Abstract: Microstructure, micro-hardness and wear properties of Aluminium-Zinc-Copper (Al-Zn-Cu) alloys of various chemical compositions are investigated. Stir casting process is used to prepare the various alloy compositions with permanent metallic mould. Six different alloy compositions were developed by varying Zn and Cu content in aluminium matrix. The wear and frictional properties were studied using Pin-on-Disc wear tester in dry sliding condition under normal atmosphere. The developed Al-Zn-Cu alloy has inter-metallic stable θ (CuAl2) phase in the inter-dendrite region and is due to the addition of Cu from 1 to 5 wt. % in 60Al-(40-x) Zn alloy. When the Cu composition increases up to 2 wt %, the corresponding hardness increases significantly and is due to the formation of Cu-rich θ phase and also due to the solid solution hardening of Cu in Al-Zn alloy matrix. But after 2 wt % Cu addition it is observed that the hardness increase is marginal. Wear rate (WR) and specific wear rate (SWR) were increases with increase of load and sliding velocity and decreases with Cu addition. Coefficient of friction (COF) remains constant for entire load and velocity for each alloy. However, when the alloys were tested at elevated temperatures, it was found that initially WR, SWR and COF decreases with temperature and then increases rapidly.
Abstract: This paper studied the effects of cellulosic and basic flux on the chemical composition, microstructure, formation of inclusions and micro hardness of X42 steel SMAW welds. The commercialized chemical compositions of flux used are: E6010, E8010-P1 and E8018-G, with electrodes of low carbon content. Welding conditions are not constant. The microstructure of the fusion zone for each flux consists mainly of acicular ferrite. It is found that manganese increases in the fusion zones (C, B and A) respectively .The change in mass concentration of manganese is homogeneous through the three points with all the used flux. Regardless of the flux used, the non-metallic inclusions observed are of two types: white and black. The micro-hardness decreasing values were obtained in the fusion zones (C, B and A).
Abstract: The Tafel extrapolation and linear polarization methods were used as effective measures for determining the corrosion susceptibility of a spheroidized 0.35%C steel with sea water as the electrolyte. Eight pieces of steel were machined to length 5mm by 10mm in diameter. Two pieces each were heat treated at 600°C, 700°C and 800°C respectively and two pieces left as control. Electro-chemical experiments were carried out to obtain the best potential and anodic current of samples immersed in an electrolyte (seawater) at varying anodic potential of-0.7mv, -0.6mv, -0.5mv and-0.4mv respectively. The results showed that the sample with the least corrosion rate were the samples spheroidized at 700°C. They appeared to have the highest electrode potential value of-0.6mv and 800°C spheroidized samples had the least electrode potential value of-0.65mv at the end of 2000seconds respectively. From the results obtained, the samples spheroidized at 700°C appeared to be most suitable for seawater environment.
Abstract: The growing need for building material resources, and the requirements to preserve the environment, in a vision of sustainable development, has become necessary to study reinforcement techniques, using composite materials. Using local organic or inorganic materials in construction fields and public works is particularly important. Polymer mortar composites (PMC) are usually employed in the building industry as finishing materials, tile adhesive (mortar-adhesive) or façade coating. In repair applications, the addition of soluble polymer (latex) allows improving the adhesion properties of the materials used as coating. The use of mineral additives as partial substitutes for cement, in construction sites as well as in ready-to-use mortars, is an unknown practice in our country. For this reason, we thought it is crucial to study and assess the influence of these additions on the properties of cured composite. Supplementary cementitious materials (SCM) used in this study are silica fume and natural pozzolan, which necessarily need to be valorized.The present research work aims to use a specific experimental methodology that is able to identify the relationship between the degree of substitution by the mineral additives, the polymer and the modifications to the properties of fresh and hardened cement mixtures. Therefore, five PMC combinations were formulated from different percentages of additions, i.e. natural pozzolan (NP: 25%w), silica fume (Sf: 5%w) and polymer latex (P: 0, 5, 7.5, 10, 12.5 and 15%w). Their durability factors, such as the porosity accessible to water and capillary absorption rate (sorptivity), were characterized, at different maturities. An attempt was also made to determine the thermal coefficients. The results obtained were compared with those of the reference mortars, made with Portland cement (CEMI). They showed that the decrease in porosity, sorptivity and thermal conductivity depends on the pair “SCMs/polymer”. But overall, the addition of polymer latex and pozzolanic additions have a beneficial effect on the durability and thermal properties of the composite materials.
Abstract: Reactive distillation, being an intensified process of combining reaction and distillation in a single vessel, is an ongoing research. This work considered the use of this novel process to investigate how the purity of a fatty acid methyl ester (oleic acid methyl ester – methyl oleate), which is an alternative fuel that has a potential economic bedrock, vary with variations in reflux ratio and reboiler duty with the aid of Aspen Plus model of the process. The column employed in developing the model of the process was a RadFrac type having 29 stages, which was divided into five sections, namely condenser (top), rectifying, reaction, stripping and reboiler (bottom) sections. After the development, the model was simulated using UNIversal QUAsiChemical model (UNIQUAC) base method. In order to investigate the sensitivity of the system, reflux ratio and reboiler duty were varied from 2.0-5.5 and 1350-1800 W, respectively. The results obtained from the steady-state simulation of the process revealed that the developed Aspen Plus model of the system was table because it was able to converge when simulated. Furthermore, it was discovered from the sensitivity analysis carried out that a methyl oleate having a mole fraction of approximately 0.7627 could be obtained from the process when the reflux ratio and the reboiler duty were 2.0 and 1800 W respectively. Also, it was observed that the mole fraction of methyl oleate was sensitive to both reflux ratio and reboiler duty because the variations in them (reflux ratio and reboiler duty) resulted in corresponding variation in the methyl oleate mole fraction obtained from the system.
Abstract: In the article offered technology hightemperature gasification of the municipal solid wastes with electrothermal stabilization of the process. Technology was adapted for conditions of Ukraine for goal of the experimental verification of the effectivity. Pyrolysis of municipal solid wastes (MSW) and process of the gasification MSW were adapted to the conditions of existing advanced technology of the hightemperature gasification of the carbon containing materials with electrothermal stabilization of the process (HTGTES). Autothermal process parameters of MSW gasification is proved by calculation of the heat and mass balance in conditions of Ukraine.
Abstract: In order to study the qualitative and quantitative relationship of the configuration characteristics of motion / force transformation (transmission), the dimension and the performance of motion and force, this paper extends the configuration synthesis of mechanical system to the state space method for the integration synthesis of mechanism configuration, scale and performance. By defining the basic function / performance transformation mechanism, extracting the dual state vector of the input and output performance of mechanism unit, discussing the state space property of mechanism combination (system) including mechanism configuration subspace, mechanism dimension subspace, and performance transformation subspace of mechanism motion / force, and investigating the spatial measurement of mechanism motion / force transformation, the measurement model of mechanical system is established. The motion design of mechanical system is transformed into the problem of finding a connected path (or path planning problem) between two given vectors: input and output dual vector. Finally, an actual example is given to show the details.
Abstract: We propose in this paper the development of a new rectangular finite element for thin plate bending based on the strain approach with linear elastic behavior. An analytical integration is used to evaluate the element stiffness matrix. The present element possesses the three main degrees of freedom (d.o.f) per node, namely, one transverse displacement (w) and two normal rotations about x and y axis respectively (Ɵx, Ɵy). The proposed displacement field represents exactly the rigid body motion and satisfies the compatibility equations. The numerical results converges rapidly to the Kirchhoff solution for thin plates, this makes the present element robust, better suitable for computations, and particularly interesting in modeling this type of structures.
Abstract: This study presents random load forecasts for the Nigerian 330 kV 38-bus transmission grid using a complex trend analysis technique. By considering randomness of monthly load peaks and normal distribution function, yearly load mean and confidence intervals were predicted for the transmission buses from an obtained 10-year historical load population. Also using the proposed algorithm of the mentioned technique, long-term random load forecasts for the transmission system were obtained. The obtained forecasts were compared with results from an earlier prediction model created for the same grid, which comprises a Monte Carlo technique that considers the location’s predominant control variables as population and GDP growth; the maximum obtainable error was 24%. The obtained results of forecasts and comparison are applicable for determining effective transmission system planning policy in Nigeria for the forecast period.
Abstract: Reactive distillation is a process that combines chemical reaction and separation in a single piece of equipment (distillation column). The process has a lot of benefits especially for those reactions occurring at conditions suitable for the distillation of the process components, and these result in significant economic advantages. However, owing to the complexities resulting from the integration of reaction and separation, its control is still a challenge to process engineers because it requires a control method that is robust enough to handle its complexities. Therefore, in this work, model predictive control (MPC) has been applied to a reactive distillation process used for developing a renewable energy known as biodiesel. The control algorithm of the MPC was formulated with the aid of MPC toolbox of MATLAB/Simulink in which the closed-loop models of the process were developed and simulated. The analysis of the results obtained from the simulations carried out for the optimization of the tuning parameters revealed that, among the tuning parameters considered, integral absolute error of the control system was less affected by the control horizon because its p-value was greater than 0.05 based on 95% confidence level. Furthermore, the simulation of the closed-loop system of the process using model predictive control tuned with control horizon of 11, prediction horizon of 18, weight on manipulated variable rate of 0.05 and weight on output variable of 2.17, which were the optimum parameters obtained using Excel Solver, showed that the system was well handled by the controller under servo control because it was able to get settled at desired mole fractions within 60 min. However, the settling time recorded in the case of regulatory control system of the process with the same controller was found not to be encouraging. Therefore, it is recommended that further work should be carried out on this subject matter in an attempt to obtain tuning parameters that will make the settling time of the closed-loop system of the process under regulatory control simulation very reasonable.