International Journal of Engineering Research in Africa Vol. 6

Abstract: First results of the influence of Equal Channel Angular Pressing (ECAP) on the wear behavior of the magnesium alloy AZ80 have been discussed. The evident grain refinement and redistribution of second phases in the 4 pass processed materials resulted in an increase of the hardness state in the AZ80 alloy. Wear tests conducted on a pin-on-disc set-up revealed better wear resistance for the 4 pass processed materials. Isothermal aging treatment, at 210°C for 10 hrs, of the ECAP processed materials showed that wear resistance properties are improved markedly. For incremental sliding speeds during the wear test, wear rate of the AZ80 alloy was found to increase.

Abstract: This study formulated maize-starch based cutting fluids and determined the performance of the cutting fluids for use in turning AISI 304 stainless steel with P35 coated carbide tool. This was with a view to determining the effect of the maize-starch based cutting fluids on power consumption and temperature developed at the tool-workpiece interface during turning of AISI 304 stainless steel using P35 coated carbide tool. The results showed that the temperature at the cutting zone increase with increase in depth of cut while the power consumed decreased with increase in the cutting fluid flow rate. At the best machining data point, maize-starch based cutting fluid showed reduced temperatures and power consumed as compared to the conventional cutting fluids used for the study: 34oC and 0.735 W for maize starch mixed with soluble oil, 40oC and 0.733 W for maize starch mixed with coconut oil respectively. Corresponding values for straight coconut oil were 47.5oC and 0.942 W and for soluble oil mixed with water, 37.5oC and 1.729 W, respectively. It is concluded that maize-starch based cutting fluids are effective in reducing the temperature and power consumed during cylindrical turning. The results indicated that maize-starch mixed with soluble oil has remarkable potentials for use as a cutting fluid.

Abstract: This paper reports work done which seeks to enhance the insulating property of locally mined clays with application to the building and insulation of medium temperature furnaces. Mixtures of locally mined clays with kaolin obtained from Teleku bokasso in the Western Region of Ghana were made. Samples were mixed in different ratios to form composite bodies in the form of bricks of dimensions 7mm×7mm×7mm cast at constant pressure and sintering temperature of 1000 °C. The clays used were characterized in terms of their particle size and chemical composition. The thermal resistivity, water absorption, weight loss, shrinkage, porosity and strength of samples were determined. The results showed that for all samples studied, an increase in Teleku bokasso clay enhanced the insulating properties of the samples from an average of 0.24% for samples containing 20% Teleku bokasso to approximately 2% for samples containing 60% of Teleku bokasso. Mixtures of Teleku bokasso with Afari clay were on the average 1% more thermally resistant than those of Mfensi. Sample A3 (with 40% Teleku bokasso with Afari) is recommended for the building of local furnaces because it had its strength more than doubled (105%) and was by 2% more resistant to heat than M3 (40% Teleku bokasso with Mfensi). All samples showed low weight loss levels, low water absorption, good linear shrinkage and compressive strength.

Abstract: The effect of image resolution on the measured geometry and topological characteristics of network models extracted from 3-D micro-computer tomography images has been investigated. The study was conducted by extracting geologically realistic networks from images of two rock samples, imaged at different resolutions. The rock samples involved were a Castlegate Sandstone and a Carbonate-28 reservoir rock. Two-dimensional images of these rocks were obtained at a magnification of ×50. The carbonate sample was studied at two different resolutions of 0.133 microns and 1.33 microns, while the sandstone was studied at 5.60 microns. Three-dimensional images of these 2-D images were obtained via image reconstruction, to generate the pore architecture models (PAMs) from which networks models of the imaged rocks were extracted with the aid of Pore Analysis software Tools (PATs). The measured geometry and topology (GT) properties included Coordination Number, Pore Shape Factor, Pore Size Distribution, and Pore Connectivity. The results showed that the measured geometry-topology (GT) characteristics of a network model depend greatly on the image resolution used for the model. Depending on the micro-structure of the reservoir rock, a minimum image resolution is necessary to properly define the geometrical and topological characteristics of the given porous medium.

Abstract: Desiccation studies are an integral part of material selection for waste containment systems. Laboratory studies on compacted tropical clay (with illite as the dominant clay mineral sourced from an excavation site) treated with up to 16% rice husk ash (RHA); an agro-industrial waste to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment systems were carried out. Soil-RHA mixtures were compacted using three compactive efforts at -2, 0, 2 and 4% of optimum moisture content (OMC). Compacted samples, extruded from the compaction mould were allowed to air dry in the laboratory for a 30 day period after which they were subjected to two cycles of wetting and drying. Results show that changes in mass and volumetric shrinkage strain (VSS) were large within the first five days of drying and were affected by the compactive effort. VSS increased with higher moulding water content, water content relative to optimum and RHA treatments. VSS were affected by the compactive effort. Acceptable compaction planes were obtained for up to 12% RHA treatment. After two cycles of wetting and drying, it was observed that the rate of capillary rise within the compacted soil increased with lower compactive effort and higher rice husk ash treatment. Lower amount of cracking was observed in soil specimen with higher rice husk ash treatment and higher cracking in soils with lower rice husk ash content. Increased compactive effort reduced the effect of swelling during wetting; showing the suitability of the material as a cover in municipal waste containment facility and beneficial reuse of this agro waste product.

Abstract: Three commonly used expressions for modeling soil-water infiltration were evaluated for a tropical rainforest watershed in southwestern Nigeria under conditions of old, highly weathered soils and high rainfall intensities. The evaluation focused on the suitability of the expressions in assessing the decrease in infiltration opportunities that usually accompany deforestation. The equations were fitted into data spanning nine years obtained from infiltrometer experiments of the type where infiltration and runoff are generated onsite in response to single rainfall intensity without allowing for any modification due to inflow. The analysis revealed that soil-water infiltration into these tropical alfisols is better described by the Kostiakov’s model. Effects of duration of cultivation for different years following deforestation of the secondary vegetation were highlighted.

Abstract: The effects of varying distances on wireless signal propagation in indoor and outdoor built sites is presented in this paper. In indoor and outdoor built sites the major RF signal attenuation is due to multi-path interference, signal loss (fading), and non-line of sight signal blockage. A number of mobile communication systems is currently and frequently being used in indoor environments based on IEEE 802.11b standards which is on 2.4GHz frequency ISM band at the rate of 11Mbps. To determine the effects of varying distances on signal strength at 2.457 GHz, a Spykee spy Wi-Fi robot was used as the transmitter and laptop installed with a Wi-Fi card and Spykee console software to control the robot was used as the receiver. Results showed that the signal attenuation levels increased as distances increased.