International Journal of Engineering Research in Africa Vol. 48

Abstract: This present work consists of studying the synthesis and the effect of Sn and Co content on the density and hardness of binary systems (Cu_100-x-Sn_x, Cu_100-x-Co_x). In this work we have study the influence of the addition of tin and cobalt (X = 5, 10 and 12 % by weight) in the metastable domain. The hardness of the Cu-Sn and Cu-Co alloys becomes high with the increase of the content of these two additive elements, the compacting pressure and the sintering temperature and even the effect of these on the increase of the density in an almost linear way. The porosity rate is proportional to the compaction pressure. SEM observation shows that the dispersion and particle size of tin and cobalt in the copper matrix is ​​irregular.

Abstract: Three novel bio-polymers were synthesized by cationic polymerization of Thevetia peruviana seed oil with styrene and divinylbenzene using modified boron trifluoride etherate as initiator. The cured thermosets ranging from soft to hard, were found to contain between 74.8 to 85.5 % cross linked materials with crosslink densities ranging from 1.33 x 10³ to 1.84 x 10³ mol/m³. The ultimate tensile strength of the materials varied from 0.52 to 0.55 Mpa, the young moduli is between 38.4 to 53.9 Mpa, the elongation at break varied from 55 to 64 %, the density of the polymers ranged between 0.850 to 0.866 gcm^-3, the impact strength is between 2.31 to 2.81 J, while hardness ranged between 3.40 to 3.90 BHN. Overall, the newly synthesized materials from Thevetia peruviana oil have many potentials as new polymeric materials.

Abstract: This paper contributes to the body of knowledge on the efforts to develop nanodielectrics as the next generation of insulation material. The time-to-failure under electrical tree-induced degradation of 1.09-1.35 vol.% hexagonal BN/Epoxy was found to be 3 times longer than in clean epoxy. For 0.31-0.33 vol.% CNS/Epoxy the time-to-failure was 24 times longer than the clean epoxy. The electrical treeing partial discharge behaviour in the BN/Epoxy and CNS/Epoxy showed distinct time-evolution characteristics different from those in the clean epoxy. The improved electrical tree endurance in BN/Epoxy relative to the clean epoxy can be attributed to increased mechanical stiffness. The superiority of the CNS/Epoxy as a nanodielectric is notable. The effect is suggested to be due to the electron affinity properties of the carbon nanospheres at appropriate dispersion levels.

Abstract: This article deals with the heat transfer in a Walter’s liquid B fluid through a stretching sheet subject to elastic deformation. We have incorporated the combined effects of aligned magnetic field and viscous dissipation. The effect of viscous dissipation regulating the heat transfer is considered. In addition, prescribed power law surface temperature and prescribed power law surface heat flux boundary conditions are introduced. The transformed non-linear coupled governing equations are solved analytically using hyper geometric function. The effects of various embedded pertinent parameters on velocity and temperature profiles are well discussed with the aid of appropriate graphs and tables. Our results are verified with previously published results of some noteworthy researchers. It is found that the augmenting aligned magnetic field strength reduces the flow velocity and the related momentum boundary layer thickness.

Abstract: We proposed a performance-improved finite-time adaptive synchronizing controllers and parameter update laws for coupling the dynamics of identical 4D hyperchaotic flows. The four-dimensional hyperchaotic flows consists of 12 terms and 11 system parameters and possessed very rich dynamics and larger parameter space. The performance of the proposed finite-time adaptive synchronizing controller was enhanced by the introduction of scalar quantities known as global controller strength coefficients and parameter update strength coefficients respectively, into the algebraically-derived control and parameter update structures, in order to constrained overshoots of the trajectories of the coupled systems and accelerate their rate of uniform convergence in finite time. Numerical simulation results obtained confirmed that the uniform asymptotic convergence rate of the coupling trajectories was faster, while the parameter update laws give a stable identification of the unknown system parameters in a global synchronizing time. A comparative analysis of the convergence time of the proposed adaptive controllers with recently published works indicated that the proposed controller has faster rates of uniform convergence of system trajectories.

Abstract: This study presents the analysis of thin rectangular orthotropic plate, simply supported at all edges (SSSS) subjected to both in-plane compression and lateral loads. The total potential energy functional was used in the analysis. The general variation of the total potential energy functional was done and the governing equation was obtained. The solution of the direct integration of the governing equation gave the deflection of the plate as a product of the coefficient of deflection and an orthogonal polynomial shape function. The expression for the coefficient of deflection was obtained by the direct variation of the total potential energy functional. This was used to derive the equation for the Lateral load parameter of an orthotropic thin rectangular plate carrying both in-plane compression and lateral loads based on the maximum deflection condition and also based on the elastic stability (yield strength) condition. The peculiar deflection equation for the SSSS plate was obtained using the formulated polynomial shape function. Numerical examples were carried out to determine the lateral load parameters corresponding to various plate thickness and permissible deflection for orthotropic thin SSSS plate carrying both in-plane compression and lateral load. In the same way, the lateral load parameters using the elastic stability condition (yield strength) were obtained for yield strength of 275 MPa, 355 MPa and 410 MPa

Abstract: Various national and international standards recommend potable water for mixing concrete; however, the availability of potable water is virtually a daunting task in some developing communities. Concrete workers in such environments tend to utilize any available water for mixing concrete, and this may be detrimental to the quality of the concrete being produced. This study investigates the rheological, mineralogical and strength variability of concrete due to construction water impurities. Water samples were collected from four different construction sites within Southwestern region of Nigeria for production of concrete. The physical and chemical properties of the waters were determined so as to measure their rate of contamination, prior to their use for mixing concrete. The rheological properties of the fresh concrete, compressive strength, split tensile strength, and microscale features of hardened concrete, that were produced with each water sample were determined. From the results, the rheological features of concrete were found not to be affected by water impurities, however, the mechanical test results revealed about 10% reduction in strength between concrete made with water having least and higher concentration of impurities. Also, it was evident from the microscale tests that the water impurities do alter the hydration rate of concrete, which results in strength reduction. The study suggests pretreatment of concrete mixing water before use in order to avoid its damaging effect on concrete life.

Abstract: Design an e-drive transmission gear, it is very crucial, to understand the failure modes since gears should be sized correctly to withstand loads that will expect to act on the gear teeth and make sure that still be within reasonable load-carrying capacity, compact and lightweight. Fatigue failure can happen on gears under repeated loading due to fatigue such as tooth root bending and contact stress of gear. Materials used in this study were two candidate alloy steels of Cr-Mo and Cr-Mo-Ni and methods employed to design the e-drive transmission gear were by iteration through KISSsoft gear simulation software as well as AGMA of Matlab script, it approaches various parameters such as helix angle, face-width, and input torque. Investigations on safety factors of root bending and contact, stresses of contact and bending, weight, compactness, quiet and smooth functioning have been done by altering the variable design parameters. To conclude that by increasing face width and helix angle both safety factors were increased uniformly regardless of the input torque as we calculated by both approaches. Similarly, the results showed that by increasing the helix angle and face width it brings to reduce the contact and bending stresses of transmission gear. As we comparing the results, the KISSsoft values are a little higher than the analytical (AGMA) values as proven in all fatigue of safety factors versus variable gear design parameter. Based on the safety factor, compactness, lightweight and quiet for smooth function of the designed e-drive mating gears are proven as the face width is 24.5 mm and the helix angle is 25^o.

Abstract: The friction of ship main engine mechanical moving parts, combined with the internal combustion of fuel, generate a great amount of heat, leading to the increase of their running temperature and acceleration of their wear. If the temperature and wear phenomena are not controlled and kept within the maker’s thresholds, it will result in a partial or total damage of the propulsion system. However, the oil lubrication system plays a vital role in reducing the friction of the moving parts and ensuring their cooling and cleaning. Therefore, it must be reliable enough and continuously available for a safe operation of the main engine. This work aims at studying the main engine lubrication oil system’s reliability. This will be achieved through using Bayesian Network method, in order to identify the system components weak points to improve their reliability and to propose a highly reliable system that may either be installed on board of a conventional ship or an autonomous ship. The benchmark of the improved system and the formal system shows a significant enhancement in reliability that has become close to 1. In the case of an autonomous ship, this system must operate autonomously without human intervention. An autonomous and remote monitoring system concept is proposed. In case of system failure or need of change of its functioning parameters, the shore control center team takes over the control and executes the necessary adjustment remotely.

Abstract: The monitoring of granaries were earlier implemented with wired networks in most Asia countries with obvious challenges that include high installation and maintenance costs, data acquisition delay, and high energy consumption. Most other works being implemented with wireless approaches presented inherent drawbacks that include inefficient coverage of the grain storage bins and high rate of node failure. This paper presents the design and tremendous advantages of deploying distributed wireless sensor network based on Digimesh network protocol, to monitor the environmental temperature, humidity and illumination of a granary system. The monitoring system has only one node type, and consists of a homogenous network in which all nodes route data and they are interchangeable. A node consists of Xbee transceiver modules, Arduino microcontroller and DHT22 Temperature/Humidity sensor, and it is being configured as low battery powered devices. The results were logged real-time on a personal computer for analysis, display and record. The results indicate a system which provides a better sleeping scheme and eliminate the single point of failure associated with Zigbee and some other network protocols.