Papers by Keyword: Roughness

Abstract: Removable dentures aim to improve masticatory function, esthetics and phonetics. Different materials have been used as denture base materials but poly(methyl methacrylate) (PMMA) is most frequently used in most countries. Surface related properties of denture base materials (roughness, surface free energy, wettability, hydrophobicity, etc.) are of clinical importance since they affect plaque accumulation and staining. Surface roughness specifically influences the adhesion and retention of Candida Albicaans, which has a particular importance in denture-induced stomatitis pathogenesis. Bacterial plaque retention directly affects oral hygiene even if the patient achieves an appropriate cleaning of the denture. Ideally, denture base materials should be smooth so plaque adherence is reduced or even avoided. Test specimens of four heat polymerized materials were obtained by a classical press-pack dough molding technique of 1.5 mm thick wax-plate flasked in class III Moldano followed by the recommended polymerization regime. One of the materials was processed through a fast polymerization cycle. Injection-type materials were automatically produced using a dedicated injection unit. All plates were sectioned in 10 mm x 10 mm samples. No finishing protocol was applied. The selected specimens were examined under field emission scanning electron microscope (SEM). A large variation of surface topography was recorded between materials. There were visual differences between the four heat polymerized resins but also between the two injection-type materials. Surface topography was also influenced by the polymerization regime. Within the limitations of our study, we found that surface topography is influenced by the chemical composition of each material, the heat cure cycle and the processing method.

Abstract: Titanium alloy is finding increased application in aeronautical, automobile and structural applications. During post processing of titanium alloy, milling is one of the mostly used machining processes. In this study, the relationship between temperature and milling parameters was developed by response surface methodology (RSM), and a temperature model for milling titanium alloy is proposed. The model is found to be adequate through ANOVA. The result indicates that the increase in cutting speed and feed rate increases the temperature. The radial depth of cut and depth of cut do not show a general trend on temperature in milling of titanium alloy.

Abstract: The surface acoustic wave (SAW) technique is a precise and nondestructive method to detect the mechanical characteristics of the precision-machined surface. The paper is concerned with the effect of the roughness of the machined surface on the dispersion of surface acoustic waves propagating in the precision-machined surface which indicates mechanical characteristics of the machined surface. The finite element method (FEM) is employed by establishing a series of models with different roughness Ra value to analyze influences from different roughness Ra value on surface acoustic wave dispersion. The models are established by applying a combined method based on fractal theory and wavelet analysis. The simulation results showed that the roughness of machined surface will cause the dispersion of surface acoustic wave propagation, the effect varies with the different roughness Ra values. A critical Ra value influencing on the surface acoustic wave propagation exists. Accordingly, that the factor of roughness should be considered in advance or not, the situation can be determined through studying and determining the critical roughness Ra value above mentioned. Consequently, the study has the important meaning regarding the detection for mechanical characteristics of the machined surface.

Abstract: The effect of substrate surface roughness on the wettability of SAC237 (Sn 99.9%, Ag 0.3%, Cu 0.7%) with difference percentage of CNT on copper substrate was investigated. Solder paste of SAC 237 without CNT, 0.01% and 0.04% of CNT were reflowed at 270°C on different surface roughness of Cu substrate (abrasive number 240, 400, 600, 800). Contact angle of soldered samples measured by Infinite Focus Microscope (IFM). As a result, contact angle value of investigated solders range 7° to 20°. Contact angle obtained decreases with the increasing surface roughness of Cu substrate. This demonstrates that rougher substrate enhance the wettability of the solders. Addition of CNT also effects the wettability of investigated solders. Higher composition of CNT show better wettability.

Abstract: The present paper examines the influence of the tribofinishing process on the surface state of steel parts XC48, while taking into account the variation in hardness and mass. The tribofinishing process is a mechanical-chemical process, which comprises the use of low frequency impact vibration in the presence of abrasive and chemical additives [1]. The treatment regime (frequency and amplitude) has a great influence on geometrical, mechanical and metallographic treated surfaces. The improvement of the surface quality is determined as a function of the treatment time from 30 to 240 minutes. The tribofinishing process has many technical and economic advantages for the treatment of mechanical parts of simple and complex shapes, which have a better surface finish and improved life of parts etc.

Abstract: In the paper a new method has been proposed for the determining of the very fine machining uniformity over the elaborated surface and could be applied to different machined materials and machining procedures. The proposed methodology is relatively simple and is essentially formulated in the few subsequent steps: taking surface roughness 3D profile accordingly proposed scheme; estimation of the roughness statistical parameters: R_p, R_v, R_t, R_a, R_q, R_skew, R_kurt, and if need be – surface rugosity Ru; calculation of the centroid of the obtained data due to the measurement fields, calculation of the barycentre of the obtained data with the weighting variable chosen for the appropriate evaluation of the surface machining uniformity. As the main Cartesian coordinates of the centroid calculation we propose (R_skew, R_kurt), although other data organization schemes have also been provided as the example solutions. The final evaluation of the surface machining uniformity is based upon the Euclidean distance between the centroid and barycentre of the surface roughness data. The proposed method has been applied to experimental results obtained with the AFM technique used on samples of the polished AZ31 magnesium alloy. The surface machining procedure comprised of four stages performed with using different abrasive media, finally lead to the highest grade of the surface roughness.

Abstract: Turning is a utilized machining work. It is performed with a large types of tools adapted for required geometries. If starting from a full blank, a drilling operation is called in the beginning. In that case, the number of utilized tools increased. The use of a multifunctional tool for drilling followed by bore turning is an efficient solution. In this research, the case of single insert multifunctional tool is studied. The paper describes the quality of the surfaces obtained by using of this tool. The general idea is to verify the use of only one multifunctional tool for execution of all operations, from full drilling to finished surface. This was made by measuring the roughness Ra in three experiments with different materials: titanium, stainless steel and low carbon steel. Performed experiments lead to the idea of a recommended limit for feed speed to obtain a roughness Ra value below 0.8μm. This limit depends with the material type, but for some materials, it seems impossible to achieve this value!

Abstract: This study presents an integrated approach to the teaching of surface metrology and the regulation of electrochemical polishing process control parameters. The electropolishing processes permits different ranges of surface finish through different combinations of the process parameters of current density (J) and electropolishing time (t), and students must have a sound knowledge of the procedure for selecting filters (λ_s, λ_c, λ_f). Thus, experimental trials are undertaken to establish the influence of current density (J) and electropolishing time (t) on surface finish by measuring the arithmetic average roughness parameter (Ra), and setting the filters and measurement procedure for each range of surface finish. The integrated learning of both disciplines enables students to consolidate their knowledge on the methodology for measuring surface roughness (Ra), and to establish direct correlations between variation in process control parameters and the surface finish obtained by characterizing the behaviour of the process.

Abstract: The Al-brasses are considered corrosion resistant construction materials often used to pipe systems in energy industry, where they are exposed to flowing liquids environments. In that system the brasses are loaded chemically and mechanically. The aim of our research work is to compare corrosion properties of four Al-brasses produced by different manufactures because in operation conditions they have dissimilar reliability and durability. The examined Al-brasses have similar chemical composition but differ in microstructure, surface state what affects their corrosion and mechanical properties. The effect of the mentioned parameters on corrosion and mechanical susceptibility to degradation are investigated by chosen experimental methods.

Abstract: Grinding is currently still an important method for surface finishing. At FPTM JEPU is realized the research, which deals with this issue. There are carried out experiments with grinding various materials under different conditions and then are evaluated the selected components of the surface integrity, which are generally roughness Ra, Rz, Rt and Rmax, material ratio curve (Abbott Firestone curve) and also obtained roudness. This article deals with grinding nickel alloy Inconel 718, when selected cutting grinding conditions were used and subsequently the surface roughnesses Ra, Rz, Rt and Rmax were measured and evaluated.