Volume 5, Issue 2 , 2017

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    Open Access
    Assessing Susceptibility to Chromium Carbide Precipitation in Cr-Mn Austenitic Stainless Steel Welds
    (University of Lagos Press, Akoka, 2017) Amuda, M.O; Enumah, K.S; Onitiri, M.A; Osoba, L.O
    Chromium-manganese austenitic stainless steel is a low cost grade with metallurgical and mechanical properties approximating a standard nickel-chromium austenitic stainless steel. It serves as a good substitute to the standard nickel-chromium grade owing to the high cost of nickel. But, there is little information on its weldability particularly the influence of welding parameters on chromium carbide precipitation in the heat affected zone. This limits its structural application through fusion welding. Therefore, in this paper, carbide precipitation in chromium-manganese austenitic stainless steel welds was investigated in the heat input range 180 - 300 J/mm under different combinations of arc current and welding speeds. Microstructural analysis after 10% oxalic acid electrolytic etch revealed that increasing heat input produced significant changes in microstructure of the welds with wider sensitized structure at heat input greater than 206 J/mm. Microstructure of welds produced at heat input lower than 206 J/mm was free of chromium carbide precipitation. This level of heat input which corresponds to arc current of 110 -125A and welding speeds in the range 319- 395 mm/min show that sensitized region associated with chromium carbide precipitation can be safely avoided during fusion welding of this grade of austenitic stainless steel through carefully selected welding parameters.
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    Open Access
    Wear Behaviour of Low Alloy Grey Cast Iron (NF-Grey 7): The Effect of Ferrosilicon and Carbonised Coconut Shell Nanoparticle Addition
    (University of Lagos Press, Akoka, 2017) Agunsoye, J.O; Bello, S.A; Odunmosu, A.K
    Effect of ferrosilicon and carbonised coconut shell nanoparticle additions on wear resistance of (NF-Grey 7) cast iron were studied. Alloys of (NF-Grey 7) cast iron were produced by a gradual increase in masses of the ferrosilicon and carbonised coconut shell nanoparticle additions using a green sand mould and stir cast technique. The behaviour of the material under shock energy impact and dry sliding wear conditions were studied. Results revealed that addition of the ferrosilicon and carbonised coconut shell nanoparticle additions to the (NG-Grey 7) cast iron enhanced the wear resistance and impact energy absorption more than what obtained in the earlier NG-Grey 7 cast iron reinforced with ferrosilicon and graphite micro particles. Hence, new alloy of cast iron for jaw crusher and other heavy equipment applications where wear resistance and energy absorption are a prime prerequisite has been developed.
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    Open Access
    Table of Content
    (2017) Journal of Medicine, Science & Technology
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    Open Access
    A Simpson Type Trigonometrically Fitted Block Scheme for Numerical Integration of Oscillatory Problems
    (University of Lagos Press, Akoka, 2017) Abdulganiy, O.A; Akinfenwa, O.A; Okunuga, S.A
    The construction of Second Derivative Trigonometrically Fitted Block Scheme of Simpson Type (TFBSST) of algebraic order 6via collocation techniques is considered for the solution of oscillatory problems. A Continuous Second Derivative Trigonometrically Fitted method (CSDTF) whose coefficients depend on the frequency and step size is constructed using trigonometric basis function. The CSDTF is used to generate the main method and one additional method which are combined and applied in block form as simultaneous numerical integrators. The investigation of the stability properties of the method shows that the method is zero stable, consistent and convergent. Numerical examples presented show that the method is accurate and efficient.
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    Open Access
    The Effect of Process Parameters on Mechanical and Wear Properties of Alluminium-fired Clay Composites
    (University of Lagos Press, Akoka, 2017) Agbeleye, A.A; Hassan, S.B; Esezobor, D.E; Balogun, S.A; Agunsoye, J.O
    In this paper, the mechanical and tribological behaviours of as cast and rolled samples of Aluminium AA1070/fired clay (Al-Clay) composites were studied. The composites were developed through stir casting route with 0-20 wt.% clay particles of grain sizes250, 177 and 150 μm. The samples were cold rolled to final reduction of 20 and 35%.Hardness, tensile, impact and wear tests were performed on the developed composite samples and their microstructure were examined to determine the phases present in the composite. The results showed improvement in the mechanical and wear properties of Al-Clay composites with increase in wt.% clay addition. Increase in percent reduction also showed a reasonable increase in the mechanical and wear properties of the rolled samples. The results obtained clearly shows that Al-clay composite can be produced by stir casting and possess superior properties to the Aluminium AA1070 in terms of wear properties, impact energy, tensile strength as well as hardness.
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    Open Access
    Cytogenetic Evaluation of Microsporocytes of Setcreasea Purpurea (Boom) Flower
    (University of Lagos Press, Akoka, 2017) Sifau, M.O.; Adekoya, K.O.; Oboh, B.O.; Williams, G.O.
    Setcreasea purpurea Boom (Wandering Jews) belongs to the family Commelinaceae of the order Commelinales. The family, made up of 38 genera and about 600 species, occurs mostly in the tropical and warm regions of the world. Many are popular as garden or house ornamentals. It is a flower-bearing plant yet it is mostly propagated vegetatively due to the formation of sterile pollen grains thereby making pollination impossible. Cytogenetic study was carried out to observe the chromosome behaviour in the microsporocytes during meiosis with the aim of understanding the reasons behind the sterility of the pollen grains. Immature flower buds of Setcreasea purpurea were dissected in a Petri dish containing tap water. The microsporocytes were squashed using lactic acetic-orcein stain. Most microsporocytes observed from slides contained 12 bivalents. However, a few contained 10 bivalents and one quadrivalent or 8 bivalents and 2 quadrivalents. This shows that 2n = 24 in the microsporocytes. Other irregularities observed included laggards, abnormal disjunction, chromosome bridges and chromosome fragments all at anaphase-1 and micronuclei at telophase-1. Occurrence of laggards, chromosome bridge formation and micronuclei were low ranging from 1 to 3 in the population of S. purpurea studied. The consequence of these irregular chromosomes is their loss and non-inclusion in the daughter nuclei at telophase-I. The loss of these segments would result in loss of genes on them resulting in the unviable microspores at the end of meiosis. These microspores are the pollen grains in which a large number of them (about 90%) have been found to be sterile thereby making the plant to reproduce asexually by stem-tip cuttings.
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    Open Access
    A P-stable Linear Multistep Method for Solving Stiff Delay Differential Equations
    (University of Lagos Press, Akoka, 2017) Akinfenwa, O.A; Abdulganiy, R.I; Okunuga, S.A; Obinna, U.K
    In this paper, a P-stable linear multistep method is derived for the numerical solution of delay differential equations (DDEs). The method has order k+1 and implemented using a constant step size in a block by block fashion. The Pstability region of the method is discussed. The numerical results revealed that the method is efficient and reliable for the solutions of first order delay differential equations. Tables 1-4 presented for some standard delay problems show theaccuracy of the method when compared to those in the literature.
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    Open Access
    Mechanical and Wear Characteristics of Aluminium Brass
    (University of Lagos Press, Akoka, 2017) Esezobor, D.E; Agbeleye, A.A; Onovo, H.O; Bodude, M.A
    In this paper, the influence of the processing parameters on the wear and mechanical properties of 5 – 12 % aluminum red brass (Al-brass) was studied. The wear characteristics of developed Al brass in dry sliding conditions were exposed through a series of pin-on-disc sliding wear tests. Three load levels of 2, 7 and 12N, sliding speeds of 125 and 250 rpm and two sliding distances of 392.7 and 785.4m were investigated. The mechanical properties of the Al brass were determined using standard techniques. The results showed an increase in tensile strength from 225 MPa at 5 % aluminum addition to a maximum of 248 MPa at 10% Al and then a decline to 240 MPa at 12 % Al. The peak stress value increases as the weight percentage composition of Al increases until at 11%Al when it reduces. The impact energy and the hardness values of the as-cast Al brass rose from 54.2 Joules and 81HRC to 122 Joules and 92.4 HRC respectively at 12 % aluminum addition. At lower load of 2N, the addition of 5 % of Al brought a drastic improvement (65 %) to the wear resistance at 125 rpm and 250rpm, but the improvement became consistent thereafter. The same trends occurred at load of 7 N, but with lower degree of improvement (approximately 40 %). In contrast, under higher load of 12 N, the addition of Al brought slight and consistent improvement (10 -15 %) to the wear resistance.
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    Open Access
    Investigation of Metallurgical and Microhardness Properties of Titanium Alloy in Laser Metal Deposition Process
    (University of Lagos Press, Akoka, 2017) Mahamood, R.M; Abdulkareem, S; Ajao, K.R; Aweda, J.O
    This paper reports on the investigation of metallurgical and microhardness properties of laser metal deposition of Titanium alloy- Ti-6Al-4V. Ti-6Al-4V substrate and Ti-6Al-4V powder (150-200 μm) both at 99.6% purity were used in this study. The input laser power varied between 0.8 and 4.0 kW while other processing parameters were kept constant. They include the scanning speed of 0.005 m/sec, powder flow of 1.44 g/min and the gas flow rate of 4 l /min. The microstructure and the microhardness were examined under the optical and scanning electron microscope. The microhardness was measured using the Vickers hardness tester. The study revealed that the layer band occurred in all the samples except those samples at very high laser powers. The microstructure of the heat affected zone is characterized with fine globular primary alpha and beta grains at low laser power and become coarse as the laser power was increased. The microhardness was found to initially increase and then decrease as the laser power was increased beyond 3 kW.
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    Open Access
    Growth and Bulb Yield of Allium Sativum L. (Garlic) in Sandy Loam and Silt Loam Soils
    (University of Lagos Press, Akoka, 2017) Ade-Ademilua, O.E; Utibe, U
    The differences in the growth and bulb yield of Allium sativum L. (garlic) in sandy loam and silt loam soils were studied. Vegetative growth of plants in sandy loam was significantly higher than that of plants grown in silt loam. The plant height, number of leaves, fresh weight and dry weight of plants grown in sandy loam was significantly higher than those of plants grown in silt loam. The weight of bulbs produced by plants grown in silt loam (2.52 ± 0.46 g) was significantly higher at p<0.05 than that of plants grown in sandy loam (1.57 ± 0.21 g). There was no significant difference in the numbers of cloves per bulb produced by plants from both soil types. Cloves of bulb produced by plants grown in silt loam had significantly higher allicin concentration (2.11 ± 0.17 μg/g fresh clove) than plants grown in sandy loam (1.19 ± 0.33 μg/g fresh clove). This report shows that while garlic plants grew vegetatively better in sandy loam, bulb yield (weight and allicin concentration) was enhanced in silt loam. A luxuriant vegetative growth of garlic appears not to results in a better bulb yield.
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    Open Access
    Technical Feasibility and Economics of Direct Aplication of the Nigerian Tar Sand Deposits as Road Asphalt
    (University of Lagos Press, Akoka, 2017) Akinmosun, A; Olufowobi, S.O
    This study present, the technical feasibility and the Economics of the direct application of Nigerian Tar sand deposits as road asphalt. Twenty Tar sand samples were selected from nine locations in parts of Southwestern Nigeria and several engineering tests were conducted on twenty samples. The tests involved Bitumen extraction to determine the percentage of bitumen content, Sieve analysis, Specific gravity and Marshall tests which include the Stability, Flow, Density and Void determination. The percentage of bitumen saturation ranges from 5.6 to 28.6%, the stability values ranges from 2.1 to 6.3KN, the flow values ranges from 27.8 to 63.1mm10, specific gravity values ranges from 1.79 to 2.35g/ml and density values ranges from 1.75 to 2.01g/ml. The sieve analysis results indicate that none of the samples could be applied directly in road construction, though some of them possess stability and flow values that meet the standard specification for wearing course of asphalt. Design mix analysis which involves modification of mineral aggregates was carried out on ten out of the twenty samples to improve their gradation. From economic point of view, using the modified aggregates of tar sand (@₦7,000-9,500 per ton) as against current asphalt concrete (₦20,000 per ton) would have potentially large cost saving in Nigeria.