Documents disponibles écrits par cet auteur

Application of elastic-plastic static friction models to rough surfaces with asymmetric asperity distribution / Chul Hee Lee 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) . - 11 p. Titre : Application of elastic-plastic static friction models to rough surfaces with asymmetric asperity distribution Type de document : texte imprimé Auteurs : Chul Hee Lee, Auteur ; Melih Eriten, Auteur ; Andreas A. Polycarpou, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Rough  surfaces  Sliding  friction  Stiction  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Asymmetric height distribution in surface roughness is important in many engineering surfaces, such as in constant velocity (CV) joints, where specific manufacturing processes could result in such surfaces. Even if the initial surfaces exhibit symmetric roughness, the running-in and sliding processes could result in asymmetric roughness distributions. In this paper, the effect of asymmetric asperity height distribution on the static friction coefficient is investigated theoretically and experimentally. The asymmetry of the surface roughness is modeled using the Pearson system of frequency curves. Two elastic-plastic static friction models, the Kogut–Etsion (KE) and Cohen–Kligerman–Etsion (CKE) models are adapted to account for asymmetric roughness and employed to obtain the tangential and normal contact forces. Static friction experiments using CV joint roller and housing surfaces, which exhibit different levels of surface roughness, were performed and directly compared with the KE and CKE static friction models using both a symmetric Gaussian as well as Pearson distributions of asperity heights. It is found that the KE model with the Pearson distribution compares favorably with the experimental measurements. Note de contenu : Erratum: “Application of Elastic-Plastic Static Friction Models to Rough Surfaces With Asymmetric Asperity Distribution” [Journal of Tribology, 2010, 132(3), p. 031602] Chul-Hee Lee et al. J. Tribol. 132, 047001 (2010) DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Application of elastic-plastic static friction models to rough surfaces with asymmetric asperity distribution [texte imprimé] / Chul Hee Lee, Auteur ; Melih Eriten, Auteur ; Andreas A. Polycarpou, Auteur . - 2011 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Mots-clés : Rough  surfaces  Sliding  friction  Stiction  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Asymmetric height distribution in surface roughness is important in many engineering surfaces, such as in constant velocity (CV) joints, where specific manufacturing processes could result in such surfaces. Even if the initial surfaces exhibit symmetric roughness, the running-in and sliding processes could result in asymmetric roughness distributions. In this paper, the effect of asymmetric asperity height distribution on the static friction coefficient is investigated theoretically and experimentally. The asymmetry of the surface roughness is modeled using the Pearson system of frequency curves. Two elastic-plastic static friction models, the Kogut–Etsion (KE) and Cohen–Kligerman–Etsion (CKE) models are adapted to account for asymmetric roughness and employed to obtain the tangential and normal contact forces. Static friction experiments using CV joint roller and housing surfaces, which exhibit different levels of surface roughness, were performed and directly compared with the KE and CKE static friction models using both a symmetric Gaussian as well as Pearson distributions of asperity heights. It is found that the KE model with the Pearson distribution compares favorably with the experimental measurements. Note de contenu : Erratum: “Application of Elastic-Plastic Static Friction Models to Rough Surfaces With Asymmetric Asperity Distribution” [Journal of Tribology, 2010, 132(3), p. 031602] Chul-Hee Lee et al. J. Tribol. 132, 047001 (2010) DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Assessment of elliptical conformal hertz analysis applied to constant velocity joints / Chul Hee Lee in Transactions of the ASME . Journal of tribology, Vol. 132 N° 2 (Avril 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 2 (Avril 2010) . - 03 p. Titre : Assessment of elliptical conformal hertz analysis applied to constant velocity joints Type de document : texte imprimé Auteurs : Chul Hee Lee, Auteur ; Andreas A. Polycarpou, Auteur Année de publication : 2011 Article en page(s) : 03 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Ball  bearings  Finite  element  analysis  Mechanical  contact  Rolling  bearings Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : To analyze the contact between two spherical bodies with different radii of curvature, the three-dimensional (3D) Hertz theory for elliptical contact is typically used. When the two contacting bodies have high conformity, such as the case for ball-in-groove, the Hertz theory may break down. In this research, finite element analysis (FEA) was used to assess the validity of 3D Hertz theory as found in the roller-housing contact of constant velocity joints. The contact area, normal approach, and contact pressure results show that Hertz agrees with FEA predictions for low compressive loads, where the contact ellipse is within the geometrical contact dimensions. At higher loads the contact ellipse extends beyond the contacting geometrical dimensions and the simplified analytical Hertz results diverge from the FEA results. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Assessment of elliptical conformal hertz analysis applied to constant velocity joints [texte imprimé] / Chul Hee Lee, Auteur ; Andreas A. Polycarpou, Auteur . - 2011 . - 03 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 2 (Avril 2010) . - 03 p. Mots-clés : Ball  bearings  Finite  element  analysis  Mechanical  contact  Rolling  bearings Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : To analyze the contact between two spherical bodies with different radii of curvature, the three-dimensional (3D) Hertz theory for elliptical contact is typically used. When the two contacting bodies have high conformity, such as the case for ball-in-groove, the Hertz theory may break down. In this research, finite element analysis (FEA) was used to assess the validity of 3D Hertz theory as found in the roller-housing contact of constant velocity joints. The contact area, normal approach, and contact pressure results show that Hertz agrees with FEA predictions for low compressive loads, where the contact ellipse is within the geometrical contact dimensions. At higher loads the contact ellipse extends beyond the contacting geometrical dimensions and the simplified analytical Hertz results diverge from the FEA results. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Tribological characteristics modification of magnetorheological fluid / Chul Hee Lee in Transactions of the ASME . Journal of tribology, Vol. 133 N° 3 (Juillet 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 3 (Juillet 2011) . - 06 p. Titre : Tribological characteristics modification of magnetorheological fluid Type de document : texte imprimé Auteurs : Chul Hee Lee, Auteur ; Deuk Won Lee, Auteur ; Jae Young Choi, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Carbon  steel  Differential  scanning  calorimetry  Friction  Magnetic  fluids  Magnetorheology  Scanning  electron  microscopy  Surface  roughness  Wear  Wear  testing Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Recently, research on the application of magnetorheological (MR) fluid in mechanical engineering has been widely expanded, while the performance of MR fluid in tribology has also been investigated. In this study, a modification of MR fluid, which is modified by adding certain additives, is attempted to improve tribological performance. After modification, wear and friction are measured by four-ball wear tester and linear-oscillation (SRV) tester under no magnetic fields. Subsequently, the oxidation induction time (OIT) is evaluated by pressure differential scanning calorimetry (PDSC). Then, to observe the tribological performance under magnetic fields, pin-on-disk test is conducted to confirm the effects of the commercial MR fluid and modified MR fluid on friction and wear in different operating and magnetic conditions. Also, the modification effects on surface roughness are investigated by using a profilometer. Moreover, the microscopic changes of surfaces and MR particles are investigated by using scanning electron microscopy (SEM). DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Tribological characteristics modification of magnetorheological fluid [texte imprimé] / Chul Hee Lee, Auteur ; Deuk Won Lee, Auteur ; Jae Young Choi, Auteur . - 2012 . - 06 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 3 (Juillet 2011) . - 06 p. Mots-clés : Carbon  steel  Differential  scanning  calorimetry  Friction  Magnetic  fluids  Magnetorheology  Scanning  electron  microscopy  Surface  roughness  Wear  Wear  testing Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Recently, research on the application of magnetorheological (MR) fluid in mechanical engineering has been widely expanded, while the performance of MR fluid in tribology has also been investigated. In this study, a modification of MR fluid, which is modified by adding certain additives, is attempted to improve tribological performance. After modification, wear and friction are measured by four-ball wear tester and linear-oscillation (SRV) tester under no magnetic fields. Subsequently, the oxidation induction time (OIT) is evaluated by pressure differential scanning calorimetry (PDSC). Then, to observe the tribological performance under magnetic fields, pin-on-disk test is conducted to confirm the effects of the commercial MR fluid and modified MR fluid on friction and wear in different operating and magnetic conditions. Also, the modification effects on surface roughness are investigated by using a profilometer. Moreover, the microscopic changes of surfaces and MR particles are investigated by using scanning electron microscopy (SEM). DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]