Numerical study of wind flow over an elevated roadway

Numerical study of wind flow over an elevated roadway

Effect of multi stage abrasive slurry jet polishing on surface generation in glass

By considering urbanization on an overland plane as a process whereby a relatively rough, permeable surface is gradually replaced by a relatively smooth, less permeable surface, the effect of urbanization sequence on the flood peak is theoretically assessed by the kinematic wave method. In the assessment, two opposing urbanization sequences are considered: one from downstream to upstream, and the other from upstream to downstream. The assessment is carried out in terms of the individual effect as well as the combined effect of the Manning resistance coefficient and the runoff coefficient. For both urbanization sequences and for all degrees of urbanization, the assessment shows that surface conversion from rough to smooth, or from permeable to less permeable causes the flood peak to increase. A comparison of the individual effects shows that for equal reductions in surface roughness and permeability, the reduction in permeability causes greater increases in the flood peak compared with the reduction in surface roughness. For a partially urbanized plane and for the same degree of urbanization, due to the partial area effect, urbanization at the downstream end generally causes greater increases in the flood peak. In terms of urbanization sequence, the downstream to upstream urbanization sequence generally causes greater increases in the flood peak. The effect of urbanization sequence on the flood peak, however, is only significant for the larger reductions in surface roughness and permeability. Finally, a comparison of the results of this study with those obtained from drainage basins shows that for most of the results from the basins, they correspond to those for the small reductions in surface roughness and permeability on an overland plane. For these cases, the effect of urbanization sequence on the flood peak is small. Copyright © 1999 John Wiley & Sons, Ltd.

Experimental and theoretical investigation into surface roughness and residual stress using ball end magnetorheological finishing

Heat generation in metal cutting leads to numerous problems. Despite the development of many different cooling and lubrication methods in industry, opportunities are still open to develop novel methods. Minimum quantity lubrication (MQL) is a recent such development that has shown promising results. However, the effect of aerosol temperature on machining performance has not yet been studied in depth. Thus, the aim of this study is to explore the ability to improve surface roughness in machining by lowering the MQL aerosol temperature. To study the effect of the aerosol temperature in MQL, an experimental investigation is carried out using a simple turning operation on AISI P20 and D2 steels, with cutting tools and cutting fluids (CF) typically used in industry. The arithmetic average surface roughness of the workpiece is measured for each of the treatments. Measurements are taken with dry cutting condition, conventional flood cooling method, and several MQL temperatures. Significantly lower surface roughness in the workpieces is observed for all considered MQL temperatures in comparison to dry cutting and flood cooling conditions. Furthermore, a reducing trend with a quadratic behaviour in surface roughness is observed with decreasing temperatures. The lowest surface roughness is observed at MQL 5 °C for both material. Interestingly, the effect of aerosol temperature is observed to be high with D2 steel and lower temperatures achieved up to 50% reduction in surface roughness. The study concludes that surface roughness can be reduced using low-temperature MQL. The effect of the aerosol temperature on other tool-work material combinations and tribology studies are suggested as further work.

Extrusion-based 3D printing (E3DP) is a popular additive manufacturing technique known for its versatility in creating prototypes and functional parts. However, achieving high surface quality has posed challenges regarding accuracy and finish. To address this issue, this study aims to enhance the surface quality of E3DP components fabricated by the fused filament fabrication (FFF) method and polylactic acid (PLA) material by applying neosanding postprocessing. The research investigates the impact of key neosanding process factors on surface roughness, namely neosanding spacing, neosanding speed, and flow rate. To ensure a comprehensive evaluation, each factor is examined at four levels, covering a wide range of values relevant to the neosanding process. Surface roughness is quantified using the average roughness parameter (Ra) and measured using both stylus profilometer and confocal profilometry methods. The results highlight a substantial decrease in surface roughness achieved through the neosanding method. At default factor levels of the neosanding method, the stylus profilometer method achieves an impressive 83% reduction in surface roughness, while the confocal profilometry method achieves an 80% reduction. Among the neosanding process factors, neosanding spacing significantly influences surface roughness values. Understanding and optimizing this factor is crucial for achieving desired surface quality in FFF-produced PLA parts. This study makes a valuable contribution to the field by optimizing surface roughness in FFF-produced PLA parts through neosanding postprocessing. By exploring the influence of neosanding tool factors and comparing measurement methods, manufacturers can enhance the surface quality of FFF-manufactured parts, paving the way for broader applications across various industries.

Electrochemical polishing of chemical vapor deposited niobium thin films

Surface roughness control in nanolaminate coatings of chromium and tungsten nitrides

Reduction of surface roughness of a laminin–apatite composite coating via inhibitory effect of magnesium ions on apatite crystal growth

Micromachining of a polydimethylsiloxane (PDMS) microstructure by wet chemical etching is explored for microelectromechanical systems (MEMS) and microfluidic applications. A 100 µm thick PDMS film was patterned with different microstructure designs by wet chemical etching using a N-methyl-2-pyrrolidone (C16H36FN) and tetra-n-butylammonium fluoride (C5H9NO) mixture solution with 3:1 volume ratio after lithography for studying etching characteristics. The patterning parameters, such as etch rate, surface roughness, pH of etchant solution with time, were thoroughly investigated. A detailed study of surface morphology with etching time revealed nonlinear behaviour of the PDMS surface roughness and etch rate. A maximum rate of 1.45 µm min−1 for 10 min etching with surface roughness of 360 nm was achieved. A new approach of wet chemical etching with pH controlled doped etchant was introduced for lower surface roughness of etched microstructures, and a constant etch rate during etching. Variation of the etching rate and surface roughness by pH controlled etching was performed by doping 5–15 gm l−1 of silicic acid (SiO2xH2O) into the traditional etchant solution. PDMS etching by silicic acid doped etchant solution showed a reduction in surface roughness from 400 nm to 220 nm for the same 15 µm etching. This study is beneficial for micromachining of various MEMS and microfluidic structures such as micropillars, microchannels, and other PDMS microstructures.

Bacterial adhesion to intra-oral, hard surfaces is firmly influenced by the surface roughness to these structures. Previous studies showed a remarkable higher subgingival bacterial load on rough surfaces when compared to smooth sites. More recently, the additional effect of a further smoothening of intra-oral hard surfaces on clinical and microbiological parameters was examined in a short-term experiment. The results indicated that a reduction in surface roughness below R(a) = 0.2 microns, the so-called "thresholds R(a)", had no further effect on the quantitative/qualitative microbiological adhesion or colonisation, neither supra- nor subgingivally. This study aims to examine the long-term effects of smoothening intra-oral hard transgingival surfaces. In 6 patients expecting an overdenture in the lower jaw, supported by endosseus titanium implants, 2 different abutments (transmucosal part of the implant): a standard machined titanium (R(a) = 0.2 microns) and one highly polished and made of a ceramic material (R(a) = 0.06 microns) were randomly installed. After 3 months of intra-oral exposure, supra- and subgingival plaque samples from both abutments were compared with each other by means of differential phase-contrast microscopy (DPCM). Clinical periodontal parameters (probing depth, gingival recession, bleeding upon probing and Periotest-value) were recorded around each abutment. After 12 months, the supra- and subgingival samples were additionally cultured in aerobic, CO2-enriched and anaerobic conditions. The same clinical parameters as at the 3-month interval were recorded after 12 months. At 3 months, spirochetes and motile organisms were only detected subgingivally around the titanium abutments. After 12 months, however, both abutment-types harboured equal proportions of spirochetes and motile organisms, both supra- and subgingivally. The microbial culturing (month 12) failed to detect large inter-abutment differences. The differences in number of colony- forming units (aerobic and anaerobic) were within one division of a logarithmic scale. The aerobic culture data showed a higher proportion of Gram-negative organisms in the subgingival flora of the rougher abutments. From the group of potentially "pathogenic" bacteria, only Prevotella intermedia and Fusobacterium nucleatum were detected for anaerobic culturing and again the inter-abutment differences were negligible. Clinically, the smoothest abutment showed a slightly higher increase in probing depth between months 3 and 12, and more bleeding on probing. The present results confirm the findings of our previous short-term study, indicating that a further reduction of the surface roughness, below a certain "threshold R(a)" (0.2 microns), has no major impact on the supra- and subgingival microbial composition.

This study aims to evaluate and compare the effect of the addition of two nanoparticles (silicon dioxide [Si-NPs] and hydroxyapatite [HA-NPs]) on the flexural strength and surface properties of three-dimensionally (3D)-printed denture base materials. In this study, Si-NP and HA-NP were added separately to two 3D-printed resins (ASIGA DentaBASE and NextDent Denture 3D+). The percentage of each nanoparticle was optimized at 0.25 and 0.50 wt%, with 3D-printed resins without nanoparticles (unmodified) as control groups. The specimens were thermally aged (5000 cycles at 5°C and 55°C). The flexural strength test of each group was conducted according to the ISO 20795-1:2013 specifications. After flexural strength, the fractured samples were analyzed under a scanning electron microscope (SEM). The surface roughness and Vickers microhardness tests were performed on disc-shaped (15 × 2mm) samples. Data analysis was performed using ANOVA followed by Tukey's post hoc test at α = 0.05. The flexural strength was significantly increased with the addition of Si-NPs to ASIGA resin (p < 0.001), while there was no significant increase with Si-NP addition to NextDent resin. The highest flexural strength value (106.75 ± 8.59MPa) was observed for 0.5% Si-NPs/ASIGA. The flexural strength was significantly decreased (p < 0.001) for both resins with the addition of two percentages of HA-NPs. The surface roughness was significantly reduced (p < 0.001) for both Si-NPs-based groups and 0.25%-based HA-NPs, whereas 0.50% HA-NPs/ASIGA showed the highest surface roughness value (0.46 ± 0.19µm). Nonsignificant change in microhardness value was observed, whereby the NextDent group showed the highest values compared with ASIGA. Overall, Si-NP had a positive impact on 3D-printed resins, resulting in an increase in flexural strength and a reduction in surface roughness compared to the HA-NP-based groups. However, no difference was observed in the microhardness testing.

The influence of alumina nanofiller and gamma irradiation on the surface potential variation of epoxy-alumina nanocomposites was investigated. The surface potential decay rate of nanocomposites has increased and the trap depth decreased with alumina nanoparticles addition to the matrix as well as upon exposure to gamma irradiation, Surface roughness was estimated using the wavelets and fractal technique. Daubechies wavelet of order 4 (db4) wavelet was chosen as the most suitable mother wavelet for surface roughness measurement. Multi resolution signal decomposition (MRSD) analysis of surface profile has revealed that with increasing wt% of alumina nanofiller in the nanocomposites, reduction in surface roughness of nanocomposites was observed. Upon gamma irradiation, the surface roughness factor at each level of MRSD has increased marginally. Fractal dimension and lacunarity were calculated for unaged and gamma ray irradiated samples and it exhibits inverse correlation.

This study describes the DLyte dry electropolishing of heat- treated Ti6Al4V samples (vertical, horizontal and semi-sphere samples) produced by laser powder bed fusion technology. The Ti6Al4V samples were divided and build-in zones according to the Argon inlet and outlet as well as the start and end areas of the powder distribution within the building plate. The as-build Ti6Al4V samples were investigated for their suitability in medical bone implant applications and were found to have a surface roughness that exceeds the standards of a bone implant irrespective of the zone in which they are built. This necessitates additional post surface finishing procedures to achieve the desired surface finish for bone implants. DLyte dry electropolishing was employed for surface finishing to enhance the surface condition of Ti6Al4V as-build samples. The Ti6Al4V as-build samples were polished according to their zones in which they were build. The efficacy of polishing was assessed based on different time intervals (30, 60 and 120 minutes) and the decrease in surface roughness. The results show that after 30 minutes of polishing there was a lower reduction in surface roughness and the higher surface reduction was observed after 120 minutes of polishing. It was noted that as the polishing time increased, the surface become progressively smoother.

Running-in of two fresh and unworn surfaces in contact is a transient phase where friction and wear vary considerably in time. During running-in the surface properties of the components are adjusted. If the initial surface roughness of the rubbing surfaces is correctly chosen, the running-in changes into the steady-state phase. At this stage, the rubbing surfaces are in general smoother and their wear rate is low and constant. On the other hand, an inappropriate choice of roughness may lead to a rapid deterioration of the rubbing surfaces. The micro-geometry of the surface is an important factor in determining the life of mechanical components. During the running-in phase, the highest asperities are “flattened”, thereby increasing the number of asperities in contact and, as a result, increasing the load-carrying capacity of the surface. Fundamental studies that attempt to consider the details of running-in phenomena are relatively rare. This research is conducted with the aim of exploring the running-in phase for the rolling, sliding and rolling-sliding contact. Finite element simulations are conducted to calculate the stress distributions for the three types of contact motions during the running-in phase. The evolution of the contact pressure for a certain rolling or sliding distance is studied to unravel the running-in phase. During running-in of rolling contacts, the change in the surface topography results in the transformation from a rough surface to a smoother surface: the flattening of the high asperities induces a reduction in surface roughness. This flattening of asperities is due to plastic deformation and causes a higher equivalent residual stress at the surface. The transition of the running-in phase to the steady-state phase of a rolling contact is governed by the transition of plastic to elastic deformation on roughness level. In sliding contacts, the proposed finite element (FE) model combined with the Archard wear equation successfully predicts the contact pressure evolution and change in the topography on a macroscopic point of view. The change in the topography in a sliding contact is mainly caused by wear. A new FE model, with respect to the artificial and real surface roughness, is discussed. It is found that the proposed model is a useful tool to study the running-in of a surface on roughness level. The changes on macroscopic and on microscopic level of the surface are also discussed in the running-in of rolling-sliding contacts considering two aspects: wear and plastic deformation. The geometrical change of the contacting surface due to wear is predicted using the present FEM model, combined with the Archard wear equation, and has been compared with results from the literature. Calculations are performed to predict the wear of an artificial rough hemisphere in rolling-sliding contact with a smooth cylinder. The model also predicts the change of real rough surfaces which were in good agreement with the experimental results. The change of a rough surface, represented by an arithmetic average surface roughness, Ra, is predicted for lubricated rolling-sliding contacts using the load-sharing concept. The results obtained are in good agreement with experimental results. A FEM based model has been developed to study the running-in of rolling, sliding and rolling-sliding contacts on macroscopic level as well as on roughness level. However, the transition between the running-in phase and the steady-state phase for sliding and rolling-sliding contacts cannot be determined by considering only one single parameter; likewise for the rolling contact situation. Wear is an ongoing process.