Arithmetic Average Roughness Research Articles

Optimization of machining parameters in face milling using multi-objective Taguchi technique

In this research, the effect of machining parameters on the various surface roughness characteristics (arithmetic average roughness (Ra), root mean square average roughness (Rq) and average maximum height of the profile (Rz)) in the milling of AISI 4140 steel were experimentally investigated. Depth of cut, feed rate, cutting speed and the number of insert were considered as control factors; Ra, Rz and Rq were considered as response factors. Experiments were designed considering Taguchi L9 orthogonal array. Multi signal-to-noise ratio was calculated for the response variables simultaneously. Analysis of variance was conducted to detect the significance of control factors on responses. Moreover, the percent contributions of the control factors on the surface roughness were obtained to be the number of insert (71.89 %), feed (19.74 %), cutting speed (5.08%) and depth of cut (3.29 %). Minimum surface roughness values for Ra, Rz and Rq were obtained at 325 m/min cutting speed, 0.08 mm/rev feed rate, 1 number of insert and 1 mm depth of cut by using multi-objective Taguchi technique.

Wrinkle reduction using a topical herbal cream in subjects with greater yin (Tae- eumin) type: A randomized double-blind placebo-controlled study

IntroductionSkin aging can be caused by both intrinsic and extrinsic factors. Ultraviolet (UV) radiation is the primary environmental factor which causes skin aging. Sasang constitutional medicine(SCM) is a unique type of traditional Korean medicine. In SCM, patients are treated with herbal drugs categorized according to their Sasang constitutional type based on the Yin-Yang theory. Scutellaria baicalensis and Raphanus sativus are herbal drugs exclusively used for Tae-eumin (TE)-type subjects. These drugs are constituents of the TE formula, which is effective for managing skin diseases such as urticaria and acne. This study investigated the potential of S. baicalensis and R. sativus (SR) herbal mixtures as active ingredients in wrinkle-care cosmetics. MethodsThe expression of matrix metalloprotease-1 (MMP-1) was measured in vitro with significant difference (p < 0.05). A 12-week placebo randomised double blind controlled trial was conducted to evaluate the safety and clinical efficacy of a cream containing SR mixtures for application to human skin. Women between the ages of 43 and 58 years who were TE-type subjects according to SCM were selected and cream containing SR mixtures was applied for 12 weeks. ResultsThe application of SR mixtures showed there was a significant improvement in both visual assessment and evaluation of wrinkle parameters (Rt; skin roughness, Rm; maximum roughness, Rz; average roughness, Rp; smoothness depth, and Ra; arithmetic average roughness) comparing the treatment group with the control group (p < 0.05). ConclusionsThe results of this study indicate that the cream containing SR mixtures may improve skin wrinkles in TE-type subjects.

IMPROVED PROPERTIES OF SnO2 THIN FILMS OBTAINED VIA SPIN COATING METHOD BY VARYING THE SOLUTION CONCENTRATION

The aim of this work is to study the solution concentration effect on the SnO2 thin film properties, which were deposited on glass substrates by spin coating technique and annealed for one hour at 500[Formula: see text]C. X-ray diffraction (XRD) spectra show that the films deposited at various solution concentrations (0.5[Formula: see text]mol/L, 0.7[Formula: see text]mol/L and 1[Formula: see text]mol/L) are polycrystalline with a tetragonal rutile type. Grains have two preferred orientations along the directions (110) and (101) corresponding to 2[Formula: see text] equal to 26.74[Formula: see text] and 34.11[Formula: see text], respectively. We have also noted that the grain size changes between 109[Formula: see text]nm and 178[Formula: see text]nm. However, the film coated at 10 deposition cycles and 0.7[Formula: see text]mol/L solution concentration has a minimum arithmetic average roughness of 0.376 nm. The optical transmittance of the films in the visible spectrum was in the range of 77–84% and the optical band gap gradually decreases with the decrease of the solution concentration from 4.11[Formula: see text]eV to 3.56[Formula: see text]eV.

Experimental investigations and empirical modeling for optimization of surface roughness and machining time parameters in micro end milling using Genetic Algorithm

Surface finish is a predominant requirement of a micro part inorder to perform satisfactory function. It is dependent on process variables such as cutting conditions, tool and work material properties, etc. In this work, an effort has been taken to propose realistic machining conditions for process improvement in micro end milling for C360 Copper alloy material. Solid Tungsten Carbide flat end mill cutter of size 700 µm and 800 µm are chosen as the tool material. Response surface methodology was incorporated for Design of experiments. First, experimental investigation was carried out to examine the effect of process condition include spindle speed and feed rate on Arithmetic Average Surface Roughness (Ra) and machining time values and also uncertainty in measured values. Analysis of variance was performed to establish the significant effect of cutting conditions on response values. Empirical model has been developed by experimental results using regression techniques in order to frame the fitness function. Parameters optimization for fine surface finish with minimum machining time has been carried out using Genetic Algorithm (GA). Confirmation experiments were carried out to validate the correctness of GA result and micro channels are fabricated successfully.

Analysis of enamel surface roughness after different adhesive removal techniques for orthodontic bracket debonding

The objectives of this study were to explore traditional resin removal procedures in the debonding process and evaluate the Er:YAG laser as a plausible option. Sixty premolar teeth were bonded with brackets. Then, brackets were removed and five adhesive clean-up methods were tested against control teeth: (a) Er:YAG laser at 200 mJ and 20 Hz; (b) Er:YAG laser at 305 mJ and 10 Hz; (c) 20-fluted flame-shaped tungsten carbide bur at high-speed; (d) #8-fluted round tungsten carbide bur at low-speed; and (e) #5 round end tapered fine diamond bur at high speed. Quantitative measurements including average (Avg) profile height, total indicator run-out (TIR), arithmetic average roughness (Ra), and time were made using profilometry. Qualitative evaluation of tooth surfaces was done using SEM. The two laser settings produced a statistically higher TIR, Ra, and time compared to the controls (P < 0.001). There was no statistical difference between the three bur techniques in regards to surface texture or time. Qualitatively, the 20-fluted carbide bur left the smoothest surface. The Er:YAG laser at the tested settings would not be appropriate for adhesive removal. The interaction of the Er:YAG wavelength under these conditions was not comparable to the 20-fluted flame-shaped tungsten carbide bur at high speed for orthodontic adhesive removal leaving a smoother enamel surface.

Effect of surface roughness of trench sidewalls on electrical properties in 4H-SiC trench MOSFETs

The effects of the surface roughness of trench sidewalls on electrical properties have been investigated in 4H-SiC trench MOSFETs. The surface roughness of trench sidewalls was well controlled and evaluated by atomic force microscopy. The effective channel mobility at each measurement temperature was analyzed on the basis of the mobility model including optical phonon scattering. The results revealed that surface roughness scattering had a small contribution to channel mobility, and at the arithmetic average roughness in the range of 0.4–1.4 nm, there was no correlation between the experimental surface roughness and the surface roughness scattering mobility. On the other hand, the characteristics of the gate leakage current and constant current stress time-dependent dielectric breakdown tests demonstrated that surface morphology had great impact on the long-term reliability of gate oxides.

Relationship between Er,Cr:YSGG laser power and surface roughness of lased radicular dentin.

Background: This study sought to assess the effect of Er,Cr:YSGG laser power on the surface roughness of lased radicular dentin using atomic force microscopy (AFM). Methods: Fifteen human radicular dentin samples were randomly divided into five groups: one control (G1, intact) and four experimental groups treated with 0.25W (G2), 0.5W (G3), 0.75W (G4) and 1W (G5) powers of Er,Cr:YSGG laser (2.78µm) at a repetition rate of 20 Hz, with a 600-µm-diameter sapphire tip. After irradiation, surface topography was analyzed by AFM using a Si probe in tapping mode. Quantitative information concerning the arithmetic average roughness (Ra) and quadratic mean roughness (Rq) was obtained from three 5×5µm areas of each sample. The data were analyzed using one-way ANOVA (P<0.05). Results: The Ra and Rq values increased in G2 and G5 and decreased in G3 and G4 groups compared to the control group. The maximum Ra and Rq values were noted in G5, which were significantly higher than the corresponding values in G3 (P<0.05). Conclusion: No direct correlation was found between Er,Cr:YSGG laser power and surface roughness of lased radicular dentin. Laser therapy with a mean power of 0.5W and 1W caused the lowest and highest surface roughness, respectively.

Multi-objective statistical analysis and optimisation in turning of aluminium matrix particulate composite using genetic algorithms

Material removal processes are fundamental manufacturing operations from which high quality parts are produced and see service in a great variety of industrial applications. In this study, a multi-parameter design of experiments, using Taguchi method, has been conducted to investigate the optimum cutting conditions in turning of 316-L stainless steel flakes (SSF) reinforced aluminium matrix. Cutting speed and feed rate were treated as the independent variables in a L9 Taguchi orthogonal array addressing three levels each, while depth of cut was kept constant. Pre-selected quality objectives, reflecting surface quality and process productivity (arithmetic average roughness, Ra and machining time, Tm), were examined. Regression models were formulated to predict the aforementioned quality objectives and taken as a common fitness function for optimization through a genetic algorithm. The results obtained demonstrated that the application of the genetic algorithm used, is quite promising in identifying the optimal process parameters to effectively machine AMPCs.

Finish machining-induced surface roughness, microhardness and XRD analysis of selective laser melted Inconel 718 alloy

Selective laser melting (SLM) is one of the most commonly used additive manufacturing (AM) techniques to manufacture metal components; however, during building process partially melted powders and/or pores on the outer surface of metallic parts results in very high surface roughness and eventually poor surface quality of components manufactured by selective laser melting. Thus, post-processing is needed to improve surface quality and also control subsurface characteristics. Hence, this study presents the effects of finish machining process on surface integrity characteristics including surface roughness, microhardness and XRD analysis of selective laser melted (SLMed) Inconel 718 alloy. In machining process of SLMed Inconel 718 alloy, the effect feed rate on measured outputs was also examined. Besides, the role of cold air on surface integrity characteristics was also presented in this study. This study reveals that arithmetic average surface roughness of as-built SLMed Inconel 718 can be lowered more than 90% with finish machining post processing operation. Increased feed rate results in work hardening on the surface and subsurface and eventually microhardness of surface and subsurface increases notably as compared to as-built SLMed Inconel. Finish machining process deeply influences XRD patterns of SLMed Inconel 718 alloy.

Theoretical models for surface roughness in turning considering inclination and rake angles

New analytical four-parameter models for surface roughness are proposed based on the feed rate, nose radius as well as the inclination and rake angles. These models were derived to determine the maximum peak-to-valley roughness Rt and arithmetic average roughness Ra using homogeneous transformation matrices and are verified by digital simulation. The model for Rt was used to study two sequential effects of introducing the inclination and rake angles. The Rt and Ra values obtained from the four-parameter models and the existing two-parameter models, based on nose radius and feed rate, were compared. The comparison shows maximum percentage differences of 8.18% and 10.98% in Rt and Ra, respectively. The results demonstrate that the inclination and rake angles can influence the surface roughness by affecting the tool-workpiece contact geometry. The proposed four-parameter model can be employed for a more accurate theoretical surface roughness evaluation compared to the existing two-parameter models.

Theoretical models for surface roughness in turning considering inclination and rake angles

New analytical four-parameter models for surface roughness are proposed based on the feed rate, nose radius as well as the inclination and rake angles. These models were derived to determine the maximum peak-to-valley roughness Rt and arithmetic average roughness Ra using homogeneous transformation matrices and are verified by digital simulation. The model for Rt was used to study two sequential effects of introducing the inclination and rake angles. The Rt and Ra values obtained from the four-parameter models and the existing two-parameter models, based on nose radius and feed rate, were compared. The comparison shows maximum percentage differences of 8.18% and 10.98% in Rt and Ra, respectively. The results demonstrate that the inclination and rake angles can influence the surface roughness by affecting the tool-workpiece contact geometry. The proposed four-parameter model can be employed for a more accurate theoretical surface roughness evaluation compared to the existing two-parameter models.

Influence of surface residual stresses on the fatigue life and crack propagation behavior of turned Inconel 718 super-alloy

The effects of surface roughness parameters and residual stresses induced by finish turning on fatigue life and crack propagation behavior of Inconel 718 super-alloy are investigated. A criterion serving as a good indicator of surface quality is also discovered. This is carried out for some specific turning conditions in order to control surface characteristics including surface roughness and the bi-axial state of surface residual stresses and to investigate the effects of these characteristics on fatigue behavior. Rotating bending fatigue (RBF) tests are performed on the machined specimens at room temperature. Characterization techniques including X-ray diffraction (XRD), laser confocal microscopy, and opto-digital microscopy are used to investigate surface residual stresses in axial (ARS) and hoop (HRS) directions, surface roughness, and secondary fatigue cracks, respectively. The huge dispersion in fatigue life of smooth turned Inconel 718 with very low arithmetic average roughness (Ra) values indicates that surface finishing is not the only reliable criterion for quality control of machined components. Multivariate statistical analyses show that axial surface residual stress is the most important surface characteristic affecting the fatigue life of machined Inconel 718 for the conditions tested. Changing ARS from compressive to tensile increases the number of secondary cracks and also decreases the fatigue life of turned specimens.

Influence of surface roughness of additive manufacturing polymer on surface flashover voltage

In recent years, additive manufacturing has been one of the most noteworthy technologies in the industry segment comprising high-voltage engineering and insulating materials. In this study, the influence of the surface roughness of an additive manufacturing polymer on the surface flashover voltage is investigated. We prepared two types of sample plate having the same volume resistivity and surface resistivity but different surface roughness by changing the building orientation (horizontally built and vertically built) of a 3D printer. By surface profile measurement and analysis of the arithmetic average roughness, it was revealed that the vertically built sample plate has a groove-like structure on the surface. Furthermore, it was shown that the surface flashover voltage in the direction perpendicular to the groove structure is about 20% times larger than in the parallel direction. In addition, it became clear that the relationship between the surface flashover voltage and the inter-electrode distance is well expressed in a flashover model in vacuum.

Mechanical and tribological behavior of Ti/TiN and TiAl/TiAlN coated austempered ductile iron

Bilayer Ti/TiN and TiAl/TiAlN coatings were deposited onto austempered ductile iron (ADI) substrates by cathodic arc deposition in an industrial device. Structure and mechanical properties of the coated samples were comparatively examined. Wear behavior of the coated samples was investigated in comparison with uncoated ADI by means of rolling contact fatigue (RCF) tests, performed in a flat washer type testing rig and using lubricated pure rolling conditions. RCF tests results were analyzed using the two-parameter Weibull distribution and the Weibayes method.The results indicate that TiN and TiAlN coatings grew with a cubic-NaCl type structure. The arithmetic average roughness of the coated samples is similar for both coating variants. The surface hardness and residual stresses are higher for the TiAl/TiAlN coated samples. The coating hardness and elastic modulus are also higher for TiAl/TIAlN. The critical loads at massive delamination and the evolution of the friction coefficients are quite similar for both coating variants. Regarding RCF, failures in coated samples were characterized by substrate spalling. No massive delamination was observed in Ti/TiN and TiAl/TiAlN coatings. The statistical analysis indicates that the deposition of Ti/TiN improves noticeably the RCF resistance of ADI while the deposition of TiAl/TiAlN does not produce significant changes. The properties mismatch between substrate and coating seems to play an important role in the RCF behavior of coated samples, since Ti/TiN coatings possess a lower mismatch with respect to ADI substrates as compared to TiAl/TiAlN.

Effect of anti-corrosive performance, roughness and chemical composition of pre-treatment layer on the overall performance of the paint system on cold-rolled steel

Many fundamental researches about the effect of some basic properties of a pre-treatment layer, such as anti-corrosive performance, surface roughness and chemical composition on the overall performance of paint systems were investigated. Three kinds of pre-treatment layers: bare polyacrylic acid (PAA) layer, Mo based layer and Mo doped PAA layer were deposited on cold-rolled steel surfaces through immersing the steel samples in the corresponding solution. The electrochemical measurements results indicated that after been treated in PAA solution, the steels became vulnerable to corrosion and the Mo based layer and Mo doped PAA layer could improve the corrosion resistance of steel to a certain degree. The values of root-mean-square roughness of the bare steel, bare PAA layer, Mo based layer and Mo doped PAA layer were 15.0nm, 11.3nm, 13.0nm and 59.1nm, respectively. The corresponding values of arithmetic average roughness of the samples were 16.9nm, 10.5nm, 9.1nm and 41.0nm, respectively. The spectroscopy results indicated that the surface of the bare PAA and Mo doped PAA layer covered steels contained abundant COOH groups and the composition of Mo based layer covered steel surface was mainly oxides. According to the impact test and neutral salt spray test results, the corrosion mitigation performance, microstructure and chemical composition of the pre-treatment layer could all affect the overall performance of the paint system. All the results indicated that the anti-corrosive performance was not the only index, the microstructure and chemical composition also needed to be considered in the development of a new generation pre-treatment layer.

Comparison of tool life and surface roughness with MQL, flood cooling, and dry cutting conditions with P20 and D2 steel

Minimum quantity lubrication (MQL) is a cutting fluid (CF) application method that has given promising results in improving machining performances. It has shown that, the performance of cutting systems, depends on the work and tool materials used. AISI P20, and D2 are popular in tool making industry. However, the applicability of MQL in machining these two steels has not been studied previously. This experimental study is focused on evaluating performances of MQL compared to dry cutting, and conventional flood cooling method. Trials were carried out with P20, and D2 steels, using coated carbides as tool material, emulsion cutting oil as the CF. Tool nose wear, and arithmetic average surface roughness (Ra) were taken as response variables. Results were statistically analysed for differences in response variables. Although many past literature has suggested that MQL causes improvements in tool wear, and surface finish, this study has found contradicting results. MQL has caused nearly 200% increase in tool nose wear, and nearly 11-13% increase in surface roughness compared flood cooling method with both P20 and D2. Therefore, this study concludes that MQL affects adversely in machining P20, and D2 steels.

Reducing surface roughness by varying aerosol temperature with minimum quantity lubrication in machining AISI P20 and D2 steels

Heat generation in metal cutting leads to numerous problems. Despite the development of many different cooling and lubrication methods in industry, opportunities are still open to develop novel methods. Minimum quantity lubrication (MQL) is a recent such development that has shown promising results. However, the effect of aerosol temperature on machining performance has not yet been studied in depth. Thus, the aim of this study is to explore the ability to improve surface roughness in machining by lowering the MQL aerosol temperature. To study the effect of the aerosol temperature in MQL, an experimental investigation is carried out using a simple turning operation on AISI P20 and D2 steels, with cutting tools and cutting fluids (CF) typically used in industry. The arithmetic average surface roughness of the workpiece is measured for each of the treatments. Measurements are taken with dry cutting condition, conventional flood cooling method, and several MQL temperatures. Significantly lower surface roughness in the workpieces is observed for all considered MQL temperatures in comparison to dry cutting and flood cooling conditions. Furthermore, a reducing trend with a quadratic behaviour in surface roughness is observed with decreasing temperatures. The lowest surface roughness is observed at MQL 5 °C for both material. Interestingly, the effect of aerosol temperature is observed to be high with D2 steel and lower temperatures achieved up to 50% reduction in surface roughness. The study concludes that surface roughness can be reduced using low-temperature MQL. The effect of the aerosol temperature on other tool-work material combinations and tribology studies are suggested as further work.

Modeling surface roughness for polishing process based on abrasive cutting and probability theory

ABSTRACTThe surface roughness is a variable used to describe the quality of polished surface. This article presents a surface roughness model based on abrasive cutting and probability theory, which considers the effects of abrasive grain shape, grit and distribution feature, pressure on surface roughness. The abrasive grain protrusion heights are thought to close to Gaussian distribution, and then the relationship between the indentation depth and the pressure based on Hertz contact theory is obtained. Surface roughness prediction model is established by calculating indentation depth of the abrasive grains on workpiece surface. The maximum surface profile height (Ry) is approximately equal to the maximum indentation depth of the abrasive grain. The arithmetic average surface roughness (Ra) is equal to the average indentation depth of the abrasive grain. The effects of process parameters such as pressure and grit on Ry and Ra were simulated and analyzed in detail.

Fracture, roughness and phase transformation in CAD/CAM milling and subsequent surface treatments of lithium metasilicate/disilicate glass-ceramics

This paper studied surface fracture, roughness and morphology, phase transformations, and material removal mechanisms of lithium metasilicate/disilicate glass ceramics (LMGC/LDGC) in CAD/CAM-milling and subsequent surface treatments. LMGC (IPS e.max CAD) blocks were milled using a chairside dental CAD/CAM milling unit and then treated in sintering, polishing and glazing processes. X-ray diffraction was performed on all processed surfaces. Scanning electron microscopy (SEM) was applied to analyse surface fracture and morphology. Surface roughness was quantitatively characterized by the arithmetic average surface roughness Ra and the maximum roughness Rz using desktop SEM-assisted morphology analytical software. The CAD/CAM milling induced extensive brittle cracks and crystal pulverization on LMGC surfaces, which indicate that the dominant removal mechanism was the fracture mode. Polishing and sintering of the milled LMGC lowered the surface roughness (ANOVA, p < 0.05), respectively, while sintering also fully transformed the weak LMGC to the strong LDGC. However, polishing and glazing of LDGC did not significantly improve the roughness (ANOVA, p > 0.05). In comparison of all applied fabrication process routes, it is found that CAD/CAM milling followed by polishing and sintering produced the smoothest surface with Ra = 0.12 ± 0.08µm and Rz = 0.89 ± 0.26µm. Thus, it is proposed as the optimized process route for LMGC/LDGC in dental restorations. This route enables to manufacture LMGC/LDGC restorations with cost effectiveness, time efficiency, and improved surface quality for better occlusal functions and reduced bacterial plaque accumulation.

Atmospheric deposition process for enhanced hybrid organic–inorganic multilayer barrier thin films for surface protection

In this study, organic polymer poly-vinyl acetate (PVA) and inorganic aluminum oxide (Al2O3) have been used together to fabricate a hybrid barrier thin film for the protection of PET substrate. The organic thin films of PVA were developed through roll to roll electrohydrodynamic atomization (R2R-EHDA) whereas the inorganic thin films of Al2O3 were grown by roll to roll spatial atmospheric atomic layer deposition (R2R-SAALD) for mass production. The use of these two technologies together to develop a multilayer hybrid organic-inorganic barrier thin films under atmospheric conditions is reported for the first time. These multilayer hybrid barrier thin films are fabricated on flexible PET substrate. Each layer of Al2O3 and PVA in barrier thin film exhibited excellent morphological, chemical and optical properties. Extremely uniform and atomically thin films of Al2O3 with average arithmetic roughness (Ra) of 1.64nm and 1.94nm respectively concealed the non-uniformity and irregularities in PVA thin films with Ra of 2.9nm and 3.6nm respectively. The optical transmittance of each layer was∼80-90% while the water vapor transmission rate (WVTR) of hybrid barrier was in the range of∼2.3×10−2gm−2day−1 with a total film thickness of∼200nm. Development of such hybrid barrier thin films with mass production and low cost will allow various flexible electronic devices to operate in atmospheric conditions without degradation of their properties.