276 results found
Ewen JP, Heyes DM, Dini D, 2018, Advances in nonequilibrium molecular dynamics simulations of lubricants and additives, Friction, ISSN: 2223-7690
Ewen JP, Kannam S, Todd B, et al., 2018, Slip of Hexadecane on Organic Friction Modifier Monolayers, APS March Meeting 2018
Ewen JP, Kannam SK, Todd BD, et al., 2018, Slip of Alkanes Confined between Surfactant Monolayers Adsorbed on Solid Surfaces., Langmuir, Vol: 34, Pages: 3864-3873
The slip and friction behavior of n-hexadecane, confined between organic friction modifier surfactant films adsorbed on hematite surfaces, has been studied using nonequilibrium molecular dynamics simulations. The influence of the surfactant type and coverage, as well as the applied shear rate and pressure, has been investigated. A measurable slip length is only observed for surfactant films with a high surface coverage, which provide smooth interfaces between well-defined surfactant and hexadecane layers. Slip commences above a critical shear rate, beyond which the slip length first increases with increasing shear rate and then asymptotes toward a constant value. The maximum slip length increases significantly with increasing pressure. Systems and conditions which show a larger slip length typically give a lower friction coefficient. Generally, the friction coefficient increases linearly with logarithmic shear rate; however, it shows a much stronger shear rate dependency at low pressure than at high pressure. Relating slip and friction, slip only occurs above a critical shear stress, after which the slip length first increases linearly with increasing shear stress and then asymptotes. This behavior is well-described using previously proposed slip models. This study provides a more detailed understanding of the slip of alkanes on surfactant monolayers. It also suggests that high coverage surfactant films can significantly reduce friction by promoting slip, even when the surfaces are well-separated by a lubricant.
Forte AE, Galvan S, Dini D, 2018, Models and tissue mimics for brain shift simulations, BIOMECHANICS AND MODELING IN MECHANOBIOLOGY, Vol: 17, Pages: 249-261, ISSN: 1617-7959
Kanca Y, Milner P, Dini D, et al., 2018, Tribological evaluation of biomedical polycarbonate urethanes against articular cartilage, Journal of the Mechanical Behavior of Biomedical Materials, ISSN: 1751-6161
Kanca Y, Milner P, Dini D, et al., 2018, Tribological properties of PVA/PVP blend hydrogels against articular cartilage, JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, Vol: 78, Pages: 36-45, ISSN: 1751-6161
Lu J, Reddyhoff T, Dini D, 2018, 3D Measurements of Lubricant and Surface Temperatures Within an Elastohydrodynamic Contact, TRIBOLOGY LETTERS, Vol: 66, ISSN: 1023-8883
Menga N, Carbone G, Dini D, 2018, Do uniform tangential interfacial stresses enhance adhesion?, Journal of the Mechanics and Physics of Solids, Vol: 112, Pages: 145-156, ISSN: 0022-5096
© 2017 Elsevier Ltd We present theoretical arguments, based on linear elasticity and thermodynamics, to show that interfacial tangential stresses in sliding adhesive soft contacts may lead to a significant increase of the effective energy of adhesion. A sizable expansion of the contact area is predicted in conditions corresponding to such scenario. These results are easily explained and are valid under the assumptions that: (i) sliding at the interface does not lead to any loss of adhesive interaction and (ii) spatial fluctuations of frictional stresses can be considered negligible. Our results are seemingly supported by existing experiments, and show that frictional stresses may lead to an increase of the effective energy of adhesion depending on which conditions are established at the interface of contacting bodies in the presence of adhesive forces.
Tajabadi-Ebrahimi M, Dini D, Balint DS, et al., 2018, Discrete crack dynamics: a planar model of crack propagation and crack-inclusion interactions in brittle materials, International Journal of Solids and Structures, ISSN: 0020-7683
The Multipole Method (MPM) is used to simulate the many-body self-consistentproblem of interacting elliptical micro-cracks and inclusions in single crystals. Acriterion is employed to determine the crack propagation path based on the stressdistribution; the evolution of individual micro-cracks and their interactions withexisting cracks and inclusions is then predicted using what we coin the DiscreteCrack Dynamics (DCD) method. DCD is fast (semi-analytical) and particularlysuitable for the simulation of evolving low-speed crack networks in brittle orquasi-brittle materials. The method is validated against finite element analysispredictions and previously published experimental data.
Vakis A, Yastrebov V, Scheibert J, et al., 2018, Modeling and simulation in tribology across scales: an overview, Tribology International, ISSN: 0301-679X
This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and micro-scales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions.
Arana C, Evangelou SA, Dini D, 2017, Series Active Variable Geometry Suspension application to comfort enhancement, CONTROL ENGINEERING PRACTICE, Vol: 59, Pages: 111-126, ISSN: 0967-0661
Bodnarchuk MS, Dini D, Heyes DM, et al., 2017, Molecular Dynamics Studies of Overbased Detergents on a Water Surface, LANGMUIR, Vol: 33, Pages: 7263-7270, ISSN: 0743-7463
Bodnarchuk MS, Doncom KEB, Wright DB, et al., 2017, Polyelectrolyte pK(a) from experiment and molecular dynamics simulation, RSC ADVANCES, Vol: 7, Pages: 20007-20014, ISSN: 2046-2069
Ewen JP, Gattinoni C, Zhang J, et al., 2017, On the effect of confined fluid molecular structure on nonequilibrium phase behaviour and friction, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 19, Pages: 17883-17894, ISSN: 1463-9076
Ewen JP, Restrepo SE, Morgan N, et al., 2017, Nonequilibrium molecular dynamics simulations of stearic acid adsorbed on iron surfaces with nanoscale roughness, TRIBOLOGY INTERNATIONAL, Vol: 107, Pages: 264-273, ISSN: 0301-679X
Forte AE, Gentleman SM, Dini D, 2017, On the characterization of the heterogeneous mechanical response of human brain tissue, BIOMECHANICS AND MODELING IN MECHANOBIOLOGY, Vol: 16, Pages: 907-920, ISSN: 1617-7959
Gurrutxaga-Lerma B, Balint DS, Dini D, et al., 2017, A Dynamic Discrete Dislocation Plasticity study of elastodynamic shielding of stationary cracks, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, Vol: 98, Pages: 1-11, ISSN: 0022-5096
Gurrutxaga-Lerma B, Shehadeh MA, Balint DS, et al., 2017, The effect of temperature on the elastic precursor decay in shock loaded FCC aluminium and BCC iron, INTERNATIONAL JOURNAL OF PLASTICITY, Vol: 96, Pages: 135-155, ISSN: 0749-6419
Hajishafiee A, Kadiric A, Ioannides S, et al., 2017, A coupled finite-volume CFD solver for two-dimensional elasto-hydrodynamic lubrication problems with particular application to rolling element bearings, TRIBOLOGY INTERNATIONAL, Vol: 109, Pages: 258-273, ISSN: 0301-679X
Heyes DM, Dini D, Smith ER, et al., 2017, Nanowire Stretching by Non-Equilibrium Molecular Dynamics, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Vol: 254, ISSN: 0370-1972
Hu H, Wen J, Bao L, et al., 2017, Significant and stable drag reduction with air rings confined by alternated superhydrophobic and hydrophilic strips, SCIENCE ADVANCES, Vol: 3, ISSN: 2375-2548
Knight C, Abdol Azis MH, O'Sullivan C, et al., 2017, Sensitivity analysis of Immersed Boundary Method simulations of fluid flow in dense polydisperse random grain packings, ISSN: 2101-6275
© The Authors, published by EDP Sciences, 2017. Polydisperse granular materials are ubiquitous in nature and industry. Despite this, knowledge of the momentum coupling between the fluid and solid phases in dense saturated grain packings comes almost exclusively from empirical correlations [2-4, 8] with monosized media. The Immersed Boundary Method (IBM) is a Computational Fluid Dynamics (CFD) modelling technique capable of resolving pore scale fluid flow and fluid-particle interaction forces in polydisperse media at the grain scale. Validation of the IBM in the low Reynolds number, high concentration limit was performed by comparing simulations of flow through ordered arrays of spheres with the boundary integral results of Zick and Homsy  . Random grain packings were studied with linearly graded particle size distributions with a range of coefficient of uniformity values (C u = 1.01, 1.50, and 2.00) at a range of concentrations (Φ ∈ [0.396; 0.681]) in order to investigate the influence of polydispersity on drag and permeability. The sensitivity of the IBM results to the choice of radius retraction parameter  was investigated and a comparison was made between the predicted forces and the widely used Ergun correlation .
Ma S, Scaraggi M, Lin P, et al., 2017, Nanohydrogel Brushes for Switchable Underwater Adhesion, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 121, Pages: 8452-8463, ISSN: 1932-7447
Mackowiak S, Heyes DM, Pieprzyk S, et al., 2017, Non-Equilibrium Phase Behavior of Confined Molecular Films at Low Shear Rates, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Vol: 254, ISSN: 0370-1972
McCarron R, Stewart D, Shipway P, et al., 2017, Sliding wear analysis of cobalt based alloys in nuclear reactor conditions, WEAR, Vol: 376, Pages: 1489-1501, ISSN: 0043-1648
Profito FJ, Vladescu S-C, Reddyhoff T, et al., 2017, Transient experimental and modelling studies of laser-textured micro-grooved surfaces with a focus on piston-ring cylinder liner contacts, TRIBOLOGY INTERNATIONAL, Vol: 113, Pages: 125-136, ISSN: 0301-679X
Profito FJ, Vladescu S-C, Reddyhoff T, et al., 2017, Experimental Validation of a Mixed-Lubrication Regime Model for Textured Piston-Ring-Liner Contacts, MATERIALS PERFORMANCE AND CHARACTERIZATION, Vol: 6, Pages: 112-129, ISSN: 2379-1365
Putignano C, Dini D, 2017, Soft Matter Lubrication: Does Solid Viscoelasticity Matter?, ACS APPLIED MATERIALS & INTERFACES, Vol: 9, Pages: 42287-42295, ISSN: 1944-8244
Shen L, Denner F, Morgan N, et al., 2017, Marangoni effect on small-amplitude capillary waves in viscous fluids, Physical Review E, Vol: 96, Pages: 053110-053110, ISSN: 1539-3755
We derive a general integro-differential equation for the transient behavior of small-amplitude capillary waves on the planar surface of a viscous fluid in the presence of the Marangoni effect. The equation is solved for an insoluble surfactant solution in concentration below the critical micelle concentration undergoing convective-diffusive surface transport. The special case of a diffusion-driven surfactant is considered near the the critical damping wavelength. The Marangoni effect is shown to contribute to the overall damping mechanism, and a first-order term correction to the critical wavelength with respect to the surfactant concentration difference and the Schmidt number is proposed.
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