Superficial Roughness Research Articles

Influência dos agentes clareadores com alta concentração de peróxidos sobre a rugosidade superficial de diferentes tipos de compósitos

This study aimed to evaluate the surface roughness of different types of composites after the application of two bleaching agents with high concentrations of peroxides. This study is an in vitro research that evaluated the microparticulate composite resin (Durafill, Heraeus-Kulzer), the microhybrid (Z250, 3M-ESPE), and nanohybrid composites (IPS Em press Direct, Ivoclar Vivadent), that were submitted to the action of 40% hydrogen peroxide (Opalescence Boost PF, Ultradent) and 37% carbamide peroxide (Power Bleaching Office 37%, BM4), simulating in-office dental bleaching. For this, 90 samples were made, 30 for each composite, divided into 9 groups (n = 10): G1, G4, and G7 did not receive any bleaching treatment (control groups); G2, G5, and G8 treated with 40% hydrogen peroxide; and G3, G6, and G9 treated with 37% carbamide peroxide. Each sample was submitted to avaliation of the superficial roughness with a rugosimeter. The data were submitted to statistical analysis using ANOVA and Tukey Test at a level of significance of 1%. There were statistically significant differences (p<0.01) between the control groups and the experimental groups submitted to the use of both bleaching agents, for all composites. The microparticulate composite was the most affected material by the use of these peroxides. Thus, bleaching agents in high concentration were able to negatively affect, increasing the surface roughness value of the three types of composites tested, and care should be taken with their application on restorations made with these restorative materials.

Impact of the Drainage Slope Experimental Study on the Manning Roughness Coefficient

It was Determined the current persistence components were significant in hydraulic designs of highland zone with sharp slopes. It was defined to examine the consequence of gradient, rapidity, depth and dimension of coarseness on the manning coarseness factor in this superficial river area. This is an investigational education about manning coarseness defined for highland zones protected by elements in three diverse dimensions and three slopes for dissimilar hydraulic situations in a flume of 8.3 m long, 0.8 m width and 0.5 m height under bed gradient of 0.0005. The current variations in contradiction of the Manning coarseness quantity were exposed, which comprises above hydraulic components considered. The herbal management, water balance are significant component drainage slope experimental. It was determined soil superficial roughness and hydraulic roughness factor are significant hydraulic resistance feature components. Exactly approximating the hydraulic roughness factor is significant to considerate instruments of drainage slope.

Chemical Composition, Knoop Hardness, Surface Roughness, and Adhesion Aspects of Additively Manufactured Dental Interim Materials.

To measure the chemical composition, Knoop hardness, surface roughness, and composite bond strength of additive manufactured (AM) and conventional interim materials. Disks were prepared using conventionally (CNV group) and additively manufactured (AM group) materials: CNV-1 (Protemp 4; 3M ESPE), CNV-2 (Anaxdent new outline dentin; Anaxdent), AM-1 (FreePrint temp; Detax), AM-2 (E-Dent 400 C&B MFH; Envisiontec), AM-3 (NextDent C&B MFH; 3D Systems), and AM-4 (Med620 VEROGlaze; Stratasys). Each group was subdivided into 3 subgroups (n = 20) for analyzing Knoop hardness (KHN), chemical composition, superficial roughness (Ra), and composite shear bond strength. The first subgroup was exposed to a microhardness test. Subsequently, EDAX analysis was selected to analyze the chemical composition. The second subgroup was selected to measure the superficial roughness (Ra) using a contact profilometer. The third subgroup was used to measured composite shear bond strength using a universal testing apparatus. A digital microscope was used to analyze the fracture mode. The Shapiro-Wilk test showed normally distributed data. One-way ANOVA and post hoc Sidak tests were selected (α = 0.05). Major variances in chemical composition were observed among the specimens. Significant differences in Knoop hardness (p < 0.001) and surface roughness (p < 0.001) were detected. The AM-4 (13.45± 2.93KHN), the CNV-2 (13.35± 5.84 KHN), the AM-2 (13.03± 3.29 KHN), and the AM-1 (12.55± 2.93KHN) groups obtained the highest Knoop hardness values, followed by the AM-3 and the CNV-1 groups (p < 0.05). The AM-1 group (1.88± 1.11 Ra) obtained the highest surface roughness values among the groups, followed by the AM-3 group (0.90± 0.14 Ra) (p < 0.05). However, no significant differences in shear bond strength values were found between the groups ranging from 23.18± 8.88MPa to 33.29± 9.17MPa (p = 0.061). All the groups showed a cohesive mode of failure. The AM interim materials tested had significant chemical composition variations compared to conventional materials. For the mechanical properties evaluated, the AM materials obtained appropriate mechanical properties for use as an interim dental restoration. However, further studies are required to evaluate more extensively its mechanical properties and verify their applicability in the oral cavity, clinical behavior, and biocompatibility.

In vitro efficacy of commercial and experimental proteolytic enzyme-based whitening dentifrices on enamel whitening and superficial roughness.

To evaluate the whiteness index (WID ) and surface roughness (Ra) of bovine enamel after simulated tooth brushing with different commercial and experimental whitening dentifrices. Cylindrical enamel bovine specimens were acid etched, stained, and divided in nine groups (n= 8): Colgate® Optic White®, Crest® Baking Soda and Peroxide, Arm and Hammer® Advanced White™ Extreme Whitening, Rembrandt® Deeply White® + Peroxide, Close up® White Attraction Natural Glow, Hinode Prowhite, and experimental dentifrice containing papain (PP), bromelain (PB), or papain and bromelain (PPB). Ra and WID were obtained initially and after 600, 1200, and 3,600 cycles of simulated tooth brushing. Data were analyzed using two-way analysis of variance test (α= 0.05). Ra was significantly influenced by both dentifrice (p= 0.043) and period of tooth-brushing simulation (p< 0.001). Except for PP and PPB, all groups showed a statistically significant increase in Ra after simulated tooth brushing. After staining and brushing, none of the materials tested increased the initial WID . The effect of commercial whitening dentifrices may be related to their high abrasiveness. Experimental formulations tested provided a similar effect without undesired wear of enamel. Whitening dentifrices only act through an abrasive effect rather than bleaching the tooth structures. When used, special care must be taken for avoid undesired wear of enamel. Experimental dentifrices provided similar removal of extrinsic stains without undesired abrasiveness; however, this effect may be due to the use of less aggressive abrasives in their formulations.

Study of Surface Roughness Effect on a Bluff Body—The Formation of Asymmetric Separation Bubbles

Turbulent flows around bluff bodies are present in a large number of aeronautical, civil, mechanical, naval and oceanic engineering problems and still need comprehension. This paper provides a detailed investigation of turbulent boundary layer flows past a bluff body. The flows are disturbed by superficial roughness effect, one of the most influencing parameters present in engineering applications. A roughness model, recently developed by the authors, is here employed in order to capture the main features of these complex flows. Starting from subcritical Reynolds number simulations (Re = 1.0 × 105), typical phenomena found on critical and supercritical flow regimes are successfully captured, like non-zero lift force and its direction change, drag crisis followed by a gradual increase on this force, and separation and stagnation points displacement. The main contribution of this paper is to present a wide discussion related with the temporal history of aerodynamic loads of a single rough circular cylinder capturing the occurrence of asymmetric separation bubbles generation. The formation of asymmetric separation bubbles is an intrinsic phenomenon of the physical problem, which is successfully reported by our work. Unfortunately, there is a lack of numerical results available in the literature discussing the problem, which has also motivated the present paper. Previous study of our research group has only discussed the drag crisis, without to investigate its gradual increase and the change on lift force direction. Our results again confirm that the Lagrangian vortex method in association with Large-Eddy Simulation (LES) theory enables the development of two-dimensional roughness models.

Structural Analysis of Kevlar Fabric Treated with Oxygen Plasma

The purpose of this work was to study the effects of low-pressure oxygen plasma treatment on the surface characteristics of kevlar fabric. For comparison purposes, samples treated with oxygenated plasma were prepared and characterised under different experimental conditions, i.e. a treatment time variation of 10, 30 and 60 minutes under a constant pressure of 4 mBar, using a pulsed current source. We analysed the effects of chemical and physical changes to the surface of the material aiming at improved hydrophilicity attributed to the formation of roughness on the surface of fibres, thus obtaining optimal parameters for future works. Changes in the chemical composition of the surface as well as in the superficial roughness of fibres before and after treatment were determined by FTIR, TGA, XRD and wettability testing. SEM was used as a complementary technique to monitor the changes triggered by the procedures using oxygen plasma.

Surface roughness effects on the fatigue behaviour of gyroid cellular structures obtained by additive manufacturing

Surface roughness effects on the fatigue behaviour of gyroid cellular Ti-6Al-4 V structures obtained by additive manufacturing were investigated. The normalized fatigue strength values for 10^6 cycles, obtained from the S-N curves, were in the range of 0.21–0.23. Finite element analyses showed that stress peak points were located on the stress concentrators due to surface defects, and scanning electron microscopy images showed that crack initiation was located at the surface. It is concluded that the expected good fatigue behaviour due to the curvature in the junctions of the struts, is diminished because of the superficial roughness contributing to the notch effect.

Comparing geometric tolerance capabilities of additive manufacturing systems for polymers

In all manufacturing processes, there are several factors for which the final product exhibits dimensional and shape deviations from its ideal nominal geometry. In additive manufacturing (AM) and 3D printing, a part is built layerwise in a single manufacturing step and is often net-shaped. In most cases, no finishing operation is applied to change the dimensions of the product, apart from a reduction of the superficial roughness through sandblasting or polishing. Therefore, knowing the dimensional tolerance of AM processes in advance is of fundamental importance, but little information is currently available in the literature. A benchmarking analysis of three different AM systems for polymers is presented in this paper. The compared machines are based on different AM techniques which are fused filament fabrication (FFF), selective laser sintering (SLS) and Arburg plastic freeforming (APF). The dimensional accuracy of the machines has been defined using the ISO IT grades of a reference artifact. In the analysis of the benchmarking results, a specific focus is made on the importance of the thermal household in SLS and a parameter named SLS modulus is proposed to identify critical heat concentrations in the powder bed that may influence the dimensional accuracy of the manufactured part.

Analysis of Density, Roughness, and Accuracy of the Atomic Diffusion Additive Manufacturing (ADAM) Process for Metal Parts.

Atomic Diffusion Additive Manufacturing (ADAM) is a recent layer-wise process patented by Markforged for metals based on material extrusion. ADAM can be classified as an indirect additive manufacturing process in which a filament of metal powder encased in a plastic binder is used. After the fabrication of a green part, the plastic binder is removed by the post-treatments of washing and sintering (frittage). The aim of this work is to provide a preliminary characterisation of the ADAM process using Markforged Metal X, the unique system currently available on the market. Particularly, the density of printed 17-4 PH material is investigated, varying the layer thickness and the sample size. The dimensional accuracy of the ADAM process is evaluated using the ISO IT grades of a reference artefact. Due to the deposition strategy, the final density of the material results in being strongly dependent on the layer thickness and the size of the sample. The density of the material is low if compared to the material processed by powder bed AM processes. The superficial roughness is strongly dependent upon the layer thickness, but higher than that of other metal additive manufacturing processes because of the use of raw material in the filament form. The accuracy of the process achieves the IT13 grade that is comparable to that of traditional processes for the production of semi-finished metal parts.

Subject-specific finite element analysis of a lumbar cage produced by electron beam melting.

The aim of this study was the analysis of the mechanical behaviour of a partially porous lumbar custom-made cage by means of a subject-specific finite element analysis (FEA). The cage, made of Ti6Al4V ELI alloy, was produced via electron beam melting (EBM) process and surgically implanted in a female subject, 50 years old. The novelty of this study was the customized design of the cage and of its internal structure, which is impossible to obtain with the traditional production techniques. The 3D model of the spine was obtained from the computed tomography (CT) of the patient. Moreover, high-resolution industrial CT was also used to reconstruct a 3D model of the cage, with its real (as-produced) features, such as superficial roughness, morphology of the bulk and of the porous structure. The workflow was divided in several steps: the main finite element analyses were non-linear and quasi-static regarding: the rhombic dodecahedron (RD) unit cell of the porous structure; the device; the whole L4-L5 motion segment with the implanted cage. Stress distribution was calculated under compression load for all models. For the RD unit cell, the maximum stress appeared at the connected cross nodes, where notch effect was present. For the cage subjected to a load of 1 kN, the porous structure did not present any functional failure. For the whole biomechanical system subjected to a physiological load of 360 N, the calculated stress in the bone was smaller than its yield strength value. On the axial view, a zone with higher compressive stresses was present on the L5 vertebral body. This was due to the contact stress between the cage and the vertebra. From the comparison between FE results and the CT images of the spine, bone remodelling was supposed, with the formation of new bone. Graphical abstract Workflow showing the phases of the research.

Superficial roughness and flexural strength of glass‐infiltrated zirconia based on the FGM concept

Superficial roughness and flexural strength of glass‐infiltrated zirconia based on the FGM concept

Effect of Er:YAG laser irradiation on deciduous enamel roughness and bacterial adhesion: An in vitro study.

Laser irradiation has been proposed as a preventive method against dental caries since it is capable to inhibit enamel demineralization by reducing carbonate and modifying organic matter, yet it can produce significant morphological changes. The purpose of this study was to evaluate the influence of Er:YAG laser irradiation on superficial roughness of deciduous dental enamel and bacterial adhesion. Fifty-four samples of deciduous enamel were divided into three groups (n = 18 each). G1_control (nonirradiated); G2_100 (7.5 J/cm2 ) and G3_100 (12.7 J/cm2 ) were irradiated with Er:YAG laser at 7.5 and 12.7 J/cm2 , respectively, under water irrigation. Surface roughness was measured before and after irradiation using a profilometer. Afterwards, six samples per group were used to measure bacterial growth by XTT cell viability assay. Adhered bacteria were observed using confocal laser scanning microscopy (CLSM) and a scanning electron microscopy (SEM). Paired t-, one-way analysis of variance (ANOVA), Kruskal-Wallis and pairwise Mann-Whitney U tests were performed to analyze statistical differences (p < .05). Before treatment, samples showed homogenous surface roughness, and after Er:YAG laser irradiation, the surfaces showed a significant increase in roughness values (p < .05). G3_100 (12.7 J/cm2 ) showed the highest amount of Streptococcus mutans adhered (p < .05). The increase in the roughness of the tooth enamel surfaces was proportional to the energy density used; the increase in surface roughness caused by laser irradiation did not augment the adhesion of Streptococcus sanguinis; only the use of the energy density of 12.7 J/cm2 favored significantly the adhesion of S. mutans.

Anisotropy of the triboelectric effects in polymeric slabs

Abstract The paper contributes to the understanding of triboelectric charging mechanisms. It brings evidence of the fact that in polymer slabs this effect may present significant direction dependence (anisotropy) related to the initial superficial roughness. The study was carried out on Polyvinyl Chloride (PVC) slabs in frictional sliding conformal contact with Acrylonitrile Butadiene Styrene (ABS) slices. It showed that the anisotropy of tribocharging is correlated to that of initial surface patterns (texturing) specific to polymer manufacturing process. The effect is preserved for small numbers of repeated movements even when moderate wearing occurs. Conclusions are derived for improving triboelectric energy harvesters, sensors, and other applications.

Comprehensive (S)TEM characterization of polycrystalline GaN/AlN layers grown on LTCC substrates

Three GaN layers grown on polished AlN buffer films previously sputtered on Low-Temperature Co-fired Ceramic substrates have been studied by X-Ray Diffraction, Atomic Force Microscopy and Electron Microscopy related techniques. This allowed to assess the quality of the whole fabricated III-N/LTCC heterostructures considering factors such as superficial roughness, crystallinity, structural features (e.g.: lattice defects) and chemical homogeneity. All the AlN and GaN films were chemically uniform. However, for different regions and growth conditions, properties like the GaN average grain size or roughness varied significantly, and polycrystalline or partially single-crystalline GaN areas, with an elevated density of lattice defects, were identified. The particular surface structure of the LTCC substrate was regarded as key for the formation of these features, as it notably affected the AlN structure. Additional characteristics, like a different degree of c-axis orientation of the GaN grains or formation of small cubic GaN domains depending on the fabrication conditions, were also detected.

Effect of Soybean Biodiesel Addition on Tribological Performance of Ultra-Low Sulfur Diesel

The purpose of this work was to study the influence of soybean biodiesel addition in ultra-low sulfur diesel (ULSD) on its tribological behavior under low-amplitude reciprocating conditions, simulating the operation of a fuel injector system. The methodology was divided into three parts: the first was the fuel preparation and its physicochemical characterization, where were studied four fuels (diesel, soybean biodiesel, and mixtures of them).The following step was the evaluation of the fuel tribological properties, using the high-frequency reciprocating rig (HFRR) test. These tests were carried out by steel ball-on-disk lubricated contact, on which the friction coefficient of friction (COF), the film percentage, and the wear scar diameter (WSD) were measured, according to ASTM D6079-11. In the end, the analysis of the damages presented on the worn disk surfaces was characterized by scanning electronic microscopy (SEM) and atomic force microscopy (AFM) techniques. Results showed that the addition of biodiesel to ULSD is an excellent option to restore the lubricating ability of this fuel. The biodiesel incorporation reduces the friction coefficient and improves the film formation. Besides, the evaluation of worn disk surfaces using SEM and AFM techniques showed that biodiesel avoids damages to surface through protective film formation and reduces the superficial roughness.

Mechanical properties and superficial characterization of a milled CAD-CAM glass fiber post.

Computer-aided design and computer-aided manufacturing (CAD-CAM) technology may be used to produce custom intraradicular posts, but studies are lacking. The purpose of this in vitro study was to evaluate the flexural properties (strength and modulus), failure mode, superficial morphology, and roughness of two CAD-CAM glass fiber posts (milled at different angulations) compared with a commercially available prefabricated glass fiber post. Three groups were tested (n = 10): PF (control group)- prefabricated glass fiber post; C-Cd-diagonally milled post; and C-Cv-vertically milled post. A 3-dimensional virtual image was obtained from a prefabricated post, which guided the posterior milling of posts from a glass fiber disk (Trilor Blanks; Bioloren). Surface roughness and morphology were evaluated using confocal laser microscopy. Flexural strength and modulus were evaluated with the 3-point bend test. Data were submitted to one-way analysis of variance followed by the Student-Newman-Keuls post hoc test (α = 0.05). The fractured surfaces were evaluated with scanning electron microscopy. The superficial roughness was highest for PF and similar for the experimental groups. Morphological analysis shows different sizes and directions of the glass fibers along the post. The flexural strength was highest for PF (900.1 ± 30.4 > C-Cd - 357.2 ± 30.7 > C-Cv 101.8 ± 4.3 MPa) as was the flexural modulus (PF 19.3 ± 2.0 GPa > C-Cv 10.1 ± 1.9 GPa > C-Cd 7.8 ± 1.3 GPa). A CAD-CAM milled post seems a promising development, but processing requires optimizing, as the prefabricated post still shows better mechanical properties and superficial characteristics.

Effects of sodium carbonate on the performance of epoxy and polyester coir-reinforced composites

Surface modification induced by sodium carbonate on coir fibres was studied in view of its application as a reinforcing agent in polyester and epoxy polymer fibre-reinforced composites. Coir fibres were treated with a 10 wt% sodium carbonate solution for different periods of time (24, 96 and 168 h) at room temperature. The surface treatment was evaluated by scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. Tensile, flexural and impact properties of treated and untreated coir fibre-reinforced composites were compared. Coir-reinforced epoxy and polyester composites were manufactured by the uniform dispersion of randomly oriented coir fibres within the polymeric matrix. Tensile and flexural modulus of coir-reinforced polyester composites increased nearly 28% and 25%, respectively after 96 h of coir treatment. An analogous increase of 31% and 17% was obtained for coir-reinforced epoxy composites. In addition, coir-polyester composites achieved superior tensile (∼17%) and flexural (∼5%) modulus and impact strength (∼193%) compared with coir-epoxy-derived composites. In contrast, coir-epoxy composites led to superior tensile and flexural strength. The experimental results revealed that sodium carbonate solution effectively removes hemicellulosic compounds, promotes swelling and increases superficial roughness of the fibres, improving the mechanical properties (modulus and strength) of the coir-reinforced composites studied.

INFLUÊNCIA DA CONCENTRAÇÃO E DO TEMPO DE CONDICIONAMENTO COM ÁCIDO HIDROFLUORÍDRICO NA RUGOSIDADE E MORFOLOGIA SUPERFICIAL DE UMA ZIRCÔNIA GLAZEADA

Objetivo: Avaliar o efeito da concentração e do tempo de condicionamento com ácido fluorídrico na rugosidade e morfologia superficial de uma zircônia glazeada. Materiais e Métodos: Blocos de cerâmica à base de zircônia (5×5×3 mm) (Vita YZ-2000-Cubes, Vita-Zahnfabrik, Alemanha) foram confeccionados e divididos em 6 grupos, de acordo com os fatores “concentração do ácido fluorídrico (HF)” (5% e 10%) e “tempo de condicionamento” (20 s, 60 s e 90 s) (n=2): HF10/20 = HF 10% + 20 s; HF10/60 = HF 10% + 60 s; HF10/90 = HF 10% + 90 s; HF5/20 = HF 5% + 20 s; HF5/60 = HF 5% + 60 s; HF5/90 = HF 5% + 90 s. O glaze (Vita Akzent, Vita-Zahnfabrik, Alemanha) foi aplicado com o auxílio de um pincel e sinterizado de acordo com as recomendações do fabricante. Após os diferentes protocolos de condicionamento, foram aferidas cinco medições de rugosidade (Ra) para cada espécime em Perfilômetro Digital (Wyko®, Modelo NT-1100, Veeco, EUA). Os dados (µm) obtidos foram analisados estatisticamente com análise de variância (ANOVA 2-fatores) e Teste de Tukey (95%). Resultados: O fator “concentração do ácido fluorídrico” (p=0,149) não foi significante estatísticamente. No entanto, o fator “tempo de condicionamento” (p=0,009) foi significante. A interação entre os fatores também apresentou significância estatística (p=0,00). As médias de rugosidade (±desvio-padrão) obtidas foram (µm): GHF10/20=1,94(±0,72)A, GHF5/90=1,92(±0,19)A, GHF5/20=1,38(±0.48)AB, GHF5/60=1,18(±0,63)B, GHF10/60=1,17(±0,30)B, GHF10/90=0,82(±0,27)B (Tukey). Conclusão: Conclui-se que o ácido fluorídrico (10%) em maior concentração, associado a um menor tempo de condicionamento (20 s), promoveu maior rugosidade superficial da zircônia glazeada.&#x0D; DESCRITORES: Cerâmica. Zircônio. Vitrificação.

Experimental Study of Water Film Dynamics Under Wind Shear and Gravity

Aircraft icing poses a serious threat to flight safety. Unfrozen impinging water on the surface of the aircraft will run back under the effect of high-speed airflow, altering liquid distribution and heat transfer characteristics. In this paper, a series of experiments are conducted over a wide range of wind speeds (), film Reynolds numbers (), and inclined angles (, , ) to investigate the dynamics of thin water film on an aluminum substrate. The superficial morphology of the water film is investigated by a high-speed camera, and the instantaneous film thicknesses are measured by a laser focus displacement meter based on a confocal chromatic technique. The interface shape is found to consist of an underlying thin film and multiple scaled fluctuations; therefore, the results are divided into two parts for analysis: the mean film thickness and the root-mean-square thickness. A relationship between the mean film thickness and the wind speed, the film Reynolds number, the inclined angle is proposed. After nondimensionalized processing based on the triangular relationship, the averaged film thickness data agree with the previous model of an error within 25%. New correlations to calculate the interfacial shear stress and superficial roughness are suggested within the experimental range.

Experimental investigation of shear-driven water film flows on horizontal metal plate

In this article, an experimental investigation has been conducted to characterize the instantaneous thickness of the surface water film driven by high-speed airflow pertinent to aerodynamic icing and anti-icing modeling. Non-intrusive results of the film flowing on a metal plate were obtained using the high-speed camera and confocal chromatic technique. The wind speed (Ua) ranges from 17.8 m/s to 52.2 m/s, and the film Reynolds number (Ref) ranges from 26 to 128. The effect of the high-speed airflow on the structure of the wave film was observed and analyzed qualitatively. A new correlation of the interfacial shear factor was proposed for the prediction of the average film thickness. The predictions were compared with the previous annular flow models by applying the dimensionless analysis method and a good agreement is achieved. The superficial roughness, characterized by root-mean-square of the thickness, was well-correlated using a piecewise linear function of the average film thickness. Furthermore, a comprehensive description of the superficial waves including spectrum analysis and division of film thickness data between underlying film and large waves was presented. Transformations of the wave frequency and amplitude with the wind speed and the film Reynolds number were also addressed.