International Journal of Engineering Research in Africa Vol. 40

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Authors: Olumoyewa Dotun Atoyebi, Adeolu Adesoji Adediran, Adisa Cephas Oluwatimilehin
Abstract: The current work reports on the fabrication of composite matrix from saw dust (SD) and recycled polyethylene terephthalate (PET) at different weight ratio by flat-pressed method. Wood plastic composites (WPCs) were made with a thickness of 15 mm after mixing the saw dust and PET followed by a three phase press cycle. Physical properties (Density, Water Absorption (WA) and Thickness Swelling (TS)) and Mechanical properties (Modulus of Elasticity (MOE) and Modulus of Rupture (MOR)) were determined base on the mixing ratios according to the standard. WA and TS were measured after 2 h and 24 h of immersion in water. The results showed that as the density increased, the SD content decreased from 90 % to 50 % into the matrix. However, WA and TS decreases when the PET content increased in the matrix. Remarkably, the MOE and MOR attained a maximum point at 964.199 N/mm2 and 9.03 N/mm2 respectively in 50 % SD content. In comparism with standard, boards D and E can be classified as medium density boards while A, B and C are low density boards. The results indicated that the fabrication of WPCs from sawdust and PET would technically be feasible for indoor uses in building due to favorable physical properties exhibited. The mechanical properties response showed that it cannot be used for structural or load bearing application.
Authors: Peter Kayode Farayibi
Abstract: Laser deposition is an advanced manufacturing technology capable of enhancing service life of engineering components by hard-facing their functional surfaces. There are quite a number of parameters involved in the process and also desirable output characteristics. These output characteristics are often independently optimised and which may lead to poor outcome for other characteristics, hence the need for multi-objective optimisation of all the output characteristics. In this study, a laser deposition of Ti-6Al-4V wire and tungsten carbide powder was made on a Ti-6Al-4V substrate with a view to achieve a metallurgical bonded metal matrix composite on the substrate. Single clads were deposited with a desire to optimise the composite clad characteristics (height, width and reinforcement fraction) for the purpose of surface coating. Processing parameters (laser power, traverse speed, wire feed rate, powder feed rate) were varied, the experiment was planned using Taguchi method and output characteristics were analysed using principal component analysis approach. The results indicated that the parameters required for optimised clad height, width, and reinforcement fraction necessary for surface coating is laser power of 1800 W, traverse speed of 200 mm/min, wire feed rate 700 mm/min and powder feed rate of 30 g/min. The powder feed rate was found to most significantly contribute 43.99%, followed by traverse speed 39.77%, laser power 15.87% with wire feed rate having the least contribution towards the multi-objective optimisation. Confirmation results showed that clad width and reinforcement fraction were significantly improved by the optimised parameters. The multi-objective optimisation procedure is a useful tool necessary to identify the process factors required to enhance output characteristics in laser processing.
Authors: Joseph A. Ige, Mukaila A. Anifowose, Samson O. Odeyemi, Suleiman A. Adebara, Mufutau O. Oyeleke
Abstract: This research assessed the effect of Nigerian rice husk ash (RHA) and calcium chloride (CaCl2) as partial replacement of cement in concrete grade 20. Rice husk ash (RHA) is obtained by combustion of rice husk in a controlled temperature. The replacement of OPC with rice husk ash (RHA) were 0%, 5%, 10%, 15% and 20%. 1% of Calcium Chloride was blended with OPC/RHA in all the test specimens except from control mix. Concrete cubes of sizes 150mm x 150mm x 150mm were cast and cured in water for 7, 14 and 28 days respectively. Slump test was conducted on fresh concrete while density test and compressive strength test were conducted on hardened concrete. The slump results revealed that the concrete becomes less workable (stiff) as percentage increases. The compressive strength result at 28 days revealed that 5%RHA/1%CaCl2 have the highest strength of 26.82N/mm2 while 20%RHA/1%CaCl2 have the lowest strength (21.48N/mm2). Integration of 5%RHA/1%CaCl2 and 10%RHA/1%CaCl2 as cement replacement will produce a concrete of higher compressive strength compared to conventional concrete in grade 20 concrete.
Authors: Njarazo Rakotondrabezaharinoro, Moutari Ado, Willy Hermann Juimo Tchamdjou
Abstract: In many developing country’s mining exploitations are the main activities sources, and its exploitation is generating many mining wastes and environmental impacts. In order to use these waste, an innovative powder and aggregate were designed, aimed at providing alternative materials by cementitious supplementary materials and sand in Portland cement mortars. This paper investigates the use of raw mineral waste from some developing countries, namely Granite Residue (GR), from Niger, Mining Tailings (MT), from Madagascar, and red Volcanic Scoria (VS), from Cameroon as building materials. These raw materials were valorized as supplementary cementitious materials (GR powder, MS powder and VS powder) and as sand (GR sand and VS sand). GR sand and VS sand were used by 100% replacement of standard sand and GR powder, MS powder and VS powder were used by 5, 15, 25, or/and 35% cement replacement. Physical properties and mechanical properties of raw materials used and mortars obtained were investigated. The effects of these raw materials on properties of mortar mixes were studied and reported. Results show that, with sand from raw mineral waste materials, the compressive and flexural strengths of the produced mortar represented up than 70% and up than 85% respectively in comparison with mortar produce with siliceous standard sand. The reduction of strength of mortar with raw powder as ordinary Portland cement replacement is generally smaller than replacement ratio. Activity index of each raw powder is about 75% for ratio replacement of 5, 15 and 25%. Particle size distribution of raw powder and sand have an influence on the workability and mechanical properties of mortars. In conclusion, the use of raw mineral waste as a raw powder or as sand for mortar production presents an economical and environmental advantage for developing countries where mining exploitations are abundant.
Authors: Samia Louadj, Ramdane Bahar, Nasser Laouami
Abstract: The Boumerdes earthquake of May 21, 2003 in Algeria, which widely felt within a radius of ~ 400 km, caused damage in five provinces. Numerous structures have been devastated, others suffered of damages. Keddara rockfill dam which is situated approximately at 20 km from the epicentre was strongly shaken during this seismic event and can undergo significant deformations. In this study, numerical analysis of Keddara rockfill dam under Boumerdes earthquake is performed. It is mainly focus on the seismic amplification at different level of the dam under the main shock with dominant frequency close to the natural frequency of the dam. The low coherence between the input and the structural output indicates the need of nonlinear analysis of the dam under the spatial variation in excitation. Furthermore, the effect of plasticity on the seismic response is investigated by using maximum acceleration which is one of the most important properties selected. The analysis of the dam under stochastic non-uniform excitation is conducted using a 2-D finite difference modeling by using the software Fast Lagrangian Analysis of Continua (FLAC). The final results obtained after successive analyses on the dam configuration incorporating the nonlinear soil properties are presented.
Authors: Samuel A. Ola, Bukola Ogunmokun-Akinmolu, Oluwapelumi O. Ojuri, Opeyemi E. Oluwatuyi
Abstract: The study focused on the model analysis of failure susceptibility for some roads in the South-western part of Nigeria using TDRAMS model along with its modified version. TDRAMS, a model prepared through an analyzed weight-rating system was used to analyze pavement failure manifestation in the present study area and to what possible extent. Different pavement failure causative factors which include: Traffic load {T}, depth of water table {D}, soaked California bearing ratio {R}, cambering{A}, maximum dry density {M}, and asphalt thickness {S} were proposed. Their field data were analyzed and simulations were done to postulate a model for road failure susceptibility. The weights and ratings of the collected field data were also varied/modified to determine its effect on the model. Simulations on the varied weight showed that the most significant parameters were {T}Traffic load and {D}depth of the water table. The optimum weights were discovered to be 32 (81% weight increase) and 23 (78% weight increase) for {T}Traffic load and {D}depth to water table respectively. Simulations on the varied ratings showed that alongside with {R}soaked California bearing ratio [CBR], {T}Traffic load and {D}depth of water table were also the most significant parameters. The roads studied indicated high failure susceptibility when analyzed.
Authors: Rachid Zegait, Boualem Remini
Abstract: The reuse of treated wastewater can reduce the water deficit in Saharan areas, especially in Ghardaia. The M'Zab wastewater treatment plant (WWTP) is designed to treat wastewater by the natural lagoon system, and to reuse the treated water for irrigation of agricultural perimeters in order to contribute to sustainable development efforts in the region. Indeed the present work aims to search for the study of the possibility of reusing treated wastewater of M 'Zab in irrigation, to do this, we established and followed the evolution of the various physical-chemical and bacteriological analysis for two years (2013-2015), to study the effectiveness of biological treatment in the reduction of wastewater pollution, and then compare the results of treated water with national and international standards in the field of 'irrigation. The results showed that the treated water is considered as poor quality water is not usable only for some salt-tolerant species and on well-drained soil and leached, require additional treatments for ensured the quality of this precious resource.
Authors: S.V. Veretennikov, Sh.A. Piralishvili, Oleg A. Evdokimov, A.I. Guryanov, M.M. Guryanova, A.A. Shaikina
Abstract: The main trends and prospects of water resources consumption, as well as existing ways of obtaining fresh drinking water, were analyzed. The design of a vortex condenser of atmospheric moisture has been provided. Its operating principle is based on the organization of free-convective flow under the temperature drop effect and air-cooling to a temperature below the dew point. The designed vortex condenser of atmospheric moisture runs on solar energy and do not require using additional energy sources. The results of numerical simulation of the flow structure in a vortex condenser of atmospheric moisture and experimental data, which confirms the formation of air flow inside the condenser and moisture condensation in its lower part, are presented.
Authors: M.A. Abdelkader, Mostafa A. Elshahed, Zeinab H. Osman
Abstract: Due to the rapid increase in electricity consumption, there is a tendency to install distributed generations (DGs) at the level of distribution systems. Therefore, the distribution systems become active, and special load flow methods have to be developed and applied due to its radial structure and the relatively high ratio of resistance to reactance components. This paper presents a new forward algorithm for balanced three-phase load-flow analysis of radial distribution networks (RDNs). Kirchhoff’s Current Law and Kirchhoff’s Voltage Law are utilized. However, a new arrangement of these equations is presented based on formation of virtual slack buses and subsystems truncated from the original network during iteration. The proposed algorithm firstly applied on three IEEE benchmark RDNs with different cases such as different load models, various loading levels to illustrate the convergence even high loading, and inserted DGs,; then it is applied on a real system in Egypt. Its high convergence rate is tested for the DG optimization problem. Further, the virtual subsystems can be utilized to recognize quickly the effect of load changes on the bus voltage profile. The results show that the proposed algorithm is more accurate, not sensitive to initial value, simple equations are used, and robust with high convergence rate because of employing the updated bus voltages immediately after determining their value.
Authors: Elutunji Buraimoh, Funso Kehinde Ariyo, Micheal Omoigui, Innocent Ewaen Davidson
Abstract: Electrical power systems are often required to operate at full loading capacity due to ever increasing demand and transmission line contingencies with limited grid expansion. This results in line overload and operating near system limit, thereby threatening system security. Utilization of existing system can be achieved using Flexible Alternating Current Transmission System (FACTS) devices without violating system limits. This research investigation involves static security assessment of a modelled IEEE 30-bus test system in MATLAB/SIMULINK/PSAT environment. The security status with the incorporation of combined Static Var Compensator (SVC), Thyristor Controlled Series Compensator (TCSC) and Interline Power Flow Controller (IPFC) were determined. Prior to this, Contingency Severity Index (CSI) based on Performance Index (PI) of Voltage and Active Power was employed to determine the optimal location of the FACTS devices. Sequential Quadratic Programming (SQP) was applied to determine the optimal sizing/percentage compensation of FACTS. Subsequently, power system with and without the incorporation of FACTS devices were modelled. The ability of the compensated system to withstand credible transmission line contingencies without violating the normal operating limits (bus voltage and line thermal) was examined and presented. The paper presents how combined SVC/TCSC and an IPFC aided the power system to boost its steady state security in the face of possible line contingencies.

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