Mean Roughness Values Research Articles

Influence of Cutting Surface Condition and Composition on High-Temperature Oxidation Behavior of Ti2 Al C MAX Phase Ceramics

Ti2AlC, one of the MAX phase ceramics, has metal-like properties (electrical conductivity, high fracture toughness and good machinability) and ceramic-like properties (low density, high-temperature oxidation resistance and high bending strength). Ti2AlC ceramics can be cut with cemented carbide tools and the mechanical strength does not decrease significantly after cutting. Ti2AlC ceramics have potential as high-strength machinable ceramics for use in high temperature components. However, the oxidation resistance of Ti2AlC ceramics decreases after cutting because the cutting damages inhibit the formation of protective Al2O3 scale. There are few discussions on the effect of cutting surface conditions on oxidation resistance of Ti2AlC ceramics. The continued growth of the protective Al2O3 scale requires a sufficient Al supply during high-temperature oxidation. The oxidation resistance of Ti2AlC ceramics is reduced when a non-protective TiO2 scale forms on the surface. As one of the common methods to prevent the growth of the TiO2 scale is Nb addition in Ti-based alloys and compounds. The oxidation resistance of as-machined Ti2AlC ceramics may be improved by increasing the amount of Al and Nb additions. This study reports the influences of cutting surface conditions and composition on oxidation behavior of Ti2AlC ceramics. Commercial Ti, Al, C and Nb powders were mixed in Ti:Al:C:Nb molar ratios of 2:1.2:0.9:0 and 1.9:1.2:0.9:0.1 with the corresponding samples receiving the designations Al1 and Al1.2Nb. The powder mixture was annealed for 12 h in a vacuum at 1300°C. The synthesized powder was consolidated over 15 min using a pulsed electric current sintering technique at 1300°C, in a vacuum, and under a uniaxial pressure of 30 MPa. The phases present in the sintered samples were also identified by XRD. Milling tests were performed on a 4 x 4 mm sample surface using a 2 mm diameter end-mill mounted on a plane milling machine. Dry cutting was performed with a spindle speed, feed rate, and cut depth of 4000 rpm, 46 mm/min, and 100 μm. Threading tests were cut into an JIS-M6 bolt shape with a thickness of 3 mm with a lathe and diamond saw. The surface roughness of each sample was measured using a surface texture measuring instrument. The samples were heated in an electric furnace at 1200°C for 4 h in laboratory air. The surface and cross-sections of the oxidized samples were observed via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX).The main peaks of all sintered samples in these XRD patterns were identified as originating from Ti2AlC and minor peaks originating from TiAl3 (Al-rich phase). The average arithmetic mean roughness (R a) values of the end-milled and threaded surfaces were 0.8 and 4.5 μm. The SEM and EDX results show that a continuous Al2O3 scale formed on the end-milled surface of Al1.2 and Al1.2Nb after the oxidation test. The results of SEM and EDX investigations indicate that a non-protective TiO2 scale had formed on the threaded surface of Al1 and a continuous Al2O3 scale with a thickness of less than 4 μm was formed on the threaded surface of Al1.2Nb after the oxidation test. The Al-rich phase provided the Al necessary for the formation of a continuous Al2O3 scale on the end-milled surface. The oxidation resistance of Ti2AlC ceramics was greatly reduced in the case of screw-like shapes with high R a values and many corners on the cutting surface. The addition of Nb improves the oxidation resistance of Ti2AlC ceramics under such cutting surface conditions. The cause of non-protective oxidation was the destruction of the Al2O3 scale because of the growth of TiO2 scale. The TiO2 scale tends to form at corners where continuous Al2O3 scale formation is difficult. One of the factors that improves the oxidation resistance of Ti2AlC ceramics with screw shapes is the suppression of TiO2 growth by Nb addition. The higher Al concentration and the addition of Nb remarkably increase the oxidation resistance of the Ti2AlC ceramics after cutting.

Fractal analyses of AlxGa1−xN thin film surfaces on AlN at different annealing temperatures

The determination of heteromorphological structures formed on the surface during annealing of AlxGa1−xN thin film grown on sapphire substrate using the metal organic chemical vapor deposition technique at different temperatures was investigated by fractal analysis method. The images of the surfaces of the thin films were taken by atomic force microscopy (AFM) at temperatures of 900, 1000, 1050 and 1200 °C respectively. AFM images were digitised in bitmap format according to the annealing temperatures. It was determined that the fractal dimensions obtained a linear correlation with the annealing temperatures. The results confirm the hypothesis that surface relaxation by the thermal action can produce fractal-like structures at particle or cluster boundaries. It is found that the observed cluster formation of superficial particles decreases as increasing temperature. The increase in temperature reduces the rate of superficial particle coating. To determine the surface roughness of the AlxGa1−xN thin film according to the annealing temperature, the AFM images were digitized in tagged image file format and the statistical root mean square, mean value, mean roughness, skewness and kurtosis values of the films were calculated. The roughness is a result of the thin film surface heteromorphology formed due to the specific annealing process. It is proved that the fractal dimensions of the AlxGa1−xN thin film increase as the annealing temperature rises. The particles coalesce on the surface and cluster in different types and sizes at each different annealing temperature, forming islets of different sizes. The skewness and kurtosis values show a different and irregular change.

Evaluation of the Loss of Surface Roughness Following the Use of Four Different Instruments for Mechanical Debridement of Dental Implants: An In-vitro Pilot Study

To compare the dental implant surface properties such as mean surface roughness, roughness depth, and the surface loss produced by different prophylactic instrument types. Twenty-four surfaces of twelve dental implants were treated using titanium curettes, titanium-coated curettes, an air abrasion unit, and titanium brushes. The dental implants were inserted partially into a Styrofoam base, exposing one-third to simulate cases of peri-implantitis. The exposed surface was coated with artificial dental calculus (ADC) and divided into four groups for treatment. The arithmetic mean surface roughness (Ra) and the mean roughness depth (Rz) were assessed using the confocal microscope, and the surface loss (SL) area was calculated from the scanning electron microscopic images using an image analysis software. The Ra value varied between 1.08 to 0.29 µm, the Rz value between 10.3 to 70.5 µm, and the mean surface loss area between 154 to 9410 µm2. The One-way ANOVA analysis showed a statistically significant difference between the four groups (P < 0.05). The air abrasion unit showed the highest mean roughness value of 1.08 ± 0.14 µm, mean roughness depth of 70.5 ± 2.21 µm, and a minor surface area loss of 154 ± 132 µm2. In comparison, the titanium brushes showed the least Ra and Rz of 0.29 ± 0.05 µm and 10.3 ± 2.32 µm, respectively, whereas the titanium-coated curettes showed the highest loss of surface area 9410 ± 91.6 µm2. The air abrasion unit was shown to have the least detrimental effect on the implant surface when removing the artificial dental calculus compared to the other three methods.

Konvansiyonel, Eksiltmeli ve Eklemeli İmalat Tekniklerinde Kullanılan Geçici Kron Materyallerinin Yüzey Pürüzlülüğüne Diş Fırçalama ve Yüzey İşlemlerinin Etkisi: İn Vitro Çalışma

Background: This study aimed to compare the effect of the surface treatment and toothbrushing abrasion on the surface roughness of interim crown material specimens manufactured using conventional, subtractive, and additive processing techniques.&#x0D; Material and methods: 80 disk-shaped specimens were prepared from 4 different interim crown materials; one auto-polymerized polymethyl methacrylate resin (PMMA);(IM) and one bis-acryl composite resin;(AC) for conventional technique, one computer-aided design/computer-aided manufacturing (CAD-CAM) PMMA block;(TC) for subtractive process, one 3-dimensionally (3D) printed resin;(CB) for additive process. Specimens of each interim crown material were divided into two subgroups according to applied surface treatments; conventional polishing or surface sealant agent coupling (n=10). The surface roughness values of specimens before (Ra0) and after 10,000 cycles of toothbrushing (Ra1) were measured with a profilometer. Data were statistically analyzed.&#x0D; Results: The polished groups of all interim crown materials showed significantly higher Ra0 values compared to the sealant groups before toothbrushing (p˂0.05). While the polished IM groups exhibited the highest Ra0 value (0.44±0.08), the sealed TC groups exhibited the lowest Ra0 value (0.23±0.06). The Ra values of all material groups increased after simulated 1-year toothbrushing. While the polished IM group exhibited the highest Ra1 value (0.45±0.14), the sealed CB group had the lowest Ra1 value (0.31±0.09).&#x0D; Conclusion: It was observed that toothbrushing caused an increase in the surface roughness of all interim materials. The application of a surface sealant agent to these materials is more effective than polishing to reduce surface roughness. Sealed 3D printed resin for additive process exhibited the lowest mean roughness value after toothbrushing.&#x0D; Keywords: Additive Manufactured, Interim Crown Material, Roughness, Subtractive Manufactured, Toothbrushing Abrasion

Study of structural, optical and electrical properties of Nickel doped ZnO (Ni–ZnO) nanorods grown by chemical bath deposition

To investigate the effect of Nickel on ZnO thin films, doped ZnO (Ni–ZnO) thin films were synthesized using chemical bath deposition on seed layers which were first grown using the conventional spray pyrolysis method. Structural, optical and electrical properties were studied at different doping levels of Ni (0, 2, 4, 6, 8 %). All samples exhibited a highly defined (002) peak indicating a strong hexagonal crystal structure orientation. The samples showed a red shift at E2L and E2H Raman modes indicative of structural alterations. The undoped, 2 % and 4 % Ni doping levels showed lower mean roughness values compared to the 6 % and 8 % Ni doping. The Introduction of Ni into the ZnO structure appears to reduce the grain size from 167 nm to the lowest 79 nm at 2 % Ni concentration. Optical and electrical properties showed that the introduction of Ni as a dopant led to improved transmittance of up 70 % within the visible range and reduced resistivity from 3.590*10−3 (Ωcm) at undoped ZnO to 0.616*10−3 (Ωcm) 2 % Ni doped ZnO concentration.

Surface Roughness Evaluation of Resin Composites after Finishing and Polishing Using 3D-Profilometry

The purpose of this study was to evaluate the effect of two finishing and polishing methods on the surface roughness of different resin composites. Twenty-two disk-shaped specimens of five resin composites Zirconfill® (ZF), Filtek™ Supreme XTE (FS), Brilliant EverGlow™ (BG), Ceram.X® Duo (CD), and Harmonize™ (HA) were prepared for each one using a silicon mold. Both surfaces of each specimen were first grinded with 600-grit silicon carbide paper in a moistened environment. The polishing methods used included the two-step Enhance® and PoGo® polishing system (E/P) or the four-step SwissFlex® discs (SFD). Surface roughness was evaluated using a noncontact 3D-optical profilometer. Surface morphology was examined by scanning electron microscopy. Data were analyzed using two-way analysis of variance and pairwise comparisons with Tukey’s test ( α = 0.050 ). Surface roughness was affected by both the type of resin composite ( p &lt; 0.001 ) and the finishing and polishing system ( p &lt; 0.001 ), with a significant interaction between these two factors ( p = 0.025 ). The E/P system produced smoother surfaces than the SFD system ( p &lt; 0.001 ). For the E/P system, the highest mean roughness value was obtained with ZF and was statistically different from all other composites, whereas inhomogeneous results among resin composites could be found for the SFD system. Surface roughness was material-dependent, and the polishability of the resin composites was best accomplished using the E/P system. Within each F/P system studied, BG showed the lowest average surface roughness and ZF registered the highest.

SURFACE ROUGHNESS OF THREE DIFFERENT GLASS IONOMERS WITH OR WITHOUT FINISHING/POLISHING: AN IN VITRO STUDY

Purpose: This study aimed to compare the surface roughness among 3 types of glass ionomers (GI) before (no polishing) and after polishing with three different materials.Methods: 20 discs for each GI group were obtained (A-Ionolux; B-IonoStar Plus; C-Ketac). Those groups were subdivided according to finishing and polishing: subgroups 1 (control) - no polishing, 2 - polishing with prophylactic brush and pumice paste, 3 - Enhance tips with water, and 4 - Sof-Lex system with Easy Glaze and polymerization. For each disc face, the total distance analyzed was 2.88cm (6x48mm). Then, the roughness was compared using the Kruskal-Wallis with Bonferroni test, with significant data if p&lt;0.05.Results: The mean of roughness within Group A was lower for subgroup 4 (1.07±0.54 μm) and higher for subgroup 2 (2.33±1.17 μm). Within group B, B4 had the lowest mean of roughness (0.93±0.38 μm) and B2 (1.24 ± 0.78 μm) the highest roughness. Within group C, Group C4 had the lowest mean roughness value (0.84±0.54 μm), and C3 had the highest mean (2.48±1.05 μm). After polishing, subgroup 4 had the general lowest values for surface roughness (mean Ra 0.95), followed by subgroup 1 (Ra=1.27), subgroup 2 (Ra=1.89), and higher values for subgroup 3. All intragroup analysis for A, B, and C were statistically significant. Group A presented the highest roughness (p&lt;0.05), and no statistically significant evidence existed between groups B and C (p&gt;0.05).Conclusion: The reduction of the roughness of the materials is dependent on their composition and the polishing and finishing techniques applied. Keywords: Glass ionomers; Surface; Roughness; Polishing; Finishing

Effect of microwave polymerization on the thermomechanical and surface properties of ocular prosthetic acrylic resins.

Polymerization conditions affect the physical-mechanical properties of acrylic resins used for craniofacial prostheses. The aim of this study was to evaluate the effect of microwave polymerization on the thermomechanical properties and surface morphology of ocular prostheses fabricated with polymethyl methacrylate (PMMA). PMMA discs were polymerized with microwave energy and with conventional heat polymerization (CHP) method. Ocular prostheses were fabricated to determine whether there were changes according to the polymerization method. The surface morphology and roughness were observed under SEM and AFM. The Vickers Hardness number (VHN) and flexural strength were measured. Thermal properties were evaluated with TGA/DSC, and chemical composition with FTIR. The PMMA acrylic resin polymerized with microwave energy showed a smooth surface with some relief areas. In the internal surface of the ocular prosthesis with microwave energy the PMMA is more compact. The mean roughness values were higher and statistically significant with CHP (P <0.05), while the surface hardness and flexural strength were higher with microwave energy (P <0.05). There were no changes in the calorimetry with either method, TGA showed an exothermic peak around 120°C with CHP method. PMMA polymerized with microwave energy improved the mechanical and surface properties of the ocular prostheses.

Analysis of surface roughness of chemically impregnated Scots pine processed using frame-sawing machine

ABSTRACT The objective of this work was to evaluate the effect of the impregnation process of pine wood (Pinus sylvestris L.) on roughness parameters of the surface processed on a frame sawing. The samples were dried and impregnated using a commercial procedure by a local company. The touch method with the use of measuring stylus (pin) was employed to determine of surface roughness of the samples considering parameters, namely, arithmetical mean roughness value (Ra), total height of the roughness profile (Rt), maximum height of roughness profile (Rz) and root-mean-square roughness (Rq). All measured values of the analysed surface roughness parameters were normalised by the raw density of wood in order to eliminate the effect of differences in wood density and moisture content of the tested samples of impregnated and non-impregnated pine. Generally, no effect of feed per tooth was observed for the analysed values of f z1 = 0.11 mm and f z2 = 0.22 mm on the surface roughness parameters. Only for the parameter Rq of impregnated wood was a significant effect of feed per tooth observed. The effect of the pine wood impregnation process on all analysed surface roughness parameters was observed for both analysed feeds per tooth.

Evaluation of the Influence of Build Orientation on the Surface Roughness and Flexural Strength of 3D-Printed Denture Base Resin and Its Comparison with CAD-CAM Milled Denture Base Resin.

The purpose of this study was to determine the surface roughness and flexural strength of a three-dimensional (3D)-printed denture base resin printed with two different build plate orientations and to compare them with a computer-aided design-computer-aided manufacture (CAD-CAM) milled denture base resin. Sixty-six specimens (n = 22/group) were prepared by 3D printing and CAD-CAM technology. The group A and B specimens were 3D-printed bar-shaped denture base specimens printed at 120-degree and 135-degree build orientation, respectively, whereas group C specimens were milled using a CAD-CAM technology. The surface roughness was assessed using a noncontact profilometer with a 0.01 mm resolution and the flexural strength was determined using a three-point bend test. The maximum load in Newtons (N) at fracture, the flexural stress (MPa), and strain (mm/mm) was also measured. Data were analyzed by a statistical software package. One-way analysis of variance test was applied to determine whether significant differences existed among the study groups, followed by Bonferroni post-hoc test to determine which resin group significantly differed from the others in terms of flexural strength and surface roughness (p ≤ 0.05). The flexural stress (MPa) of group C was 200% of group A and 166% of group B. The flexural modulus was 192% of group A and 161% of group B. In contrast, group A had the lowest mean value among the three groups for all the parameters. No significant difference was seen between group A and group B. The mean roughness values of the CAD-CAM denture base resin specimens (group C) were the least (127356 nm) among all the three groups. The mean surface roughness of the 3D-printed denture base specimens (group A) was 1,34,234 nm and that of group B was (1,45,931 nm); however, it was statistically nonsignificant (p > 0.05) CONCLUSIONS: The CAD-CAM resin displayed superior surface and mechanical properties compared to the 3D-printed resin. The two different build plate angles did not have any significant effect on the surface roughness of the 3D-printed denture base resin.

Alternating Additive Manufacturing and Forming—An Innovative Manufacturing Approach

In this work, an innovative manufacturing approach that includes a fully linked and integrated manufacturing system consisting of a laser-based directed energy deposition (DED-LB/M) module and a forming press is presented. The alternating additive manufacturing (AM) process is based on a combination of a DED-LB/M process using a laser power of 600 W and a feed rate of 400 mm/min and a subsequent forming process, in which the structure is upset with a hydraulic press using a constant forming force of 500 kN in order to smooth the surface and influence the accuracy of the components. For the generation of a fundamental process understanding, a cuboid, basic shape was chosen as geometry for the investigations. The aim is to improve part properties by applying the process steps to generate part properties, which are superior to solely additive manufactured material. It is shown that the geometry of additive manufactured structures can be adapted, and the top surface can be smoothed due to the forming operation. The mean roughness value Rz decreases up to 50% after the forming operation. The hardness can be increased by work hardening. Of special interest is that the higher hardness can be kept up even though a further DED-LB/M process step and forming operation are applied to the additively manufactured and formed structure again. Finally, an analysis of the new manufacturing approach regarding its potential is given.

Application of batch manufactured flexible micro-grinding tools on copper and oxidized copper surfaces

As copper is a rather difficult material to machine due to its ductility compared to aluminium, this study presents the approach of oxidizing the surface to improve the results of the grinding process. Therefore, batch manufactured flexible micro-grinding tools are used for grinding of copper and oxidized copper surfaces to machine microstructure or local areas of functional surfaces. Besides, we show a comparison of the performance of an abrasive layer made of silicon carbide (SiC) and cubic boron nitride (cBN). The tools are made of a polyimide-based abrasive layer and silicon as substrate and are fabricated by photolithography and deep reactive ion etching. The oxidation of copper surfaces is done by electrochemical processes and are directly machined with grinding tools. The surface quality is evaluated concerning the surface roughness by optical measurements with confocal microscopy. Lower roughness values are achieved on both, the pure copper and the oxidized copper by using SiC grinding tools. On pure copper this is reflected in a reduction of the arithmetical mean roughness value Ra to 0.04 µm. The unprocessed reference surface shows an Ra of 0.24 µm. In addition, the machined oxidized surfaces show a reduction of the mean roughness depth Rz from 7,60 µm to 1.10 µm, which is an optimization of factor 2 compared to the machined non-oxidized copper surfaces (2.32 µm). The machining of copper with cBN micro-grinding tools also shows improved roughness values, but in comparison to the SiC tools these are 50 % higher for machined copper surfaces and similar for machined oxidized copper surfaces. While the oxidation of the copper surface has a positive effect on the surface quality, no effect on tool wear can be observed.

AFM Analysis of a Three-Point Flexure Tested, 3D Printing Definitive Restoration Material for Dentistry.

Three-dimensional printing is a rapidly developing technology across all industries. In medicine recent developments include 3D bioprinting, personalized medication and custom prosthetics and implants. To ensure safety and long-term usability in a clinical setting, it is essential to understand material specific properties. This study aims to analyze possible surface changes of a commercially available and approved DLP 3D printed definitive restoration material for dentistry after three-point flexure testing. Furthermore, this study explores whether Atomic Force Microscopy (AFM) is a feasible method for examination of 3D printed dental materials in general. This is a pilot study, as there are currently no studies that analyze 3D printed dental materials using an AFM. The present study consisted of a pretest followed by the main test. The resulting break force of the preliminary test was used to determine the force used in the main test. The main test consisted of atomic force microscopy (AFM) surface analysis of the test specimen followed by a three-point flexure procedure. After bending, the same specimen was analyzed with the AFM again, to observe possible surface changes. The mean root mean square (RMS) roughness of the segments with the most stress was 20.27 nm (±5.16) before bending, while it was 26.48 nm (±6.67) afterward. The corresponding mean roughness (Ra) values were 16.05 nm (±4.25) and 21.19 nm (±5.71) Conclusions: Under three-point flexure testing, the surface roughness increased significantly. The p-value for RMS roughness was p = 0.003, while it was p = 0.006 for Ra. Furthermore, this study showed that AFM surface analysis is a suitable procedure to investigate surface changes in 3D printed dental materials.

Surface profile analysis of laminated transfemoral prosthetic socket fabricated with different ratios of epoxy resin and acrylic resin

Acrylic and epoxy are common types of resin used in fabricating sockets. Different types of resin will affect the internal surface of a laminated socket. This paper is to determine the best combination of ratio for epoxy and acrylic resin for a laminated prosthesis socket and to evaluate the surface profile analysis of different combinations of laminated prosthetic sockets for surface roughness. Transfemoral sockets were created using various resin-to-hardener ratios of 2:1, 3:1, 3:2, 2:3, and 1:3 for epoxy resin and 100:1, 100:2, 100:3, 100:4, and 100:5 for acrylic resin. Eight layers of stockinette consisting of four elastic stockinette and four Perlon stockinette were used. A sample with a size of 4 cm × 6 cm was cut out from the socket on the lateral side below the Greater Trochanter area. The Mitutoyo Sj-210 Surface Tester stylus was run through the sample and gave the Average Surface Roughness value (Ra), Root Mean Square Roughness value (Rq), and Ten-Point Mean Roughness value (Rz). Epoxy resin shows a smoother surface compared to acrylic resin with Ra values of is 0.766 µm, 0.9716 µm, 0.9847 µm and 1.5461 µm with 3:2, 3:1, 2:1 and 2:3 ratio respectively. However, for epoxy resin with ratio 1:3, the resin does not cure with the hardener. As for acrylic resin the Ra values are 1.0086 µm, 2.362 µm, 3.372 µm, 4.762 µm and 6.074 µm with 100: 1, 100:2, 100:5, 100:4 and 100:3 ratios, respectively. Epoxy resin is a better choice in fabricating a laminated socket considering the surface produced is smoother.

Efeito de diferentes materiais para confecção de prótese parcial removível provisória: um estudo in vitro sobre rugosidade superficial e resistência à fratura

ABSTRACT The use of removable partial dentures is considered a common and inexpensive treatment option to rehabilitate edentulous areas. The aim of this study was to evaluate the effect of different materials for provisional removable partial dentures, an in vitro study on surface roughness and fracture resistance. Thermopolymerizable acrylic resin and thermoplastic resin specimens with dimensions of 10 x 10 x 2 mm (blocks) (n=10) and with dimensions of 65 x 20 x 3 mm (bars) (n=10 were analyzed for their surface roughness (Ra) and three-point flexural strength test. All specimens were subjected to oven aging for 60 days at 37°C±0.5°C in distilled water. The statistical analysis was performed with a significance level of 5%, and the surface roughness data were submitted to the Two-way Anova statistical test (P &lt; 0.05) and the mechanical strength data were subjected to One-way Anova statistical test (P &lt; 0.05). For roughness, the factor resin type (P = 0.000) and the factor aging (P = 0.000) were statically significant, as well as showing interaction (P = 0.228). The Thermopolymerizable acrylic resin had the lowest mean roughness values compared to the thermoplastic resin and showed no statistical difference after aging. The same scenario was repeated for flexural strength values; Thermopolymerizable acrylic resin was statistically superior to thermoplastic resin (P = 0.000). Thermopolymerized acrylic resin showed lower surface roughness values and higher flexural strength values compared to thermoplastic resin.

The Effect of Shot Peening on Residual Stress and Surface Roughness of AMS 5504 Stainless Steel Joints Welded Using the TIG Method.

This article presents the influence of the Shot Peening (SP) process on residual stress and surface roughness of AMS 5504 joints welded using the Tungsten Inert Gas (TIG) method. Thin-walled steel structures are widely used in the aviation and automotive industries, among others. Unfortunately, the fatigue properties become worse during the welding process. Samples of 1 mm-thick AMS 5504 steel plates were first prepared using TIG welding and then strengthened by the Shot Peening (SP) process. The technological parameters of the SP process were changed in the range of time t from 2 min to 4 min and of pressure p from 0.4 MPa to 0.6 Mpa. The residual stresses were measured by X-ray diffraction in three zones: fusion zone (FZ), heat-affected zone (HAZ) and base metal (BM). The results showed that SP introduced compressive residual stresses in all of the zones measured, especially in the FZ. The greatest value of compressive residual stresses σ = -609 MPa in the FZ was observed for the maximum parameters of SP (p = 0.6 MPa, t = 4 min). The increase in value of residual stress is about 580% when compared to welding specimens without treatment. As a result of shot peening in the FZ, the mean roughness value Ra decreased in range 63.07% to 77.67% in the FZ, while in the BM increased in range 236.87% to 352.78% in comparison to specimen without treatment. Selected surface roughness parameters in FZ and BM were analyzed using neural networks. In FZ, it was demonstrated that the most correlated parameters with residual stresses are Rt and Rsk. On the other hand, in the BM zone, the most correlated parameters were Rv, Rt and Rq. This enables the estimation of stresses in the welded joint after SP on the basis of selected roughness parameters.

Relationship between Leaf Traits and PM-Capturing Capacity of Major Urban-Greening Species

High concentrations of airborne particulate matter (PM) in urban areas are of great concern to human health. Urban greening has been shown to be an effective and eco-friendly way to alleviate particle pollution, and attention to its role in mitigating particle pollution has increased worldwide. The species-specific PM-capturing capacity of ten urban-greening species in Seoul was evaluated by leaf functional traits (average leaf area (ALA), specific leaf area (SLA), and leaf width-to-length ratio (W/L)), microstructures (roughness, stomata, and trichomes), and physicochemical traits (contact angle (θw), surface free energy (rs), the work of adhesion for water (Wa), and epicuticular wax loads (EWL)). The relationships between leaf traits and PM adsorption by leaves were revealed by Pearson’s correlations and principal component analysis (PCA). A gravimetric method was used to quantify, by particle size, the PM adsorbed on leaf surfaces or embedded in leaf epicuticular wax layers. The key factors for PM adsorption on leaf surfaces were the SLA, the mean roughness value (Ra), and stomatal size. The SLA and Ra of adaxial leaf surfaces were negatively correlated with PM accumulation on leaf surfaces, while stomatal length and width were positively correlated with surface PM load. The rs and EWL positively affected the in-wax PM load. Species-specific PM deposition was the result of complicated mechanisms of various leaf traits. Three evergreen shrub species, Buxus sinica (Rehder &amp; E.H. Wilson) M.Cheng var. insularis (Nakai) M.Cheng, Taxus cuspidata Siebold &amp; Zucc., and Euonymus japonicus Thunb., were efficient in capturing both surface PM and in-wax PM. The PCA revealed that the high PM accumulation efficiency of these three species might be attributable to the interaction between stomatal size and EWL. Aesculus turbinata Blume, Chionanthus retusus Lindl. &amp; Paxton, and Rhododendron schlippenbachii Maxim. had intermediate PM adsorption ability, which might be a result of interactions among stomatal density, the Wa of adaxial surfaces, and ALA. Magnolia denudata Desr., Styphnolobium japonicum (L.) Schott, Liriodendron tulipifera L., and Ginkgo biloba L. had low PM accumulation efficiency. These four species exhibited correlations among SLA, the Ra of adaxial leaf surfaces, and W/L, which had negative effects on PM adsorption.

The Effect of Additional Finishing and Polishing Sequences on Hardness and Roughness of Two Different Dental Composites: An In Vitro Study

Aim: The aim of this study was to evaluate the effect of additional finishing and polishing sequences on a new structural colored (Omnichroma) and a conventional dental composite (Estelite Sigma Quick). Materials and Method: Forty disk-shaped dental composite specimens were prepared from each dental composite and assigned to four groups in terms of additional finishing polishing sequences. Group 1: Mylar strip (control). Group 2: Abrasive disks. Group 3: After abrasive disks, application of a felt brush with abrasive paste. Group 4: After abrasive disks, application of a felt brush with abrasive paste. Then, a single-bottle adhesive was applied as a surface sealer. Hardness and surface roughness were measured using the Vickers hardness test and a profilometer, respectively. SEM images of one of each group were captured at 500x, 1500x, and 3500x magnifications. Two-way analysis of variance, Tukey HSD, and Shapiro–Wilk tests were used for the statistical analysis. Results: Mean hardness values differ in terms of finishing-polishing sequences ( P &lt; .001), dental composites ( P &lt; .001), and interaction of finishing-polishing sequences-dental composites ( P &lt; .001). Mean roughness values differ in terms of finishing-polishing ( P = .002). The main effect of composites on roughness values was not found statistically significant ( P = .990). Also, there is no difference between the mean roughness values in terms of the interactions of finishing-polishing and composites ( P = .967). Conclusion: Finishing-polishing with abrasive disks and abrasive paste are important steps for these dental composites. However, the application of a single-bottle adhesive as a surface sealant on these composites decreases the hardness of the materials.

OPTIMIZATION OF LASER CUTTING ENGRAVING PERFORMANCE WITH ACRYLIC MATERIAL USING THE TAGUCHI METHOD APPROACH

Today's laser cutting machining process is often utilized in large industries as well as individual and student scientific projects. Acrylic is one of the materials whose processing involves a lot of laser cutting, but currently many laser cutting, especially low power ones, are not optimally optimized. In this study, the author wants to optimize laser cutting with 6.5 Watt power using the Taguchi optimization method on solid black acrylic material with a thickness of 3 mm, with reference to the surface roughness value of the workpiece after being subjected to the laser cutting process using the Ra unit. The control factors included are laser distance, laser power, cutting speed and cooling time. The experimental process was carried out 27 times with replication of measurements 2 times. The best result from the experiment was the roughness measurement value of 0.782 µm while the mean roughness value was 2.271 µm. After conducting the experiment, it is known that the best results are obtained with a laser distance factor of 20.6mm, cutting speed of 70 mm/min, laser power of 6.5 watts and cooling time of 10 s. Meanwhile, the effect of factors on the surface roughness results is the laser distance 27%, cutting speed 40.9%, laser power 18.9% and cooling time 7.05%. After calibrating the laser cutting, the cutting accuracy increased from ± 1mm to ± 0.4 mm or an increase of 60%, with an average final dimension measurement of 24.87 mm.

Determination of roughness coefficient in 3D digital representations of rocks

The roughness property of rocks is significant in engineering studies due to their mechanical and hydraulic performance and the possibility of quantifying flow velocity and predicting the performance of wells and rock mass structures. However, the study of roughness in rocks is usually carried out through 2D linear measurements (through mechanical profilometer equipment), obtaining a coefficient that may not represent the entire rock surface. Thus, based on the hypothesis that it is possible to quantify the roughness coefficient in rock plugs reconstructed three-dimensionally by the computer vision technique, this research aims to an alternative method to determine the roughness coefficient in rock plugs. The point cloud generated from the 3D model of the photogrammetry process was used to measure the distance between each point and a calculated fit plane over the entire rock surface. The roughness was quantified using roughness parameters (R_a) calculated in hierarchically organized regions. In this hierarchical division, the greater the quantity of division analyzed, the greater the detail of the roughness. The main results show that obtaining the roughness coefficient over the entire surface of the three-dimensional model has peculiarities that would not be observed in the two-dimensional reading. From the 2D measurements, mean roughness values (R_a) of 0.35,upmu hbox {m} and 0.235,upmu hbox {m} were obtained for samples 1 and 2, respectively. By the same method, the results of the R_a coefficient applied three-dimensionally over the entire rocky surface were at most 0.165,upmu hbox {m} and 0.166,upmu hbox {m}, respectively, showing the difference in values along the surface and the importance of this approach.