Browsing by Author "Oluwole, O."

Now showing 1 - 16 of 16

3-D geometric modeling for finite element analysis using MATLAB® C programming
(2012) Eyere, E.; Oluwole, O.
Most finite element analysts in Nigeria develop own codes for their analysis due to inability to purchase commercial finite element analysis software packages that come with GUI geometric modelers and difficulty in managing coordinate data from imported CAD files. General purpose computer-aided design software packages are good drafting tools but do not have imbedded facilities to carry out finite element analyses of descretized (mesh) models. This paper demostrates how MATLAB® programming language can be used to generate 3-D geometric models suitable for finite element anaylsis. In this work, model of a water storage tanker was drawn using AutoCAD®, and then the same model was generated using MATLAB®. The results showed that MATLAB® can be used to obtain meshed and surface model suitable for finite element analysis.
Artificial Neural Network Modeling for Al-Zn-Sn sacrificial anode protection of low carbon steel in saline media
(2012) Oluwole, O.; Idusuyi, N.
This work presents the artificial neural network(ANN) modeling for sacrificial anode cathodic protection of low carbon steel using Al-Zn-Sn alloys anodes in saline media. Corrosion experiments were used to obtain data for developing a neural network model. The Feed forward Levenberg-Marquadt training algorithm with passive time, pH, conductivity,% metallic composition used in the input layer and the corrosion potential measured against a silver/silver chloride(Ag/AgCl) reference electrode used as the target or output variable. The modeling results obtained show that the network with 4 neurons in the input layer, 10 neurons in the hidden layer and 1 neuron in the output layer had a high correlation coefficient (R-value) of 0.850602 for the test data, and a low mean square error (MSE) of 0.0261294. 9
Effect of silicon content and shake-out time on hardness and grain size properties of GL 250 cast iron
(2011) Atanda, P.; Oluwadare, G.; Oluwole, O.
"The properties of cast iron grade GL 250 are dependent on the microstructures developed during casting. These microstructures are in turn dependent on the composition of the alloy, type of mould and other numerous casting practice variables such as shake-out time, pouring temperature, mould ambient conditions and inoculating technique. In this work, the effect of silicon content and shake-out time on the grain size (GS) and hardness properties of GL 250 cast iron was studied using a pouring temperature of 14000C and sand mould casting. Using charge materials consisting of pig iron and other additives, GL 250castings containing silicon contents of 1.7, 2.1 and 2.7% were casted using a constant pouring temperature of 14000C, molding sand of specified properties and ambient mould temperature of 320C. Results showed that type A flake type was obtained at 30mins shakeout time for all samples for the C.I composition under study. Increasing shake-out time decreased hardness and increased carbide grain size. Increasing silicon content was observed to increase grain size and reduce free graphite but with resultant decrease in hardness. Two mathematical relationships were derived. One related grain-size to silicon content and shakeout time while the second related Brinnel Hardness to Silicon content and shake-out time. They are: Grain Size=0.40 Si+0.17Shake-out Time-0.15 and BHN=-60.53Si-7.15Shake-out Time+329.35 at 14000C pouring temperature in a molding sand of specified properties and sand mould ambient temperature of 320C. "
Effect of silicon content and shake-out time on hardness and grain size properties of GL 250 cast iron
(2011) Atanda, P.; Oluwadare, G.; Oluwole, O.
"The properties of cast iron grade GL 250 are dependent on the microstructures developed during casting. These microstructures are in turn dependent on the composition of the alloy, type of mould and other numerous casting practice variables such as shake-out time, pouring temperature, mould ambient conditions and inoculating technique. In this work, the effect of silicon content and shake-out time on the grain size (GS) and hardness properties of GL 250 cast iron was studied using a pouring temperature of 14000C and sand mould casting. Using charge materials consisting of pig iron and other additives, GL 250castings containing silicon contents of 1.7, 2.1 and 2.7% were casted using a constant pouring temperature of 14000C, molding sand of specified properties and ambient mould temperature of 320C. Results showed that type A flake type was obtained at 30mins shakeout time for all samples for the C.I composition under study. Increasing shake-out time decreased hardness and increased carbide grain size. Increasing silicon content was observed to increase grain size and reduce free graphite but with resultant decrease in hardness. Two mathematical relationships were derived. One related grain-size to silicon content and shakeout time while the second related Brinnel Hardness to Silicon content and shake-out time. They are: Grain Size=0.40 Si+0.17Shake-out Time-0.15 and BHN=-60.53Si-7.15Shake-out Time+329.35 at 14000C pouring temperature in a molding sand of specified properties and sand mould ambient temperature of 320C. "
Effect of some process variables on nickel electroplating of low carbon steel
(2015) Oloruntoba, D.; Eghwubare, O.; Oluwole, O.
"This research work investigated the effect of current density, bath concentration, bath solution volume and electroplating time on nickel electroplating of low carbon steel. Varying voltage between 0.3 and 0.8 V, bath concentration between 0.27 g/cm3 (0.79 mol/dm3) and 0.35 g/cm3 (1.02 mol/dm3), electroplating time between 10 and 30 minutes and bath solution volume between 200 and 700 cm3, the effect of these process variables on electroplating was studied. The temperature was kept in conformity with Watt’s method at 50 ±5°C. It was observed that a bath concentration of 0.31 g/cm3 (0.89 Mol/ dm3) concentration gave the best nickel deposit at 0.5V for 15 minutes. This would correspond to a Watt solution of composition: nickel sulphate-230 g/l, nickel chloride- 46.5 g/l and boric acid-30.8 g/l with a pH of 4.18. Higher Watt bath concentration did not yield good results as plating thickness decreased and there was no luster. It was also observed that increasing time of plating served to increase plating thickness and did not affect brightness of plating. However non-uniform nickel deposition was observed for longer plating time. Increase in voltage served to increase rate of electrodeposition with the exceptions of 0.7 V where a long streak of plating was observed on substrate instead of uniform plating and 0.8V where plating lacked brightness having a burnt appearance. Bath volumes of between 200-500 cm3 were observed to be best for the coupons used (15mm × 20mm). Bath volumes above 500cm3 gave black plating appearance. "
Effects of cassava juice on corrosion of mild and high yield steel bars in concrete structures
(2009-03) Oluwadare, G. O.; Akindahunsi, A. A.; Oluwole, O.; Agbaje, I. A
Nigeria is the highest producer of cassava in the world and cassava juice is rich in hydrocynic acid, a by-product from the extraction process. This paper examines the effect of cyanide ions, the reacting ions from hydrocyanic acid on reinforcing bars when cassava tubers are processed on reinforced concrete palteforms. Mild and high yield steel reinforcing bars are embedded in concrete cubes cast and cure for 21 and 28 days. These steel bars were used to model the experiment. Half-cell potential apparatus was used to take potentials measurement of both steel bars with concrete cubes immersed in hydrocyanic acid and ordinary water for 32 days. Corrosion rates under these different conditions were monitored. The results demostrated that both steel types will corrode in hydrocynaic acid, however, high yiled steel has better corrosion resistance than mild steel: this is due to the mechanical properites and chemical composition of the steel. It was also observed that with increase in curing age the degree of probability of corrosion decreased.
Finite element analysis of von-mises stress distribution in a spherical shell of liquified natural gas (LNG) pressure vessels
(2011) Adeyefa, O.; Oluwole, O.
"This research work investigated the modeling of Von Mises stress in LNG Spherical Carbon Steel Storage tank using assumed displacement Finite Element analysis based on shallow shell triangular elements. Using equations of elasticity, constant thickness carbon steel spherical storage tanks were subjected to different loading conditions. This paper stresses the need for proper definition of shallow element using sector angles to obtain the shallowness. The shallow spherical triangular element has five degrees of freedom at each of its corner node, which are the essential external degrees of freedom. The assumed displacement fields of these shallow triangular elements satisfied the exact requirement of rigid body modes of motion. The FORTRAN 90 programming language was used for the programme coding to solve finite element equations resulting from the model while Von Mises stresses distribution within the spherical storage tank shell subjected to different internal pressures were determined. The results showed that the use of non-shallow elements due to improper sector angles resulted in unreliable results while real shallow elements produced results that tallied with ASME Section VIII Div 1, Part UG values. "
Finite element analysis of von-mises stress distribution in a spherical shell of liquified natural gas (LNG) pressure vessels
(2011) Adeyefa, O.; Oluwole, O.
"This research work investigated the modeling of Von Mises stress in LNG Spherical Carbon Steel Storage tank using assumed displacement Finite Element analysis based on shallow shell triangular elements. Using equations of elasticity, constant thickness carbon steel spherical storage tanks were subjected to different loading conditions. This paper stresses the need for proper definition of shallow element using sector angles to obtain the shallowness. The shallow spherical triangular element has five degrees of freedom at each of its corner node, which are the essential external degrees of freedom. The assumed displacement fields of these shallow triangular elements satisfied the exact requirement of rigid body modes of motion. The FORTRAN 90 programming language was used for the programme coding to solve finite element equations resulting from the model while Von Mises stresses distribution within the spherical storage tank shell subjected to different internal pressures were determined. The results showed that the use of non-shallow elements due to improper sector angles resulted in unreliable results while real shallow elements produced results that tallied with ASME Section VIII Div 1, Part UG values. "
Finite element modeling of low heat conducting building bricks
(Scientific Research, 2012-08) Oluwole, O.; Joshua, J.; Nwagwo, H.
Heat conduction through conventional and interlocking building bricks with cavities was studied in this work. Heat transfer analysis was carried out using MATLAB® partial differential equation toolbox. Regular and staggered hole arrangements were studied. Results showed that four staggered holed interlocking bricks were effective in thermal resistance into the bricks and increasing the holes beyond four did not give any thermal resistance advantage. For the conventional bricks staggered holes did not give any thermal resistance advantage but the four-holed bricks were also adjudged to be effective in thermal resistance into the brick surface. Increasing the number of holes beyond four in conventional bricks did give some thermal resistivity advantage but very minimal. Structural strengths of holed bricks were not considered in this study
Finite element modeling of seismic response of field fabricated liquefied natural gas (LNG) spherical storage vessels
(Scientific Research, 2013-06) Adeyefa, O.; Oluwole, O.
All real physical structures behave dynamically when subjected to loads or displacements. This research paper, therefore, presents seismic response of field fabricated liquefied natural gas spherical storage vessels using finite element analysis. The seismic analysis procedure used represents a practical approach in quantifying the response of spherical storage vessel with its content when it is subjected to seismic loading. In the finite element method approach, six degrees of freedom per node is used for legs/column of the spherical storage tanks. Lumped mass procedure is employed to determine system mass matrix of the structure. Computer programme code is developed for the resulting matrix equation form finite element analysis of the structure using FORTRAN 90 programming language. The modeling of the seismic load utilizes the ground acceleration curve of a site. From the results of the modal analysis, the system is uncoupled thereby gives way to the application of Newmark’s method. Newmark’s method as one of the widely used time-step approach for the seismic response is applied. The developed programme coding is validated with analytical results (P > 0.5). It shows that the approach in this research work can be successfully used in determine the stability of large spherical storage vessels against seismic loadings when base acceleration spectral of the site are known. This approach gives better results than the static-force approach which gives conservative results. While the approach used in this research treats seismic loads as time event, static-force approach assumed that the full ground force due to seismic motion is applied instantaneously.
Finite element modelling of insulation thickness for cryogenic products for spherical storage pressure vessels
(Scientific Research, 2012-06) Adeyefa, O.; Oluwole, O.
This study investigates various insulation thicknesses requirements for double-walled spherical pressure vessels for the storage of cryogenic liquids. The inner tank is suspended from the outer tank by straps or cables and the annular space between the tanks is filled with insulation. The outer tank is not subjected to the freezing temperatures and is thus assumed to be a standard carbon steel sphere. In the Finite Element Analysis model of the system, one dimensional analysis was employed. This is due to the assumption that temperature gradient does only exist along the spherical radial direction. In the developed model, once the thickness of the inner shell has been determined based on relevant standards and codes—ASME Sec VIII Div 1 or 2, BS 5500 etc. and the thickness of the outer shell is known; the required insulation material thicknesses were calculated for different insulating materials. Set of equations resulting from Finite Element Analysis were solved with computer programme code which was written in FORTRAN 90 programming language. The results obtained are validated by analytical method. The results showed no significant difference (P > 0.05) with values obtained through analytical method. The thicknesses for different insulating materials in-between inner and outer tank shells were compared. The results showed that as the insulating material thickness was increased, the heat flux into the stored product was decreasing and at a certain thickness; it started increasing. The insulating thickness at which this happens is termed as critical thickness of insulating material—the thickness of insulation at which the heat influx to the stored products is minimal; this would therefore reduce boil-off of the stored cryogenic product. High thermal conductivity insulating materials need to be thicker than lower thermal conductivity insulating materials if the system is conditioned to have the same heat flux into the stored product for all insulating materials. In the simulation, different insulating material gives different minimal heat influx into the stored products.
Microstructural study of heat treated chromium alloyed grey cast iron
(2010) Atanda, P.; Okeowo, A.; Oluwole, O.
"This work investigated the effect of annealing, normalizing and quenching heat treatments on the microstructure of some chromium alloyed grey cast iron. Three sets of ten samples each having chromium contents of 0.5, 1.5 and 2.5% were heat treated above the upper critical temperature, to austenitizing temperatures (800oC, 850oC, 900oC) for one hour each and then annealed, normalized and water quenched. Metallographic analyses of the heat treated samples were done. The results showed carbides content increased with increasing Chromium addition. "
Sensitisation study of normalized 316L stainless steel
(2010) Atanda, P. O.; Fatudimu, A.; Oluwole, O.
"Austenitic stainless steels with excellent corrosion resistance and good weldability have wide applications in industry. These iron-based alloys contain a high level of chromium which form protective oxide film on the surface hence resisting corrosion. The oxide film regenerates when damaged, making the steel 'stainless'. However, carbide precipitation due to a welding process or heat treatment can cause the occurrence of chromium-depleted zones at the boundaries, leading to a phenomenon known as sensitisation, in which the depleted zones become the focus of the intense corrosion. The present work was concerned with the study of the sensitization and desensitisation of 316L steel at the normalizing temperatures of 750- 9500 C and soaking times of 0.5, 1, 2 and 8 hrs. 316L stainless steel was observed to be sensitized when heated to 750- 8500 C and held for short soaking times of 0.5 – 2hrs before normalizing. Increasing soaking times at these temperatures to 8 hrs triggered the desensitization process which was fully accomplished at 7500 C but ongoing at 800 and 8500 C. At 9000 C, sensitization did not occur at 30 mins soaking time but observed at soaking times of 1 and 2hrs. At a longer soaking time of 8 hrs, there was full desensitization. At 9500 C, sensitization was already observed at 30 mins. Soaking time and desensitization was observed to be in progress at 1 and 2 hrs soaking time. By 8 hrs there was full desensitization. Thus it was observed that at 9500 C, diffusion of Cr was thermally aided making desensitization fast. The hardness of normalized 316L stainless steel was also observed to decrease with soaking time and normalization temperature "
Simulation studies of shear stresses in reinforced and non-reinforced concrete structures
(2009-06) Akindahunsi, A. A.; Ajayi, J. A.; Oluwole, O.
A simulation study of the shear stresses in non-reinforced and reinforced structures was carried in this work. Using the finite element method and equations of elasticity, columns and concrete deck of a simple storey structure were subjected to plane strian conditions. The results showed that proper reinforcement causes stresses to be directed into the reinforcements with the resultant transverse shear at critical joints of the structure. In the insufficiently reinforced member, the resultant shear of the concrete resulted in load transfered to the reinforcement itself with the resultant buckling of reinforcement and eventual collapse of structure.
Stress effects on microstructure and failure morphology of low carbon steel sheet
(2011-12) Onurisi, N. O.; Oluwole, O.
"This paper presents experimental and simulation study of the effects of stress on microstructure and failure morphology of low carbon steel under plane stress conditions. The study has revealed large extension of grains at the point of fracture and, stress and strain looped around the pearlitic faces of the microstructure matrix. The stress and strain distributions in the microstructure have shown that concentration of stress and strain on the pearlite were instrumental to oblique fracture near the constrained region. "
Stress effects on microstructure and failure morphology of low carbon steel sheet
(2011-12) Onurisi, N. O.; Oluwole, O.
"This paper presents experimental and simulation study of the effects of stress on microstructure and failure morphology of low carbon steel under plane stress conditions. The study has revealed large extension of grains at the point of fracture and, stress and strain looped around the pearlitic faces of the microstructure matrix. The stress and strain distributions in the microstructure have shown that concentration of stress and strain on the pearlite were instrumental to oblique fracture near the constrained region.