230 research outputs found
Dynamics of contact line motion during the wetting of rough surfaces and correlation with topographical surface parameters
No full textDynamics of contact line motion and wettability is essential in many industrial applications such as liquid coating, lubrication, printing, painting, condensation, etc. However, the wettability of surfaces depends not only on liquid–solid chemical properties but also can be strongly affected by surface roughness. As a practical application of controlled wettability, we can mention the self-cleaning surfaces, protective clothing, microfluidics devices, electro wetting, etc. In this article, we experimentally investigate the spreading of droplets deposited onto rough surfaces. Anisotropic surfaces were prepared by abrasive polishing on the following materials: aluminium alloy AA7064, titanium alloy Ti-6Al-4V, steel AISI 8630, copper alloy UNS C17000, machinable glass ceramic, and poly-methylmethacrylate. Topographical 2D parameters were calculated according to the following standards, defining Geometrical Product Specifications (GPS): ISO 4287, ISO 12085, ISO 13565, ISO 12780, and ISO 12181. The influence of topographical parameters on wettability and spreading phenomenon has been evaluated by statistical covariance analysis. The following parameters have strong influence on fluid spreading on rough surfaces: Rmr is the relative material ratio of the roughness profile, Trc is the microgeometric material ratio, Pmr is the relative material ratio of the raw profile, Kr is the mean slope of the roughness motifs, RONt is the peak to valley roundness deviation, and Psk is the Skewness of the raw profile. The physical meaning of selected parameters is discussed, and Kr (the mean slope of the roughness motifs) is selected as the most important and physically meaningful parameter. It has been found that for all tested materials, fluid spreading shows increasing tendency when mean slope of the roughness motifs (Kr) increases. SCANNING 33: 1–8, 2011. © 2011 Wiley Periodicals, Inc
Influence of roughness on ZDDP tribofilm formation in boundary lubricated fretting
No full textInfluence of initial surface topography on tribofilm formation in ZDDP lubricated contact was analysed. A small displacement fretting tests with sinusoidal motion were carried out in classical sphere/plane configuration. A range of surfaces with different initial roughness were prepared by milling and grinding processes. Tests were carried out using variable displacement method where amplitude of imposed displacement was gradually increased after every 1000 cycles from 2 to 30 µm. The surfaces after tribological tests were measured by interferometric profiler. Main findings confirm that initial roughness has a significant influence on antiwear tribofilm formation in boundary lubricated contact. Tribofilm form faster and require less energy to activate in case of rough surface obtained by milling process than in case of smooth grinded surface. However, in contact lubricated by ZDDP additive a significant transfer of material occurred from plane to sphere specimen
Influence of roughness on contact interface in fretting under dry and boundary lubricated sliding regimes
No full textThis paper presents experimental results of wear process under dry and boundary lubricated metallic (AISI 1034/AISI 52100) contacting bodies with different surfaces morphologies subjected to a wide range of kinematic fretting conditions. Analysis of damage mode observed under such fretting conditions is elucidated in context of surfaces morphologies therefore associated with surface manufacturing processes. Various surface topographies due to specific machining processes (cutting and abrasive modes) have been investigated. Under boundary lubricated (ZDDTP zinc-dialkyl-dithiophosphate) fretting contact paradoxally has a high coefficient of friction at the transition between Partial and Full slip sliding regime. This paper attempts to bridge the gap between the damage mode, sliding conditions and surface roughness to provide an approach to evaluate the surface finishing as a factor in friction and wear damage processes
Wettability versus roughness of engineering surfaces
No full textWetting of real engineering surfaces occurs in many industrial applications (liquid coating, lubrication, printing, painting, ...). Forced and natural wetting can be beneficial in many cases, providing lubrication and therefore reducing friction and wear. However the wettability of surfaces can be strongly affected by surface roughness. This influence can be very significant for static and dynamic wetting [1]. In this paper authors experimentally investigate the roughness influence on contact angle measurements and propose a simple model combining Wenzel and Cassie-Baxter theories with simple 2D roughness profile analysis. The modelling approach is applied to real homogeneous anisotropic surfaces, manufactured on a wide range of engineering materials including aluminium alloy, iron alloy, copper, ceramic, plastic (poly-methylmethacrylate: PMMA) and titanium alloy
Interface roughness effect on friction map under fretting contact conditions
No full textIn many industrial applications where fretting damage is observed in the contact (e.g. rotor/blade, electrical contacts, assembly joint, axe/wheel, clutch) the external loadings or geometry design cannot be changed. Therefore, the surface preparation and finishing process become essential to control and reduce the damage caused by fretting. In this paper, the authors present the experimental study of the initial surface roughness and machining process influence on fretting conditions in both partial and full sliding regimes. Surfaces prepared by milling and smooth abrasive polishing processes have been analysed. The influence of roughness on sliding behaviour and analysis of friction have been reported. Also, the contact pressure influence and qualitative analysis of fretting wear scar have been presented
Dynamic evolution of interface roughness during friction and wear processes
No full textDynamic evolution of surface roughness and influence of initial roughness (Sa=0.282 to 6.73 µm) during friction and wear processes has been analyzed experimentally. The mirror polished and rough surfaces (28 samples in total) have been prepared by surface polishing on Ti-6Al-4V and AISI 1045 samples. Friction and wear have been tested in classical sphere/plane configuration using linear reciprocating tribometer with very small displacement from 130 to 200 microns. After an initial period of rapid degradation, dynamic evolution of surface roughness converges to certain level specific to a given tribosystem. However, roughness at such dynamic interface is still increasing and analysis of initial roughness influence revealed that to certain extent, a rheology effect of interface can be observed and dynamic evolution of roughness will depend on initial condition and history of interface roughness evolution. Multiscale analysis shows that morphology created in wear process is composed from nano, micro and macro scale roughness. Therefore, mechanical parts working under very severe contact conditions, like rotor/blade contact, screws, clutch etc. with poor initial surface finishing are susceptible to have much shorter lifetime than a quality finished parts
Wear resistant multilayer nanocomposite WC1−x/C coating on Ti–6Al–4V titanium alloy
No full textA significant improvement of tribological properties on Ti–6Al–4V has been achieved by developed in this study multilayer treatment method for the titanium alloys. This treatment consists of an intermediate 2 μm thick TiCxNy layer which has been deposited by the reactive arc evaporation onto a diffusion hardened material with interstitial O or N atoms by glow discharge plasma in the atmosphere of Ar+O2 or Ar+N2. Subsequently, an external 0.3 μm thin nanocomposite carbon-based WC1−x/C coating has been deposited by a reactive magnetron sputtering of graphite and tungsten targets. The morphology, microstructure, chemical and phase compositions of the substrate material after treatment and coating deposition have been investigated with use of AFM, SEM, EDX, XRD, 3D profilometry and followed by tribological investigation of wear and friction analysis. An increase of hardness in the diffusion treated near-surface zone of the Ti–6Al–4V substrate has been achieved. In addition, a good adhesion between the intermediate gradient TiCxNy coating and the Ti–6Al–4V substrate as well as with the external nanocomposite coating has been obtained. Significant increase in wear resistance of up to 94% when compared to uncoated Ti–6Al–4V was reported. The proposed multilayer system deposited on the Ti–6Al–4V substrate is a promising method to significantly increase wear resistance of titanium alloys
Tetraether lipid inventory of upper slope marine sediments deposited over the last 30 thousand years north of the Svalbard archipelago
No full textThe dataset presented was used to reconstruct the origin of terrestrial material deposited during the last 30 thousand years on the upper continental slope of the Svalbard archipelago, north of Nordaustlandet (81°16'N, 26°13'E). The material analyzed consisted in muddy sediments from the 4.66 m long gravity core HH11-09GC, retrieved at a water depth of 488 m in September 2011 during a scientific cruise of the R/V Helmer Hanssen. Data on isoprenoid (i-), hydroxylated (OH-), and branched (br-) glycerol dialkyl glycerol tetraethers (GDGTs) were obtained extracting with organic solvents about 1.5 g of dry sediment of 77 samples according to the method reported in Tesi et al. (2021). Chromatographic analyses to identify and quantify each compound of interest were performed on an Agilent 1260 Infinity II ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) system, consisting of a G1712B binary pump, a G7129A vial sampler with integrated sample thermostat, a G7116A multicolumn thermostat, and a G6125C single quadrupole mass spectrometer with an atmospheric pressure chemical ionization (APCI) ion source. Sediment extraction was performed at the organic geochemistry laboratories of the Institute of Polar Sciences of the National Research Council in Bologna (Italy), while chromatographic investigations were carried out at the Alfred Wegener Institute (AWI) laboratory in Bremerhaven (Germany). Data on GDGTs were used to gain insights on the origin of the terrestrial material delivered on the study site. Additionally, we calculated indices based on brGDGTs to identify the production of bacterial tetraether lipids in marine environments.
Tesi, T., Muschitiello, F., Mollenhauer, G., Miserocchi, S., Langone, L., Ceccarelli, C., et al. (2021). Rapid Atlantification along the Fram Strait at the beginning of the 20th century. Science Advances, 7(48). https://doi.org/10.1126/sciadv.abj294
Measurement of the top-quark mass in all-jets events in pp collisions at = 7 TeV
No full textThe mass of the top quark is measured using a sample of candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at = 7 TeV in 2011 and corresponds to an integrated luminosity of 3.54 . The mass is reconstructed for each event employing a kinematic fit of the jets to a hypothesis. The top-quark mass is measured to be 173.49 0.69(stat.) 1.21(syst.) GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of 173.54 0.33(stat.) 0.96(syst.) GeV
The metrology of ground concrete surfaces morphology with 3D laser scanner
No full textThis paper is devoted to machining of concrete by grinding and the metrology of its surface
morphologies. The surface morphology is still open problem from metrological as well as
mathematical morphology points of views. In order to understand better abrasive process the
raw morphologic state is compared with the ground concrete surfaces. The most significant
results are presented in the form of profiles, 3D isometric views and isotropy analysis. Several
3D surface roughness parameters were calculated
- …
