International Journal of Engineering Research in Africa Vol. 35
International Journal of Engineering Research in Africa Vol. 34
International Journal of Engineering Research in Africa Vol. 33
International Journal of Engineering Research in Africa Vol. 32
International Journal of Engineering Research in Africa Vol. 31
International Journal of Engineering Research in Africa Vol. 30
International Journal of Engineering Research in Africa Vol. 29
International Journal of Engineering Research in Africa Vol. 28
International Journal of Engineering Research in Africa Vol. 27
International Journal of Engineering Research in Africa Vol. 26
International Journal of Engineering Research in Africa Vol. 25
International Journal of Engineering Research in Africa Vol. 24
International Journal of Engineering Research in Africa Vol. 23
International Journal of Engineering Research in Africa Vol. 29
摘要: The ANSYS® Finite Element Method (FEM) program offers a variety of elements designed to treat cases of changing mechanical contact between the parts of an assembly or between different faces of a single part. These elements range from simple, limited idealizations to complex and sophisticated, general purpose algorithms. Contact problems are highly nonlinear and require significant computer resources to solve. Recently, analysts and designers have begun to use numerical simulation alone as an acceptable mean of validation employing numerical Finite Element Method (FEM). Contact problems fall into two general classes: rigid-to-flexible and flexible-to-flexible. In general, any time a soft material comes in contact with a hard material, the problem may be assumed to be rigid-to-flexible. The other class, flexible-to-flexible, is the more common type. To model a contact problem, you first need to identify the parts to be analyzed for their possible interaction. If one of the interactions is at a point, the corresponding component of your model is a node. If one of the interactions is at a surface, the corresponding component of your model is an element. The finite element model recognizes possible contact pairs by the presence of specific contact elements. These contact elements are overlaid on the parts of the model that are being analyzed for interaction. This paper present a simulation contact friction between Two Rock bodies loaded under two types of load condition: Axial pressure Load “σ” and Tangential Load “τ”. ANSYS® software has been used to perform the numerical calculation in this paper.
摘要: In this article, the problem of a non-Newtonian fluid (micropolar) flow over a horizontal melting surface in the presence of internal heat source and dual stretching (i.e. at the wall and at the free stream) is presented. Since the magnetic-Reynold of the flow is substantial, the influence of induced magnetic field is properly accounted in the governing equation. The viscosity and thermal conductivity of the micropolar fluid are considered to vary linearly with temperature. Classical models of these thermophysical properties were modified to suit the case of melting heat transfer. A similarity transformation is applied to reduce the governing partial differential equation to coupled ordinary differential equation corresponding to dimensionless momentum, angular momentum, energy and induced magnetic field equation. These equations along with the boundary conditions are solved numerically using shooting method along with Runge-Kutta-Gill method together with quadratic interpolation. The results of the present study indicate that due to the formation of boundary layer on melting surface (region of low heat energy) in the presence of induced magnetic field, space and temperature dependent internal heat generation enhances the heat transfer rate.
摘要: An investigation has been done to study the influence of the Fe and Al doping concentration on the optical properties of zinc oxide thin films. A spray pyrolysis system was used to obtain ZnO:M films doped with Iron and Aluminum, using zinc acetate dihydrate, hydrated iron chlorate and hydrated aluminum chlorate, respectively. The temperature and the concentration were fixed at 450°C and 0.1mol/L, respectively. Our thin films deposed on glass substrate. UV-VIS spectrophotometer has been used for the layers characterization. The optical transmittance spectra showed that the 2% Al dopand improves the optical transmittance in the visible that the Fe dopand. Zinc oxide thin films is the n type semiconductor with direct optical band gap varied between 3.219-3.346eV for obtain the films in photovoltaic application. But the urbach energy of ZnO thin films undoped and doped by Iron and Aluminum is varied between 101– 202 meV.
摘要: The aim of this research paper is to fabricate a Fe-TiC composite by a novel and simple manufacturing method. The latter is based on two cumulative processes; a conventional sintering (transient liquid phase sintering) and a hot forging with steam hammer respectively. The blinder phase of the studied simples is varied from carbon steel to high alloy steel using alloying additive powders. The obtained outcomes showed that after the sintering process, the relative density of the performed simples is improved from 86% to 95.8% without any densification process. Otherwise, in order to ensure maximum densification and enhance in addition the solubility of the alloying additives the hot forging process is then applied. Indeed, the final obtained composite product is a TiC-strengthened steel with a relative density around 99% (about 6.5 g/cm3 of density) wherein 30% (wt.) of spherical and semi-spherical TiC particles are homogeneously distributed in the metal matrix.
摘要: Polycrystalline Diamond Compact (PDC) cutters have been popularly used in recent times due to their resistance against mechanical and thermal wear. This paper was focused on interface geometries between the substrate and the diamond table. Various types of interfaces were designed, to investigate how different interface geometries influence distribution of stress and strain under shear loading. The interface geometries examined in this paper included castle interface, dent interface, honeycomb interface and chase interface. Parallel to the interface, shear loading was applied to the top of diamond table to mimic the shear loading component from the rock cutting. To apply the shear loading, two locations were considered for each of the geometries. These locations differed depending on the interface features. Stress and strain distribution and values across different interface geometries were analysed with the aid of 3D Finite Element Method (FEM). The numerical simulations indicated that stress and strain magnitudes and distribution patterns varied in relation to different geometries. Some substrates showed relatively lower plastic strain representing higher durability of the geometries. Concentration of stress and strain distribution showed the areas where one could expect weakness. It also implies that rotating the PDC cutter assemblies around their cylindrical axis helps avoiding fatigue of interface elements in regions of high stress concentration; and thus, preventing premature failure of interface elements.
摘要: This paper presents the modeling of cutting performances in turning of 2017A aluminium alloy at four turning parameters: cutting speed, feed rate, depth of cut, and tool nose radius. These performances include: surface roughness, cutting forces, cutting temperature, material removal rate, cutting power, and specific cutting pressure. The experimental data were collected by conducting turning experiments on a Computer Numerically Controlled lathe and by measuring the cutting performances with forces measuring chain, an infrared camera, and a roughness tester. The collected data were used to develop multiple regression models for the pre-cited cutting performances and investigate the effects of turning parameters and their interactions on responses. To evaluate the accuracy of the developed models, two performance criteria were used: Correlation Coefficient (R²) and Average Percentage Error (APE). It was clearly seen that the multiple regression models estimate the cutting performances with high accuracy: R²>94% and APE<7%. Therefore, this method is an effective tool for modeling the cutting performances in turning process.
摘要: This work has been carried out to demonstrate the application of a process simulator known as CHEMCAD to the modelling and the simulation of a reactive distillation process used for the production of n-butyl acetate, with water as the by-product, from the esterification reaction between acetic acid and n-butanol. The esterification reaction, which is generally an equilibrium type, was modelled as two kinetic reaction types in the reaction section of the column used, which had 17 stages with the middle section (stages 6 – 12) being the reaction section. A reflux ratio of 3 and reboiler duty of 78 kJ/min as well as 30 mL/min of each of the reactants with 99% molar purity were used for the simulation of the column. The results obtained revealed that the developed model was a valid one because there was a very good agreement between the results and the theoretical knowledge of a distillation column based on the fact that the desired (which was the heavy) product (n-butyl acetate) was found to have the highest mole fraction in the bottom section of the column while the by-product of the process (water) was discovered to have a mole fraction higher than that of n-butyl acetate in the top (condenser) section of the column. Therefore, CHEMCAD has been applied to the steady-state simulation of the reactive distillation process used for the production of n-butyl acetate from the esterification reaction of acetic acid and n-butanol successfully.
摘要: In some parts of Algeria, the alluvial deposits are depleted. Optimizing the use of available resources, has become gradually urgent need and more and more important. Algeria does not remain on the sidelines of this idea, an approach is part of a sustainable development has been developed to make available to the manufacturer a steady stream of material coming from the exploitation of limestone. The importance of this production can be explained by the activity of the carrier ever growing sector. Research programs have been launched in Algeria to focus on aspects, related to the composition of concrete and influence of the nature of the constituents on the mechanical mixing quality, especially compressive strength remains the point of view of the engineer, the most important property of the material, if we exclude the sustainability indicators. Usual concretes were made using local materials. Results showed that the intrinsic properties of the constituents of concrete, and particularly studied the crushed aggregate, provide the concrete characteristics resistors quite satisfactory. To go further and in a growing cares about improving the mechanical strength of these concretes we tried to formulate a very high performance concrete (VHPC) made from local crushed aggregate, in this case the crushed limestone sands as a resource alternative to over-exploited rolled sands. The objective of this study is to enhance the crushed sand in the formulation of VHPC. The referred physical-mechanical performances are related to defer deformations within time (shrinkage) and instantaneous mechanical compressive and flexural strength.
摘要: There has been increasing incidents of collapse of reinforced concrete buildings in Nigeria. Many research works, suspecting the quality of concrete produced in Nigeria, have focused on concrete with few attention on steel, perhaps because its production is usually in a more controlled environment. Over the years, many clients of building construction projects or their representatives have shown preference for imported steel bars over the locally-produced steel bars. This research work sets out to investigate the quality of steel reinforcement produced locally and compare them with imported steel bars. The diameter of the two classes of bars available in the open market at Ilorin, Nigeria were measured and their deviations from their manufacturer’s designated diameter were determined. Also, their response to the application of load and deterioration in different environments, simulated by their immersion in water, hydrochloric acid (HCL) and sodium hydroxide (NaOH), were studied. Locally-produced bars deviated more from their designated diameter than the imported bars. The imported steel bars have higher strength and experienced lower strain compared to the locally produced steel. They also showed better corrosion resistance, when immersed in distilled water and HCL, than the locally-produced steel bars. The preference for imported steel by clients of building projects is justified.There is a need for regulatory bodies, such as the Standards Organization of Nigeria (SON), to strictly monitor and penalize local steel manufacturers that engage in corrupt practices leading to significant dimensional and strength deviations from specification. This has the potential of minimizing the incidence of building collapse in Nigeria.
摘要: The article deals with the possibility to create the cement-based material with improved electrophysical characteristics. The material can be used in the rail sleeper production, which will improve the insulation resistance of track circuits and increase transportation reliability. Besides, various kinds of structures made of it, e.g. foundations, piles, supports, bridges and tunnels, will decrease the impact from leakage and stray currents leading to intensification of electrocorrosion processes in railway structures, and will increase life cycle of the structures. It has been experimentally established that addition of bitumen emulsion to the cement and sand grout increases electrical resistance 4 times in the test samples in comparison with a check sample without additives. Insignificant increase in the setting-up time can be eliminated with early-strength admixtures or by the concrete steam treatment traditionally applied at concrete product plants.