International Journal of Engineering Research in Africa Vol. 36

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Authors: L.V. Trykoz, S.M. Kamchatnaya, O.M. Pustovoitova, A.O. Atynian
Abstract: The problem of a combined action of reinforced concrete pipe and fiberglass safety cage. The prestressed cage not only decreases deformability of a pipe under load but protects the material of a pipe from agressive external factors. The process of force transfer from concrete pipe and fiberglass has been analyzed and the equation of stress and deformation for pipes and fiberglass has been deduced. It is shown that stress in fiberglass does not remain constant varying wall thickness, reducing towards the concrete core. Hoop stresses in the concrete core increase towards the centre of a pipe. Unlike known solutions the performed calculations take into account the performance of both layers – concrete and fiberglass. The total stresses in a concrete pipe in the most dangerous section from internal pressure and the reduction by fiberglass winding have been determined. The results obtained in the given work provide with the possibility of modelling long-term properties of composite reinforced concrete constructions and optimization of winding angle of fiberglass casing depending on the diameter of a pipe, tension force and the quantity of reinforcing filler.
Authors: Asmaa F. Barakat, Ragab A. El-Sehiemy, Mohamed Elsaid, E. Osman
Abstract: This paper proposes a new optimization algorithm called JAYA algorithm for solving the optimal reactive power dispatch (ORPD) problem. Minimizing the real power losses is one of main objective functions of (ORPD) problem. The ORPD problem is subjected to non-linear equality and inequality operational constraints. The proposed JAYA is a recently developed optimization algorithm. The main merit of Jaya algorithm is that the algorithm performance is liberated of specific control parameters adjustment. Therefore, it overcomes the limitations of previous optimization algorithms in terms of achieving the global optima atless computational efforts. The effectiveness of the proposed Jaya algorithm is proven on three standard systems namely IEEE 14-bus, 30-bus and 118-bus test systems. Added to that, Jaya is successively tested on the West Delta Real Network (WDRN) as a real part of the Egyptian grid. The obtained simulation results prove that the proposed JAYA algorithm has significant reduction in power losses for the tested system compared with other optimization algorithms. The obtained results confirm that the proposed JAYA optimization algorithm can make a noticeable enhancement on solving the ORPD problem for small and large-scale power systems.
Authors: Mohammed Salah Bennouna, Benaoumeur Aour, Fatiha Bouaksa, Saad Hamzaoui
Abstract: In this paper an experimental investigation of mechanical behavior of a thermoplastic polymer (polyamide PA 66) processed by constrained groove pressing (CGP) using several passes is presented. To this end, corrugating and straightening tools are designed and manufactured. The effects of the number of passes and the hold time on the mechanical behavior of the polyamide have been highlighted. The obtained results show that the material properties and the microstructure are significantly altered under CGP process. It has been found that the microhardness and the tensile properties have been progressed accordingly to the number of cycles, especially when the samples are processed using a hold time of five minutes. Hence, it can be concluded that this latter plays a very important role on the reorientation and stabilization of the microstructure when the processed material is a polymer.
Authors: Getahun Aklilu, Sarp Adali, Glen Bright
Abstract: Glass and carbon fibre composites and hybrid glass/carbon composites are materials often used in wind turbine blades. In Africa wind turbines have to operate in warm climates. The present study presents the results of an experimental study on the mechanical properties of these composites at elevated temperatures. For this purpose, the composite specimens are fabricated by hand lay-up process to investigate their static and dynamic properties at high temperatures. The properties studied include Inter-laminar Shear Stress (ILSS), Dynamic Mechanical Properties (DMA) such as storage modulus, loss modulus and loss factor using ASTM standards. The inter-laminar shear failure strength of carbon fibre and hybrid glass-carbon fibre composites are found to be close whereas the glass transition and damping behavior of the hybrid composites are higher making them suitable for wind turbine blades operating at high temperatures. Short Beam Shear (SBS) test data are evaluated using chi-square goodness of fit statistical tests and the correlation coefficients from linear regression analysis are determined. Normal, lognormal and 2-parameter Weibull statistical distributions are used at 5% significant level.
Authors: Toufik Djimaoui, Mosbah Zidani, Mohamed Chaouki Nebbar, T. Abid, Hichem Farh, Anne Laure Helbert, Francois Brisset, Thierry Baudin
Abstract: The aim of the present work is to study the evolution of microstructure, texture and mechanical properties during drawing of mild steel wire of type F8Z used in the manufacture of welding electrodes TREFISOUD. It was found that the as received wire has a ferritic-pearlitic microstructure corresponding to an isotopic state (without texture). This microstructure is relatively heterogeneous in the wire section. On the other hand, after strong drawing structure appears relatively homogeneous, throughout the section of the drawn wire. Also the deformation process by drawing causes the hardening of wire as a function of deformation with a reinforcing component of the fiber texture <110> // ND (majority), typical for bcc materials. Characterization methods used in this work is: Optical microscopy (OM), Scanning Electron Microscopy (SEM), the Electron Back Scattered Diffraction EBSD, Vickers microhardness and the tensile tests.
Authors: Mokhtar Bayarassou, Mosbah Zidani, Hichem Farh
Abstract: The objective of the present investigation is to study the changes in microstructures and mechanical properties during ageing and homogenization treatment of Al-Mg-Si alloy wire cold drawn at the different deformation in ENICAB (Biskra), destined for the transport of electric energy. And also to understand the phase formation during the cold drawing of Al-Mg-Si alloy wires, as well as the combined influence of the plastic deformation level and the influence of aging temperature. Wire section reduction shows a change in microstructure and texture. Characterization methods used in this work is: Optical Microscopy (OM), Scanning Electron Microscope (SEM) and X-ray diffraction.
Authors: Andrii A. Plugin, Raisa F. Runova
Abstract: A thermodynamic analysis of the reactions of calcium chloride and calcium nitrate with tricalcium aluminate when used as a hardening accelerator for portland cement, as well as decomposition reactions of calcium hydrochloraluminate (CHChA) and calcium hydronitroalyuminate (CHNA) formed during the hardening was performed. The conditions of stable existence of CHChA and CHNA in the cement matrix were established.
Authors: Gerard Banzibaganye, Emmanuel Twagirimana, G. Senthil Kumaran
Abstract: The highway pavement quality and lifetime depend on its different layers such as subgrade, sub-base and base courses. It is of great importance for subgrade soil layer to have the excellent properties as it is the one to lower or increase the project cost. This paper discusses the utilization of lime and fines from concrete waste to enhance the strength of silty sand soil. California Bearing Ratio (CBR) and shear strength were evaluated. The content such as 0%, 2%, 4%, 6%, 8% and 10% were used. The CBR and shear strength of soil increased with the increase of lime or concrete content. The optimum lime and concrete content which maximized CBR were 6% and 8% respectively. The shear strength improvement was also noticed. No optimum content from both stabilizers which gave maximum shear strength.
Authors: Oladayo Adeyi, Daniel Imwansi Ogiem Ikhu-Omoregbe, Victoria A. Jideani
Abstract: The influence of vinegar concentrations on the rheological properties of 40% (w/w) sunflower oil-in-water emulsions stabilized with 7% (w/w) gelatinized bambara groundnut flour (BGNF) was investigated. The rheological properties of interest were steady shear, time dependent and viscoelastic characteristics. Rheological characterizations of the emulsions were carried out using a shear rate controlled rheometer. Both emulsions with and without vinegar were pseudoplastic, thixotropic and viscoelastic fluids. Vinegar however, significantly (p < 0.05) affected rheological properties of BGNF-stabilized emulsion. Presence of vinegar in the emulsion decreased extent of thixotropy, pseudoplasticity and viscoelasticity of BGNF-stabilized emulsions. The results indicated that the rheological properties of BGNF-stabilized emulsion can be controlled and manipulated using vinegar however, the presence of vinegar in BGNF-stabilized emulsion may be deleterious to the emulsion. The result provided the information to understand the influence of vinegar on the rheological properties of BGNF-stabilized emulsions for product and process development.
Authors: Patrick T. Sekoai, Augustine O. Ayeni, Michael O. Daramola
Abstract: In this work, parametric optimization of citric acid production (yield) from six process variables: apple pomace (AP) concentration, volume of corn steep liquor (CSL), pH, temperature, methanol concentration, and methanol addition time is reported. Fifty-four experiments were performed according to the Box-Behnken design method. A polynomial regression model was developed from the experimental data and effects of the variables were explained using response surface methodology approach. A coefficient of determination (R2) of 0.92 indicated the significance of the model. The optimum conditions for citric acid yield obtained from the model were 33.81 g/L of AP, 42.5 g/L of CSL, 2.05% (v/v) of methanol concentration, methanol addition time of 33 h, pH 4.54, and temperature of 32.88 °C with a corresponding yield of 62.00 g/L. Conducting an experiment using the optimum conditions gave citric acid yield of 68.26 g/L, a 10% increase over the model results.

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