Surface Roughness Values Research Articles

Study on the Surface Quality of Overhanging Holes Fabricated by Additive/Subtractive Hybrid Manufacturing for Ti6Al4V Alloy

Additive/subtractive hybrid manufacturing (ASHM) based on laser powder bed fusion (LPBF) enables to achieve high precision and good surface quality of complex structures such as small holes with overhanging features. However, the rapid heating and cooling rates during the ASHM results in sinkage at the alternating interface of additive manufacturing and subtractive milling, which degrades the surface quality of the components. This study employs shielding height at the alternating interface to solve this problem and improve the surface quality. The effect of internal diameters and shielding heights on the surface quality were studied experimentally for overhanging holes fabricated by ASHM of Ti6Al4V. The results show that the Ti6Al4V samples prepared by LPBF possessed high density and uniformly distributed microstructure. For overhanging holes without shielding height, the largest depth value of sinkage and surface roughness were obtained, indicating a worse surface quality; when the shielding height was increased to 0.5 mm, the smallest sinkage value and surface roughness were obtained, indicating a better surface quality. With the same shielding height, the overhanging holes with different diameters had a similar surface roughness. This study reveals that an appropriate shielding height can improve the surface quality, which provides guidance to the improvement of the surface quality for complex structures in ASHM.

Repercussion of hybridization on AWJM surface quality of cotton and corn hybrid composite

ABSTRACT Hybrid composites made of natural fibers are replacing composites made of synthetic fibers, which is better for the environment. In this study, a Cotton/Corn Hybrid Composite was prepared using compression moulding and evaluated the Abrasive Water Jet Machining (AWJM) process variables on surface quality. The AWJM investigations were conducted using experimental design approaches, with variables including water pressure, nozzle transfer speed, and standoff distance. Among these variables, it was determined that nozzle transfer speed had the most influential impact on surface quality. The optimal machining parameters P2, s1, and d1 were identified, resulting in a surface roughness of 4.459 μm. This demonstrates that accomplishing better surface quality is attainable through the suitable parameter selection. Further, the prediction model’s efficiency was validated by establishing a strong relationship between the experimental, predicted, and validated surface roughness values. This highlights the model’s reliability in predicting and optimizing surface quality in the AWJM process.

Effect of Graphene Oxide Nanoparticles Incorporation on the Mechanical Properties of a Resin-Modified Glass Ionomer Cement.

The objective of this study was to evaluate the effect of incorporating different concentrations of graphene oxide (GO) nanoparticles on the mechanical properties of a resin-modified glass ionomer cement (RMGIC). A commercial RMGIC (Resiglass R, Biodinâmica) was modified by incorporating 0.1% and 0.5% (by weight) of GO into the powder's material. An unmodified RMGIC was used as a control group. Powder samples were characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Specimens were fabricated and subjected to flexural strength (n = 15), modulus of elasticity (n = 15), Vicker's microhardness (n = 10), and surface roughness tests (n = 10). Data were analyzed using one-way ANOVA and Tukey's post hoc test (α = 5%). Experimental groups' powder demonstrated a homogeneous dispersion of GO. No statistically significant difference was observed in flexural strength (p = 0.067) and modulus of elasticity (p = 0.143) tests. The groups containing 0.1% and 0.5% GO showed significantly higher microhardness and lower surface roughness values (p < 0.001) compared to the control group. The incorporation of GO nanoparticles at concentrations of 0.1% and 0.5% improved the microhardness and surface roughness without negatively affecting the flexural strength and modulus of elasticity of an RMGIC.

Response mechanisms for the photopolymerization profiles, microstructures, and properties in ceramics prepared by stereolithography

Insight into the response mechanisms among the photopolymerization process, profile curves, microstructure, and physicomechanical properties is essential for microstructural and performance control during ceramic stereolithographic manufacturing. This work establishes and validates the photopolymerization profile equation and investigates the response mechanisms of photopolymerization profiles on microstructures and lamellar defects and the response mechanisms of cured powder concentration gradient on dimensional shrinkage, porosity, and physicomechanical properties. The results illustrate that the profile control equations perfectly predict the photopolymerization experiment profile and the lamellar profile shape to control the volume of lamellar defects, and the surface microstructures are mainly affected by the z-direction lamellar profile. The optimal surface roughness values of the green bodies before and after sintering are 3.95 μm and 3.32 μm, respectively. Besides, the attenuation of the Gaussian-distributed laser intensity in the slurry results in a gradient change in double-bond conversion to create a gradient in the cured powder concentration. The z-direction shrinkage strongly correlated with the cured powder concentration is much greater than the x- and y-direction shrinkages. The variation range of the anisotropic shrinkage is from 1.54 % to 3.77 %. Furthermore, the cured powder concentration on the top area of the cured layer near the laser irradiation is greater than that on the bottom area away from the irradiation, influencing the physicomechanical properties. Finally, the best process parameters for multiobjective optimization are achieved by combining response surface experiments and principal components analysis. The response mechanisms of the lamellar profile and cured powder concentration are expected to provide new ideas for controlling the performance of vat photopolymerization.

Biomechanical surface roughness analysis of ramie-low melt polyester nonwovens exposed to plasma

This study aims to characterize ramie-low melt polyester nonwoven fabrics treated with low-temperature plasma and to analyze 3-D images based on object-depth mapping (ODM) using the MATLAB® R2022a software. We examined the low-temperature plasma treatment of nonwoven ramie fabrics using a plasma generator with 30 kV output power, six-minute treatment times, and a 4.5 cm distance between electrodes. The fabric’s chemical properties and surface topography were investigated using scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). An analysis of the SEM images was performed using a statistical approach and image processing to determine the level of surface roughness. FTIR analysis revealed that fabrics exposed for six minutes differed from those that were not. Our findings indicated that plasma treatment caused the following: 1) Ramie fabrics to become more hydrophilic, as shown by their increased T% in the FTIR of hydrophilic functional groups such as hydroxyl (O-H), carboxyl (-COOH), and carbonyl (C=O); 2) A higher surface roughness was observed in nonwoven fabric during SEM testing and image processing; 3) Plasma treatment of fabrics resulted in a higher coefficient of variation (CV) than untreated fabrics; 4) Nonwoven fabric mass reduction. Based on this study, we found the relationship between plasma-treated ramie fabric and textiles in biomechanics. Plasma treatment reduced the mass of ramie fabric by 0.11 %, according to our findings. We found that the greater the mass reduction, the greater the surface roughness value. The novelty of this study is the use of 3-D images based on object-depth mapping (ODM) using the MATLAB® R2022a software in SEM to observe surface roughness to the physical properties of ramie fabric for the first time.

Influence of SiO2 Nanoparticles Extracted from Biomass on the Properties of Electrodeposited Ni Matrix Composite Films on Si(100) Substrate.

Lab-made biosilica (SiO2) nanoparticles were obtained from waste biomass (rice husks) and used as eco-friendly fillers in the production of nickel matrix composite films via the co-electrodeposition technique. The produced biosilica nanoparticles were characterized using XRD, FTIR, and FE-SEM/EDS. Amorphous nano-sized biosilica particles with a high SiO2 content were obtained. Various current regimes of electrodeposition, such as direct current (DC), pulsating current (PC), and reversing current (RC) regimes, were applied for the fabrication of Ni and Ni/SiO2 films from a sulfamate electrolyte. Ni films electrodeposited with or without 1.0 wt.% biosilica nanoparticles in the electrolyte were characterized using FE-SEM/EDS (morphology/elemental analyses, roundness), AFM (roughness), Vickers microindentation (microhardness), and sheet resistance. Due to the incorporation of SiO2 nanoparticles, the Ni/SiO2 films were coarser than those obtained from the pure sulfamate electrolyte. The addition of SiO2 to the sulfamate electrolyte also caused an increase in the roughness and electrical conductivity of the Ni films. The surface roughness values of the Ni/SiO2 films were approximately 44.0%, 48.8%, and 68.3% larger than those obtained for the pure Ni films produced using the DC, PC, and RC regimes, respectively. The microhardness of the Ni and Ni/SiO2 films was assessed using the Chen-Gao (C-G) composite hardness model, and it was shown that the obtained Ni/SiO2 films had a higher hardness than the pure Ni films. Depending on the applied electrodeposition regime, the hardness of the Ni films increased from 29.1% for the Ni/SiO2 films obtained using the PC regime to 95.5% for those obtained using the RC regime, reaching the maximal value of 6.880 GPa for the Ni/SiO2 films produced using the RC regime.

Development of a Fast Positioning Platform with a Large Stroke Based on a Piezoelectric Actuator for Precision Machining.

In this paper, a fast positioning platform (FPP) is proposed, able to meet simultaneously the requirements of large stroke and high frequency response, developed based on a PZT (piezoelectric actuator) and a quad-parallel flexible mechanism, for application in precision machining. The FPP is driven by a high-stiffness PZT and guided by a flexible hinge-based mechanism with a quad-parallel flexible hinge. The proposed quad-parallel flexible hinge mechanism can provide excellent planar motion capability with high stiffness and good guiding performance, thus guaranteeing outstanding dynamics characteristics. The mechanical model was established, the input and output characteristics of the FPP were analyzed, and the working range (output displacement and frequency) of the FPP was determined. Based on the mechanical model and the input and output characteristics of the FPP, the design method is described for of the proposed FPP, which is capable of achieving a large stroke while responding at a high frequency. The characteristics of the FPP were investigated using finite element analysis (FEA). Experiments were conducted to examine the performance of the FPP; the natural frequency of the FPP was 1315.6 Hz, while the maximum output displacement and the motion resolution of the FPP in a static state were 53.13 μm and 5 nm, respectively. Step response testing showed that under a step magnitude of 50 μm, the stabilization times for the falling and rising edges of the moving platform were 37 ms and 26 ms, respectively. The tracking errors were about ±1.96 μm and ±0.59 μm when the amplitude and frequency of the signal were 50 μm, 50 Hz and 10 μm, 200 Hz, respectively. The FPP showed excellent performance in terms of fast response and output displacement. The cutting test results indicated that compared with the uncontrolled condition, the values of surface roughness under controlled conditions decreased by 23.9% and 12.7% when the cutting depths were 5 μm and 10 μm, respectively. The developed FPP device has excellent precision machining performance.

Hole quality geometrical measurement and surface roughness for α-Phase titanium alloy (α-Ti-6Al-4V) materials by using L-PBF (laser powder bed fusion) orthopedic implant application

This study examines the quality of circular-hole 3D-printed objects using laser powder bed fusion (L-PBF) on Ti-6Al-4V titanium alloy that typically used for orthopedic implants. Meanwhile measuring surface roughness and hole dimension deviations in AM specimens is very challenging. Thus, the specimens were printed with varying process parameters, followed by an L9 orthogonal array experiment, where parameters included laser power (LP) at 175, 185, and 195 W; scanning speed (SS) at 600, 900, and 1200 mm/s; and hatch distance (HD) at 70, 90, and 110 µm. Thus the, minimum surface roughness values are Ra 2.4 µm for the top surface and Ra 16.06 µm for the inside hole curve. Whereas the smallest hole deviations are 0.1102 mm for external and 0.2094 mm for internal diameters. Therefore, this analysis include FESEM, EDX, XRD, profilometry and stereomicroscopy. Where the best settings are LP 195 W, SS 900 mm/s, and HD 70 µm, producing well-fused, uniform α-phase Ti-6Al-4V specimens that are suitable for biomedical applications.

Determination of the significance of atomic concentration on surface properties of Ba x Mg1-x F2 alloy coatings via microscopic and spectroscopic techniques.

Both BaF2 and MgF2 compounds and Ba x Mg1-x F2 alloy thin films were deposited on glass and silicon (Si) substrates in nanometric sizes (100 ± 10 nm) in a high vacuum environment by radio frequency (rf) magnetron sputtering. Using BaF2 (99% purity) and MgF2 (99% purity) target materials and adjusting the power levels applied to these targets, Ba x Mg1-x F2 alloy coatings at different atomic concentrations were formed under the same vacuum conditions. The microstructure and surface characteristics of the samples were analysed with the help of spectroscopic and microscopic methods. For the surface characterization, with scanning acoustic microscopy (SAM), 2-dimensional surface acoustic images of the samples were mapped, the surface acoustic impedance values were determined, and information about the micro hardness of the materials was obtained. Surface roughness values and grain sizes were obtained by taking 3-dimensional surface images of investigated materials using atomic force microscopy (AFM). Average nanometric particle sizes were determined for each sample with scanning electron microscopy (SEM), therefore, information about surface homogeneity was obtained. For the microstructural characterization, quantitative elemental analysis was performed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS), and stoichiometric ratios of atomic compositions were identified. By evaluating the data obtained from the microscopic and spectroscopic measurements, the effect of the atomic concentration parameter on the morphological properties of the material was determined. The usability of the produced binary fluoride alloy thin film coatings is promising for emerging optoelectronic, ceramic industry, biomedical and surface acoustic wave applications.

Atomic scale smoothing of nanoscale quartz mold using amorphous carbon films

Abstract Surface roughness control of end products is increasingly becoming significant, especially with the miniaturization trends in the semiconductor industry. Ultra-thin amorphous carbon (a-C) films offer a prime solution to optimize surface roughness due to their outstanding characteristics. In this study, hydrogenated a-C films are deposited on two-dimensional quartz plates and three-dimensional quartz molds to evaluate the growth mechanisms and changes in the surface roughness, which is supported by molecular dynamics simulations. Results reveal that surface roughness encounters multiple variations until it reaches stable values. These fluctuations are categorized into four different stages which provide a concrete understanding of various growing mechanisms at each stage. Different behavior of the atoms in the top layers is recorded in the cases of normal and grazing incidents of carbon atoms. Lower surface roughness values are obtained at low-angle deposition. Interestingly, surface smoothing is attained on the sidewalls of the nanotrench mold where the deposition occurs with high incident ion angles.

Experimental investigation of the distribution patterns of micro-scratches in abrasive waterjet cutting surface

The existence of striations, and scratches in Abrasive waterjet (AWJ) cutting surface necessitates an exploration of these features for enhancing the cutting accuracy of AWJ machining. This article investigates surface roughness and micro-scratch morphology characteristics on brass cutting surfaces. According to the variation law of surface roughness values, the cutting section can be divided into three regions: the initial region, smooth region, and rough region. Numerous micron-scale scratches were observed in the cutting section. The scratch length, width, and depth values all show an increasing trend as the cutting depth increases, with the scratch length experiencing the greatest growth and variability. The influence of position and traverse speed on scratch size was studied using variance analysis. Furthermore, the length and width of the scratches on the cutting surface are significantly influenced by their position, accounting for 89.19% and 81.13%, respectively. Traverse speed had a minor effect on scratch length and width, accounting for 0.01% and 2.64% respectively. The depth of the scratches is influenced by their position on the cutting surface at a rate of 41.12%, while traverse speed had an impact of 38.10%. Finally, a mathematical method based on standard scores was proposed to assess the quality of the cutting section based on micro-scratch dimension.

Comparative Analysis of Surface Roughness and Plastic Deformation of Reciprocating Instruments after Clinical Use.

This study assessed the surface topography and plastic deformation (PD) of new and used contemporary reciprocating instruments. Twenty-six WaveOne Gold (WOG) and EdgeOne Fire (EO) instruments were photographed under magnification. The instruments were randomly assigned to a control group of new instruments preserved for surface roughness analysis (n = 6 each), or to an experimental group to shape the root canal system of a single molar (n = 20 each), making a total of four groups (WOGnew, EOnew, WOGused, EOused). Used instruments were also photographed after instrumentation. The presence of fractures was registered. Preoperative and postoperative images were randomly ordered for evaluation. Two blinded calibrated examiners evaluated the presence of PD. Inter-observer agreement was calculated with the Kappa coefficient (K = 0.89). 3D profilometry was also used for the surface roughness analysis of six randomly selected instruments from the WOGused and EOused groups. Chi-square and two-way ANOVA tests were used to, respectively, compare PD and changes in surface roughness among the groups. No instruments fractured; however, a significantly greater percentage of EO instruments suffered plastic deformation than WOG instruments (p < 0.001), (OR = 11.09 (CI 95% 2.6-56.3)). The overall surface roughness was higher for most parameters in the EO instruments (p < 0.05). Single uses of EO instruments produced significantly higher chances of PD and increased surface roughness values compared to WOG.

The effect of laser therapy for the treatment of dentin hypersensitivity on surface roughness and bacterial adhesion

The aim of the study was to measure the degree of dentine surface roughness caused by five distinct lasers used to treat dentine hypersensitivity, as well as to evaluate the subsequent bacterial colonization on these irradiated surfaces. Sixty human maxillary premolar teeth without caries or restoration which were extracted for periodontal reasons were used in this study. Five different types of lasers were applied to the root dentin surface. Tested samples were divided into six groups of 10 samples each; control, diode (810 nm), diode (980 nm), Nd: YAG, Er: YAG, and Er, Cr: YSGG laser groups. The arithmetic mean of the surface roughness values (Ra) and the average roughness over a measurement area (Sa) were measured pre- and post-application using any of the laser types. Swab samples were then collected from the dentin surface. Following a 24-hour incubation period at 37 °C, the colony forming units were counted using a stereoscope. The results demonstrated a statistically significant difference in the surface roughness values pre- and post-application (Ra and Sa, respectively) in the Er, Cr: YSGG laser group (p = 0.037,p = 0.007). No significant difference was observed in the other groups (p > 0.05). There was no statistically significant difference in the number of bacterial colonies observed between the test and control groups. Diode and Nd: YAG lasers showed either a decrease or no change in surface roughness; however, the hard tissue lasers (Er: YAG, Er, Cr: YSGG) showed an increase. The Er: YAG and Nd: YAG laser groups exhibited decreased bacterial adhesion compared to the other groups.

Investigation of open air and under water laser surface texturing on surface roughness and wettability of Al-Mg alloy

Aluminum-Magnesium (Al-Mg) alloy is widely used in aerospace and marine related applications due to its high corrosion resistance, tensile strength and ductility properties. However, due to hydrophilic nature, its applications are restricted in areas where water absorption may cause problems like corrosion. In this research work, high speed laser texturing was carried out on Al-Mg alloy (AA5754) to improve hydrophobic properties of the material surface. Four different types of pattern, namely lines, grids, concentric circles and concentric rectangles were created on the material surface using a nanosecond fiber laser. Scanning speed was varied at two levels i.e., 500 mm/s and 1000 mm/s. Line density of texture designs was also varied at two levels of 10 lines per mm and 15 lines per mm. The texturing process was carried out in two different processing environment namely open air and in underwater condition. Distilled water with 1 mm thickness above the surface was used during underwater texturing condition. Surface morphology, surface roughness and wettability of all the surfaces were studied for all the experimental conditions. It was observed that lower scanning speed of 500 mm/s resulted in higher values of surface roughness and contact angles. Also, larger texture density leads to lower surface roughness and contact angles for all the pattern designs. Among all the studied texture patterns, grid structures, textured at 500 mm/s of scanning speed resulted in largest surface roughness and surface hydrophobicity.

Surface roughness of different types of resin composites after artificial aging procedures: an in vitro study

BackgroundThe temperature changes, chemical agents, and brushing activity that resin composite restorations are exposed to in the oral environment can cause changes in surface roughness. In this study, the aim was to investigate in vitro the clinical one-year surface roughness changes of different types of composites (flowable or conventional) from the same companies by subjecting them to immersion in solutions, brushing, and thermal cycling procedures to simulate intraoral conditions.MethodsFour different resin composite brands were included in the study using both their conventional (Charisma Smart, 3M Filtek Ultimate Universal, Omnichroma, Beautifil II) and flowable resin composites (Charisma Flow, 3M Filtek Ultimate Flowable, Omnichroma Flow, Beautifil Flow Plus F00), giving 4 groups with 2 types of resin composite in each. 40 samples were prepared for each group/resin type, for a total of 320 samples. After initial surface roughness measurements by a mechanical profilometer, the samples were divided into 4 subgroups (n = 10) and immersed in solutions (distilled water, tea, coffee, or wine) for 12 days. The samples were then subjected to 10,000 cycles of brushing simulation and 10,000 cycles of thermal aging. Surface roughness measurements were repeated after the procedures. For statistical analysis, the 3-way analysis of variance and the Tukey test were used (p < 0.05).ResultsIt was concluded that composite groups and types had an effect on surface roughness at time t0 (p < 0.001). At time t1, the highest surface roughness value was obtained in the Beautifil-conventional interaction. When the surface roughness values between time t0 and t1 were compared, an increase was observed in the Beautifil II and Beautifil Flow Plus F00, while a decrease was observed in the other composite groups.ConclusionComposite groups, types, and solutions had an effect on the surface roughness of resin composites. After aging procedures, it was concluded that the Beautifil group could not maintain the surface structure as it exceeded the threshold value of 0.2 μm for bacterial adhesion.

Fabrication and growth mechanism of Al-Si coatings deposited on Mo substrate by hot dip plating technology

The Al-Si coatings with a low surface roughness were deposited on Mo substrate via the hot-dip plating technology, and the effects of deposition parameters on the microstructure, phase composition and surface roughness were systematically investigated. The results show that the hot-dip Al-Si coating is consist of a Mo(Si, Al)2 inner layer and an Al(Si)-Mo(Si, Al)2 outer layer. The coating surface is composed of Si(70.21–92.66 at%)-Al alloy phase containing Mo (Si, Al)2 grains and Al(73.83–92.32 at%)-Si alloy phase. With the increase of deposition temperature and the extension of time, the average grain area of Mo (Si, Al)2 increases from 0.264 μm2 to 0.623 μm2. The coating surface becomes smoother with the increase of deposition temperature, while rougher with the time. The maximum and minimum average surface roughness(RSa) values of the coating are 0.847 and 0.431μm, respectively. The coating thickness increased with the increase of deposition temperature and times. When the deposition temperature is 1000 ℃, the thickness value of the Mo (Si, Al)2 layer of the coating increases in a parabolic law with deposition time, and the Kp(reaction rate constant) is 4.5 ×10−13 m2/s. The growth of coatings is essentially a process of depositing Al, Si elements in the form of Mo (Si, Al)2 intermetallic compounds on Mo substrate.

DEVELOPMENT AND PERFORMANCE EVALUATION OF A MODEL CUTTING FLUID DEVELOPED FROM SHEA BUTTER OIL

This research was carried out to develop a model cutting fluid from Shea Butter oil and evaluate its performance in relation to temperature and surface roughness when compared to a commercial cutting fluid. The effectiveness of the cutting fluid was evaluated on a mild steel using a turning operation on the lathe machine. Temperature variations during the turning operation were measured using an infra-red gun thermometer while surface roughness was evaluated by employing a surface roughness tester. In this work Taguchi method was used to guide the selection of machine parameters such as cutting speed (rev/min), feed rate (mm/rev), and depth of cut (mm). Using Minitab, the cutting temperature and resulting surface roughness were measured for both the developed cutting and commercial fluids. The results obtained for the average cutting temperature of ~ 30oC and overall surface roughness value of 0.32μm for shea butter oil show a significant difference from that of ~ 35oC and 0.47 μm respectively for commercial grade cutting fluids. These results show that the shea butter oil-based cutting fluid not only exhibits great potential but also surpasses the current capabilities of commercial cutting fluids in terms of its cooling and surface finishing performances.

STUDY OF INNER AND OUTER POCKET CHARACTERISTICS USING AREA ROUGHING METHOD

Pocket milling is one of the CNC milling processes. This research aims to analyze the characteristics of pocket milling using Area Roughing on surface roughness and machining time. The method applied is experimental research on the Area Roughing method for working on inner and outer pockets. Research variables include depth cut 0.5, 1, 1.5, and 2 mm, stepover percent 40, 50, and 60%. The test is in the form of surface roughness value, while the analysis of the machining process is the time during the milling process. The workpiece material is 2024 aluminum and a flat endmill tool with a diameter of 12 mm. The expected result is the parameter that has the most optimal value for the processing time and surface roughness value. So it can be a guide for milling processes, especially those that use Area Roughing. The machining results show that the faster machining time results from larger settings for depth cut and stepover percent. Average machining time increase of 28%. Meanwhile, the surface roughness value will increase as the depth cut and stepover settings increase, namely 17.65% for the outer pocket and 18.61% for the inner pocket. The surface roughness value of the ordering results ranges from 2.4-4.8 µm.

Examination of Surface Hardness and Roughness of AISI 1050 Steel Material in Milling Based on Surface Processing Conditions

It is known that material hardness and surface conditions have a significant impact on the operating life of machine elements working with each other. In this study, Surface roughness values obtained depending on processing conditions and hardness changes on the machined surfaces during milling of AISI 1050 steel were examined. In experimental studies, ideal machining conditions were determined by taking into account surface roughness values and hardness changes using the Taguchi L18 experimental design method. In all experiments, it was observed that the lowest surface hardness was achieved under dry conditions when 6500 1/min speed, 4000 mm/min feed rate, and 0.4 mm cutting depth values were applied. When the speed increased from 5500 1/min to 6000 1/min and the feed rate increased from 4500 mm/min to 5000 mm/min, improvements in surface quality were observed in both machining conditions. In conclusion; In experiments where coolant was applied at high cutting speeds, it was determined that surface hardness and surface roughness values were higher than in dry machining conditions.

The effect of simulated food liquids on the surface structure and solubility of various esthetic restorations

Aims: The aim of this study is to investigate the surface roughness and solubility of restorative materials when exposed to foodstuffs in the oral environment using simulated food liquids as defined by the Food and Drug Administration. Methods: In this study, a total of four esthetic restorative materials were used: one universal compomer (Dyract XP, Dentsply), one conventional microhybrid composite (FiltekTM Z250, 3M ESPE), one nanofilled, and one high-viscosity glass ionomer cement (ChemFil Rock, Dentsply). A total of 160 samples, each 8 mm in diameter and 2 mm in thickness, were prepared using molds. The initial weights of the samples were recorded in micrograms using a precision balance to determine solubility values. Initial surface roughness values were measured using an atomic force microscope device. The samples were immersed in four different simulated food liquids (ethanol, heptane, citric acid, and distilled water) for a period of 7 days. After removal from the solutions, the samples were desiccated to a constant weight, and the second set of weights was recorded. Subsequently, the second surface roughness values were measured Results: Among the materials immersed in the simulated food solutions, ChemFil Rock exhibited the highest solubility and increase in surface roughness. Citric acid was found to be the solution that caused the highest increase in surface roughness values and solubility for this material (p