Browsing by Author "Adeyemi, M.B."
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Item The effect of selected parameters on temperature distributions in axisymmetric extrusion process(Journal of Mechanical Science and Technology, 2007-09-30) Ajiboye, J.S.; Adeyemi, M.B.A numerical method was developed to simulate the transient temperature distributions during forward extrusion process. The computer program simulates the extrusion process and takes into account some extrusion variables such as extrusion velocity, extrusion ratio, die preheat temperature, and percentage reduction in area. It can be seen that the higher the percentages reduction in areas, the higher the temperature rises during the extrusion process. Also, increasing speed of deformation shows an increasing dead zone temperature rise than a more gradual die land temperature rise. It is further seen that extrusion temperature increase is a function of the container temperature.Item Effects of extrusion variables on temperature distribution in axisymmetric extrusion process(International Journal of Mechanical Sciences, 2007-09-01) Ajiboye, J.S.; Adeyemi, M.B.A numerical method was developed to simulate the non-steady-state temperature distributions during forward extrusion process. The velocity, strain rates, and strain fields within the deformation zones during extrusion were obtained, using upper bound method of analysis to obtain internal heat generations coupled to the necessary heat transfer conduction equations. The computer program written in C++ language essentially simulates the extrusion process and takes into account extrusion variables such as material properties, friction conditions, extrusion velocity, extrusion ratio, die preheat temperature, billet height, percentage reduction in area, and die land length. The effects of billet height and percentage reduction in area on the temperature distributions within the dead metal zone give good agreements with experimental results. It is found that the higher the billet’s heights and higher the percentages reduction in areas, the higher the temperature rises during the extrusion process. The die land zone shows increasing temperature rise with increasing friction coefficient, while increasing friction coefficient has no effect on the dead zone temperature. Also, increasing speed of deformation shows an increasing dead zone temperature rise than a more gradual die land temperature rise. It can be stated that the extrusion temperature increases proportionally to the increase of the container temperature.Item Temperature changes with die profiles in axisymmetric forward extrusion process(Journal of Applied Scence, Engineering and Technology, 2008) Ajiboye, J.S.; Adeyemi, M.B.Transient heat transfer and temperature change due to varying die opening shapes in a direct extrusion of lead have been numerically investigated and presented. Upper bound method of analysis was used to evaluate the internal heat generation due to plastic deformation and frictional heat at various stages of the extrusion process. At the extrusion die land region, temperature rises with increasing complexity of die openings geometry with I-shaped section, giving the highest temperature rise, followed by T-shaped section, rectangular, circular shaped die openings with square section die opening, giving the least temperature rise for any given extrusion parameter. The die land zone shows increasing temperature rise with increasing friction coefficient, while increasing friction coefficient has no overall effect on the dead metal zone temperature rise. Increasing die land length leads to increasing contact area between the extrudate and the die resulting in increasing frictional power. It is, therefore, seen that die land is one of the critical factors to consider avoiding surface cracking or hot-shortness in extrusion.Item Upper bound analysis for extrusion at various die land lengths and shaped profiles(International Journal of Mechanical Sciences, 2006-10-06) Ajiboye, J.S.; Adeyemi, M.B.The effects of die land lengths, a rarely investigated die extrusion parameter on the die-shaped profiles, on the extrusion pressures are investigated and presented. The analyses of the extrusion pressures by the upper bound method have been extended for the evaluations of the extrusion pressures to complex extruded sections such as square, rectangular, I,- and T-shaped sections with power of deformation due to ironing effect at the die land taken into account. The extrusion pressure contributions due to the die land evaluated theoretically for shaped sections considered are found to increase with die land lengths for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. The effect of die land lengths on the extrusion pressure increases with increasing complexity of die openings geometry with I-shaped section giving the highest extrusion pressure followed by T-shaped section, rectangular, circular-shaped die openings with square section die opening, giving the least extrusion pressure for any given die reduction at any given die land lengths.