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RISS 인기검색어
- 검색키워드
- 저자 : Joseph S. Ajiboye (검색결과 2 건)
- 무료
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Sensitivity study of frictional behavior by dimensional analysis in cold forging
Ajiboye, Joseph S.,Jung, Ki-Ho,Im, Yong-Taek 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
In metal forming operations, material flow and quality of the product depend on the conditions at the billet/tools interface friction, lubrication, and surface finish. Of these parameters, friction is the most difficult to characterize and its influence is often difficult to predict because of its dependency on a variety of factors. Recently, through a number of investigations conducted, a linear relationship among shear friction factor, dimensionless load and tip distance was obtained. The aim of the present study is to see whether the linear relationship obtained in the previous works was fortuitous or genuine by applying a dimensional analysis introducing processing parameters such as contact pressure, ram velocity, viscosity of the lubricant, load, surface roughness and shear friction factor. From the dimensional analysis based on Buckingham ${\pi}$ theorem and the data obtained from the tip test experiment, the present theoretical work derives dimensionless parameters and analysis of variance determines any correlation between the dimensionless parameters obtained. This work reconfirms the theoretical background of the previous experimental findings in the literature.
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Upper bound analysis of extrusion from square billets through circular and square/rectangular dies
Joseph S. Ajiboye 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.2
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.
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