Documents disponibles écrits par cet auteur

Measurement of load-carrying capacity of thin lubricating films / Xia Li in Transactions of the ASME . Journal of tribology, Vol. 134 N° 04 (Octobre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 134 N° 04 (Octobre 2012) . - 05 p. Titre : Measurement of load-carrying capacity of thin lubricating films Type de document : texte imprimé Auteurs : Xia Li, Auteur ; Feng Guo, Auteur ; Shuyan Yang, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : tribology Langues : Anglais (eng) Mots-clés : fixed-incline  slider  bearing;  load-carrying  capacity;  convergence  ratio;  hydrodynamic  lubrication Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper presents an experimental procedure to evaluate the load-carrying capacity of a fixed-incline slider bearing (dimensionless load W versus convergence ratio K) using a slider-on-disk lubricating film test rig. In general, the applied load is the dependent variable and is directly measured for different convergence ratios such that the relation of the load-carrying capacity W and the convergence ratio K can be obtained. The load and slider inclination are fixed in the present approach, and the film thickness is measured at different speeds. As the dimensionless load can be a function of speed and film thickness, the variation of load-carrying capacity with respect to speed can be obtained even under a constant load and a fixed incline. It is shown that the measured load-carrying capacity is lower than that predicted by the classical hydrodynamic theory. Nevertheless, the experimental results acquire the same trend in the variation of dimensionless loads with convergence ratios. The theory holds that the load-carrying capacity is a single function of the convergence ratio. However, the experimental results show that the dimensionless load-carrying capacity is affected by the inclination angle of the slider, load, and the properties of lubricating oils. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE9000134000004 [...] [article] Measurement of load-carrying capacity of thin lubricating films [texte imprimé] / Xia Li, Auteur ; Feng Guo, Auteur ; Shuyan Yang, Auteur . - 2012 . - 05 p. tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 134 N° 04 (Octobre 2012) . - 05 p. Mots-clés : fixed-incline  slider  bearing;  load-carrying  capacity;  convergence  ratio;  hydrodynamic  lubrication Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper presents an experimental procedure to evaluate the load-carrying capacity of a fixed-incline slider bearing (dimensionless load W versus convergence ratio K) using a slider-on-disk lubricating film test rig. In general, the applied load is the dependent variable and is directly measured for different convergence ratios such that the relation of the load-carrying capacity W and the convergence ratio K can be obtained. The load and slider inclination are fixed in the present approach, and the film thickness is measured at different speeds. As the dimensionless load can be a function of speed and film thickness, the variation of load-carrying capacity with respect to speed can be obtained even under a constant load and a fixed incline. It is shown that the measured load-carrying capacity is lower than that predicted by the classical hydrodynamic theory. Nevertheless, the experimental results acquire the same trend in the variation of dimensionless loads with convergence ratios. The theory holds that the load-carrying capacity is a single function of the convergence ratio. However, the experimental results show that the dimensionless load-carrying capacity is affected by the inclination angle of the slider, load, and the properties of lubricating oils. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE9000134000004 [...]

Micro-macro quantification of the internal structure of granular materials / Xia Li in Journal of engineering mechanics, Vol. 135 N° 7 (Juillet 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 7 (Juillet 2009) . - pp. 641-656 Titre : Micro-macro quantification of the internal structure of granular materials Type de document : texte imprimé Auteurs : Xia Li, Auteur ; Xiang-Song Li, Auteur Article en page(s) : pp. 641-656 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Granular  materials  Microstructures  Stress  strain  relations  Anisotropy  Deformation. Résumé : We have attempted a multiscale quantification of the internal structure of granular materials. The internal structure of granular materials, i.e., the geometrical information on granular particles and their spatial arrangement, was described mathematically on the particle scale using Voronoi–Delaunay tessellations. These tessellations were further modified into two cell systems: a solid cell system and a void cell system, with the internal supporting structure properly reflected. By doing so, the two cell systems were geometrically and physically significant. Taking solid/void cells as the microscopic basic elements, the behavior of granular materials was expressed as the volumetric average of the microcell behavior. Macroscopically, the internal structure could be characterized by the statistical measures from the geometry of the microcells. Our approach was used to investigate the anisotropic behavior of granular materials. A study on the void cells explains how the spatial arrangement affects the strength and dilatancy of granular materials. A new anisotropic fabric tensor was defined based on the void cell anisotropy. The correlation between the anisotropic fabric tensor and the macro behavior of granular materials was verified with numerical simulations. The results showed that the new material anisotropic tensor is a more effective definition than the existing ones based on particle orientations and contact normals. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Micro-macro quantification of the internal structure of granular materials [texte imprimé] / Xia Li, Auteur ; Xiang-Song Li, Auteur . - pp. 641-656. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 7 (Juillet 2009) . - pp. 641-656 Mots-clés : Granular  materials  Microstructures  Stress  strain  relations  Anisotropy  Deformation. Résumé : We have attempted a multiscale quantification of the internal structure of granular materials. The internal structure of granular materials, i.e., the geometrical information on granular particles and their spatial arrangement, was described mathematically on the particle scale using Voronoi–Delaunay tessellations. These tessellations were further modified into two cell systems: a solid cell system and a void cell system, with the internal supporting structure properly reflected. By doing so, the two cell systems were geometrically and physically significant. Taking solid/void cells as the microscopic basic elements, the behavior of granular materials was expressed as the volumetric average of the microcell behavior. Macroscopically, the internal structure could be characterized by the statistical measures from the geometry of the microcells. Our approach was used to investigate the anisotropic behavior of granular materials. A study on the void cells explains how the spatial arrangement affects the strength and dilatancy of granular materials. A new anisotropic fabric tensor was defined based on the void cell anisotropy. The correlation between the anisotropic fabric tensor and the macro behavior of granular materials was verified with numerical simulations. The results showed that the new material anisotropic tensor is a more effective definition than the existing ones based on particle orientations and contact normals. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]