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The effect of deformation speed on frictional behavior by tip test / Jung, Ki-Ho in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Titre : The effect of deformation speed on frictional behavior by tip test Type de document : texte imprimé Auteurs : Jung, Ki-Ho, Auteur ; Yong-Taek Im, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Finite  element  analysis  Friction  Greases  Lubrication  Oils  Plastic  deformation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this study, a tip test was carried out under various ram velocities of 0.01 mm/s, 0.1 mm/s, 1.0 mm/s, and 5.0 mm/s to investigate the effect of deformation speed on friction using the commercially available AL6061-O. For experiments, four different lubrication conditions with grease, corn oil, VG100, and VG32 were used to investigate the lubrication characteristics. During the test, temperature was measured in the specimen by a K-type thermocouple to determine the temperature increase induced by heat generation due to plastic deformation. In the present investigation, the linearity between tip distance and experimentally measured maximum load was consistently observed in spite of different orders of ram velocity and types of lubrication. As the ram velocity increased, loads were reduced for liquid lubricants and increased for grease. To better understand such a lubrication phenomenon, white-light interferometer microscopy and laser confocal microscopy were used to observe and compare surface topographies on the bottom and circumferential side of the deformed specimens at various experimental conditions, which formed lubrication pockets incurring hydrodynamic pressure of liquid lubricants. Finally, the effect of deformation speed on the level of shear friction factors at the punch and die interfaces was characterized by the finite element simulations and was determined to be expressed as an exponential function depending on the lubricant. This investigation demonstrates the capability of the tip test to experimentally characterize the effect of deformation speed on the frictional behavior for practical use. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] The effect of deformation speed on frictional behavior by tip test [texte imprimé] / Jung, Ki-Ho, Auteur ; Yong-Taek Im, Auteur . - 2011 . - 06 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Mots-clés : Finite  element  analysis  Friction  Greases  Lubrication  Oils  Plastic  deformation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this study, a tip test was carried out under various ram velocities of 0.01 mm/s, 0.1 mm/s, 1.0 mm/s, and 5.0 mm/s to investigate the effect of deformation speed on friction using the commercially available AL6061-O. For experiments, four different lubrication conditions with grease, corn oil, VG100, and VG32 were used to investigate the lubrication characteristics. During the test, temperature was measured in the specimen by a K-type thermocouple to determine the temperature increase induced by heat generation due to plastic deformation. In the present investigation, the linearity between tip distance and experimentally measured maximum load was consistently observed in spite of different orders of ram velocity and types of lubrication. As the ram velocity increased, loads were reduced for liquid lubricants and increased for grease. To better understand such a lubrication phenomenon, white-light interferometer microscopy and laser confocal microscopy were used to observe and compare surface topographies on the bottom and circumferential side of the deformed specimens at various experimental conditions, which formed lubrication pockets incurring hydrodynamic pressure of liquid lubricants. Finally, the effect of deformation speed on the level of shear friction factors at the punch and die interfaces was characterized by the finite element simulations and was determined to be expressed as an exponential function depending on the lubricant. This investigation demonstrates the capability of the tip test to experimentally characterize the effect of deformation speed on the frictional behavior for practical use. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

The effect of surface conditions on friction by tip test / Jung, Ki-Ho in Transactions of the ASME . Journal of tribology, Vol. 132 N° 1 (Janvier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 1 (Janvier 2010) . - 07 p. Titre : The effect of surface conditions on friction by tip test Type de document : texte imprimé Auteurs : Jung, Ki-Ho, Auteur ; Lee, Hyun-Chul, Auteur ; Ajiboye, Joseph S., Auteur Année de publication : 2010 Article en page(s) : 07 p. Langues : Anglais (eng) Mots-clés : Tip  test  Friction  measurement  Tip  distance  Backward  extrusion  Surface  roughness  Surface  topology Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the present investigation, a tip test based on upsetting and backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools, and the type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O, and single punch and two die sets with different surface topologies, were used with four lubricants such as VG32, VG100, corn oil, and grease. The load levels and tip distances were measured for both materials, and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately, depending on the variation in surface topologies and lubrications using finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at the punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation in surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data. This value can be used for characterizing the relative effect on friction due to surface conditions at the punch and counter punch, and lubrication quality of the lubricant for the given processing conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013200 [...] [article] The effect of surface conditions on friction by tip test [texte imprimé] / Jung, Ki-Ho, Auteur ; Lee, Hyun-Chul, Auteur ; Ajiboye, Joseph S., Auteur . - 2010 . - 07 p. Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 1 (Janvier 2010) . - 07 p. Mots-clés : Tip  test  Friction  measurement  Tip  distance  Backward  extrusion  Surface  roughness  Surface  topology Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the present investigation, a tip test based on upsetting and backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools, and the type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O, and single punch and two die sets with different surface topologies, were used with four lubricants such as VG32, VG100, corn oil, and grease. The load levels and tip distances were measured for both materials, and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately, depending on the variation in surface topologies and lubrications using finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at the punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation in surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data. This value can be used for characterizing the relative effect on friction due to surface conditions at the punch and counter punch, and lubrication quality of the lubricant for the given processing conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013200 [...]