Dépouillements

Investigation of the high speed rolling bearing temperature rise with oil-air lubrication / Jiang, Shuyun in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Titre : Investigation of the high speed rolling bearing temperature rise with oil-air lubrication Type de document : texte imprimé Auteurs : Jiang, Shuyun, Auteur ; Hebing Mao, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Ball  bearings  Ceramics  Life  testing  Lubricants  Lubrication  Nozzles  Pipes  Rolling  bearings  Steel  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The oil-air lubrication system has been widely used for rolling ball bearing. However, as the rotation speed increases, the temperature rise will increase dramatically, resulting in shortening the service life of the ball bearing. The existing literature has offered valuable fundamental data about the oil-air lubrication of rolling bearing; however, there are still some problems that concerned the oil-air lubrication, which are not addressed. In this study, an experiment setup to investigate the oil-air lubrication for the high speed ball bearing has been developed, and performance tests of hybrid ceramic and steel ball bearings under the extensive operating conditions including oil-air supply pipe length, bearing preload, lube interval, oil type, oil viscosity, nozzle design, and rotation speed have been conducted. The test results show that the bearing has the lowest temperature rise with the pipe length of 1.5 m. For the steel ball bearing, the proper preload decreases with increasing of the rotating speed, and the temperature rise of the hybrid ceramic ball bearing is not sensitive to the axial preload. There exists a proper amount of lubricant for the bearing at each rotational speed; and a larger amount of lubricant is required for the bearing as the rotating speed increases. The tested bearings under different speeds have almost the same lowest temperature rise under the lubricant with the viscosity of 100 cSt; a higher or lower viscosity will increase the bearing temperature rises. The nozzle design is an important factor to affect the temperature rise of the ball bearing, and the suitable geometric parameter of the nozzle is closely related to the cage landing method of the bearing. The temperature rise of tested bearings increases with the increase in the rotation speed; and the hybrid ceramic ball bearing always has a lower temperature rise than that of the steel ball bearing at the same operating conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Investigation of the high speed rolling bearing temperature rise with oil-air lubrication [texte imprimé] / Jiang, Shuyun, Auteur ; Hebing Mao, Auteur . - 2012 . - 09 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Mots-clés : Ball  bearings  Ceramics  Life  testing  Lubricants  Lubrication  Nozzles  Pipes  Rolling  bearings  Steel  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The oil-air lubrication system has been widely used for rolling ball bearing. However, as the rotation speed increases, the temperature rise will increase dramatically, resulting in shortening the service life of the ball bearing. The existing literature has offered valuable fundamental data about the oil-air lubrication of rolling bearing; however, there are still some problems that concerned the oil-air lubrication, which are not addressed. In this study, an experiment setup to investigate the oil-air lubrication for the high speed ball bearing has been developed, and performance tests of hybrid ceramic and steel ball bearings under the extensive operating conditions including oil-air supply pipe length, bearing preload, lube interval, oil type, oil viscosity, nozzle design, and rotation speed have been conducted. The test results show that the bearing has the lowest temperature rise with the pipe length of 1.5 m. For the steel ball bearing, the proper preload decreases with increasing of the rotating speed, and the temperature rise of the hybrid ceramic ball bearing is not sensitive to the axial preload. There exists a proper amount of lubricant for the bearing at each rotational speed; and a larger amount of lubricant is required for the bearing as the rotating speed increases. The tested bearings under different speeds have almost the same lowest temperature rise under the lubricant with the viscosity of 100 cSt; a higher or lower viscosity will increase the bearing temperature rises. The nozzle design is an important factor to affect the temperature rise of the ball bearing, and the suitable geometric parameter of the nozzle is closely related to the cage landing method of the bearing. The temperature rise of tested bearings increases with the increase in the rotation speed; and the hybrid ceramic ball bearing always has a lower temperature rise than that of the steel ball bearing at the same operating conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Effects of grease types on vibration and acoustic emission of defective linear-guideway type recirculating ball bearings / Ohta, Hiroyuki in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Titre : Effects of grease types on vibration and acoustic emission of defective linear-guideway type recirculating ball bearings Type de document : texte imprimé Auteurs : Ohta, Hiroyuki, Auteur ; Shinya Hayashi, Auteur ; Kato, Soichiro, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Acoustic  emission  Ball  bearings  Greases  Impact  testing  Lubrication  Vibrations  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper deals with effects of grease types on vibrations and acoustic emissions (AEs) of linear-guideway type recirculating ball bearings with a millimeter-sized artificial defect in the carriage. First, the vibration and AE of one normal bearing without a defect (Type N) and six defective bearings (Types D1–D6) were measured using a linear velocity of 1 m/s. Three types of grease are used for the lubrication of test bearings. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the root-mean-square (RMS) values, and component amplitudes in the spectra) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle (the increasing rates of the RMS values) are reduced when a grease with higher base oil viscosity is used. To explain these experimental results, grease impact tests are carried out. The grease impact tests show that a grease with higher base oil viscosity reduces the impact velocity and the maximum impact forces. This implies that a grease with higher base oil viscosity generate greater viscous resistance to balls in the test bearings then reduces the ball impact forces in the ball circulation collisions and ball-defect collisions. Because of the reduction of the ball impact forces, both the vibration and AE amplitudes as well as the increasing rate of the RMS values are reduced. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Effects of grease types on vibration and acoustic emission of defective linear-guideway type recirculating ball bearings [texte imprimé] / Ohta, Hiroyuki, Auteur ; Shinya Hayashi, Auteur ; Kato, Soichiro, Auteur . - 2012 . - 09 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Mots-clés : Acoustic  emission  Ball  bearings  Greases  Impact  testing  Lubrication  Vibrations  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper deals with effects of grease types on vibrations and acoustic emissions (AEs) of linear-guideway type recirculating ball bearings with a millimeter-sized artificial defect in the carriage. First, the vibration and AE of one normal bearing without a defect (Type N) and six defective bearings (Types D1–D6) were measured using a linear velocity of 1 m/s. Three types of grease are used for the lubrication of test bearings. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the root-mean-square (RMS) values, and component amplitudes in the spectra) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle (the increasing rates of the RMS values) are reduced when a grease with higher base oil viscosity is used. To explain these experimental results, grease impact tests are carried out. The grease impact tests show that a grease with higher base oil viscosity reduces the impact velocity and the maximum impact forces. This implies that a grease with higher base oil viscosity generate greater viscous resistance to balls in the test bearings then reduces the ball impact forces in the ball circulation collisions and ball-defect collisions. Because of the reduction of the ball impact forces, both the vibration and AE amplitudes as well as the increasing rate of the RMS values are reduced. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Simulation of deep spherical indentation using eulerian finite element methods / D. Anderson in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 08 p. Titre : Simulation of deep spherical indentation using eulerian finite element methods Type de document : texte imprimé Auteurs : D. Anderson, Auteur ; A. Warkentin, Auteur ; R. Bauer, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Deformation  Finite  element  analysis  Friction  Indentation  Steel Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Simulation of deep indentation, and the associated pile-up effects, requires a robust and accurate finite element model capable of naturally handling the large deformations present. This work successfully demonstrates that the Eulerian formulation is capable of accurately reproducing the forces and general material response of deep indentation. It was found that, in the absence of friction, sink-in dominates at indentation depths less than 1.1% of the indenter radius, there is a transition from sink-in to pile-up from 1.1% to 2.3% of the indenter radius, and pile-up is fully developed at indentation depths larger than 13.2% of the indenter radius for the 4340 steel workpiece and the 0.508 mm radius indenter presented in this work. Friction tended to marginally increase the sink-in and transition depths as well as reduce the material height at the onset of fully developed pile-up due to a reduction in the tensile radial strain directly under the indenter. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Simulation of deep spherical indentation using eulerian finite element methods [texte imprimé] / D. Anderson, Auteur ; A. Warkentin, Auteur ; R. Bauer, Auteur . - 2012 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 08 p. Mots-clés : Deformation  Finite  element  analysis  Friction  Indentation  Steel Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Simulation of deep indentation, and the associated pile-up effects, requires a robust and accurate finite element model capable of naturally handling the large deformations present. This work successfully demonstrates that the Eulerian formulation is capable of accurately reproducing the forces and general material response of deep indentation. It was found that, in the absence of friction, sink-in dominates at indentation depths less than 1.1% of the indenter radius, there is a transition from sink-in to pile-up from 1.1% to 2.3% of the indenter radius, and pile-up is fully developed at indentation depths larger than 13.2% of the indenter radius for the 4340 steel workpiece and the 0.508 mm radius indenter presented in this work. Friction tended to marginally increase the sink-in and transition depths as well as reduce the material height at the onset of fully developed pile-up due to a reduction in the tensile radial strain directly under the indenter. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Fretting wear modeling of coated and uncoated surfaces using the combined finite-discrete element method / Benjamin D. Leonard in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 12 p. Titre : Fretting wear modeling of coated and uncoated surfaces using the combined finite-discrete element method Type de document : texte imprimé Auteurs : Benjamin D. Leonard, Auteur ; Pankaj Patil, Auteur ; Trevor S. Slack, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Coatings  Elastic  moduli  Finite  element  analysis  Friction  Mechanical  contact  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A new approach for modeling fretting wear in a Hertzian line contact is presented. The combined finite-discrete element method (FDEM) in which multiple finite element bodies interact as distinct bodies is used to model a two-dimensional fretting contact with and without coatings. The normal force and sliding distance are used during each fretting cycle, and fretting wear is modeled by locally applying Archard's wear equation to determine wear loss along the surface. The FDEM is validated by comparing the pressure and frictional shear stress results to the continuum mechanics solution for a Hertzian fretting contact. The dependence of the wear algorithm stability on the cycle increment of a fretting simulation is also investigated. The effects of friction coefficient, normal force, displacement amplitude, coating thickness, and coating modulus of elasticity on fretting wear are presented. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Fretting wear modeling of coated and uncoated surfaces using the combined finite-discrete element method [texte imprimé] / Benjamin D. Leonard, Auteur ; Pankaj Patil, Auteur ; Trevor S. Slack, Auteur . - 2012 . - 12 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 12 p. Mots-clés : Coatings  Elastic  moduli  Finite  element  analysis  Friction  Mechanical  contact  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A new approach for modeling fretting wear in a Hertzian line contact is presented. The combined finite-discrete element method (FDEM) in which multiple finite element bodies interact as distinct bodies is used to model a two-dimensional fretting contact with and without coatings. The normal force and sliding distance are used during each fretting cycle, and fretting wear is modeled by locally applying Archard's wear equation to determine wear loss along the surface. The FDEM is validated by comparing the pressure and frictional shear stress results to the continuum mechanics solution for a Hertzian fretting contact. The dependence of the wear algorithm stability on the cycle increment of a fretting simulation is also investigated. The effects of friction coefficient, normal force, displacement amplitude, coating thickness, and coating modulus of elasticity on fretting wear are presented. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Comparative study on dry sliding wear behavior of various railroad steels / S. M. Shariff in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 P. Titre : Comparative study on dry sliding wear behavior of various railroad steels Type de document : texte imprimé Auteurs : S. M. Shariff, Auteur ; T. K. Pal, Auteur ; G. Padmanabham, Auteur Année de publication : 2012 Article en page(s) : 09 P. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Abrasion  Austenitic  steel  Plastic  deformation  Rails  Railways  Sliding  friction Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Understanding the wear behavior of various railroad steels used in different components such as rails, wheels, crossings, and curves has a direct impact on the performance of the rail-wheel system in railroad technology. In the present investigation, the wear behavior of steels having varying microstructures (pearlite, ferrite-pearlite, austenite, and bainite) and different chemical compositions has been studied, utilizing a ball-on-disk sliding tribometer under prototypic load and dry conditions. Results indicate that the wear performance of the steel and the mechanism responsible for its wear are significantly governed by the microstructure as well as changes that occur in the contact region during sliding. The formation of tribo-particles comprising oxides of Fe and their possible smearing resulted in high wear resistance in pearlitic steels with considerable plastic deformation of ferrite lamellae compared with austenitic and bainitic steels. In the case of bainitic steel, the absence of any significant smearing of oxide debris, combined with the presence of some distributed tungsten from the ball, contributed to severe wear. On the other hand, in the case of austenitic steel, third-body abrasion by debris particles, comprising a mix of hard metallic and oxide particles, contributed to severe wear despite its high work-hardening ability. On the whole, the pearlitic steel exhibited superior wear resistance with a lower friction coefficient compared with the bainitic and austenitic steels. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Comparative study on dry sliding wear behavior of various railroad steels [texte imprimé] / S. M. Shariff, Auteur ; T. K. Pal, Auteur ; G. Padmanabham, Auteur . - 2012 . - 09 P. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 P. Mots-clés : Abrasion  Austenitic  steel  Plastic  deformation  Rails  Railways  Sliding  friction Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Understanding the wear behavior of various railroad steels used in different components such as rails, wheels, crossings, and curves has a direct impact on the performance of the rail-wheel system in railroad technology. In the present investigation, the wear behavior of steels having varying microstructures (pearlite, ferrite-pearlite, austenite, and bainite) and different chemical compositions has been studied, utilizing a ball-on-disk sliding tribometer under prototypic load and dry conditions. Results indicate that the wear performance of the steel and the mechanism responsible for its wear are significantly governed by the microstructure as well as changes that occur in the contact region during sliding. The formation of tribo-particles comprising oxides of Fe and their possible smearing resulted in high wear resistance in pearlitic steels with considerable plastic deformation of ferrite lamellae compared with austenitic and bainitic steels. In the case of bainitic steel, the absence of any significant smearing of oxide debris, combined with the presence of some distributed tungsten from the ball, contributed to severe wear. On the other hand, in the case of austenitic steel, third-body abrasion by debris particles, comprising a mix of hard metallic and oxide particles, contributed to severe wear despite its high work-hardening ability. On the whole, the pearlitic steel exhibited superior wear resistance with a lower friction coefficient compared with the bainitic and austenitic steels. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Effects of particle-induced crystallization on tribological behavior of polymer nanocomposites / David Huitink in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Titre : Effects of particle-induced crystallization on tribological behavior of polymer nanocomposites Type de document : texte imprimé Auteurs : David Huitink, Auteur ; Tahira Zarrin, Auteur ; Matthew Sanders, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Biomedical  materials  Crystal  structure  Crystallisation  Filled  polymers  Friction  Gold  Nanocomposites  Nanomedicine  Nanoparticles  Particle  reinforced  composites  Pharmaceuticals  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Similar to conventional engineering fabrication processes, tribological performance of drugs and pills in pharmaceutical manufacturing plays an important role in quality and product yields. In the present research, we investigate the effects of crystal structures of workpiece materials on their tribological performance in conditions typical of pharmaceutical manufacturing processes. Sorbitol composites containing gold nanoparticles were evaluated for material properties and tribological performance. It was found that the control exhibited nonordered gamma forms of sorbitol, while the samples containing rod nanoparticles showed a collection of tiny needlelike crystals of gamma phase. Spherical nanoparticles precipitated beta and alpha phases of sorbitol, which were not seen in the other samples. These variations in the crystal structure resulted in an unusual wear behavior, leading to high friction and softness in the case of the nanocomposites. The nanoparticles were found to influence the crystal structure of the sorbitol matrix, resulting in mechanical and tribological behaviors. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Effects of particle-induced crystallization on tribological behavior of polymer nanocomposites [texte imprimé] / David Huitink, Auteur ; Tahira Zarrin, Auteur ; Matthew Sanders, Auteur . - 2012 . - 09 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Mots-clés : Biomedical  materials  Crystal  structure  Crystallisation  Filled  polymers  Friction  Gold  Nanocomposites  Nanomedicine  Nanoparticles  Particle  reinforced  composites  Pharmaceuticals  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Similar to conventional engineering fabrication processes, tribological performance of drugs and pills in pharmaceutical manufacturing plays an important role in quality and product yields. In the present research, we investigate the effects of crystal structures of workpiece materials on their tribological performance in conditions typical of pharmaceutical manufacturing processes. Sorbitol composites containing gold nanoparticles were evaluated for material properties and tribological performance. It was found that the control exhibited nonordered gamma forms of sorbitol, while the samples containing rod nanoparticles showed a collection of tiny needlelike crystals of gamma phase. Spherical nanoparticles precipitated beta and alpha phases of sorbitol, which were not seen in the other samples. These variations in the crystal structure resulted in an unusual wear behavior, leading to high friction and softness in the case of the nanocomposites. The nanoparticles were found to influence the crystal structure of the sorbitol matrix, resulting in mechanical and tribological behaviors. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Theoretical study of static and dynamic characteristics for eccentric cylinders lubricated with ferrofluid / Kadry Zakaria in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 18 p. Titre : Theoretical study of static and dynamic characteristics for eccentric cylinders lubricated with ferrofluid Type de document : texte imprimé Auteurs : Kadry Zakaria, Auteur ; Magdy A. Sirwah, Auteur ; M. Fakharany, Auteur Année de publication : 2012 Article en page(s) : 18 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Lubricants  Lubrication  Machine  bearings  Magnetic  fluids  Magnetohydrodynamics  Non-Newtonian  flow  Non-newtonian  fluids  Shapes  (structures) Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The aim of this study is to explore the static and dynamic performance characteristics of finite journal bearings lubricated with a non-Newtonian ferrofluid in the presence of an external magnetic field using the spectral method technique. The modified Reynolds equation governing the film pressure, coming out from the combination of the momentum and continuity equations, is derived. We use the pressure distribution function to study the static and dynamic characteristics and the stability of the given system. Numerical applications are achieved in order to investigate the influence of the various parameters on the stability behavior of the system. For instance, it is observed that the journal loci get stable as the magnetic force increases. The non-Newtonian, the distance ratio, and the magnetic parameters play an important role in administrating the stability behavior. The non-Newtonian parameter is found to stabilize the system, while the magnetic force coefficient destabilizes it. Furthermore, for law eccentricity ratios, the stability of this system is significant. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Theoretical study of static and dynamic characteristics for eccentric cylinders lubricated with ferrofluid [texte imprimé] / Kadry Zakaria, Auteur ; Magdy A. Sirwah, Auteur ; M. Fakharany, Auteur . - 2012 . - 18 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 18 p. Mots-clés : Lubricants  Lubrication  Machine  bearings  Magnetic  fluids  Magnetohydrodynamics  Non-Newtonian  flow  Non-newtonian  fluids  Shapes  (structures) Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The aim of this study is to explore the static and dynamic performance characteristics of finite journal bearings lubricated with a non-Newtonian ferrofluid in the presence of an external magnetic field using the spectral method technique. The modified Reynolds equation governing the film pressure, coming out from the combination of the momentum and continuity equations, is derived. We use the pressure distribution function to study the static and dynamic characteristics and the stability of the given system. Numerical applications are achieved in order to investigate the influence of the various parameters on the stability behavior of the system. For instance, it is observed that the journal loci get stable as the magnetic force increases. The non-Newtonian, the distance ratio, and the magnetic parameters play an important role in administrating the stability behavior. The non-Newtonian parameter is found to stabilize the system, while the magnetic force coefficient destabilizes it. Furthermore, for law eccentricity ratios, the stability of this system is significant. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Comparison of iterative methods for the solution of compressible-fluid reynolds equation / Nenzi Wang in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 07 p. Titre : Comparison of iterative methods for the solution of compressible-fluid reynolds equation Type de document : texte imprimé Auteurs : Nenzi Wang, Auteur ; Shih-Hung Chang, Auteur ; Hua-Chih Huang, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Compressible  flow  Computational  fluid  dynamics  Conjugate  gradient  methods  Differential  equations  Newton  method Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This study presents an efficacy comparison of iterative solution methods for solving the compressible-fluid Reynolds equation in modeling air- or gas-lubricated bearings. A direct fixed-point iterative (DFI) method and Newton's method are employed to transform the Reynolds equation in a form that can be solved iteratively. The iterative solution methods examined are the Gauss–Seidel method, the successive over-relaxation (SOR) method, the preconditioned conjugate gradient (PCG) method, and the multigrid method. The overall solution time is affected by both the transformation method and the iterative method applied. In this study, Newton's method shows its effectiveness over the straightforward DFI method when the same iterative method is used. It is demonstrated that the use of an optimal relaxation factor is of vital importance for the efficiency of the SOR method. The multigrid method is an order faster than the PCG and optimal SOR methods. Also, the multigrid and PCG methods involve an extended coding work and are less flexible in dealing with gridwork and boundary conditions. Consequently, a compromise has to be made in terms of ease of use as well as programming effort for the solution of the compressible-fluid Reynolds equation. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Comparison of iterative methods for the solution of compressible-fluid reynolds equation [texte imprimé] / Nenzi Wang, Auteur ; Shih-Hung Chang, Auteur ; Hua-Chih Huang, Auteur . - 2012 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 07 p. Mots-clés : Compressible  flow  Computational  fluid  dynamics  Conjugate  gradient  methods  Differential  equations  Newton  method Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This study presents an efficacy comparison of iterative solution methods for solving the compressible-fluid Reynolds equation in modeling air- or gas-lubricated bearings. A direct fixed-point iterative (DFI) method and Newton's method are employed to transform the Reynolds equation in a form that can be solved iteratively. The iterative solution methods examined are the Gauss–Seidel method, the successive over-relaxation (SOR) method, the preconditioned conjugate gradient (PCG) method, and the multigrid method. The overall solution time is affected by both the transformation method and the iterative method applied. In this study, Newton's method shows its effectiveness over the straightforward DFI method when the same iterative method is used. It is demonstrated that the use of an optimal relaxation factor is of vital importance for the efficiency of the SOR method. The multigrid method is an order faster than the PCG and optimal SOR methods. Also, the multigrid and PCG methods involve an extended coding work and are less flexible in dealing with gridwork and boundary conditions. Consequently, a compromise has to be made in terms of ease of use as well as programming effort for the solution of the compressible-fluid Reynolds equation. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Transient thermal behavior of preloaded three-pad foil bearings / Donghyun Lee in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 11 p. Titre : Transient thermal behavior of preloaded three-pad foil bearings : modeling and experiments Type de document : texte imprimé Auteurs : Donghyun Lee, Auteur ; Daejong Kim, Auteur ; Ramesh P. Sadashiva, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Convection  Electric  power  generation  Fuel  cells  Machine  bearings  Rotors  Solar  cells  Stability  Turbomachinery Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Oil-free turbomachinery have emerged as one of the core technologies for the future green power generation systems as stand-alone systems or hybridized with high temperature fuel cells or solar systems. Oil-free technology allows compact, clean, and maintenance-free operation, and foil bearings are at the center of the technology. Since their first commercial applications in the air cycle machines and auxiliary power units in 1970s, significant improvement has been made to the computational models for rotordynamic behavior. However, many technical issues still remain unsolved or poorly understood, and one of them is thermal management. This paper presents transient three-dimensional thermohydrodynamic (3D THD) model of radial foil bearings to predict transient thermal behavior of the bearing-rotor system. The transient model involves transient energy equations applied to all the mechanical structures and gas film. The model was verified through extensive experimental measurements of transient thermal behavior of three-pad foil bearing for various cooling air pressures, external loads, and speeds. The predictions showed very good agreements with the experiments, and also the 3D THD model could predict potential thermal instability observed in the experimental measurements. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Transient thermal behavior of preloaded three-pad foil bearings : modeling and experiments [texte imprimé] / Donghyun Lee, Auteur ; Daejong Kim, Auteur ; Ramesh P. Sadashiva, Auteur . - 2012 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 11 p. Mots-clés : Convection  Electric  power  generation  Fuel  cells  Machine  bearings  Rotors  Solar  cells  Stability  Turbomachinery Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Oil-free turbomachinery have emerged as one of the core technologies for the future green power generation systems as stand-alone systems or hybridized with high temperature fuel cells or solar systems. Oil-free technology allows compact, clean, and maintenance-free operation, and foil bearings are at the center of the technology. Since their first commercial applications in the air cycle machines and auxiliary power units in 1970s, significant improvement has been made to the computational models for rotordynamic behavior. However, many technical issues still remain unsolved or poorly understood, and one of them is thermal management. This paper presents transient three-dimensional thermohydrodynamic (3D THD) model of radial foil bearings to predict transient thermal behavior of the bearing-rotor system. The transient model involves transient energy equations applied to all the mechanical structures and gas film. The model was verified through extensive experimental measurements of transient thermal behavior of three-pad foil bearing for various cooling air pressures, external loads, and speeds. The predictions showed very good agreements with the experiments, and also the 3D THD model could predict potential thermal instability observed in the experimental measurements. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Performance analysis of full-film textured surfaces with consideration of roughness effects / Y. Qiu in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 10 p. Titre : Performance analysis of full-film textured surfaces with consideration of roughness effects Type de document : texte imprimé Auteurs : Y. Qiu, Auteur ; M. M. Khonsari, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Cavitation  Density  Force  Friction  Liquid  films  Machine  bearings  Sealing  materials  Surface  roughness  Surface  texture Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A mass-conservative algorithm that implements the Jakobsson–Floberg–Olsson cavitation theory is used to predict the performances of seal-like structures and thrust bearings with a dimpled surface texture. The results of a series of simulations for load-carrying capacity, film thickness, dimple depth, dimple density, cavitation pressure, leakage, and friction force are presented, and the relationship between these performance parameters is studied. It is shown that, under the conditions simulated, surface roughness can improve the load-carrying capacity, but its effect is limited. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Performance analysis of full-film textured surfaces with consideration of roughness effects [texte imprimé] / Y. Qiu, Auteur ; M. M. Khonsari, Auteur . - 2012 . - 10 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 10 p. Mots-clés : Cavitation  Density  Force  Friction  Liquid  films  Machine  bearings  Sealing  materials  Surface  roughness  Surface  texture Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A mass-conservative algorithm that implements the Jakobsson–Floberg–Olsson cavitation theory is used to predict the performances of seal-like structures and thrust bearings with a dimpled surface texture. The results of a series of simulations for load-carrying capacity, film thickness, dimple depth, dimple density, cavitation pressure, leakage, and friction force are presented, and the relationship between these performance parameters is studied. It is shown that, under the conditions simulated, surface roughness can improve the load-carrying capacity, but its effect is limited. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Homogenization of the reynolds equation governing hydrodynamic flow in a rotating device / Andreas Almqvist in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 08 p. Titre : Homogenization of the reynolds equation governing hydrodynamic flow in a rotating device Type de document : texte imprimé Auteurs : Andreas Almqvist, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Friction  Hydrodynamics  Lubrication  Rotational  flow  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this paper, a method facilitating the analysis of the effects of surface roughness on the lubrication of a rotating device is presented. The analysis utilizes homogenization—a suitable technique for averaging the effects of roughness as modeled by the Reynolds equation. The originality of this work lies in a novel way of deriving the so called local problems, also known as microbearing problems. It is clearly shown how this increases the computational efficiency by eliminating the dependence of the global coordinates on the formulation of these local problems. This does not only speed up the computation, it also means that the derived flow factors or flow tensors require less storage space. To provide for good usability, alongside the flow factors for the averaged Reynolds equation, the correction factors for the averaged friction torque (and force) and the expression for averaged load carrying capacity are presented here. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Homogenization of the reynolds equation governing hydrodynamic flow in a rotating device [texte imprimé] / Andreas Almqvist, Auteur . - 2012 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 08 p. Mots-clés : Friction  Hydrodynamics  Lubrication  Rotational  flow  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this paper, a method facilitating the analysis of the effects of surface roughness on the lubrication of a rotating device is presented. The analysis utilizes homogenization—a suitable technique for averaging the effects of roughness as modeled by the Reynolds equation. The originality of this work lies in a novel way of deriving the so called local problems, also known as microbearing problems. It is clearly shown how this increases the computational efficiency by eliminating the dependence of the global coordinates on the formulation of these local problems. This does not only speed up the computation, it also means that the derived flow factors or flow tensors require less storage space. To provide for good usability, alongside the flow factors for the averaged Reynolds equation, the correction factors for the averaged friction torque (and force) and the expression for averaged load carrying capacity are presented here. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Synthesis and tribological properties of S- and P-free borate esters with different chain lengths / Guangbin Yang in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 07 p. Titre : Synthesis and tribological properties of S- and P-free borate esters with different chain lengths Type de document : texte imprimé Auteurs : Guangbin Yang, Auteur ; Zhanming Zhang, Auteur ; Guihui Li, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Chemical  structure  Fourier  transform  spectra  Friction  Hydrogen  bonds  Infrared  spectra  Lubricating  oils  Lubrication  Materials  preparation  Organic  compounds  Scanning  electron  microscopy  Steel  Surface  morphology  Thermal  analysis  Thermal  stability  Wear  Wear  resistance  Wear  testing  X-ray  photoelectron  spectra Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Three kinds of S- and P-free borate esters containing N with different alkyl chain lengths were prepared by using boric acid, ethanolamine, and alkyl-alcohol as the starting materials. The chemical structure of the products was analyzed by means of Fourier transformation infrared spectrometry, elemental analysis, and so on. The thermal stability of the products was evaluated by thermogravimetric analysis. The tribological properties of the synthesized borate esters as lubricating oil additives in liquid paraffin were evaluated using a four-ball friction and wear tester while the morphologies of the worn scars of the steel balls were observed using a scanning electron microscope. The chemical components on the worn surfaces of the steel balls were analyzed using an X-ray photoelectron spectroscopy. Results show that all the three kinds of synthetic borate esters as additives in liquid paraffin possess good antiwear performance and may be used as promising S- and P-free environmentally acceptable lubricating oil additives. Particularly, borate ester with short alkyl chain length at a low concentration in liquid paraffin was more effective in reducing wear, and the antiwear ability of the additives decreased with increasing alkyl chain length. The antiwear ability of the N-containing borate esters as additives in liquid paraffin might be closely related to the formation of hydrogen bonds via N with a high electronegativity and small atomic radius and the easy permeation of electron-deficient B on the rubbing steel surfaces. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Synthesis and tribological properties of S- and P-free borate esters with different chain lengths [texte imprimé] / Guangbin Yang, Auteur ; Zhanming Zhang, Auteur ; Guihui Li, Auteur . - 2012 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 07 p. Mots-clés : Chemical  structure  Fourier  transform  spectra  Friction  Hydrogen  bonds  Infrared  spectra  Lubricating  oils  Lubrication  Materials  preparation  Organic  compounds  Scanning  electron  microscopy  Steel  Surface  morphology  Thermal  analysis  Thermal  stability  Wear  Wear  resistance  Wear  testing  X-ray  photoelectron  spectra Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Three kinds of S- and P-free borate esters containing N with different alkyl chain lengths were prepared by using boric acid, ethanolamine, and alkyl-alcohol as the starting materials. The chemical structure of the products was analyzed by means of Fourier transformation infrared spectrometry, elemental analysis, and so on. The thermal stability of the products was evaluated by thermogravimetric analysis. The tribological properties of the synthesized borate esters as lubricating oil additives in liquid paraffin were evaluated using a four-ball friction and wear tester while the morphologies of the worn scars of the steel balls were observed using a scanning electron microscope. The chemical components on the worn surfaces of the steel balls were analyzed using an X-ray photoelectron spectroscopy. Results show that all the three kinds of synthetic borate esters as additives in liquid paraffin possess good antiwear performance and may be used as promising S- and P-free environmentally acceptable lubricating oil additives. Particularly, borate ester with short alkyl chain length at a low concentration in liquid paraffin was more effective in reducing wear, and the antiwear ability of the additives decreased with increasing alkyl chain length. The antiwear ability of the N-containing borate esters as additives in liquid paraffin might be closely related to the formation of hydrogen bonds via N with a high electronegativity and small atomic radius and the easy permeation of electron-deficient B on the rubbing steel surfaces. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Understanding friction behavior in automatic transmission fluid LVFA test / Hongyuan Zhao in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Titre : Understanding friction behavior in automatic transmission fluid LVFA test : a new positive curve parameter to friction coefficient ratio index evaluation Type de document : texte imprimé Auteurs : Hongyuan Zhao, Auteur ; Ardian Morina, Auteur ; Anne Neville, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Clutches  Detergents  Lubricating  oils  Mechanical  contact  Sliding  friction  Steel Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The frictional characteristics of some basic additive systems used in automatic transmission fluids (ATFs) were assessed using a variable speed friction test machine. The test evaluates the coefficient of friction in unidirectional sliding contact over a range of speeds, loads, and temperatures. Tests were performed on a steel-versus-clutch friction material tribocouple, mainly to establish the link between the lubricant/surface interactions and additive system performance. A new parameter that measures the positive µ-v curve slope speed range was applied, together with friction coefficient ratio index, to show the antishudder property. It is suggested that this is a good complimentary method to the friction coefficient ratio index evaluation. Lubricant formulation is important to the overall friction performance. Both friction modifiers and detergents are shown to be important to the ATF antishudder performance. Oil absorption ability of the post-test friction material surface is proposed to be an important parameter to indicate the antishudder durability in the test. The detergent and antiwear agents are also suggested to be responsible for the decreased oil absorption and pore plugging of the friction material surface. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Understanding friction behavior in automatic transmission fluid LVFA test : a new positive curve parameter to friction coefficient ratio index evaluation [texte imprimé] / Hongyuan Zhao, Auteur ; Ardian Morina, Auteur ; Anne Neville, Auteur . - 2012 . - 09 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 09 p. Mots-clés : Clutches  Detergents  Lubricating  oils  Mechanical  contact  Sliding  friction  Steel Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The frictional characteristics of some basic additive systems used in automatic transmission fluids (ATFs) were assessed using a variable speed friction test machine. The test evaluates the coefficient of friction in unidirectional sliding contact over a range of speeds, loads, and temperatures. Tests were performed on a steel-versus-clutch friction material tribocouple, mainly to establish the link between the lubricant/surface interactions and additive system performance. A new parameter that measures the positive µ-v curve slope speed range was applied, together with friction coefficient ratio index, to show the antishudder property. It is suggested that this is a good complimentary method to the friction coefficient ratio index evaluation. Lubricant formulation is important to the overall friction performance. Both friction modifiers and detergents are shown to be important to the ATF antishudder performance. Oil absorption ability of the post-test friction material surface is proposed to be an important parameter to indicate the antishudder durability in the test. The detergent and antiwear agents are also suggested to be responsible for the decreased oil absorption and pore plugging of the friction material surface. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Numerical solution of the boltzmann based lubrication equation for the air-bearing interface between a skewed slider and a disk with discrete data tracks / James White in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 14 p. Titre : Numerical solution of the boltzmann based lubrication equation for the air-bearing interface between a skewed slider and a disk with discrete data tracks Type de document : texte imprimé Auteurs : James White, Auteur Année de publication : 2012 Article en page(s) : 14 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Boltzmann  equation  Knudsen  flow  Lubrication  Magnetic  disc  storage  Magnetic  recording  Numerical  analysis  Surface  roughness  Surface  topography Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Discrete track recording (DTR) is a method for increasing the recording density of a data storage disk by use of a pattern arrangement of discrete tracks. The DTR track structure consists of a pattern of very narrow concentric raised areas and recessed areas underneath a magnetic recording layer. In order to design the air-bearing slider platform that houses the magnetic transducer for DTR application at very low fly heights, the influence of the disk surface topography as a surface roughness effect must be taken into account. This paper is focused on the numerical solution of the roughness averaged lubrication equation reported recently in the work of White (2010, “A Gas Lubrication Equation for High Knudsen Number Flows and Striated Rough Surfaces,” ASME J. Tribol., 132, p. 021701) and is specialized for the influence of discrete disk data tracks on the recording head slider-disk air-bearing interface subject to a nonzero skew angle formed between the slider longitudinal axis and the direction of disk motion. The generalized lubrication equation for a smooth surface bearing and appropriate for high Knudsen number analysis is quite nonlinear. And including the averaging process required for treatment of a nonsmooth disk surface, as well as the rotational transformation required to allow for a nonzero skew angle, increases further the nonlinearity and general complexity of the lubrication equation. Emphasis is placed on development of a numerical algorithm that is fast, accurate, and robust for air-bearing analysis of complex slider surfaces. The numerical solution procedure developed utilizes a time integration of the lubrication equation for both steady-state and dynamic analyses. The factored-implicit scheme, a form of the more general alternating-direction-implicit numerical approach, was chosen to deal with the two-dimensional and highly nonlinear aspects of the problem. Factoring produces tightly banded coefficient matrices and results in an algorithm that is second-order accurate in time while requiring only the solution of tridiagonal systems of linear equations in advancing the computation from one time level to the next. Numerical solutions are presented that demonstrate the performance of the computational scheme and illustrate the influence of some discrete track parameters on skewed air-bearing performance as compared with a flat surface data storage disk. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Numerical solution of the boltzmann based lubrication equation for the air-bearing interface between a skewed slider and a disk with discrete data tracks [texte imprimé] / James White, Auteur . - 2012 . - 14 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 14 p. Mots-clés : Boltzmann  equation  Knudsen  flow  Lubrication  Magnetic  disc  storage  Magnetic  recording  Numerical  analysis  Surface  roughness  Surface  topography Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Discrete track recording (DTR) is a method for increasing the recording density of a data storage disk by use of a pattern arrangement of discrete tracks. The DTR track structure consists of a pattern of very narrow concentric raised areas and recessed areas underneath a magnetic recording layer. In order to design the air-bearing slider platform that houses the magnetic transducer for DTR application at very low fly heights, the influence of the disk surface topography as a surface roughness effect must be taken into account. This paper is focused on the numerical solution of the roughness averaged lubrication equation reported recently in the work of White (2010, “A Gas Lubrication Equation for High Knudsen Number Flows and Striated Rough Surfaces,” ASME J. Tribol., 132, p. 021701) and is specialized for the influence of discrete disk data tracks on the recording head slider-disk air-bearing interface subject to a nonzero skew angle formed between the slider longitudinal axis and the direction of disk motion. The generalized lubrication equation for a smooth surface bearing and appropriate for high Knudsen number analysis is quite nonlinear. And including the averaging process required for treatment of a nonsmooth disk surface, as well as the rotational transformation required to allow for a nonzero skew angle, increases further the nonlinearity and general complexity of the lubrication equation. Emphasis is placed on development of a numerical algorithm that is fast, accurate, and robust for air-bearing analysis of complex slider surfaces. The numerical solution procedure developed utilizes a time integration of the lubrication equation for both steady-state and dynamic analyses. The factored-implicit scheme, a form of the more general alternating-direction-implicit numerical approach, was chosen to deal with the two-dimensional and highly nonlinear aspects of the problem. Factoring produces tightly banded coefficient matrices and results in an algorithm that is second-order accurate in time while requiring only the solution of tridiagonal systems of linear equations in advancing the computation from one time level to the next. Numerical solutions are presented that demonstrate the performance of the computational scheme and illustrate the influence of some discrete track parameters on skewed air-bearing performance as compared with a flat surface data storage disk. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Thermal fly-height control slider instability and dynamics at touchdown / Sripathi Vangipuram Canchi in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 13 p. Titre : Thermal fly-height control slider instability and dynamics at touchdown : explanations using nonlinear systems theory Type de document : texte imprimé Auteurs : Sripathi Vangipuram Canchi, Auteur ; David B. Bogy, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Hard  discs  Mechanical  contact  Nonlinear  dynamical  systems  Vibrations Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Thermal fly-height control sliders are widely used in current hard disk drives to control and maintain subnanometer level clearance between the read-write head and the disk. The peculiar dynamics observed during touchdown/contact tests for certain slider designs is investigated through experiments and analytical modeling. Nonlinear systems theory is used to highlight slider instabilities arising from an unfavorable coupling of system vibration modes through an internal resonance condition, as well as the favorable suppression of instabilities through a jump condition. Excitation frequencies that may lead to large amplitude slider vibrations and the dominant frequencies at which slider response occurs are also predicted from theory. Using parameters representative of the slider used in experiments, the theoretically predicted frequencies are shown to be in excellent agreement with experimental results. This analytical study highlights some important air bearing surface design considerations that can help prevent slider instability as well as help mitigate unwanted slider vibrations, thereby ensuring the reliability of the head-disk interface at extremely low head-disk clearances. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Thermal fly-height control slider instability and dynamics at touchdown : explanations using nonlinear systems theory [texte imprimé] / Sripathi Vangipuram Canchi, Auteur ; David B. Bogy, Auteur . - 2012 . - 13 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 13 p. Mots-clés : Hard  discs  Mechanical  contact  Nonlinear  dynamical  systems  Vibrations Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Thermal fly-height control sliders are widely used in current hard disk drives to control and maintain subnanometer level clearance between the read-write head and the disk. The peculiar dynamics observed during touchdown/contact tests for certain slider designs is investigated through experiments and analytical modeling. Nonlinear systems theory is used to highlight slider instabilities arising from an unfavorable coupling of system vibration modes through an internal resonance condition, as well as the favorable suppression of instabilities through a jump condition. Excitation frequencies that may lead to large amplitude slider vibrations and the dominant frequencies at which slider response occurs are also predicted from theory. Using parameters representative of the slider used in experiments, the theoretically predicted frequencies are shown to be in excellent agreement with experimental results. This analytical study highlights some important air bearing surface design considerations that can help prevent slider instability as well as help mitigate unwanted slider vibrations, thereby ensuring the reliability of the head-disk interface at extremely low head-disk clearances. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

A modification of the switch function in the elrod cavitation algorithm / M. Fesanghary in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 04 p. Titre : A modification of the switch function in the elrod cavitation algorithm Type de document : texte imprimé Auteurs : M. Fesanghary, Auteur ; M. M. Khonsari, Auteur Année de publication : 2012 Article en page(s) : 04 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Cavitation  Lubrication  Numerical  analysis Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The implementation of the mass-conservative cavitation algorithm, as derived by Elrod, requires an automatic setting of a binary switch function that delineates the full-film and cavitation zones. Abrupt changes associated with this function often causes convergence and instability issues. A method is that which improves numerical instability and overcomes the convergence issues caused by the conventional binary switch function. Two test cases are presented, which show that by using the new switching algorithm together with a successive over-relaxation solver, the Elrod cavitation algorithm converges up to 61% faster while it is less prone to numerical instabilities. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] A modification of the switch function in the elrod cavitation algorithm [texte imprimé] / M. Fesanghary, Auteur ; M. M. Khonsari, Auteur . - 2012 . - 04 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 04 p. Mots-clés : Cavitation  Lubrication  Numerical  analysis Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The implementation of the mass-conservative cavitation algorithm, as derived by Elrod, requires an automatic setting of a binary switch function that delineates the full-film and cavitation zones. Abrupt changes associated with this function often causes convergence and instability issues. A method is that which improves numerical instability and overcomes the convergence issues caused by the conventional binary switch function. Two test cases are presented, which show that by using the new switching algorithm together with a successive over-relaxation solver, the Elrod cavitation algorithm converges up to 61% faster while it is less prone to numerical instabilities. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Determining a surrogate contact pair in a hertzian contact problem / Anthony P. Sanders in Transactions of the ASME . Journal of tribology, Vol. 133 N° 2 (Avril 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 06 p. Titre : Determining a surrogate contact pair in a hertzian contact problem Type de document : texte imprimé Auteurs : Anthony P. Sanders, Auteur ; Rebecca M. Brannon, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Mechanical  contact  Shapes  (structures)  Tensors Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Laboratory testing of contact phenomena can be prohibitively expensive if the interacting bodies are geometrically complicated. This work demonstrates means to mitigate such problems by exploiting the established observation that two geometrically dissimilar contact pairs may exhibit the same contact mechanics. Specific formulas are derived that allow a complicated Hertzian contact pair to be replaced with an inexpensively manufactured and more easily fixtured surrogate pair, consisting of a plane and a spheroid, which has the same (to second-order accuracy) contact area and pressure distribution as the original complicated geometry. This observation is elucidated by using direct tensor notation to review a key assertion in Hertzian theory; namely, geometrically complicated contacting surfaces can be described to second-order accuracy as contacting ellipsoids. The surrogate spheroid geometry is found via spectral decomposition of the original pair's combined Hessian tensor. Some numerical examples using free-form surfaces illustrate the theory, and a laboratory test validates the theory under a common scenario of normally compressed convex surfaces. This theory for a Hertzian contact substitution may be useful in simplifying the contact, wear, or impact testing of complicated components or of their constituent materials. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Determining a surrogate contact pair in a hertzian contact problem [texte imprimé] / Anthony P. Sanders, Auteur ; Rebecca M. Brannon, Auteur . - 2012 . - 06 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 2 (Avril 2011) . - 06 p. Mots-clés : Mechanical  contact  Shapes  (structures)  Tensors Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Laboratory testing of contact phenomena can be prohibitively expensive if the interacting bodies are geometrically complicated. This work demonstrates means to mitigate such problems by exploiting the established observation that two geometrically dissimilar contact pairs may exhibit the same contact mechanics. Specific formulas are derived that allow a complicated Hertzian contact pair to be replaced with an inexpensively manufactured and more easily fixtured surrogate pair, consisting of a plane and a spheroid, which has the same (to second-order accuracy) contact area and pressure distribution as the original complicated geometry. This observation is elucidated by using direct tensor notation to review a key assertion in Hertzian theory; namely, geometrically complicated contacting surfaces can be described to second-order accuracy as contacting ellipsoids. The surrogate spheroid geometry is found via spectral decomposition of the original pair's combined Hessian tensor. Some numerical examples using free-form surfaces illustrate the theory, and a laboratory test validates the theory under a common scenario of normally compressed convex surfaces. This theory for a Hertzian contact substitution may be useful in simplifying the contact, wear, or impact testing of complicated components or of their constituent materials. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

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