Browsing by Author "Aremu, Ishaq Na'Allah"

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    Assessment of Crack Propagation Mode in Martensitic Stainless Steel HAZ with Electron Back Scatter Diffraction: Effects of Environmental Variables
    (Universitatea Politehnica Timisoara (UPT), Romania, 2016-05) Ahmed, Ismaila Idowu; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Aremu, Ishaq Na'Allah; Sherry, Andrew H.
    In this study, an assessment of crack propagation mode in martensitic stainless steels heat affected zone was carried out with electron back scatter diffraction (EBSD) with focus on the effect of environmental variables. Girth welded samples were subjected to four point bend tests in sour and sweet environments. Scanning electron microscope and electron back scatter diffraction technique were both used to study the crack propagation mode and interaction of crack tip with microstructures. Study showed that sample tested in sour environment failed with transgranular cracking and samples tested in sweet environment failed with intergranular stress corrosion cracking mode. The proposed mechanism for the failure was sulphide stress corrosion cracking and intergranular precipitation of carbide by sensitisation process respectively. The correlation between crack path and grains misorientation was studied with aid of EBSD technique.
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    Assessment of Deformation Twinning in Cold Rolled Austenitic Stainless Steels with Electron Back Scatter Diffraction
    (Faculty of Engineering and Technology, University of Ilorin, 2014-06-09) Ahmed, Ismaila Idowu; Wright, David; Adebisi, Jeleel Adekunle; Aremu, Ishaq Na'Allah; Yahaya, Taiwo; Quita da Fonseca, Joao
    Deformation twinning has traditionally been studied with Transmission Electron Microscopy (TEM). In this study, an assessment of deformation twinning in Austenitic Stainless Steel (ASS), type 304L, cold rolled to 20% reduction was investigated using Scanning Electron Microscopy (SEM) and Electron Back Scatter Diffraction (EBSD) techniques rather than the conventional TEM. The study revealed the presence of deformation twins in the cold rolled grains of ASS. It emerged from the study that the deformation twins observed may facilitate localised heterogeneous deformation and development of internal stresses within the grain.
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    Numerical Modelling of Petroleum Underground Storage Tank Dip Gauge
    (SAGE, 2014-05) Ahmed, Ismaila Idowu; Abdulkarim, Kazim Olawale; Yahaya, Taiwo; Aremu, Ishaq Na'Allah; Alabi, Abdul Ganiyu Funsho
    This work describes numerical modelling of underground hydrocarbon storage tank dip gauge. The work was carried out at the request of a petroleum company faced with predicament, whereby three underground tanks, for the storage of hydrocarbon products, namely, Petroleum Motor Spirits, Automotive Gas Oil, and Dual Purpose Kerosene, were fully installed and buried in the earth without provision for the fluid measuring gauge. The objective was to design and fabricate a dip gauge with the design capacity of measuring up to 30,000 L of hydrocarbon from the underground storage tank. To achieve the objective of designing an accurate and reliable gauge, mathematical analysis of the available data of tanks was carried out using Newton–Raphson iteration method. A model dip gauge was designed and calibrated with the results of mathematical analysis. The dip gauge was designed with measurement capability between the range of 200–15,886 L and 400–31,765 L of hydrocarbon in the smaller and bigger tanks, respectively. Aluminium alloy 6063-T6 was used for fabrication of the gauge on account of its excellent strength and good corrosion resistance in relevant hydrocarbon environment.
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    Stress Corrosion Cracking of Austenitic Stainless Steel in Chloride Environment
    (Faculty of Engineering, Ahmadu Bello University Zaria, 2015) Ahmed, Ismaila Idowu; Alabi, Abdul Ganiyu Funsho; Odusote, Jamiu Kolawole; Aremu, Ishaq Na'Allah; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Talabi, Segun Isaac; Yahya, Raheem Abolore; Lyon, Stuart B.
    This study was carried out to assess the effect of applied potentials on stress corrosion cracking of Austenitic Stainless Steels (ASS), Type 304L in a potentiostatically controlled chloride environment at ambient temperature. The stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Post-mortem analyses of failed specimens were carried using optical microscopy. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Post-mortem analysis of failed samples showed evidences of SCC and ductile failure on the fracture surface.
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    Stress Corrosion Cracking of Austenitic Stainless Steels in Potentiostatically Controlled Chloride Environments at Ambient Temperature
    (Universitatea Politehnica Timisoara (UPT), Romania, 2015-11-04) Ahmed, Ismaila Idowu; Yahaya, Taiwo; Adebisi, Jeleel Adekunle; Aremu, Ishaq Na'Allah; Alabi, Abdul Ganiyu Funsho; Lyon, Stuart B.
    In the earlier study carried out to assess the effect of applied potentials on stress corrosion cracking of Austenitic Stainless Steels (ASS), Type 304L in a potentiostatically controlled chloride environment at ambient temperature, the assessment of cracks in failed specimen was limited to optical microscope. In this present study, Scanning Electron Microscope (SEM) was used in addition to optical microscope to gain a better understanding of the Stress Corrosion Cracking (SCC) mechanism in the failed specimen. Stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Post-mortem assessments of failed specimens were carried out using both optical and SEM. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Post-mortem assessment of failed specimens showed evidences of SCC and ductile failure on the fracture surface. The cross sectional analysis of the failed samples showed cracks that were predominantly transgranular stress corrosion cracks.