Browsing by Author "Oyinbo, S.T."

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    Atomistic Simulations of Interfacial deformation and bonding mechanism of Pd-Cu Composite Metal Membrane using Cold Gas Dynamic Spray Process.
    (Vacuum, 2020-12-01) Oyinbo, S.T.; Jen, T.C.; Zhu, Y.; Ajiboye, J.S.; Ismail, S.O.
    Abstract The creation of atomic structures and the study of the deformation processes through molecular dynamics simulations have shown many advantages. However, gaps associated with the development and evolution of microstructure in the coating zone and dynamic processes that take place during cold gas dynamic sprayed materials still exist. The focus of this study was to investigate the interfacial deformation behaviours and the mechanism of bonding between atoms of palladium (Pd) and copper (Cu) composite metal membrane (CMM) using molecular dynamic simulations. The results confirmed that asymmetric deformation occurred during cold gas dynamic spray at the Pd-Cu interfacial region. As the impact time increases, the layer thickness at the interface also increases. The concentrations of Pd-Cu CMM at the interfacial zone showed the presence of phase transitions at relatively long impact time. Furthermore, CGDS deformation was found to be an unsteady and dynamic process. Explicit bond analysis in this study also has shown that breaking of atomic bonds is not the key mechanism for the initial Pd-Cu plastic deformation occurrence. The higher interfacial bonding energy and interfacial shearing strength at the Pd-Cu CMM interface expressed the bonding strength and compatibility of Pd and Cu.
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    Load Prediction for the Extrusion from Circular Billet to Symmetric and Asymmetric Polygons using Linearly converging die profiles
    (Key Engineering Materials, 2014-09-01) Ajiboye, J.S.; Oyinbo, S.T.
    The deformation load is the most important parameter in the press design as it affects the structure and the general integrity of the final product. Therefore, every other parameter such as die shape, friction, type of process (hot or cold), and speed considered in modeling is optimized to cut back on the metal forming load. The flow of metal is largely influenced by the geometry of the die and hence the geometric shape of the tools is the main factor by which an optimum load can be evaluated. In extrusion process the strain distribution, resulting from deformation load, and other important variables that influence material structure, such as a hydrostatic stress, are strongly dependent on the geometry of the die. In the present investigation using linearly converging die profiles, the extrusion of symmetric and asymmetric polygons such as circular, square, triangular, hexagonal, heptagonal, octagonal, and L-, T- and H-, respectively sections from round billet have been numerically simulated. Mathematical equations describing the die profiles were derived, and then using MATLAB R2009b the co-ordinate of the die profiles was evaluated. A solid CAD model for the linearly converging die profile was made using Autodesk Inventor 2013 software and numerical analysis using DEFORM software for extrusion of the above sections from round billet was then performed to predict, for dry and lubricated condition, the extrusion load during deformation. It is found that the predictive loads for asymmetric shapes are found to be higher than that of the symmetric shapes. While there is no marked difference between the predictive loads for symmetric shapes that of the asymmetric shapes is significant where L-section has the highest extrusion load, followed by T-section and the H-section given the least pressure.
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    Numerical Simulation of Axisymmetric and Asymmetric Extrusion Process Using Finite Element Method
    (International Journal of Scientific & Engineering Research, 2015-06-01) Oyinbo, S.T.; Ikumapayi, O.M.; Ajiboye, J.S.; Afolalu, S.A.
    The deformation load is the most important parameter in the press design. The flow of metal, consequently load, is largely influenced by the geometry of the die and hence the geometric shape of the tools is the main factor by which an optimum load can be developed. In extrusion process the strain distribution, resulting from deformation load, and other important variables that influence material structure, such as a hydrostatic stress, are strongly dependent on the geometry of the die. In the present investigation using linearly converging die profiles, the extrusion of simple and advanced polygons such as circular, square, triangular, hexagonal, heptagonal, octagonal, L-, T-, and H- sections from round billet have been numerically simulated. Mathematical equations describing the die profiles were evaluated. A solid CAD model for the linearly converging die profile was made using Autodesk Inventor 2013 software and numerical analysis using DEFORM 3D software for extrusion of the above sections from round billet was then performed to determined, for dry and lubricated condition, the load prediction, effective stress, effective strain, strain rate, velocity and temperature distribution during the deformation. It is found that the predictive loads for advance (asymmetric) shapes are found to be higher than that of the simple shapes. While there is no marked difference between the predictive load for simple (axisymmetric) shapes, the L-section has the highest extrusion load, followed by T-section and the H-section given the least pressure.