43 results found
Ponjavic A, Chennaoui M, Wong JSS, 2013, Through-Thickness Velocity Profile Measurements in an Elastohydrodynamic Contact, Tribology Letters
The through-thickness flow profile of a lubricant within an elastohydrodynamic contact is challenging to obtain due to its small thickness. Yet, this information is crucial to the accurate friction estimation of the tribological system. In this work, a novel fluorescence based technique has been developed to extract such information in situ. The local through-thickness flow profiles map within a tribological contact is obtained for the first time. The profiles obtained are position depends with slip boundary condition observed in high normal stress locations.
Wong J, Ponjavic A, 2013, Flow-profile mapping in elastohydrodynamic lubrication region
Chennaoui M, Wong JSS, 2012, Corrosion of Aluminum in Oil-Based Nanoemulsion
While metal components immersed in oil-based lubricants suffer from corrosion, very few studies investigate such phenomenon. As water-in-oil nanoemulsions can be formed intentionally and accidently in oil lubricants, they were used as model systems in this corrosion study to investigate the effect of surface topography on corrosion of Aluminium. The initiation sites of corrosion were identified using fluorescence imaging with a resolution of 1 micrometer. It shows for the first time metal corrodes in oil-based nanoemulsion. It was found that corrosion preferentially occurred at regions with surface irregularity. The corrosion mechanisms are discussed using percolation theory and charge transfer in surfactant networks of semi-dilute micelle solutions.
Wong JSS, Hong L, Bae SC, et al., 2011, Polymer Surface Diffusion in the Dilute Limit, Macromolecules, Vol: 44
Wong JSS, Hong L, Bae SC, et al., 2010, Fluorescence Recovery after Photobleaching Measurements of Polymers in a Surface Forces Apparatus, Journal of Polymer Science. Part B, Polymer Physics, Vol: 48
Bae SC, Wong JSS, Kim M, et al., 2008, Using light to study boundary lubrication: spectroscopic study of confined fluids, Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, Vol: 366
Wong JSS, Granick S, 2007, Open questions about polymer friction, Journal of Polymer Science. Part B, Polymer Physics, Vol: 45
Granick S, Zhu Y, Lin Z, et al., 2006, Reply to comment on reassessment of solidification in fluids confined between mica sheets, Langmuir, Vol: 22, Pages: 2399-2401, ISSN: 0743-7463
Mai YW, Wong JSS, Li RKY, et al., 2004, On the tearing toughness and permeability modelling of polymer nanocomposites, Pages: 1785-1789
This paper presents preliminary studies on two aspects of nylon-based nanoclay composite films: their out-of-plane tearing fracture resistance and moisture diffusion characteristics. Attempts to analyze the out-of-plane tearing fracture based on the essential work of fracture analysis will be presented. Also, theoretical modelling of the permeability of these polymer nanocomposites is also presented which takes into account the degree of exfoliation, orientation, aspect ratio and volume fraction of the nanoclay sheets; crystallinity of polymer matrix; and the affinity of polymer and clay with the diffusing species. Comparisons with published permeability data are given.
Wong J, Sue HJ, Zeng KY, et al., 2004, Surface damage of polymers in nanoscale, Pages: 1934-1937
Surface damage of polymers in the nanometer-range is examined and results correlated with material characteristics and surface roughness of epoxies. Under a constant loading and constant scratch rate testing condition, surface roughness plays little or no role in surface damage formed during the course of this study. Material characteristics influence the damage occurred in terms of variations in elastic recovery, damage pattern and damage mechanism. The variations in scratch head geometry, which, in turn, lead to the variations in magnitude of stress and stress field distribution, give rise to various scratch features on the polymer.
Recent advances in nanoscience and nanotechnology have led to the development of miniaturized devices and components based on polymeric materials. These polymeric components and devices are subject to surface damage in the nanoscale range. Since the surface properties of polymers may be different from those of the bulk, techniques that focus on nanoscale surface damage have been applied to correlate surface damage with material characteristics and surface roughness of epoxies, polycarbonate, and polymethylmethacrylate. Under a constant loading and constant scratch rate testing condition, the results suggest that surface damage encountered is mainly material specific. Surface roughness plays little or no role in surface damage formed during the course of this study. Material characteristics influence the damage occurred when varying the penetration depth. Such variations can be assessed in terms of elastic recovery, damage pattern and damage mechanism. The variations in scratch head geometry, which, in turn, lead to the variations in magnitude of stress and stress field distribution, give rise to various scratch features on the polymer. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Wong JSS, Ferrer-Balas D, Li RKY, et al., 2003, On tearing of ductile polymer films using the essential work of fracture (EWF) method, Acta Materialia, Vol: 51, Pages: 4929-4938, ISSN: 1359-6454
The essential work of fracture (EWF) technique has been well established and accepted for the fracture characterization of ductile polymer films under in-plane (mode I) loading. In the present study, the technique has been further developed for the characterization of out-of-plane (mode III) tearing fracture of some ductile polymer films including PETG (polyethylene-terephthalate-glycol), PP homopolymer (H0) and a PP copolymer (C1). A two-zone model was proposed to describe the deformation and fracture behaviour of the tearing ligament. In the first zone, which is called zone A and is adjoining the initial crack-tip, the outer plastic zone height increases with the torn ligament length. At the end of zone A, the height of the plastic zone has saturated, and the deformation has entered zone B. The height of the outer plastic zone remains constant with further increase of torn ligament length. The zone B model is applicable to films with a large stabilized plastic zone (such as H0 and C1). It is observed that the tearing specific essential fracture work as measured from the zone A and zone B models are similar confirming the EWF concept can be applied to the mode III out-of-plane tearing of polymer films. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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