271 results found
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
© 2017, The Author(s). We present an infrared microscopy technique, capable of measuring the temperature of both the bounding surfaces and the oil film in an elastohydrodynamic contact. This technique can, for the first time, spatially resolve the oil film temperature in three dimensions. The contact is produced by loading a steel ball against a sapphire disc, and the film is viewed using an infrared microscope focussing through the disc. Two band pass filters are used to isolate the radiation from the oil film, and Planck’s law is applied to data obtained at a known temperature as part of the calibration procedure. The proposed technique requires the emissivity of the oil film to be measured, which is acquired in situ and is shown to vary strongly as a function of thickness and temperature. The technique is validated under pure rolling conditions, when the temperature of the oil film is equal to the controlled lubricant reservoir temperature, and also compared to an equation commonly used to predict average film temperatures, confirming the value of the unknown constant. The technique is then used to gain insights into the thermal/rheological behaviour within a contact. This is important since the temperature of elastohydrodynamic contacts is critical in determining friction and hence the efficiency of machine components and this technique enables much needed validation and provides input data for CFD and numerical simulations.
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.
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, Galvan S, Dini D, 2017, Models and tissue mimics for brain shift simulations., Biomech Model Mechanobiol
Capturing the deformation of human brain during neurosurgical operations is an extremely important task to improve the accuracy or surgical procedure and minimize permanent damage in patients. This study focuses on the development of an accurate numerical model for the prediction of brain shift during surgical procedures and employs a tissue mimic recently developed to capture the complexity of the human tissue. The phantom, made of a composite hydrogel, was designed to reproduce the dynamic mechanical behaviour of the brain tissue in a range of strain rates suitable for surgical procedures. The use of a well-controlled, accessible and MRI compatible alternative to real brain tissue allows us to rule out spurious effects due to patient geometry and tissue properties variability, CSF amount uncertainties, and head orientation. The performance of different constitutive descriptions is evaluated using a brain-skull mimic, which enables 3D deformation measurements by means of MRI scans. Our combined experimental and numerical investigation demonstrates the importance of using accurate constitutive laws when approaching the modelling of this complex organic tissue and supports the proposal of a hybrid poro-hyper-viscoelastic material formulation for the simulation of brain shift.
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
Kanca Y, Milner P, Dini D, et al., 2017, Tribological properties of PVA/PVP blend hydrogels against articular cartilage., J Mech Behav Biomed Mater, Vol: 78, Pages: 36-45
This research investigated in-vitro tribological performance of the articulation of cartilage-on- polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) blend hydrogels using a custom-designed multi-directional wear rig. The hydrogels were prepared by repeated freezing-thawing cycles at different concentrations and PVA to PVP fractions at a given concentration. PVA/PVP blend hydrogels showed low coefficient of friction (COF) values (between 0.12 ± 0.01 and 0.14 ± 0.02) which were closer to the cartilage-on-cartilage articulation (0.03 ± 0.01) compared to the cartilage-on-stainless steel articulation (0.46 ± 0.06). The COF increased with increasing hydrogel concentration (p = 0.03) and decreasing PVP content at a given concentration (p < 0.05). The cartilage-on-hydrogel tests showed only the surface layers of the cartilage being removed (average volume loss of the condyles was 12.5 ± 4.2mm3). However, the hydrogels were found to be worn/deformed. The hydrogels prepared at a higher concentration showed lower apparent volume loss. A strong correlation (R2 = 0.94) was found between the COF and compressive moduli of the hydrogel groups, resulting from decreasing contact congruency. It was concluded that the hydrogels were promising as hemiarthroplasty materials, but that improved mechanical behaviour was required for clinical use.
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.
Smith ER, Heyes DM, Dini D, 2017, Towards the Irving-Kirkwood limit of the mechanical stress tensor, JOURNAL OF CHEMICAL PHYSICS, Vol: 146, ISSN: 0021-9606
Tan Z, Bernardini A, Konstantinou I, et al., 2017, Diffusion Measurement and Modelling, European Robotics Forum 2017
Tan Z, Forte AE, Parisi C, et al., 2017, Composite hydrogel: A new tool for reproducing the mechanicalbehaviour of soft human tissues, WTC 2017
Verschueren J, Gurrutxaga-Lerma B, Balint DS, et al., 2017, The injection of a screw dislocation into a crystal: Atomistics vs. continuum elastodynamics, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, Vol: 98, Pages: 366-389, ISSN: 0022-5096
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