International Journal of Engineering Research in Africa Vol. 37

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Authors: Mohamdi Djemoui, Outtas Toufik
Abstract: Knowing the stresses and pressures in the contact between two deformable solids is fundamental in order to optimize the strength and the lifetime of mechanical components such as bearings or gears. These constraints can be determined by the calculation (finite element method or Hertz theory) or by experimental methods such as photoelasticity. The objective of this study is to model and compute the stress field and contact pressure using 3D finite element software. The validation of obtained results is done by comparison with the classical results of the non linear Hertz theory between two deformable cylinders. An application to spur gears with a circle involute profile is done and also validate with the same Hertz theory.
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Authors: S. Nallusamy, R. Suganthini Rekha, S. Saravanan
Abstract: In global manufacturing system, reduction of weight for automobile components is the main concern in automotive manufacturing industries. This research work focuses to improve the high strength ratio by reducing the weight of steel plate composite cart spring. The objective is to investigate the total load carrying capacity, stiffness and weight savings of composite cart spring and compare with that of steel cart spring at specified loading and over loading conditions. The examination was done for the cart spring made up of steel and composite materials of epoxy resin, e-glass fiber and nano particles. The specimens were fabricated by laminated composite with two dissimilar wagering progressions of resin with clay and nanoparticles. The constant thickness and width for cross section was maintained on the moulding techniques. The proposed design of multi level composite cart spring was modeled through PTC developed software of Pro Engineer and imported in simulation and 3-D design software of ANSYS R16.0. The existing measurements of a multi level cart spring was considered for modeling and investigation of a proposed laminated composite cart spring under same loading conditions. From the results it was found that, about 80% of the weight was reduced in the proposed laminated composite cart spring by replacing steel plates with composite materials.
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Authors: Victor Geantă, Ionelia Voiculescu, Bogdan Istrate, Diana Maria Vrânceanu, Robert Ciocoiu, Cosmin Mihai Cotruț
Abstract: Many high entropy alloy systems have been exploited in the past decade and among them AlCrFeCoNi alloy is widely studied. The structural and mechanical properties of AlCrxFeCoNi alloy was studied in this paper for different content of chromium (atomic ratio, x= 0.2 to 2.0 at. %). In this study, ten samples having different chemical composition were prepared from raw materials using RAV equipment, type MRF ABJ 900. The microstructure features, crystallite sizes and microhardness depends on chemical composition of the alloy. The microhardness values for AlCrxFeCoNi (x = 0.2 to 2 at. %) increases from 389.6 to 562.6 HV0.1. The maximum value of microhardness for the high entropy alloy AlCrxFeCoNi (x = 1), has been obtained for 20.55 wt% Cr and has the value 562.6 HV0.1.
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Authors: Abderrahmane Mokhtari, Mohammed Belkheiri
Abstract: This paper addresses the problem of fault detection and isolation (FDI) in wind turbine benchmark model using data driven and multi-class support vector machine (SVM) approach. Since, the fault detection is fundamental for any active system, isolation is similarly vital, and identification is decisive for fault reconfiguration as well as maintenance addition to monitoring purposes. The need for man-made dynamic system to work automatically when sensor, actuator, or system faults occur was constantly developed in order to increase reliability and decrease unavailability and maintenance costs. The key step of our approach based on extraction of mean features from sensors measurements by applying the statistical methods such as moving standard deviation and the exponential weighted moving average (EWMA). The fault detection step is invoked later based on the multi-class SVM classifier that decides the presence or not of the fault. Another important contribution of this paper is the simulation of combined sensor and actuator faults simultaneously for the first time in wind turbine benchmark model. The FDI performances are illustrated through simulation study for seven different scenario tests. The results demonstrate clearly the effectiveness of statistical and SVM approach to detect and isolate single, multiple sensor and actuator faults and outperforms many results reported in the literature for solving this problem.
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Authors: Adetifa Babatunde Olusola, Samuel Taiwo Moses
Abstract: Certain characteristics of the work settings of the local method of gari frying have potential for harm which must be identified to prevent or reduce these harms. The sitting posture is one of such characteristics. In this paper, the risk of work-related musculoskeletal disorders (WMSDs) in the stirring task of gari-frying was assessed. This assessment covered two different sitting postures i.e. “sitting in front” and “sitting sideways” postures. A preliminary assessment was carried out using questionnaire and oral interview. Further assessment was done with a Quick Exposure Check (QEC). Gari frying in the location under study was dominated by women above 40 years while, the “sitting sideways” posture was mostly used. Most of the workers complained of discomfort at their shoulder/arm and back regions but, workers who take the “sitting sideways” posture complained of pains at their neck region. Discomfort in the wrist/hand region was the additional complain of workers who adopted the “sitting in front” posture. For the “sitting sideways” posture, QEC assessment revealed that the back, wrist/arm and neck regions were at a high risk of WMSDs, while for the “sitting in front” posture, only the neck region had a high risk of WMSDs. This paper reveals that the stirring task of the gari frying process is very tedious and has a risk of WMSDs that varies to different degrees depending on the sitting posture adopted
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Authors: Ogunboyo Patrick Taiwo, Melodi O. Adegoke
Abstract: This paper presents an investigative study on a selected 11 kV distribution feeder network in Akure township, Nigeria, aimed at evaluating power distribution problems and solution proposals for effective application of existing 11 kV feeders for power supply within Nigeria. Based on peak loads recorded on the feeder for 8 years a long term load forecast up to 2021 was carried out using “Trend’ and “Growth’ functions in Excel worksheet. These functions use Method of Least Squares. The peak network load is 8 MW and the expected load in 2021 is 14.5 MW (18.5 MVA at 0.8 power factor) after an exponential growth rate of 0.6 MW per annum. There is need to increase the rating of the power transformer feeding the feeder in order to enhance the security power supply to the network. Furthermore, the Power Company must provide standard input voltage (1.05x11 kV) to the network in order to normalize end-users voltage quality.
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Authors: Chika O. Yinka-Banjo, Ukamaka Hope Agwogie
Abstract: In the present world, mobile robot has been widely used for many functions across different areas of life. These mobile robots can be engaged in a static or dynamic environment where they are expected to accomplish a task optimally against all odds. Path planning for mobile robot is a very crucial problem in robotics that has been greatly researched upon; it is aimed at finding an optimal path in a given environment from a start point to the goal point. Several techniques have been employed in solving this crucial problem. These techniques are broadly classified as classical and heuristics. The Swarm Intelligence Techniques form a sub-class of the heuristics approach. The aim of this research is to review the swarm intelligence techniques in solving the mobile robot path planning problem. The drawbacks and merits of each of the techniques were discussed and a comparative analysis was given.
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Authors: Simbarashe Magidi
Abstract: In this paper, we have evaluated the performance of DPSK advanced modulation format in a bidirectional passive optical network for a triple play scenario at a constant symmetrical data rate of 10 Gbps. Data, voice and video signal has been successfully transmitted to a maximum of 128 users for a maximum distance of 100 km. Network performance was measured in terms of the Q factor, BER and eye opening, as a function of the number of users and distance of reach.
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Authors: Sanae el Mimouni, Mohamed Bouhdadi
Abstract: The objective of this paper aims at modeling and analysis of communication properties of an E-commerce protocol with the Event-B language. NetBill protocol is developed for selling and buying of information and goods through the Internet. In this approach, we have used Event-B as proof-based development method which integrates proof techniques for writing specifications and building the model systematically using refinement, the key point is to start with a very abstract model of the system under development. Step by step details are added to this first model by building a series of more concrete ones. This strategy eases the proof of the correctness of requirements because only a small number of proof obligations are generated at each step. The aims are constructing a model with a clear and accurate formulation of the communication protocol properties and discharge of all proof obligations. The outcome of this procedure was that we achieved a very high degree of automatic proof. We reached a good degree of automatic proof. All interactive proofs involved a small number of steps and were straightforward to reach.
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Authors: Akpabot I. Akpabot, Anthony N. Ede, Oluwarotimi M. Olofinnade, Gideon O. Bamigboye
Abstract: Buildings worldwide are one of the most essential assets of humans, and they serve as a major contributor to the sustainable development of any nation. The consequences of building collapse are colossal ranging from loss of lives, damage to properties and its attendant socio-economic implications, etc. This menace appears to be worst-off in developing countries like Nigeria where capacity to manage disaster is lacking. Recent incidence of seismic actions in hitherto geographically aseismic zone, has led to prediction of earthquake occurrence in the nearest future. This research attempts to compute the seismic hazard of buildings in Lagos State, a densely populated area of Southern Nigeria. Based on known seismic ground motion for South-Western Nigeria, a model is created that estimates the casualty and built area that would be affected by earthquakes with different seismic intensities. MATLAB software using Monte Carlo simulation to draw random data samples of built area, construction quality, probability of failure and occupancy level is used for the computational analysis. The result showed that existing construction quality is poor portending a high degree of damage during moderate intensity earthquake. A significant risk reduction is achievable for both the impending collapse and severe damage performance levels if the existing construction quality is improved.
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