Surface Roughness Values Research Articles

Analysis of wettability and contact angle of sodium bicarbonate impregnated wooden surfaces

Scots pine and spruce wood samples were vacuum impregnated with 3, 5, and 9% sodium bicarbonate solution. Contact angle measurements were made by dropping 0.05 mL of pure water and 3% saltwater solution onto the material’s surface. The surface roughness of each sample was measured, and that of Scots pine control samples was higher than that of spruce samples, but the surface roughness values of spruce wood were higher in the samples impregnated with sodium bicarbonate. When pure water or saltwater solution was dropped onto the samples, it was observed that as the waiting times increased, the contact angle value decreased, the droplet height decreased, and the droplet width increased. It was found that the contact angles were higher in the control samples of both tree species than in the samples of 5% and 7%. The contact angles of 9% impregnation solution, pure water, and salt water were higher than the control samples. As the solution ratio increased on the surfaces impregnated with sodium bicarbonate, the contact angle also increased, and the wettability behavior decreased accordingly. Sodium bicarbonate solution is effectively used in the impregnation process for pine and fir woods, making the materials more resistant to water under outdoor conditions. This solution significantly reduces the risk of deformation of wood by increasing the contact angle and reducing its water absorption properties.

EVALUATING THE MARGINAL DISCREPANCY AND SURFACE ROUGHNESS OF CAD - CAM MILLED VS 3D PRINTED PROVISIONAL CROWNS - AN INVITRO STUDY

Aims &Objectives: To evaluate Marginal discrepancy and Surface roughness of CAD-CAM Milled and 3D Printed provisional crowns after subjecting them to thermocycling. Materials and Methods: A stainless-steel metal die with ANSI/ADA specifications had been fabricated for the study. It was scanned with an intraoral scanner and the data was sent to VHF S5M CAD CAM milling and R3Pro printing machine. A total of 10 samples Milled Group A(n=10) and 10 Printed Group B(n=10) provisional crowns were fabricated from PMMA material using the scanned data. The temperatures for thermocycling are 37ºC and 60ºC. Each group is subdivided into two subgroups(n=5) based on thermocycling temperatures. The timeduration selected for Thermocycling was 7,14 and21 days. Marginal discrepancy was measured by using Stereomicroscope and Surface roughness was measured with Profilometer. Results: Marginal discrepancy values were greater in CAD CAM milled crowns(141.47 µm) than in Printed crowns(109.87 µm) at 60ºC after a time-period of 21days.Surface roughness values were higher in Milled crowns(3.915µm) than in CAD CAM Printed crowns(3.817µm) at 60ºC for a given time duration of 21days. One-way ANOVA statistical analysis was done. The mean marginal gap of CAD CAM Milled crowns was statistically significant than Printed crowns(p>0.05). Conclusion: Printed provisional restorationshad better Marginal accuracythan CAD CAM Milled provisional crowns. Surface roughness was higher in CAD CAM Milled crowns than in Printed provisional restorations.

Corrosion Behavior of Nickel-Titanium Arch Wires Following the Use of Different Mouthwashes: An In Vivo Study.

The aim of this double-blind in vivo study was to compare the extent of corrosion on the surface of nickel-titanium (NiTi) wires in various mouthwashes. A total of 80 patients who received orthodontic treatment with as-received 0.016x0.022 inch NiTi wires were included in the study, and they were split into 4 groups. The first group used 0.05% of (225ppm F-) sodium fluoride (NaF) (Colgate Plax®) containing mouthwash, 21.6% alcohol (Listerine Cool Mint®) containing mouthwash, and 0.2% clorhexidine (CHX) (Klorhex®) containing mouthwash and the control group used drinking water with melt menthol as mouthwash. After 30 days of using mouthwash, the surfaces of NiTi wires were examined with atomic force microscopy (AFM), and surface roughness values were calculated. Mouthwashes containing fluoride, essential oils, and CHX created higher surface roughness on NiTi wires than the control group. The floride-containing mouthwash group showed less corrosion than the CHX group, whereas there was no difference between the essential oil group. AFM images show supportive data with the results of the clinical study. The results were assessed using a 95% confidence interval and a significance level p<0.05. CHX, essential oil, and floride-containing mouthwashes cause corrosion of NiTi wires. Floride-containing mouthwash can be preferred over CHX mouthwash due to its lesser corrosion effect.

INVESTIGATION OF WETTABILITY, ANTIBACTERIAL ACTIVITY, THERMAL INSULATION, AND MECHANICAL CHARACTERISTICS OF ELASTOMER BLEND ADHESIVES WITH HIGH-DENSITY FIBERBOARD WOOD AND ALUMINUM

Attention has recently been given to finding alternative and sustainable raw material sources for wood and metal adhesives, such as polyvinyl alcohol (PVA), corn starch (CS), arabic gum (AG), and dextrins (D). Modifying polymer dispersion using unique substances, such as modifying reactive elastomer liquid (EL) using PVA, CS, AG, or D results in sufficiently moisture-resistant adhesive joins. In the present study, the physical characteristics of EL/blended with the natural polymers PVA, CS, AG, and D, based on high-density fiberboard (HDF) wood and aluminum (Al) adhesives and coatings, were investigated and compared to those of pure EL. The EL was blended with PVA, CS, AG, or D at a ratio of 60/40 (w/w) to form EL/blends. The chemical structures, surface and interface morphology, adhesion strengths (including shear strength and pull-off strength), surface roughness, wettings, color intensity, and thermal insulation of the prepared EL and EL/blends were investigated. A scanning electron microscopy (SEM) investigation confirmed filler dispersion and adhesion between the blends, and coated HDF wood, or Al. The developed EL/AG blend had a pull-off strength of 144±5 and 102±3 MPa and a shear strength of 771±11, and 52±3 N with HDF wood and Al substrate, respectively. The EL/PVA blend had a maximum surface roughness value 4.57 µm, and its average water contact angle (WCA) was 85.6°. A plasma jet was used to treat the surface roughness and hence the wettability of the pure EL and the EL/blends, for example, plasma treatment decreased the roughness of the EL/AG blend from 4.36 to 3.28 μm. WCA, and hence wettability, was also significantly influenced by plasma treatment, for example, plasma treatment decreased the WCA of the pure EL from 71.7±0.4° to 30.7±0.7°. The lightness value of the EL/blends was less than that of the pure EL, indicating that (the color adhesives have darkened). Similarly, the yellowness-blueness and redness-greenness values of the EL/blends were greater than those of the pure EL,( rendering the blended adhesives more reddish and bluish). The EL/AG blend was found to have a minimum thermal conductivity (of 0.27 W/m.K), indicating maximum insulation.

Effect of Hydrogen Peroxide-Based Bleaching Agents on the Color Dimensions and Surface Roughness of Different Milled Restorative Dental Materials.

To compare the color dimensions, color discrepancies (ΔE00), and surface roughness of milled materials before and after application of a bleaching agent. A total of 10 extracted molars were obtained. Each tooth was cut in transverse sections to create disks (3-mm thick, 10-mm diameter; control group). Disk specimens of eight materials (n &#61; 10 per group) were fabricated: polymethyl methacrylate (PMMA) interim material (PMMA-Telio group), two resin nanoceramics (RNC-Ultimate group and RNC-Cerasmart group), two hybrid ceramics (HC-Shofu group and HC-Enamic group), lithium disilicate (LD-Emax group), zirconia-reinforced glass ceramic (ZGC-Suprinity group), and zirconia (Zr-InCeram group). Color measurements were obtained using a spectrophotometer before and after applying 35% hydrogen peroxide-based bleaching agent. Pre- and postbleaching surface roughness (Sa) analyses were completed using a profilometer. Significant L*, a*, b*, and ΔE00 value differences were found (P < .05). Color discrepancies (ΔE00) ranged from 0.30 ± 0.14 to 4.82 ± 0.10. The highest color discrepancies were measured on the PMMA-Telio group, while the lowest color discrepancies were computed for ZGC-Suprinity, RNCUltimate, and RNC-Cerasmart. Significant surface roughness differences were found (P < .05). The largest increase of surface roughness values between the pre- and postbleaching measurements was obtained in the PMMA-Telio group with a mean ΔSa value of 4.73 ± 3.02, while the largest decrease of surface roughness values between the pre- and postbleaching measurements was obtained in the Zr-InCeram group with a mean ΔSa value of -1.58 ± 0.10. The milled materials showed significant pre- and postbleaching color and surface roughness discrepancies.

Pulsed Unipolar-Polarisation Plasma Electrolytic Polishing of Ni-Based Superalloys: A Proof of Conception

The enhanced performance of aerospace equipment drives parts development towards integration, complexity, and structural optimization. This advancement promotes metal near-net fabrication technologies like wire electrical discharge machining (WEDM) and 3D printing. However, the high initial surface roughness from WEDM or 3D printing poses significant challenges for the high-performance surface finishing required. To effectively reduce the surface roughness of the workpieces with high initial surface roughness, this paper proposes pulsed unipolar-polarisation plasma electrolytic polishing (PUP-PEP). The study examined the material removal mechanisms and surface polishing quality of PUP-PEP. This technique combines the high current density and material removal rate of the electrolytic polishing mode with the superior surface polishing quality of PEP through voltage waveform modulation. For an Inconel-718 superalloy part fabricated by WEDM, PUP-PEP reduced surface roughness from Ra 7.39 μm to Ra 0.27 μm in 6 min under optimal conditions. The roughness decreased from Ra 7.39 μm to Ra 0.78 μm in the first 3 min under pulsed unipolar-polarisation voltage, resulting in a remarkable 233% increase in efficiency compared to that with conventional PEP. Subsequently, the voltage output voltage is transformed into a constant voltage mode, and PEP is continued based on PUP-PEP to finally reduce the workpiece surface roughness value to Ra 0.27 μm. The proposed PUP-PEP technology marks the implementation of ‘polishing’ instead of conventional rough-finish machining processes, presenting a new approach to the surface post-processing of metal near-net fabrication technologies.

Investigating the erosive wear characteristics of AISI 420 martensitic stainless steel after surface hardening by boriding

Erosive wear degrades industrial components, causing surface deterioration and material loss. Understanding and mitigating this wear enhances component longevity and efficiency. Little research has been conducted to investigate the influence of particle angle, speed, and concentration on boronized surfaces. Therefore, in this study, the erosive wear behaviors of raw and boronized AISI 420 martensitic stainless steels were investigated. The samples were subjected to erosive wear testing using SiO2 abrasive particles with impact velocities of 2, 4, and 6 m/s, impact angles of 30°, 60°, and 90°, and concentration values of 5%, 10%, and 15% by weight in an abrasive sand slurry environment. Experimental runs were designed using the Taguchi L9 method. The wear test results were analyzed in terms of mass loss, surface roughness, and temperature change of the boronized and raw AISI 420 samples before and after the test. The results showed that the impact speed and concentration were statistically significant parameters compared with the impact angle, which had a negligible effect. Furthermore, with increasing impact speed and concentration, all measured responses increased in both sample groups. The surface roughness values and mass loss increased by lower margins for the boronized samples (58.40% and 188.49%, respectively) compared to those of the raw samples (61.40% and 254.38%, respectively). This study demonstrates the potential of boriding as a surface treatment technique for enhancing the erosive wear performance of martensitic stainless steels, which require improved durability and longevity of materials subjected to erosive environments.

Effect of drill gash rake angle on drillability in plain carbon and low alloy steels

In this study, the effects of the gash rake angle (γa), which is an important component of the drill geometry, on the thrust force and drilling torque occurring in the drilling of ordinary carbon steels (AISI 4140 and Ck 45) were examined through experimental and FEM-supported numerical simulation studies on surface roughness, tool surface roughness, wear and diameter deviation values were investigated experimentally. In the experiments, 6.8 mm diameter solid cementite carbide, coated and internal cooling channel drills with +10°, 0°, −10° gash rake angle were used. Three different feed rates and cutting speed levels were selected as cutting parameters. Determination of material-specific gash rake angle and cutting parameters for different materials was carried out by Taguchi-assisted variance analysis of experimental data. In experimental studies, the gash rake angle was 65.9% effective on the thrust force for AISI 4140 tempered steel, while it was the second effective parameter with 29.22% for Ck 45 manufacturing steel. While the feed rate is the more effective parameter in the drilling moments that occur when drilling different materials, it has been observed that γa also has a significant effect. It has been determined that chisel edge wear, main cutting edge wear and crater wear occur in the drill when drilling AISI 4140 tempered steel and Ck 45 manufacturing steel. The data obtained from the finite element-assisted chip removal analyses support the experimental results and provide guiding results in the selection of material-specific gash rake angle.

Analysis and Optimization of Process Parameters Affecting Form Errors and Surface Roughness in Milling of Aging-Treated AA 6063-T6 Free Form Surfaces

This study aimed to examine the microstructure and hardness changes in AA 6063 T6 specimens that underwent an ageing procedure. The second portion involves the machining of free forms surfaces on specimens with varying microstructures and hardness. Four different tool paths, four different cutting speed (Vc), and four different feed rate (f) were employed in the machining of the surfaces. Statistical analysis were conducted to ascertain the optimal cutting parameters and their impact on the output parameters. The experimental design was designed based on the Taguchi L16 index. The form errors and surface roughness values acquired from the tests were analysed statistically using the Signal/Noise (S/N) ratio and analysis of variance (ANOVA) methods. The study found that the sample immersed in 2WQ solution had a minimum hardness value of 71.7 Hv1, whereas the sample aged for 18 hours had a maximum hardness value of 117.7 Hv1. Based on the investigation, it was determined that A4B1C4 yielded the most favourable cutting parameter in terms of form error and surface roughness. This refers to the utilisation of the TP4 tool path, a f of 0.04 mm per tooth, and a Vc of 105 m/min. Based on the data collected, the ANOVA analysis of the 18AQ sample revealed that the cutting parameters with the highest efficacy in minimising form error and surface roughness were a f of 51.18% and 59.07%, respectively. These values represent the optimum values for cutting parameters.

Experimental Study on Dry Milling of Stir-Casted and Heat-Treated Mg-Gd-Y-Er Alloy Using TOPSIS

This study examines the dry milling process of a rare-earth-based magnesium alloy, emphasizing the optimization of the milling parameters and their impact on the surface quality, cutting forces, and the rate of material removal. The objective is to improve our comprehension of the milling behavior of the Mg-Gd-Y-Er alloy. The Taguchi technique is adopted to formulate the experimental design. This study methodically investigates the influence of heat treatment (T4 and T6) on milling performance, and the effects of speed, feed rate, and depth of cut. The output variables considered for this investigation are the surface roughness (Ra, Rz, Sa, and Sz), material removal rate (MRR), and cutting force. To optimize the milling parameters and achieve superior outcomes, the multi-objective optimization technique TOPSIS is used. At a feed rate of 150 mm/min, a spindle speed of 1500 rpm, and a depth of cut of 1 mm, the T4-treated sample exhibits a minimum surface roughness value of 0.0305 µm. The highest resultant force values of 96.4416 N and 176.1070 N for 200 °C and 225 °C T6-treated alloys are obtained by combining process parameters such as a spindle speed of 1500 rpm, a feed rate of 50 mm/min, and a depth of cut of 1.5 mm. Furthermore, the maximum closeness coefficient value is achieved by combining a spindle speed of 1000 to 1500 rpm, a feed rate of 150 mm/min, and a depth of cut of 0.5 mm to 1 mm. The closeness coefficient value is significantly influenced by the most significant process parameters, as indicated by the ANOVA results.

Prediction of surface roughness at the machining of densified wood surfaces

ABSTRACT In this research, modeling and interpretation of the effects of the machining parameters on surface roughness (Rz) using artificial neural networks (ANN) and analysis methods (MLP, LVQ and Taguchi Design analysis) werw studied. Black poplar (Populus nigra) was selected as the experimental material. Specimens, which were transversal densified by a thermo-mechanical (TM) process at 0%, 20% and 40% compression ratios. The densified wood was processed at 1000, 1500 and 2000 mm/min feed speeds and in 12,000, 15,000, and 18,000 rpm rotation speeds in a CNC machine by using two different cutters. Rz surface-roughness values were measured. The modeling of Rz with artificial neural networks (ANN) is discussed. While 97% success was achieved in the classification made with multilayer perceptron (MLP) in estimating Rz, this success rate is 100% in the classification made with learning vector quantization (LVQ). MLP and LVQ are operations in the MATLAB R2019b software. Taguchi values were compared with the experimental data results, it was seen that the MSE value was 4.6%, the MAE value was 1.8%, and the RMSE value was 2.1%. These results showed that the presented models can accurately determine the appropriate parameters for the desired Rz. The prediction results and presented models can be applied for targeted industrial applications.

An investigation of dynamic droplet wetting within the smoothed dissipative particle dynamics (SDPD) multi-scale modeling framework

The multi-scale numerical procedure proposed in our previous work based on smoothed dissipative particle dynamics (SDPD) is employed, and a new multi-phase interaction model based on the inter-particle force (IPF) that includes a consistent repulsion force is presented and verified. A comparative investigation utilizing smoothed particle hydrodynamics (SPH), SDPD, and our multi-scale methods is then carried out and the computational efficiency, droplet morphology, wetting flow field, and advantages of the multi-scale method are demonstrated. In addition, the droplet thickness is derived from the Navier–Stokes equations with a stochastic force, demonstrating the effect of thermal fluctuations on the mesoscopic scale. Finally, the wetting states are simulated at different surface roughness values, and the transition of states and some new mechanisms are clarified. When the roughness scale is smaller than the interaction range between particles, the wetting state may change significantly, and this effect becomes weaker when the roughness scale exceeds the interaction range. The results also show that the horizontal roughness (direction of droplet spreading) is more decisive than vertical one (perpendicular to the direction of droplet spreading), usually leading to a transition of the wetting states, while the vertical roughness usually plays a reinforcing role.

Impact of Toolpath Pitch Distance on Cutting Tool Nose Radius Deviation and Surface Quality of AISI D3 Steel Using Precision Measurement Techniques.

The selection of the right tool path trajectory and the corresponding machining parameters for end milling is a challenge in mold and die industries. Subsequently, the selection of appropriate tool path parameters can reduce overall machining time, improve the surface finish of the workpiece, extend tool life, reduce overall cost, and improve productivity. This work aims to establish the performance of end milling process parameters and the impact of trochoidal toolpath parameters on the surface finish of AISI D3 steel. It especially focuses on the effect of the tool tip nose radius deviation on the surface quality using precision measurement techniques. The experimental design was carried out in a systematic manner using a face-centered central composite design (FCCD) within the framework of response surface methodology (RSM). Twenty different experiment trials were conducted by changing the independent variables, such as cutting speed, feed rate, and trochoidal pitch distance. The main effects and the interactions of these parameters were determined using analysis of variance (ANOVA). The optimal conditions were identified using a multiple objective optimization method based on desirability function analysis (DFA). The developed empirical models showed statistical significance with the best process parameters, which include a feed rate of 0.05 m/tooth, a trochoidal pitch distance of 1.8 mm, and a cutting speed of 78 m/min. Further, as the trochoidal pitch distance increased, variations in the tool tip cutting edge were observed on the machined surface due to peeling off of the coating layer. The flaws on the tool tip, which alter the edge micro-geometry after machining, resulted in up to 33.83% variation in the initial nose radius. Deviations of 4.25% and 5.31% were noted between actual and predicted values of surface roughness and the nose radius, respectively.

Effects of thermomechanical parameters on surface texture in filament materials extrusion: outlook and trends

The material extrusion process has been widely used to manufacture custom products. However, the surface texture varies due to the additive mechanism of the process, which depends on the layer height and surface orientation, resulting in varying average surface roughness values for inclined, flat and vertical surfaces. Different strand welding conditions result in non-uniform internal stresses, surface distortions, layer traces, weak bonding, non-uniform pores and material overflow. This paper comprehensively examines material extrusion process achievements in surface texture quality and studies and summarises the most influential processing parameters. Parameter effects are critically discussed for each topic; flat, inclined, and vertical surfaces. The results of this research help reduce post-processing.

Effects of graphene oxide and silane‐grafted graphene oxide on chitosan packaging nanocomposite films for bread preservation

AbstractThis study aims to investigate the dual effects of (3‐aminopropyl)triethoxysilane (APTES)‐grafted‐GO (A‐g‐GO), and titanium dioxide (TiO2) on the novel chitosan (CS) packaging nanocomposite films developed via the solution‐casting method. The chemical properties of GO and A‐g‐GO were assessed using FTIR and XRD. Subsequently, the chemical, structural, and physical attributes of all chitosan packaging nanocomposite films were analyzed through FTIR, XRD, TGA, DSC, AFM, water contact angle analysis, and food packaging tests. Successful silanization of GO by APTES was first confirmed. The highest surface roughness value was observed in the CS/A‐g‐GO/TiO2 film (16.574 nm) compared to pristine CS and other nanocomposite films. Incorporating GO into the CS matrix improved its thermal stability, suggesting robust bonding between GO and the polymer matrix. The addition of A‐g‐GO slightly decreased the contact angle value (107.7° for CS/A‐g‐GO), whereas TiO2 increased contact angles (117.3° for CS/GO/TiO2 and 119.4° for CS/A‐g‐GO/TiO2), suggesting a more hydrophilic structure with GO and A‐g‐GO and a more hydrophobic structure with TiO2. Bread samples showed no structural distortion over 40 days. Therefore, the dual impacts of A‐g‐GO and TiO2 on the pristine CS film imply that the resulting CS/A‐g‐GO/TiO2 film exhibits potential as an exceptionally efficient packaging material for prolonging the freshness of bread.

Study on surface integrity and fatigue performance of FeCoCrNiAl₀.₆ high-entropy alloy based on thermo-mechanical coordinated control

This study investigates the effects of various lubrication techniques on the surface integrity and fatigue life of FeCoCrNiAl0.6 high-entropy alloy during machining. By combining cutting experiments, fatigue tensile tests, and Abaqus/Fe-safe simulations, the research offers a comparative analysis of surface morphology, roughness, and fatigue life across different lubrication scenarios.The findings show a marked improvement in surface quality as cutting speed increases under all lubrication conditions. However, increased cutting depth generally leads to a decline in surface flatness. Specifically, surface roughness decreases with higher cutting speeds. For example, at 1200 m/min in dry cutting, the surface roughness is around 0.77 μm, which drops to 0.40 μm at 3000 m/min, representing a 48 % reduction. Under cryogenic minimum quantity lubrication (CMQL) at 1200 m/min, the roughness is 0.49 μm, decreasing to 0.25 μm at higher speeds, reflecting a 48.9 % reduction.However, increased cutting depth significantly deteriorates surface quality, with a notable rise in surface roughness values. Among the tested lubrication techniques, surface quality ranks as follows: CMQL > MQL > Dry.Regarding fatigue life, higher cutting speeds substantially enhance tensile cycle counts under all lubrication conditions. Specimens under CMQL achieved 2,000,042 cycles, compared to 1,238,520 cycles with minimum quantity lubrication (MQL) and 702,245 cycles in dry cutting—equating to 61.9 % and 35.1 % of the tensile cycle count for CMQL, respectively.Fatigue life decreases with greater cutting depth. For example, compared to a 0.2 mm cutting depth, tensile fatigue cycles decrease by 87.9 % for CMQL, 86 % for MQL, and 91.8 % for dry cutting at a depth of 0.5 mm.

The effect of graphene solution on mixed powder electrical discharge milling of Ti6Al4V

Abstract Ti6Al4V is the most widely used materials in aerospace, medical, nuclear power and other fields. However, due to its unique properties such as low thermal conductivity, titanium alloy poses challenges in machining processes. Electrical discharge milling (EDM) is a machining method that utilizes the electrical corrosion phenomenon of pulsed spark discharge between two electrodes to remove materials, which is highly suitable for the machining of Ti6Al4V. This paper investigates a mixed powder EDM approach for titanium alloy using a graphene solution medium known for its green and sustainable characteristics. Compared to conventional deionized water medium processing which without powder particles, the material removal rate can be increased by 50%, the surface hardness after processing was 2.5 times higher than that of the substrate, the electrode wear rate could be reduced by 40%, the surface roughness values were reduced by more than 20%. Besides that, the micro-cracks and micro-pores on the workpiece surface can be significantly reduced. Subsequently, single factor experiments and orthogonal experiments were conducted using material removal rate, electrode wear rate, and surface roughness as process indicators. The influence of processing parameters on process indicators was investigated based on optimal selection method and analysis of variance (ANOVA). Finally, the optimized parameters in graphene solution mixed powder EDM for Ti6Al4V were obtained. When using the process combination A3B3C1D2, the maximum MRR can be obtained.

Evaluation of nanohardness, elastic modulus, and surface roughness of fluoride-releasing tooth colored restorative materials.

Recently, interest in tooth-colored fluoride-releasing dental materials has increased. Although physical and mechanical properties such as surface hardness, elastic modulus and surface roughness of the restorative materials have been investigated, the effect of different immersion media on these properties is still controversial. The aim of this study was to evaluate the nanohardness, elastic modulus and surface roughness of the fluoride release of tooth-colored restorative materials after immersion in acidic beverages. Prepared samples of three restorative materials (a highly viscous glass ionomer (EQUIA Forte; GC, Tokyo, Japan), a compomer (Dyract XP; Dentsply, Weybridge, UK), and a bioactive restorative material (Activa BioACTIVE; Pulpdent, MA, USA)) were randomly divided and immersed in distilled water, a cola and an orange juice for one week. The HYSITRON T1 950 TriboIndenter device (Hysitron, USA) with the Berkovich diamond indenter tip was used for all measurements. The nanohardness and elastic modulus of the samples were measured by applying a force of 6000 μN to five different points on the sample surface. Surface roughness measurements were evaluated on random samples by scanning five random 40 × 40 μm areas. The properties were measured at the initial and one week after immersion. The values of nanohardness, elastic modulus and surface roughness were tested for significant differences using a two-way analysis of variance (ANOVA) with repeated measures (p < 0.05). Tukey's honest significant difference (HSD) test was used for multiple comparisons. AB (Activa BioACTIVE) had the highest initial mean values for nanohardness. After post-immersion, the highest mean value for elastic modulus was the initial AB value. The lowest mean value for roughness of 100.36 nm was obtained for the initial DX (Dyract XP) measurement. Acidic beverages had a negative effect on the nanohardness, elastic modulus and surface roughness of the restorative materials.

Effect of Surface Treatments Applied to 3D Printed Permanent Resins on Shear Bond Strength.

3D-printed permanent resins have recently been introduced to produce permanent restorations. The aim of this study is to evaluate the effect of surface treatment methods on the shear-bond strength (SBS) between 3D-printed permanent resins and adhesive cement. In this study, samples were produced using digital light projection (DLP) and stereolithography (SLA) 3D printers with two permanent resins (Crowntec, Saremco and Permanent Crown, Formlabs) in accordance with manufacturer guidelines. The samples were separated into three groups: sandblasting, hydrofluoric acid and no surface treatment. The surface profile (Ra, Sa) of the samples was examined with a confocal microscope (Smartproof 5, Zeiss). Then, a self-adhesive resin cement was applied to the samples in a transparent mold (2.38 mm diameter) in accordance with ISO 29022:2013. A universal testing machine was used to perform SBS test. A stereomicroscope was used to analyze the different types of fractures. A two-way analysis of variance (ANOVA) test was used to assess the data (p<0.05). The samples with sandblasting applied to the surface showed higher surface roughness values than the samples with hydrofluoric acid (p<0.001). 3D printer technology and surface treatment methods affected SBS values (p<0.001). Sandblasting groups higher SBS values were than in the hydrofluoric acid group (p<0.001). Sandblasting revealed cohesion fractures, which indicated a stronger bond, while hydrofluoric acid displayed adhesive and mix fractures. When sandblasting was applied to the surface of the samples prepared using permanent resins, higher adhesion was achieved with adhesive cement. Key words:3D printing, Shear bond strength, Sandblasting, Stereolithography.

Optimisation of machining parameters in high-speed end milling of hardened AISI H13 die steel by integrating RSM and GA

ABSTRACT This study explores the potential of high-speed hard-end milling as a cost-effective alternative to the time-consuming grinding process for Chromium-molybdenum steel (AISI H13), widely used in cold and hot work tooling. The research aims to optimize machining parameters for achieving desired surface roughness, comparable to grinding and polishing. Cutting depth (0.4 - 0.8 mm), feed rate (1 - 4 μm per tooth), and cutting speed (80 - 140 m/min) were varied, and soybean oil replaced conventional lubricants. Employing Titanium Aluminum Nitride (TiAlN) coated end mills (3 mm diameter, 2 μm coating thickness) and response surface method (RSM) with Design Expert software, the study aimed at reducing tool wear and enhancing surface quality through multi-criteria optimization. Surface roughness analysis led to a streamlined surface by lowering mass flow rate and increasing cutting speed. The optimization approach predicted an optimal surface roughness value of 0.217475 μm at a cutting speed of 110 m/min, a feed rate of 1 μm/tooth, and a cut depth of 0.4 mm using genetic algorithm (GA), closely aligned with RSM’s ideal value of 0.215 μm. Both values converge around the 0.4 mm cut thickness.