The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform

M.b. Adeyemi - One of the best experts on this subject based on the ideXlab platform.

  • Effects of extrusion variables on temperature distribution in axisymmetric extrusion process
    International Journal of Mechanical Sciences, 2008
    Co-Authors: Js Ajiboye, M.b. Adeyemi
    Abstract:

    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.

  • Temperature changes associated with Die profile in axisymmetric forward extrusion process
    Journal of Applied Science Engineering and Technology, 2008
    Co-Authors: Js Ajiboye, M.b. Adeyemi
    Abstract:

    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. Keywords : Upper bound analyses, internal heat generation, plastic deformation, extrusion process, Die Land zone, Die shape, temperature distribution Journal of Applied Science, Engineering and Technology , Volume 8, 2008

  • upper bound analysis for extrusion at various Die Land Lengths and shaped profiles
    International Journal of Mechanical Sciences, 2007
    Co-Authors: J.s. Ajiboye, M.b. Adeyemi
    Abstract:

    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.

  • Upper bound analysis of Die Land Length in cold extrusion
    Journal of Materials Processing Technology, 2006
    Co-Authors: J.s. Ajiboye, M.b. Adeyemi
    Abstract:

    Abstract Upper bound analysis of the effect of Die Land Length on the cold extrusion of selected geometries is reported. The upper bound determination of extrusion pressure was extended to include the power due to ironing effect for shaped sections (rectangular, square and circular) resulting from boundary friction forces on the surface of the Die Land. The present investigation reveals that the contribution of Die Land Length to the extrusion pressure increases with increasing complexity of Die opening geometry with the rectangular section giving the highest extrusion pressure and the square section giving the least, for certain Die reduction in area at a particular Die Land Length. For a percentage reduction in area, the normalized extrusion pressure contribution, Δ P o / Y , increases with increasing Die Land Length. Also, for a particular Die Land Length, the normalized extrusion pressure increases with increasing percentage reduction in area.

  • Effects of Die Land on the cold extrusion of lead alloy
    Journal of Materials Processing Technology, 2006
    Co-Authors: J.s. Ajiboye, M.b. Adeyemi
    Abstract:

    Abstract In the present investigation, the effects of Die Land, an uncommonly investigated Die extrusion parameter, on the extrusion pressures are experimentally and theoretically evaluated. The analyses of the extrusion pressure determination by the upper bound method have been extended to include the power due to the ironing effect, resulting from frictional forces within the Die Land region. The extrusion pressure contributions due to the Die Land evaluated theoretically and practically are found to increase with Die Land Length for any given percentage reduction and also increase with increasing percentage Die reductions at any given Die Land Length. There is a good agreement between theory and experiment on the extrusion pressures evaluated. For the purpose of designing for suitable extrusion Die to extrude lead material, it is recommended that the Die Land Length should be chosen equal to or greater than 0.6 of the billet diameter for small work pieces and with Die exit clearance angle less than 10°, so as to extrude lead products with negligible bend or curvature.

J.s. Ajiboye - One of the best experts on this subject based on the ideXlab platform.

  • pressure and microstructural change with web to flange ratio and Die Land Length in cold extrusion of i shaped lead alloy
    Advanced Materials Research, 2009
    Co-Authors: J.s. Ajiboye, S A Alogu, A T Agboola, G J Eke
    Abstract:

    Plastic deformation process resulting in ultra fine grained materials which are rapidly grasping applications due to their superior mechanical properties remain an area of continued research interest. Generally, the influence of Die Land Length and web to flange ratio in grain refinement subsequent to plastic deformation process have not being adequately exploited especially in complex Die opening geometries. In the present study, the effect of these parameters on extrusion pressure and morphological change in I-shaped Die opening geometry is investigated and reported. A forward extrusion rig is designed and manufactured for the purpose of experimental investigation. The upper bound analysis shows that increasing Die Land Length leads to increasing relative extrusion pressure. Optimum web to flange ratio of 0.45 is numerically simulated and recommended to extrude I-shaped lead alloy with minimum load requirement. The experimental results reveal that increasing area ratio leads to quasi-sinusoidal pattern in surface hardness of I-shaped section irrespective of strain rate value. Increasing web to flange ratio, therefore, leads to increasing anisotropy of the I-shaped lead alloy. The extruded sections were examined with optical metallurgical microscope, and it is observed that increasing strain rate results in profound refinement of grain and inclusions in lead alloy even at room temperature.

  • Upper bound analysis of extrusion from square billets through circular and square/rectangular Dies
    Journal of Mechanical Science and Technology, 2009
    Co-Authors: J.s. Ajiboye
    Abstract:

    Upper bound elemental technique (UBET) for prediction of extrusion pressure in three-dimensional forward extrusion process is presented. Using square/rectangular billets, the study of the effect of Die Land Length has been extended for the evaluations of extrusion pressures to extrude sections such as circular, square and rectangular 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 these 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 pressures increases with increasing complexity of Die openings geometry with rectangular section giving the highest extrusion pressure followed by circular with square section Die opening, giving the least extrusion pressure for any given Die reduction at any given Die Land Lengths. The proper choice of Die Land Length is imperative if excessive pressure buildup at the emergent section is to be avoided so as to maintain good quality and metallurgical structure of the extrudates.

  • VARIATION OF PRESSURE AND MICROSTRUCTURAL CHANGES WITH WEB TO FLANGE RATIO AND Die Land Length IN COLD EXTRUSION OF T-SHAPED SECTION
    2008
    Co-Authors: J.s. Ajiboye, O. I. Ajewole
    Abstract:

    In this study, detailed experimental findings on the pressure and microstructural changes due to changing Die Land Length and web to flange ratio of cold-formed T-shaped lead alloy is presented. Increasing Die Land Length leads to increasing surface hardness of the extrudate. It was found that the extrudate hardness value decreases with increasing web to flange ratio to a minimum value at a known area ratio of Ar = 0.45 and beyond this minimum value increasing web to flange ratio leads to increasing hardness value. Therefore, to achieve homogeneous and grain structure refinement of extrudate, web to flange ratio of Ar = 0.45 is recommended. There is a good agreement between theory and the experiment. Metal flow in complex geometries, especially one with re-entrant corners can be very intricate and the need of process to achieve superplasicity with minimum cost will be a welcome development [1]. The present research seeks to predict optimum area ratio that produces this desire superplasticity in the plastic deformation of round lead billet to Tshaped section with increasing web to flange ratio. The detail theoretical formulation of the velocity field and upper bound solution is found in ref. [2]

  • upper bound analysis for extrusion at various Die Land Lengths and shaped profiles
    International Journal of Mechanical Sciences, 2007
    Co-Authors: J.s. Ajiboye, M.b. Adeyemi
    Abstract:

    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.

  • Upper bound analysis of Die Land Length in cold extrusion
    Journal of Materials Processing Technology, 2006
    Co-Authors: J.s. Ajiboye, M.b. Adeyemi
    Abstract:

    Abstract Upper bound analysis of the effect of Die Land Length on the cold extrusion of selected geometries is reported. The upper bound determination of extrusion pressure was extended to include the power due to ironing effect for shaped sections (rectangular, square and circular) resulting from boundary friction forces on the surface of the Die Land. The present investigation reveals that the contribution of Die Land Length to the extrusion pressure increases with increasing complexity of Die opening geometry with the rectangular section giving the highest extrusion pressure and the square section giving the least, for certain Die reduction in area at a particular Die Land Length. For a percentage reduction in area, the normalized extrusion pressure contribution, Δ P o / Y , increases with increasing Die Land Length. Also, for a particular Die Land Length, the normalized extrusion pressure increases with increasing percentage reduction in area.

Önder Ayer - One of the best experts on this subject based on the ideXlab platform.

  • FEM SIMULATION OF COMBINED EXTRUSION METHOD (ECAE/DIRECT EXTRUSION)
    Polish Association for Knowledge Promotion, 2015
    Co-Authors: Önder Ayer
    Abstract:

    Equal Channel Angular Extrusion (ECAE) is known as a severe plastic deformation process and material is deformed without any geometrical change. It is widely used for obtaining high mechanical properties from the product. Direct Extrusion is another plastic deformation process in which a workpiece is reduced in cross-section by forcing it through the Die opening of a small cross-sectional area than that of the original billet. In this study, these two processes are combined together via using DEFORM 3D which is a very specialized software for metal forming operations. Lead is used as workpiece material to simulate hot forming conditions and also process parameters (Die angle and Die Land Length) were investigated. The forming load and strain components were calculated from the FEM results obtained from DEFORM 3D software

  • A theoretical and experimental study for forward extrusion of clover sections
    Materials & Design, 2008
    Co-Authors: Tahir Altinbalik, Önder Ayer
    Abstract:

    Forward extrusion of clover section from different billet diameters has been investigated. The Die profile is given by radius function to construct the new kinematically admissible velocity fields for three dimensional extrusion and then by using the upper bound method total extrusion loads are obtained. In the experimental stuDies, lead billets which having same initial heights but three different diameters have been extruded with the same strokes in order to verify the analysis. Die Land Length/billet diameter ratio was taken equal or greater than 0.6 as recommended in literature. A good agreement was found between the measured and the predicted load and so it is suggested that present analysis could be used the other commercial materials.

Patrick C. Booth - One of the best experts on this subject based on the ideXlab platform.

  • Die design for rigid PVC—the effect of Die Land Length on extrudate swell
    Journal of Vinyl & Additive Technology, 1992
    Co-Authors: Elvira B. Rabinovitch, James W. Summers, Patrick C. Booth
    Abstract:

    PVC profile extrusion compounds have a unique morphology. While other polymers gradually decrease in extrusion Die swell with increasing Length/thickness (L/D) ratio, PVC profile extrusion compounds have a low Die swell, quite independent of the Die's L/D ratio in the range of 5 to 20. The fact that the Die Land Length can be changed without changing the extrudate swell is an important consideration, which makes Die design and balancing Dies simpler and easier for PVC profile extrusion compounds. While other polymers substantially increase extrudate swell with increased shear rate, the swell of the PVC profile compounds is not much affected by shear or extrusion rate. This unique behavior allows wider processing latitude in profile extrusion and faster extrusion rates than with other polymers. Another unique factor in the rheology of PVC profile extrusion compounds is that extrusion Die swell increases with increasing melt temperature, while other polymers have decreasing Die swell with increasing melt temperature. The unusual rheology of PVC profile extrusion compounds is attributed to its unique melt morphology, where the melt flow units are 1 um bundles and molecules that have low surface to surface interaction and entanglement at low processing temperatures but increased melting and increased entanglement at higher processing temperatures. Other polymers, unlike PVC, have melt flow at the molecular level.

  • Die design for rigid pvc the effect of Die Land Length on extrudate swell
    Journal of Vinyl & Additive Technology, 1992
    Co-Authors: Elvira B. Rabinovitch, James W. Summers, Patrick C. Booth
    Abstract:

    PVC profile extrusion compounds have a unique morphology. While other polymers gradually decrease in extrusion Die swell with increasing Length/thickness (L/D) ratio, PVC profile extrusion compounds have a low Die swell, quite independent of the Die's L/D ratio in the range of 5 to 20. The fact that the Die Land Length can be changed without changing the extrudate swell is an important consideration, which makes Die design and balancing Dies simpler and easier for PVC profile extrusion compounds. While other polymers substantially increase extrudate swell with increased shear rate, the swell of the PVC profile compounds is not much affected by shear or extrusion rate. This unique behavior allows wider processing latitude in profile extrusion and faster extrusion rates than with other polymers. Another unique factor in the rheology of PVC profile extrusion compounds is that extrusion Die swell increases with increasing melt temperature, while other polymers have decreasing Die swell with increasing melt temperature. The unusual rheology of PVC profile extrusion compounds is attributed to its unique melt morphology, where the melt flow units are 1 um bundles and molecules that have low surface to surface interaction and entanglement at low processing temperatures but increased melting and increased entanglement at higher processing temperatures. Other polymers, unlike PVC, have melt flow at the molecular level.

Js Ajiboye - One of the best experts on this subject based on the ideXlab platform.

  • Effects of extrusion variables on temperature distribution in axisymmetric extrusion process
    International Journal of Mechanical Sciences, 2008
    Co-Authors: Js Ajiboye, M.b. Adeyemi
    Abstract:

    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.

  • Temperature changes associated with Die profile in axisymmetric forward extrusion process
    Journal of Applied Science Engineering and Technology, 2008
    Co-Authors: Js Ajiboye, M.b. Adeyemi
    Abstract:

    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. Keywords : Upper bound analyses, internal heat generation, plastic deformation, extrusion process, Die Land zone, Die shape, temperature distribution Journal of Applied Science, Engineering and Technology , Volume 8, 2008