Search results for " roughness"
showing 10 items of 183 documents
Numerical modelling of fatigue crack initiation of martensitic steel
2010
Numerical simulation of micro-crack initiation that is based on Tanaka-Mura micro-crack nucleation model is presented. Three improvements were added to this model. Firstly, multiple slip bands where micro-cracks may occur are used in each grain. Second improvement deals with micro-crack coalescence by extending existing micro-cracks along grain boundaries and connecting them into a macro-crack. The third improvement handles segmented micro-crack generation, where a micro-crack is not nucleated in one step like in Tanaka-Mura model, but is instead generated in multiple steps. Numerical simulation of crack-initiation was performed with ABAQUS, using a plug-in that was written specially for ha…
Adhesive joining of Aluminum AA6082: the effect of resin and surface treatment
2009
Abstract In this work the effects of both the substrate surface condition and the adhesive properties on single-lap aluminium joint resistance were analysed. The aluminium sheets were mechanically treated with two abrasive surfaces evaluating the induced roughness; four different resins were used in adhesion tests. Moreover, wettability tests were performed in order to evaluate the effect of the above-mentioned parameters on the substrate/adhesive interaction. A design of experiments was defined in order to quantify the effect of the considered factors and their correlation.
The effect of the slope of irregularly distributed roughness elements on turbulent wall-bounded flows
2008
Wall roughness produces a downward shift of the mean streamwise velocity profile in the log region, known as the roughness function. The dependence of the roughness function on the height and arrangement of roughness elements has been confirmed in several studies where regular rough walls were analysed; less attention has been paid to non-regular rough walls. Here, a numerical analysis of turbulent flows over irregularly shaped rough walls is performed, clearly identifying the importance of a parameter, called the effective slope (ES) of the wall corrugations, in characterizing the geometry of non-smooth irregular walls. The effective slope proves to be one of the fundamental geometric para…
Formation of surface roughness on nanocrystalline aluminum samples under straining by molecular dynamics studies
2006
International audience; The surface roughening of nanocrystalline aluminum samples was investigated by molecular dynamics simulations. Attention was focused on the fact that roughness increases with the grain size and the strain. The elastic-plastic transition was found at around 3.5% strain and a reverse Hall-Petch effect was observed under straining conditions. Then, different strain distributions in grains and grain boundaries at the samples surface was highlighted, yielding to the formation of local roughness. Finally, a linear relationship between the magnitude of roughness and the out-of-plane strain component was found.
Nucleation and growth of ZnO on PMMA by low-temperature atomic layer deposition
2015
ZnO films were grown by atomic layer deposition at 35 °C on poly(methyl methacrylate) substrates using diethylzinc and water precursors. The film growth, morphology, and crystallinity were studied using Rutherford backscattering spectrometry, time-of-flight elastic recoil detection analysis, atomic force microscopy, scanning electron microscopy, and x-ray diffraction. The uniform film growth was reached after several hundreds of deposition cycles, preceded by the precursor penetration into the porous bulk and island-type growth. After the full surface coverage, the ZnO films were stoichiometric, and consisted of large grains (diameter 30 nm) with a film surface roughness up to 6 nm (RMS). T…
The application of the random balance method in laser machining of metals
2008
International audience; Features peculiar to laser technology offer some advantages over more traditional processes, but, like all processes, it has its limitations. This article studies the limitations of laser machining of metals, and quantifies, through an experimental design method, the influence of operating parameters on productivity and on the quality of the machined surface. Three study materials were used: an aluminium alloy, stainless steel and a titanium alloy. An initial reading of the results indicates that productivity depends mainly on the frequency of the laser pulse and that the aluminium alloy behaves differently from the other two. The quality of the machined surface, jud…
Role of plastic deformation and microstructure in the micro-electrochemical behaviour of Ti–6Al–4V in sodium chloride solution
2013
Abstract The role of alloying elements and the influence of plastic deformation on the micro-electrochemical behaviour and the pitting corrosion susceptibility of TiAl6V4 have been investigated in 10 g/L NaCl using the electrochemical microcell technique. Local electrochemical measurements have revealed that both the increase of surface roughness and the increase of dislocation density have impact on the electrochemical behaviour of TiAl6V4 after plastic deformation. It has been shown the surface roughness induced by slip band emergence is the predominant parameter responsible for the increase of the cathodic current. It has also been shown that cathodic reactions occur preferentially at su…
Surface Integrity
2008
This chapter provides comprehensive knowledge regarding the state and properties of both surface and subsurface layers generated during machining processes, including different associated mechanical and thermal influences. Basic models of the superficial layer and factors effecting surface integrity are presented. Decomposition of surface topography into roughness, waviness and form along with appropriate filtering methods is outlined. The characterization of surface roughness based on 2D and 3D roughness parameters as well as motif, fractal and frequency characteristics are presented. In particular, all standardized areal surface parameters are specified, and practical examples are provide…
Improved Cu2O/AZO Heterojunction by Inserting a Thin ZnO Interlayer Grown by Pulsed Laser Deposition
2019
Cu2O/ZnO:Al (AZO) and Cu2O/ZnO/AZO heterojunctions have been deposited on glass substrates by a unique three-step pulsed laser deposition process. The structural, optical, and electrical properties of the oxide films were investigated before their implementation in the final device. X-ray diffraction analysis indicated that the materials were highly crystallized along the c-axis. All films were highly transparent in the visible region with enhanced electrical properties. Atomic force and scanning electron microscopies showed that the insertion of a ZnO layer between the Cu2O and AZO films in the heterojunction enhanced the average grain size and surface roughness. The heterojunctions exhibi…
Whispering gallery mode resonators covered by a ZnO nanolayer
2020
Abstract The exceptional ability of whispering gallery mode resonators (WGMRs) to confine light within makes them interesting for sensing applications. The small size and high values of quality (Q) factors of the WGMR can be combined with a broad range of supporting optical elements. The surface of the resonator can be coated to enhance the desired attributes. In this paper, the impact of the ZnO layer thickness on the Q-factor of the WGMR has been studied. WGMRs were fabricated on a tip of a standard telecom fiber melted with an oxyhydrogen flame. The surface of the WGMR was coated with ZnO nanolayers of different thickness (5–100 nm) by atomic layer deposition (ALD). The Q-factor of as-pr…