Variation Of Surface Roughness Research Articles

Influence of Tool Rotation and Surface Roughness on the Shear Strength of Nylon 6 - SS 304 Dissimilar Joint Resulted by Friction Lap Welding

This research was conducted to investigate the effect of variations in tool rotation and surface roughness towards shear strength on the newly developed friction lap welding (FLW) for dissimilar joints between stainless steel (SS) 304 and Nylon 6 plates. Under constant welding traverse speed at 30 mm/min, the variation of tool rotation used were 1100 and 2200 rpm and surface roughness of 0.32; 1.25; and 1.88 μm initially obtained from different surface modification methods. The shear test was conducted at FLW dissimilar joint based on AWS D8.9-97 standard. The results showed that the shear stress increased along with the higher tool rotation and at the greater surface roughness. The highest shear strength value was found at the tool rotation of 2200 rpm and surface roughness of 1.88 μm with 9.447 MPa. The tool rotation may produce a higher heat input as well as an effect on the value of nylon hardness. On the other hand, rougher SS surfaces provide a larger area for the interfacial adhesive bond between nylon and metal; therefore, they can act as an interlocking site when the shear loading was applied. These phenomena were also confirmed by fracture morphology and microscopic image analysis.

Experimental Study and Analysis of Fretting Wear and its Influence on Functionality of Mechanical Components

Fretting occurs when there is tangentially low-amplitude vibrational motion (range tens of nanometres to tens of micrometers) between nominally stationary contact surfaces. This is a common occurrence as most machines are exposed to vibration both in transit and in operation. Contacts that appear to have no relative movement, such as press-fit, can actually slide on a scale of 1 μm with alternating pendulum loads. It is very difficult to eliminate such movements and the resulting friction. Fretting wear and frictional fatigue occur on almost every machine and otherwise cause a total failure of robust components. Studies have shown that, in contrast to other forms of wear, the frequency of machine fit problems has not diminished in the last few decades. Experiments were conducted on a fretting wear testing machine of amplitude range 10–200 μm, frequency range 4–120 Hz and surface roughness were recorded for both polished and unpolished condition. The correlation was made between changing parameters and variation in surface roughness. Friction fatigue is an important but almost unknown factor when load-bearing components are damaged at very low loads. Therefore, we will conduct an experimental study of fretting and its control parameters. For unpolished specimen, the variation of amplitude with respect to the coefficient of friction (COF) increases to 0.5, then it becomes linear. For semi-polished specimen, it increases to COF 0.45 and then it starts decreasing. For a fully polished specimen, there is no change in COF to 75 μm and then it starts increasing. According to the experimental data, for all specimens’ COF constantly decrease with increasing the load.

Optimization of Machining Parameters in Mild Steel Turning Operation by Response Surface Methodology

A lot of process variables affect the surface roughness obtained in turned machine parts. One of these variables is bearing clearance. However, there is limited information on the influence of bearing clearance on surface integrity. This paper is an optimization study in which the surface roughness of AISI 1018 mild steel is minimized with the aid of the response surface methodology. In this paper, the effect of process parameters like cutting speed, feed, depth of cut, and bearing clearance is analyzed to ascertain how the surface finish properties of mild steel can be improved. The design of the experiment used for this study involves a rotatable central composite system. This design is used to find the experimental results of machining. The analysis of variance (ANOVA) was used to determine the statistical significance of the improved quadratic model developed. The numerical and graphical optimization carried out determined the optimum values of each of the parameters used in different ways. From the ANOVA, it was revealed that the most significant factor in the model was the depth of cut. This factor was closely followed by spindle speed, bearing clearance, and feed, respectively. Numerical optimization results employing the desirability function showed optimum values to be at bearing clearance of 70um, depth of cut of 2.5mm, feed of 0.01mm/rev, and a spindle speed of 450rpm. The result obtained using the graphical optimization option was similar to the results from the other options. The variation of surface roughness with the process parameters chosen for the experiment was mathematically modeled. The model developed used the response surface methodology, and it was validated with a set of experimental values. The result from the exercise undertaken revealed that the predicted values of the surface roughness were very close to measured values. The average percentage deviation of 6.20% for all sample data utilized showed that the model developed was in close agreement with the experimental results.

Chemical and Structural Assessment of New Dental Composites with Graphene Exposed to Staining Agents.

Among the newest trends in dental composites is the use of graphene oxide (GO) nanoparticles to assure better cohesion of the composite and superior properties. Our research used GO to enhance several hydroxyapatite (HA) nanofiller distribution and cohesion in three experimental composites CC, GS, GZ exposed to coffee and red wine staining environments. The presence of silane A-174 on the filler surface was evidenced by FT-IR spectroscopy. Experimental composites were characterized through color stability after 30 days of staining in red wine and coffee, sorption and solubility in distilled water and artificial saliva. Surface properties were measured by optical profilometry and scanning electron microscopy, respectively, and antibacterial properties wer e assessed against Staphylococcus aureus and Escherichia coli. A colour stability test revealed the best results for GS, followed by GZ, with less stability for CC. Topographical and morphological aspects revealed a synergism between GZ sample nanofiller components that conducted to the lower surface roughness, with less in the GS sample. However, surface roughness variation due to the stain was affected less than colour stability at the macroscopic level. Antibacterial testing revealed good effect against Staphylococcus aureus and a moderate effect against Escherichia coli.

Thermoreflectance-based approach for surface temperature measurements of thin-film gold sensors.

A novel thermoreflectance-based diagnostic tool capable of visualizing spatial and temporal changes in surface temperature is presented. The method uses narrow spectral emission bands of blue [λ = 405nm with 10nm full-width-at-half-maximum (FWHM)] and green (λ = 532nm with 10nm FWHM) light to monitor the optical properties of gold and thin-film gold sensors, relating changes in reflectivity to temperature through a known calibration coefficient. The system is made robust to tilt and surface roughness variations through the simultaneous measurement of both probing channels with a single camera. Experimental validation is performed on two forms of gold materials heated from room temperature to 200 °C at a rate of ∼100 °C/min. Subsequent image analysis shows perceptible changes in reflectivity in the narrow band of green light, while the blue light remains temperature-insensitive. The reflectivity measurements are used to calibrate a predictive model with temperature-dependent parameters. The physical interpretation of the modeling results is given, and the strengths and limitations of the presented approach are discussed.

Effects of Automotive Test Parameters on Dry Friction Fiber-Reinforced Clutch Facing Surface Microgeometry and Wear-Part 3 Tribological Parameter Correlations and Simulation of Thermo-Mechanical Tribological Contact Behavior.

Correlations among previously determined tribological properties, such as the coefficient of friction values, wear and surface roughness differences of hybrid composite dry friction clutch facings are revealed after pin-on-disk test apparatus examinations under three pv loads, where samples are cut from a reference, unused, and several differently aged and dimensioned, used-according to two different trends: dry friction fiber-reinforced hybrid composite clutch facings. In 'normal use' facings, increasing specific wear trend is detected as a function of activation energy according to a second-degree function, while a logarithmic trend line can be fitted to the values of the clutch killer facings, showing that even at low activation energy levels, significant (~3%) wear occurs. The specific wear rate also varies as a function of the radius of the friction facing, with the relative wear values measured on the working friction diameter being higher regardless of the usage trend. In terms of surface roughness variation measured in the radial direction, normal use facings show a varying roughness difference according to a third-degree function, while clutch killer facings follow a second-degree or logarithmic trend depending on the diameter (di or dw). From the statistical analysis of the steady-state, we find three different clutch engagement phase characterizing pv level pin-on-disk tribological test results for the specific wear of the clutch killer and normal use facings, and significantly different trend curves with three different sets of functions were obtained, showing that the wear intensity can be described as a function of the pv value and the friction diameter. In terms of radial direction surface roughness difference, the values of clutch killer and normal use samples can be described by three different sets of function showing the effects of the friction radius and pv.

Mechanical properties of laser powder directed energy deposited NASA HR-1 superalloy: Effects of powder reuse and part orientation

The feasibility of NASA HR-1 powder reuse for laser powder directed energy deposition (LP-DED) of thin-walled structures in the as-built surface condition was investigated in this study. Although continuously reusing the powder five times slightly reduced the number of fine particles in the powder and increased the mean particle size, changes in powder rheological properties were negligible. The similarities in powder flow between all reused conditions resulted in no variation in surface roughness, defects’ size and spatial distributions, and microstructure of the as-deposited parts and, thus no differences on tensile and fatigue properties. The effects of different specimen orientations, loading direction being perpendicular or parallel to the building direction, on mechanical properties were also investigated. While no change in tensile strength was noted, tensile ductility was lower for the parallel specimens because of surface micro-notches being perpendicular to the loading direction, which led to an early onset of fracture. Due to accelerated crack initiation from these micro-notches, parallel specimens were also less resistant to fatigue failures. The fatigue failures always initiated from the specimen surfaces, and all specimens experienced a ductile fatigue crack growth mechanism characterized by clear striations on the fracture surface.

Self-powered visible transparent mathrm{Cu}/{mathrm{Zn}}_{left(1-xright)}{mathrm{Sn}}_{left(xright)}mathrm{O} Schottky-based ultraviolet photosensors fabricated via DC magnetron sputtering

Visible transparent mathrm{Cu}/mathrm{n}-mathrm{ZnO} and mathrm{Cu}/{mathrm{Zn}}_{left(1-xright)}{mathrm{Sn}}_{left(xright)}Oleft(x=0.14right) mathrm{TZO}, Schottky junctions were successfully fabricated on ITO-coated glass substrates via direct current magnetron reactive sputtering method. The structural, morphological, optical, and electrical properties were thoroughly investigated. The polycrystalline nature of the samples was confirmed by XRD studies. FESEM images validate the changes in surface morphology after doping and annealing, and AFM analysis confirmed the variation in surface roughness. The electrical analysis reveals the presence of a Schottky barrier in the fabricated devices. In dark condition, three-order rectification ratio was observed. A two-order increase in leakage current was also observed after illuminating 365 nm UV light of power 60 µW/cm2. The figures of merits of sensors, such as responsivity, detectivity, response speed, and linear dynamic range, were thoroughly investigated. The fabricated sensor had a responsivity of about 07.80 mA/W and a detectivity of 1.39 × 1011 Jones. At zero bias, the sensor also demonstrated a transient photocurrent response of approximately 783 ms for rise and 876 ms for fall. Similarly, 33.70 dB of linear dynamic range was observed. These findings suggests that Cu/TZO Schottky diodes could be useful for self-powered, visible transparent UV photosensors in next-generation optoelectronic devices.

The effects of surface roughness on the calculated, spectral, conical–conical reflectance factor as an alternative to the bidirectional reflectance distribution function of bare sea ice

Abstract. The conical–conical reflectance factor (CCRF) has been calculated as an alternative to the bidirectional reflectance distribution function (BRDF) for three types of bare sea ice with varying surface roughness (σ= 0.1–10) and ice thicknesses (50–2000 cm) over an incident solar irradiance wavelength range of 300–1400 nm. The comprehensive study of the CCRF of sea ice presented here is paramount for interpreting sea ice measurements from satellite imagery and inter-calibrating space-borne sensors that derive albedo from multiple multi-angular measurements. The calculations performed by a radiative-transfer code (PlanarRad) show that the CCRF of sea ice is sensitive to realistic values of surface roughness. The results presented here show that surface roughness cannot be considered independently of sea ice thickness, solar zenith angle and wavelength. A typical CCRF of sea ice has a quasi-isotropic reflectance over the hemisphere, associated with a strong forward-scattering peak of photons. Surface roughness is crucial for the location, size and intensity of the forward-scattering peak. As the surface roughness increases, a spreading of the CCRF peak is observed. The hemisphere was split in to 216 quadrangular regions or quads. The peak remains specular for the smaller surface roughnesses (σ=0.001 to σ=0.01), whereas for larger surface roughness features (above σ=0.05), the peak spreads out over multiple quads with a lower intensity than for smaller roughness features, and the highest value is displaced further out on the solar principal plane. Different types of sea ice have a similar pattern with wavelength: the CCRF increases by 30 % from first-year sea ice to multi-year sea ice at 400 nm and up to 631 % at 1100 nm, 32 % from melting sea ice to multi-year sea ice at 400 nm and a maximum of 98 % at 900 nm, and 11 % from melting sea ice to first-year sea ice at 400 nm and up to 86 % at 800 nm. The CCRF calculations presented in this study form the first set of complete CCRF values as an approximation of the BRDF for bare sea ice with a wide range of configurations.

Study on Adhesion Properties and Process Parameters of Electroless Deposited Ni-P Alloy for PEEK and Its Modified Materials

Polyetheretherketone (PEEK) and its fiber-reinforced materials are thermoplastic polymer materials with broad application prospects. Depositing Ni-P alloy on them can improve their poor conductivity and electromagnetic shielding performance, and further expand their application field. The application effect of the plated parts is significantly impacted by the bonding strength between PEEK and coating. The bonding strength between non-metallic substrate and coating is largely influenced by the surface characteristics of the substrate. Therefore, it is significant to study how the surface roughness of PEEK materials and the modified fibers in materials affect the adhesion of the coating. In this study, Ni-P alloy was electroless deposited on PEEK, 30% carbon-fiber-reinforced PEEK (CF30/PEEK), and 30% glass-fiber-reinforced PEEK (GF30/PEEK) with varying surface roughness. The influence of surface roughness and modified fibers on the coating adhesion was studied. Additionally, the effect of the concentrations of nickel sulfate, sodium hypophosphite, pH, and temperature on the deposition rate of the coating was investigated for the three materials. Based on the highest deposition rate, the process parameters were then optimized. The results demonstrated that as surface roughness increased, adhesion between substrate and coating first increased and then decreased. The surface roughness Ra of 0.4 μm produced the highest coating adhesion. Additionally, fiber-reinforced PEEK adhered to coatings more effectively than PEEK did. The mechanism of the difference in bonding strength between different PEEK-modified materials and coatings was revealed. The optimal process parameters were: nickel sulfate: 25 g/L, sodium hypophosphite: 30 g/L, pH: 5.0, and temperature: 70 °C.

Karakteristik Sifat Mekanik Hasil Pengelasan Gesek Aluminium dengan Tembaga Menggunakan Variasi Kecepatan Putar dan Kekasaran Permukaan Kontak

Friction welding is a type of welding that is used for a variety of materials. Friction welding is a method of joining two materials by swiping them together until they reach some of the melting points of the materials to be joined, then applying constant pressure. Aluminum and copper are the materials to be joined in this study. Using rotational speed and contact surface roughness variations. The purpose of this research is to determine the mechanical properties of friction welding results between aluminum and copper. The speed settings are 1230, 1500, and 2500 rpm. Use sandpaper grades #100, #800, and #1500 to achieve different levels of surface roughness. According to the results of this study, the rotational speed with the highest tensile strength and hardness values is 1230 rpm, namely 59.6 MPa and 54.6 HVN (Al), 112.1 HVN (Al) (Cu). In terms of surface roughness variations, the surface roughness using grade #1500 sandpaper has the highest value, namely 54.18 HVN (Al), 112.1 HVN (Cu). And #100 sandpaper with a value of 52.48 Mpa. The results of the microstructure test in the weld joint area at a magnification of 1000x indicated that the friction welding of aluminum and copper was successful, as evidenced by the diffusion of aluminum and copper in this area.

Investigation on the effect of machining parameters on 42CrMo4 DPS steels

Machining 42CrMo4 martensite—ferrite dual phase steel is challenging due to its high hardness and it is essential to determine the favorable requirements for the optimum machining condition. The ability to alter the martensite quantity in dual phase structure of steel leading to variation in bulk hardness is the motivation for machinability investigation. In heavy duty machining, the determination of tool life and surface roughness at various conditions of machining plays an important role in the manufacturing industry. In the present work, machinability tests are carried out on 42CrMo4 martensite—ferrite dual phase steel to assess the tool life and surface roughness. Speed, feed, and depth of cut are varied in different levels. The tests are carried out as per the full factorial method. A microstructure study is performed to correlate the various mechanical properties with phase morphology. The main objective of this study is to obtain the optimized machining process parameters for the turning operation of 42CrMo4 martensite—ferrite dual phase steel. All cutting tests are carried out under dry conditions using a carbide insert. Microstructure and mechanical property analysis shows an increase in the martensite quantity with the increase in the dual phase processing temperature. From the ANOVA results, it is found that the depth of cut is the major contributing factor to the variation of tool life and surface roughness within the range of values considered for the study. Microstructure analysis revealed the distribution of ferrite and martensite phases evenly. The optimum combination of machining parameters is calculated for obtaining a superior combination of tool life and surface roughness. The 42CrMo4 DPS steel may be used for structural applications with wide variation in the property range.

Fluorinated Polyimide/Sepia Eumelanin Nanocomposites for Aerospace Applications

Natural marine sepia eumelanin-derived additives (ASE) were used as a filler to modify highly fluorinated polyimide (FPI), acquiring the enhanced comprehensive performance by chemical bonding and pore structure construction. Stress–strain curves indicated an optimal tensile strength of 108.25 MPa and a fracture elongation of 4.83% (1 wt % ASE), respectively, 1.30 and 1.34× that of pure FPI. Thermal analysis showed that Tg was as high as 360.1, 14.4 °C higher than that of pristine FPI. The exceptional UV-shielding capabilities of the FPI/ASE films were confirmed by measurements of curcumin photodegradation, durability, and so on. FTIR and AFM manifested their superior photostability with basically unchanged carbonyl absorption peaks and much less variation in surface roughness after UV exposure for 720 h. To sum up, the covalent network structure between FPI and ASE contributed to the improvement of mechanical and thermal properties. The mechanisms, such as synergistic UV absorption of FPI and ASE, photothermal conversion, and ASE’s free radical trapping ability, were responsible for the remarkable UV-shielding and light stability. The above remarkable comprehensive performance makes the FPI/ASE film a candidate for UV shielding in aerospace applications.

Improved tensile properties, stable microstructures and isotropic deformation of nanocrystalline 304 stainless steel

The tensile properties of nanocrystalline 304 stainless steel plate (NSSP-304) produced by severe rolling technology and its conventional polycrystalline 304 stainless steel (CPSS-304) counterpart were studied at room temperature. The microstructures of fractured NSSP-304 and CPSS-304 were characterized. NSSP-304 had enough ductility (elongation 34.5%), larger strengths, elastic strain and the reduction of area despite its smaller volume fraction of strain-induced α′-martensite (SIM) and no obvious work hardening. The deformation of NSSP-304 was more isotropic, its microstructures were more stable and homogeneous during tensile process due to the following results about fractured NSSP-304: (1) the narrower variation amplitude of surface micro-hardness along and perpendicular tensile directions; (2) the smaller void density and few surface micro-cracks; (3) the smaller surface roughness and roughness variation, and their narrower fluctuation ranges at three directions; (4) only micro-cracks without macro-cracks around NSSP-304 fracture; (5) its smaller volume fraction of SIM. The voids in CPSS-304 initiated around MnS inclusion, at grain boundaries, triple junctions, the boundaries of austenite and martensite phases, and in the two phases. They became micro-cracks within their original positions and macro-cracks by passing through different grains. The voids in NSSP-304 initiated at grain boundaries, triple junctions and the boundaries of the two phases. They became micro- and macro-cracks by passing through different grain boundaries. The MnS inclusion in NSSP-304 scarcely influenced its tensile deformation. The fracture mechanisms of NSSP-304 and CPSS-304 were the intergranular fracture, and the mixture of intergranular and transgranular fracture respectively.

Mechanical Properties, Biocompatibility and Antibacterial Behaviors of TaO0.2N0.8 and TaO0.2N0.8-Ag Nanocomposite Thin Coatings

TaOx = 0.2Ny = 0.8 was reported previously to have the highest modulus (E), hardness (H), and H to E ratio attributed to the embedment of substituting oxygen atoms in the TaN crystal structure, among some TaOxNy coatings studied. In the present study, TaO0.2N0.8-Ag nanocomposite coatings were fabricated by reactive multi-target sputtering with O/N ratio adjusted to the expected value. The various Ag contents were doped to induce antibacterial behaviors. After deposition and annealing with rapid thermal process (RTP) at 400 °C for 4 min, the coatings’ mechanical and structural properties were studied. After these examinations, the samples were then studied for their cell attachment, cell viability, and biocompatibility with 3-T-3 cells, as well as for their antibacterial behaviors against Escherichia coli. It appeared that hardness and crack resistance could be improved further with suitable amount of Ag doped to the coatings, followed by rapid thermal annealing treatment. The coating with 1.5 at. % Ag had the highest hardness and good H/E ratio. It was also found that the antibacterial efficiency of TaO0.2N0.8-Ag coatings could be much improved, comparing with that of TaO0.2N0.8 coatings. The antibacterial efficiency increased with the increased Ag contents. There was no negative effect of Ag on the biocompatibility of TaO0.2N0.8-Ag. Through the cell attachment and viability testing using MTT(3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, it can be summarized that surface roughness could be the dominating factor for cell viability and attachment, which means the improvement of biocompatibility. Accordingly, the samples with 1.5 at. % and 11.0 at. % Ag show the best biocompatibility. The variation of surface roughness was affected by the incorporation of Ag and oxygen atoms after rapid thermal annealing.

Effects of machining parameters on H13 die steel using CNC drilling machine

In order to enhance the fitness of the product and in order to improve productivity in turning operations, greater amount of challenges have been faced. In this paper, we have made a comparative analysis of HSS and carbide coated HSS drills while machining with H13 steel plates. For the drilling operation, process parameters were analysed using the Taguchi design of experiments. The response performance characteristics of surface roughness of H13 die steel plates for the drilling settings, cutting speed (rpm), and feed rate (mm/min) is optimized. The design of the experiment was conducted using the Taguchi technique for the L18 orthogonal array, and an analysis of variance was observed. The effect of drilling settings on the quality of drilled holes is examined; variation in surface roughness for various levels of speed and feed and the different combinations of these levels will form an L18 orthogonal array design of experiment by Taguchi analysis. A total of 36 cutting tests were performed with two different drill bits; here three different cutting speeds of 300, 600, and 900 rpm were taken with a feed rate of 0.02, 0.04, and 0.06 mm/rev combinations. The response of SN ratio for surface roughness of HSS and carbide tool has been found out for different levels of speed and feed. From this Taguchi analysis, it is identified that the optimal parameter. As a result, the factors are analysed, and optimized parameters have been concluded for H13 material using HSS, and carbide tools were examined both statistically and experimentally. The carbide coated drill bit gives 60% better surface roughness value based on experimental data obtained. The surface roughness value based on experimentation for HSS tool was found to be 34.16% and carbide coated drill bit was 23.40%.

An Evaluation of the Colour Stability and Surface Roughness of High Translucency Zirconia Dental Ceramic after Immersion in Different Acidic Media: An In-vitro Study

Introduction: Demand for increasingly appealing metal-free ceramic restorations drives research. With its exceptional mechanical and biological properties, zirconia crown outperforms other traditional ceramic materials. With outstanding mechanical and biological qualities, zirconia has several therapeutic applications. Temperature, environment, diet, and smoking habits all affect colour and surface roughness of dental restorations. Aim: To investigate the colour stability and surface roughness of high translucency monolithic zirconia following immersion in various acidic solutions. Materials and Methods: This in-vitro study was conducted at Yenepoya Dental College, Mangalore, Karnataka, India. Duration of the study was 6 months, from December 2019 to June 2020. Thirty rectangular samples from a CAD (computer-aided Design)/ Computer Aided Manufacturing (CAM) machined Zirconia blank with 10x8x1 mm dimensions was sintered at 1350°C, tested for colour stability (E) and surface roughness prior to immersion (R). Classified into Groups CO (coffee), TO (tobacco) and CA (citric acid medium). Colour stability and surface roughness were re-evaluated post immersion on all samples using spectrophotometers and profilometer respectively. A significant difference in surface roughness and colour stability between the test groups was assessed using the paired-t test. The data was analysed using Statistical Package for Social Sciences (SPSS) version 24.0. Results: Colour stability and surface roughness variations between the baseline value and three groups were found to be unaltered by different acidic media. The intergroup comparison of spectrophotometric analysis between the three groups had a standard deviation of 0.422 for citric acid medium, 0.316 for Coffee medium and 0.422 for Tobacco medium with an overall p-value of 0.804. The intergroup comparison of profilometric analysis had a standard deviation of 0.316 for Citric acid medium, 0.00 for Coffee medium and 0.00 for Tobacco medium with an overall p-value of 0.381. The paired-t-test study showed that immersion in different acidic media had little effect on surface roughness of samples with a p-value of 0.343 but it was under clinically acceptable range. Conclusion: According to the present study, high translucency monolithic zirconia had greater colour stability when treated with citric acid, followed by tobacco and then with coffee media, whereas, zirconia in coffee media had greater surface roughness, followed by tobacco, and then with citric acid media. However, both the results were clinically acceptable, indicating a 10 year lifespan when properly glazed.

Pattern Generation using Enamel Coating in Die-sinking EDM

Pattern generation on aluminium (Al)-6061 work surface is performed using green compacts of powder metallurgical (PM) made of copper-tungsten (Cu-W) tool. Compact load (CL) and peak current (Ip) are the variable process factors and surface roughness (Ra) and edge deviation (ED) are considered performance measures. The Ra is obtained in the range of 4.20 µm - 6.56 µm whereas ED is measured in the range of 17.29 µm - 68.98 µm. Field emission scanning electron microscope (FESEM), and energy disperse spectroscopy (EDS) are performed to validate tool particle migration on the pattern surface. It can be concluded that the performance measures depend upon the masking thickness, its resisting capacity to high temperature and the uniformity of the coating.

Using Lidar Digital Elevation Models for Reflectometry Land Applications

Lidar elevation maps are utilized in a bistatic electromagnetic scattering model of the Cyclone Global Navigation Satellite System over San Luis Valley in Colorado, USA. The results are compared with results generated using the Shuttle Radar Topography Mission (SRTM) 1 arcsecond global digital elevation model (DEM). The high resolution lidar maps are also used to generate maps of surface roughness at length scales finer than the horizontal resolution of SRTM. Model results using these maps illustrate the importance of the spatial variation of surface roughness on reflectometry signals. Results also highlight the shortcomings of using SRTM in scattering models and show improvements when a lidar DEM is used.

Effects of repeated home bleaching on the surface roughness of CAD-CAM restoration materials

Aim: This study aimed to investigate the effects of the repeated usage of a home-bleaching agent (16% carbamide peroxide) on the surface roughness of commonly used computer-aided design-computer-aided manufacture (CAD-CAM) restoration materials. Methodology: Five different CAD-CAM restoration materials were used in this study: feldspathic ceramic (Vita Mark II—Group VM II), leucite-reinforced glass ceramic (IPS Empress CAD—Group EMP), lithium disilicate-reinforced glass ceramic (IPS e.max CAD—Group EMAX), polymer infiltrated network hybrid ceramic (Vita Enamic—Group VE), and resin nanoceramic (Lava Ultimate—Group LU). A home-bleaching agent containing 16% carbamide peroxide was applied in three repeated periods (10 days, 20 days, and 30 days of exposure). A surface profilometer was used to determine the roughness average (Ra) values of the specimens. The data obtained were statistically analyzed using repeated measures of the analysis of variance (ANOVA) and Bonferroni post-hoc test at a 5% level of significance. Results: All materials exhibited a rougher surface after the first treatment period (10 days of exposure). The roughness of Group VM II continued to increase for up to 20 days. With the exception of Group LU, all groups exhibited a significantly rougher surface after 30 days of exposure compared to the baseline values (p < 0.05). The greatest variation in surface roughness was observed for the ceramic-based groups (VM II, EMP, and EMAX) rather than the hybrid groups (LU and VE). Conclusion: Patients with ceramic-based CAD-CAM restorations should be careful during home-bleaching treatment, especially when repeated applications are involved. Hybrid materials, particularly Lava Ultimate, seem more resistant to the effects of repeated bleaching cycles than ceramic-based materials. How to cite this article: Çölgeçen Ö, Köse M. Effects of repeated home bleaching on the surface roughness of CAD-CAM restoration materials. Int Dent Res 2022;12(3):143-8. https://doi.org/10.5577/intdentres.2022.vol12.no3.6 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.