fractal) parameters. The results provide insight into the likelihood for cracking and plastic flow at the Surface due to the combined effects of mechanical and thermal Surface tractions.
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thermomechanical analysis of semi infinite solid in sliding contact with a Fractal Surface
ASME STLE 2004 International Joint Tribology Conference Parts A and B, 2004Co-Authors: Z Q Gong, K KomvopoulosAbstract:A thermomechanical analysis is presented for semi-infinite elastic solid sliding against a rigid rough Surface characterized by Fractal geometry. A piecewise-linear distribution of the contact pressure was obtained by superposition of overlapping triangular pressure elements. The normal Surface displacements due to the effects of contact pressure, shear traction, and thermoelastic distortion caused by frictional heating are incorporated in the influence coefficients of the matrix inversion method. Results for a smooth cylindrical Surface sliding over a semi-infinite elastic solid demonstrate the accuracy of the analysis and provide reference for comparison with results obtained with the rough (Fractal) Surface. The effects of Surface topography and interaction between neighboring asperity microcontacts on the Surface and subSurface temperature rise and stress field of the elastic semi-infinite solid are discussed in the context of numerical results. The significance of frictional heating on the contact pressure, temperature rise, and stresses in interpreted in terms of the Peclet number and topography (Fractal) parameters. The results provide insight into the likelihood for cracking and plastic flow at the Surface due to the combined effects of mechanical and thermal Surface tractions.Copyright © 2004 by ASME
Dorian A.h. Hanaor - One of the best experts on this subject based on the ideXlab platform.
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Static friction at Fractal interfaces
Tribology International, 2016Co-Authors: Dorian A.h. Hanaor, Yixiang Gan, Itai EinavAbstract:Tribological phenomena are governed by combined effects of material properties, topology and Surface-chemistry. We study the interplay of multiscale-Surface-structures with molecular-scale interactions towards interpreting static frictional interactions at Fractal interfaces. By spline-assisted-discretization we analyse asperity interactions in pairs of contacting Fractal Surface profiles. For elastically deforming asperities, force analysis reveals greater friction at Surfaces exhibiting higher Fractality, with increasing molecular-scale friction amplifying this trend. Increasing adhesive strength yields higher overall friction at Surfaces of lower Fractality owing to greater true-contact-area. In systems where adhesive-type interactions play an important role, such as those where cold-welded junctions form, friction is minimised at an intermediate value of Surface profile Fractality found here to be in the regime 1.3-1.5. Our results have implications for systems exhibiting evolving Surface structures. https://doi.org/10.1016/j.triboint.2015.09.016
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effects of Surface structure deformation on static friction at Fractal interfaces
Geotechnique Letters, 2013Co-Authors: Dorian A.h. Hanaor, Yixiang Gan, Itai EinavAbstract:The evolution of Fractal Surface structures with flattening of asperities was investigated using isotropically roughened aluminium Surfaces loaded in compression. It was found that asperity amplitude, mean roughness and Fractal dimension decrease through increased compressive stress and number of loading events. Of the samples tested, Surfaces subjected to an increased number of loading events exhibited the most significant Surface deformation and were observed to exhibit higher levels of static friction at an interface with a single-crystal flat quartz substrate. This suggests that the frequency of grain reorganisation events in geomaterials plays an important role in the development of intergranular friction. Fractal Surfaces were numerically modelled using Weierstrass– Mandelbrot-based functions. From the study of frictional interactions with rigid flat opposing Surfaces it was apparent that the effect of Surface Fractal dimension is more significant with increasing dominance of adhesive mechanisms.
