Materials Science Forum Vols. 727-728

Abstract: Modern engineering problems are often composed by a large number of variables that must be chosen simultaneously for better design performance. The optimization of phenomenological model is an impossible task in terms of computational time. To improve this disadvantage, the Response Surface Methodology (RSM), defined as a collection of mathematical and statistical methods that are used to develop, to improve, or to optimize a product or process, is configured as important alternative to model real process. In the literature, different approaches based on optimization methods have been proposed to design system engineering. In this context, the Differential Evolution algorithm (DE) is a stochastic optimization method that is based on vector operations to improve a candidate solution with regard to a given measure of quality. For illustration purposes, in the present contribution the DE is applied to optimize multiple correlated responses in a turning process. As a case study, the turning process of the AISI 52100 hardened steel is examined considering three input factors: cutting speed, feed rate and depth of cut. The outputs considered were: the mixed ceramic tool life, processing cost per piece, cutting time, the total turning cycle time, surface roughness and the material removing rate. The optimization of cutting speed, feed rate and depth of cut indicate the better configuration of process to minimize the cost.

Abstract: The nanocomposites are hybrid materials where at least one of the components has nanometric dimensions and in the same way as traditional composites are formed, one of the components is the matrix in which nanoparticles are dispersed. One of the possibilities of applications of nanocomposites is to obtain polymer films for applications in the barrier, or separation promoted by the dispersion of the clay lamellae. In this work, nanocomposites of nylon 6/bentonite clay were obtained by melt intercalation. The used clay was the Brasgel PA, and quaternary ammonium salt was Praepagen-HY, used in organophilization of the clay. By XRD, it was observed the disappearance of the characteristic peak of clay, and this can be facilitate the possible exfoliation of clay in the produced films from the nanocomposite. By SEM, it was observed, an apparently dense layer with no pores.

Abstract: The process of diamond synthesis using metal as a catalyst-solvent is a great method of industrial production by using high pressures and high temperatures. Several aromatic hydrocarbons are already studied for the process of graphitization of carbon, many have already been tried for use as raw materials for diamond synthesis. The graphitization of anthracene was carried out at a pressure of 3Gpa at a temperature of 1000°C. The graphite was produced in mixed Ni-Mn alloy for diamond synthesis process at a pressure of 4.5 GPa at a temperature of 500° to 1300°C. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were used to characterize the transformation of graphite into diamond produced with anthracene starting at high pressures and high temperatures. The results of this study show that there is a diamond shape through an aromatic hydrocarbon at high pressures and temperatures with a catalyst-solvent process.

Abstract: The time-dependent viscosity is a desirable feature in drilling fluids. The gel formation process during circulation stops avoid the settling of particles generated by the drill bit, keeping the solids in suspension in the annular space. However, when larger particles breakdown the gel strength, interfere in the recovery of circulation, causing operational problems such as stuck pipe and other drilling complications. Within this context, this study evaluated the main factors that affect fluid-gel properties or the gelling process. Understanding the factors that influence the rheological behavior of drilling fluids was possible to estimate the settling velocity of particles during oil well drilling. Non-newtonian solutions were prepared with water and xanthan gum with mass concentration of 0.2%. The results showed that the gelation of xanthan gum solutions showed a rapid and non-progressive gelling as desired for drilling fluids.

Abstract: During oil well drilling processes in reservoir-rocks, the drilling fluid invades the formation, forming a layer of particles called filter cake. The formation of a thin filter cake and low permeability helps to control the drilling operation, ensuring the stability of the well and reducing the fluid loss of the liquid phase in the interior of the rocks. The empirical determination of the constitutive equation for the stress in solids is essential to evaluate the filtration and filter cake formation in drilling operations, enabling the operation simulation. In this context, this study aims to evaluate the relationship between the porosity and stress in solids of porous media composed of bridging agents used in drilling fluids. The concentration distribution in sediments was determined using a non-destructive technique based on the measure of attenuated gamma rays. The procedure employed in this study avoids the use of compression-permeability cell for the sediment characterization.

Abstract: The filtration operation is one of the most widely used procedures in gas-solid separation due to its high removal efficiency, low cost and low sensitivity to variations in operating conditions. Therefore, the objective of this work is to study the effects of operating variables (pressure drop, filtration velocities and cleaning velocity) on the formation of filter cakes using gas-solid polypropylene filter media and particulate matter as for instance phosphate rock. The filtration velocities evaluated were 5, 7.5 and 10 cm/s with maximum pressure drops of 100, 200, 300 and 400mm H₂O and filter cleaning velocities of 15 cm/s by the reverse air flow method. The cake filtration porosity was estimated using the classical Ergun equation (1952) in the literature. The results led to important correlations for the use of fibrous filters in the removal of particles suspended in in micrometer aerosols.

Abstract: Conventional rotary dryers are used in many industrial sectors. The present work analyzes the drying of granulated fertilizers in a non-conventional dryer. The major characteristic of this new dryer is the presence of an aerated system consisting of a central pipe from which a series of mini-pipes conduct the hot air directly to the particle bed that is flowing at the bottom. This work has tested several diameters of mini pipes and the better experimental results were obtained with mini pipes of 9 mm.

Abstract: Hydrocyclones use the same principle of separation of centrifuges, but with no moving parts and no mechanical complexity. For these reasons as well as its versatility in applications, low cost, simple operation, small size, high production efficiencies with short residence times, these devices have been widely found in industry, and even suggested as a practical alternative to solid-liquid separations involving biological material. In the process of fermentation to produce ethanol, the yeast Saccharomyces cerevisiae are recovered and recycled to a new stage of fermentation. This separation process is a major challenge, because the yeasts are small and low density. In this sense, the objective of this work was to investigate the use of hydrocyclones for the separation of yeast from alcoholic fermentation. A factorial experimental design (2⁴) was applied and the results were used to determine empirical mathematical model that describes the reduced separation efficiency as a function of different geometrical and operating variables.

Abstract: This work aimed on the granulometric characterization of flotation products and to analyze the effect of the variables (that were investigated in a flotation work) on the particle size distribution parameters. Besides to compare the parameter values of the granulometric analysis for the concentrate and tailing both results were compared with the parameter values of the flotation feed samples. The analyzed parameters showed lower values for the concentrate products as compared with the parameters for tailing and feed samples. For coarse and fine particle size fractions the column height was the variable that more influenced on the parameter values.

Abstract: The application of polyamides is limited by low impact performance when notched in room temperature conditions. This situation is worsening, especially for use in temperatures below zero degrees Celsius. One way to outline this limitation is to prepare polymer blends where the dispersed phase is an elastomer, and then classified as an immiscible blend. Therefore, this study aims to develop polyamide 6/waste styrene-butadiene rubber (SBR) blends, with addition of compatibilizer PP-g-MA and PE-g-MA in order to achieve a balance between stiffness and tenacity. The results obtained with the rheological study showed that mixtures of PA6/PE-g-MA presented the best results in comparison with mixtures of PA6/PP-g-MA, indicating that there was probably a reaction between the components, which may allow a better dispersion and thus can achieve better properties.