Dépouillements

Elastohydrodynamic lubrication / Dong Zhu in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 14 p. Titre : Elastohydrodynamic lubrication : a gateway to interfacial mechanics—review and prospect Type de document : texte imprimé Auteurs : Dong Zhu, Auteur ; Q. Jane Wang, Auteur Année de publication : 2012 Article en page(s) : 14 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Deformation  Elasticity  High-pressure  effects  Hydrodynamics  Interface  phenomena  Lubrication  Mechanical  contact  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Elastohydrodynamic Lubrication (EHL) is commonly known as a mode of fluid-film lubrication in which the mechanism of hydrodynamic film formation is enhanced by surface elastic deformation and lubricant viscosity increase due to high pressure. It has been an active and challenging field of research since the 1950s. Significant breakthroughs achieved in the last 10–15 years are largely in the area of mixed EHL, in which surface asperity contact and hydrodynamic lubricant film coexist. Mixed EHL is of the utmost importance not only because most power-transmitting components operate in this regime, but also due to its theoretical universality that dry contact and full-film lubrication are in fact its special cases under extreme conditions. In principle, mixed EHL has included the basic physical elements for modeling contact, or hydrodynamic lubrication, or both together. The unified mixed lubrication models that have recently been developed are now capable of simulating the entire transition of interfacial status from full-film and mixed lubrication down to dry contact with an integrated mathematic formulation and numerical approach. This has indeed bridged the two branches of engineering science, contact mechanics, and hydrodynamic lubrication theory, which have been traditionally separate since the 1880s mainly due to the lack of powerful analytical and numerical tools. The recent advancement in mixed EHL begins to bring contact and lubrication together, and thus an evolving concept of “Interfacial Mechanics” can be proposed in order to describe interfacial phenomena more precisely and collaborate with research in other related fields, such as interfacial physics and chemistry, more closely. This review paper briefly presents snapshots of the history of EHL research, and also expresses the authors' opinions about its further development as a gateway to interfacial mechanics. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Elastohydrodynamic lubrication : a gateway to interfacial mechanics—review and prospect [texte imprimé] / Dong Zhu, Auteur ; Q. Jane Wang, Auteur . - 2012 . - 14 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 14 p. Mots-clés : Deformation  Elasticity  High-pressure  effects  Hydrodynamics  Interface  phenomena  Lubrication  Mechanical  contact  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Elastohydrodynamic Lubrication (EHL) is commonly known as a mode of fluid-film lubrication in which the mechanism of hydrodynamic film formation is enhanced by surface elastic deformation and lubricant viscosity increase due to high pressure. It has been an active and challenging field of research since the 1950s. Significant breakthroughs achieved in the last 10–15 years are largely in the area of mixed EHL, in which surface asperity contact and hydrodynamic lubricant film coexist. Mixed EHL is of the utmost importance not only because most power-transmitting components operate in this regime, but also due to its theoretical universality that dry contact and full-film lubrication are in fact its special cases under extreme conditions. In principle, mixed EHL has included the basic physical elements for modeling contact, or hydrodynamic lubrication, or both together. The unified mixed lubrication models that have recently been developed are now capable of simulating the entire transition of interfacial status from full-film and mixed lubrication down to dry contact with an integrated mathematic formulation and numerical approach. This has indeed bridged the two branches of engineering science, contact mechanics, and hydrodynamic lubrication theory, which have been traditionally separate since the 1880s mainly due to the lack of powerful analytical and numerical tools. The recent advancement in mixed EHL begins to bring contact and lubrication together, and thus an evolving concept of “Interfacial Mechanics” can be proposed in order to describe interfacial phenomena more precisely and collaborate with research in other related fields, such as interfacial physics and chemistry, more closely. This review paper briefly presents snapshots of the history of EHL research, and also expresses the authors' opinions about its further development as a gateway to interfacial mechanics. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Friction and wear of hemiarthroplasty biomaterials in reciprocating sliding contact with articular cartilage / S. M. T. Chan in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 07 p. Titre : Friction and wear of hemiarthroplasty biomaterials in reciprocating sliding contact with articular cartilage Type de document : texte imprimé Auteurs : S. M. T. Chan, Auteur ; C. P. Neu, Auteur ; K. Komvopoulos, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Alumina  Biological  tissues  Biomechanics  Biomedical  materials  Cellular  biophysics  Chromium  alloys  Cobalt  alloys  Molecular  biophysics  Molecular  weight  Polymers  Proteins  Sliding  friction  Stainless  steel  Surface  roughness  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Friction and wear of four common orthopaedic biomaterials, alumina (Al2O3), cobalt-chromium (CoCr), stainless steel (SS), and crosslinked ultra-high-molecular-weight polyethylene (UHMWPE), sliding against bovine articular cartilage explants were investigated by reciprocating sliding, nanoscale friction and roughness measurements, protein wear assays, and histology. Under the experimental conditions of the present study, CoCr yielded the largest increase in cartilage friction coefficient, largest amount of protein loss, and greatest change in nanoscale friction after sliding against cartilage. UHMWPE showed the lowest cartilage friction coefficient, least amount of protein loss, and insignificant changes in nanoscale friction after sliding. Although the results are specific to the testing protocol and surface roughness of the examined biomaterials, they indicate that CoCr tends to accelerate wear of cartilage, whereas the UHMWPE shows the best performance against cartilage. This study also shows that the surface characteristics of all biomaterials must be further improved to achieve the low friction coefficient of the cartilage/cartilage interface. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Friction and wear of hemiarthroplasty biomaterials in reciprocating sliding contact with articular cartilage [texte imprimé] / S. M. T. Chan, Auteur ; C. P. Neu, Auteur ; K. Komvopoulos, Auteur . - 2012 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 07 p. Mots-clés : Alumina  Biological  tissues  Biomechanics  Biomedical  materials  Cellular  biophysics  Chromium  alloys  Cobalt  alloys  Molecular  biophysics  Molecular  weight  Polymers  Proteins  Sliding  friction  Stainless  steel  Surface  roughness  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Friction and wear of four common orthopaedic biomaterials, alumina (Al2O3), cobalt-chromium (CoCr), stainless steel (SS), and crosslinked ultra-high-molecular-weight polyethylene (UHMWPE), sliding against bovine articular cartilage explants were investigated by reciprocating sliding, nanoscale friction and roughness measurements, protein wear assays, and histology. Under the experimental conditions of the present study, CoCr yielded the largest increase in cartilage friction coefficient, largest amount of protein loss, and greatest change in nanoscale friction after sliding against cartilage. UHMWPE showed the lowest cartilage friction coefficient, least amount of protein loss, and insignificant changes in nanoscale friction after sliding. Although the results are specific to the testing protocol and surface roughness of the examined biomaterials, they indicate that CoCr tends to accelerate wear of cartilage, whereas the UHMWPE shows the best performance against cartilage. This study also shows that the surface characteristics of all biomaterials must be further improved to achieve the low friction coefficient of the cartilage/cartilage interface. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Multiscale analysis on two dimensional nanoscale sliding contacts of textured surfaces / Ruiting Tong in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 13 p. Titre : Multiscale analysis on two dimensional nanoscale sliding contacts of textured surfaces Type de document : texte imprimé Auteurs : Ruiting Tong, Auteur ; Geng Liu, Auteur ; Tianxiang Liu, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Adhesion  Continuum  mechanics  Finite  element  analysis  Indentation  Mechanical  contact  Molecular  dynamics  method  Sliding  friction  Surface  texture  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Nanoscale sliding contacts are the major factors that influence the friction and result in wear in micro/nanoelectromechanical systems. Many experimental studies indicated that some surface textures could help improve the contact characteristics and reduce friction forces. However, the experimental results may be biased, due to the contamination of the sample surface or substantial defects in the materials. Numerical methods, such as continuum mechanics, meet great challenges when they are applied at length of nanoscale, and the time cost of molecular dynamics (MD) simulation can be extremely high. Therefore, multiscale method, which can capture atomistic behaviors in the region underlying micro/nano physical processes by MD simulations and models other regions by continuum mechanics, offers a great promise. Coupling MD simulation and finite element method, the multiscale method is used to investigate two dimensional nanoscale sliding contacts between a rigid cylindrical tip and an elastic substrate with textured surface, in which adhesive effects are considered. Two series of nanoscale surface textures with different asperity shapes, different asperity heights, and different spacings between asperities are designed. For different heights of asperities or different spacings between asperities, average potential energy, normal forces, mean normal forces, friction forces, and mean friction forces are compared to observe how these parameters influence friction characteristics; then, the optimal asperity height or spacing is discovered. Through the average potential energy, normal forces, mean normal forces, friction forces, and mean friction forces comparisons between smooth surface and textured surfaces, a better shape is advised to indicate that asperity shape plays an important role in friction force reduction. The influences of the indentation depth and radius of the rigid cylindrical tip are analyzed to find out the sensitivity of surface textures to these two parameters. Effects of sliding speed on the characteristics of nanoscale sliding contacts are also discussed. The results show that, with proper asperity height and proper spacing between asperities, surface textures can reduce friction forces effectively. Coefficients of friction (COFs) of all the cases are calculated and compared. Some negative COFs caused by significant adhesive effects are discovered, which are different from traditional macroscopic phenomena. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Multiscale analysis on two dimensional nanoscale sliding contacts of textured surfaces [texte imprimé] / Ruiting Tong, Auteur ; Geng Liu, Auteur ; Tianxiang Liu, Auteur . - 2012 . - 13 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 13 p. Mots-clés : Adhesion  Continuum  mechanics  Finite  element  analysis  Indentation  Mechanical  contact  Molecular  dynamics  method  Sliding  friction  Surface  texture  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Nanoscale sliding contacts are the major factors that influence the friction and result in wear in micro/nanoelectromechanical systems. Many experimental studies indicated that some surface textures could help improve the contact characteristics and reduce friction forces. However, the experimental results may be biased, due to the contamination of the sample surface or substantial defects in the materials. Numerical methods, such as continuum mechanics, meet great challenges when they are applied at length of nanoscale, and the time cost of molecular dynamics (MD) simulation can be extremely high. Therefore, multiscale method, which can capture atomistic behaviors in the region underlying micro/nano physical processes by MD simulations and models other regions by continuum mechanics, offers a great promise. Coupling MD simulation and finite element method, the multiscale method is used to investigate two dimensional nanoscale sliding contacts between a rigid cylindrical tip and an elastic substrate with textured surface, in which adhesive effects are considered. Two series of nanoscale surface textures with different asperity shapes, different asperity heights, and different spacings between asperities are designed. For different heights of asperities or different spacings between asperities, average potential energy, normal forces, mean normal forces, friction forces, and mean friction forces are compared to observe how these parameters influence friction characteristics; then, the optimal asperity height or spacing is discovered. Through the average potential energy, normal forces, mean normal forces, friction forces, and mean friction forces comparisons between smooth surface and textured surfaces, a better shape is advised to indicate that asperity shape plays an important role in friction force reduction. The influences of the indentation depth and radius of the rigid cylindrical tip are analyzed to find out the sensitivity of surface textures to these two parameters. Effects of sliding speed on the characteristics of nanoscale sliding contacts are also discussed. The results show that, with proper asperity height and proper spacing between asperities, surface textures can reduce friction forces effectively. Coefficients of friction (COFs) of all the cases are calculated and compared. Some negative COFs caused by significant adhesive effects are discovered, which are different from traditional macroscopic phenomena. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Contact pressure and residual strain in 3D elasto-plastic rolling contact for a circular or elliptical point contact / Thibaut Chaise in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 09 p. Titre : Contact pressure and residual strain in 3D elasto-plastic rolling contact for a circular or elliptical point contact Type de document : texte imprimé Auteurs : Thibaut Chaise, Auteur ; Daniel Nélias, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Elasticity  Elastoplasticity  Fatigue  Hardening  Mechanical  contact  Numerical  analysis  Plastic  deformation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : What is often referred to as a Hertzian contact can undergo plasticity either at the macroscale, due to an accidental overload, or at an asperity scale, due to the presence of surface defects and/or roughness. An elastic solution does not explicitly consider the surface velocity or loading history, but it is also apparent that a moving (rolling) load will not yield the same residual stress and strain distribution as a purely vertical loading/unloading. Three-dimensional (3D) analysis is also more complex than the two-dimensional (2D) problem because it implies a change in the surface conformity. This paper presents the results of a numerical investigation of frictionless elastic-plastic elliptical point contacts with a moving load, as compared to a purely vertical (indentation) load. In the present analysis, both bodies may behave in an elastic-plastic mode. Both kinematic and isotropic hardening are considered to account for repeated rolling contacts. The contact pressure and the plastic strain are found to be reduced when the two bodies are elastic-plastic, as compared to the case in which one of the bodies remains elastic. Numerical results also indicate that at a given load intensity, the maximum contact pressure and equivalent plastic strain are affected by the contact geometry (circular and elliptical point contacts) and differ significantly when the load is moving as compared to purely vertical indentation. Although the maximum elastic contact pressure (Hertz solution) is often used as a control parameter for rolling contact fatigue analysis, whatever the geometry of the contact (point, elliptical, or line contact), the results presented here show that the effective contact pressure and subsequent residual strains are strongly dependent on the contact geometry in the elastic-plastic regime. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Contact pressure and residual strain in 3D elasto-plastic rolling contact for a circular or elliptical point contact [texte imprimé] / Thibaut Chaise, Auteur ; Daniel Nélias, Auteur . - 2012 . - 09 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 09 p. Mots-clés : Elasticity  Elastoplasticity  Fatigue  Hardening  Mechanical  contact  Numerical  analysis  Plastic  deformation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : What is often referred to as a Hertzian contact can undergo plasticity either at the macroscale, due to an accidental overload, or at an asperity scale, due to the presence of surface defects and/or roughness. An elastic solution does not explicitly consider the surface velocity or loading history, but it is also apparent that a moving (rolling) load will not yield the same residual stress and strain distribution as a purely vertical loading/unloading. Three-dimensional (3D) analysis is also more complex than the two-dimensional (2D) problem because it implies a change in the surface conformity. This paper presents the results of a numerical investigation of frictionless elastic-plastic elliptical point contacts with a moving load, as compared to a purely vertical (indentation) load. In the present analysis, both bodies may behave in an elastic-plastic mode. Both kinematic and isotropic hardening are considered to account for repeated rolling contacts. The contact pressure and the plastic strain are found to be reduced when the two bodies are elastic-plastic, as compared to the case in which one of the bodies remains elastic. Numerical results also indicate that at a given load intensity, the maximum contact pressure and equivalent plastic strain are affected by the contact geometry (circular and elliptical point contacts) and differ significantly when the load is moving as compared to purely vertical indentation. Although the maximum elastic contact pressure (Hertz solution) is often used as a control parameter for rolling contact fatigue analysis, whatever the geometry of the contact (point, elliptical, or line contact), the results presented here show that the effective contact pressure and subsequent residual strains are strongly dependent on the contact geometry in the elastic-plastic regime. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Fractal analysis of cavitation eroded surface in dilute emulsions / A. Abouel-Kasem in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 09 p. Titre : Fractal analysis of cavitation eroded surface in dilute emulsions Type de document : texte imprimé Auteurs : A. Abouel-Kasem, Auteur ; F. A. Alturki, Auteur ; S. M. Ahmed, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Triboblogy Langues : Anglais (eng) Mots-clés : Emulsions  Fractals  Fracture  Stainless  steel  Water  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the present work, the topographical images of cavitation erosion surfaces at water and oil-in-water (o/w) emulsions were quantified using fractal analysis. The oil-in-water emulsion concentrations were 2, 5 and 10 wt. %, which are in the popular range used in hydraulic systems. The study showed that the variation of fractal dimension calculated from slope of linearized power spectral density for water and o/w emulsions can be used to characterize the cavitation intensity in similar manner to the weight loss. Both the fractal dimension and the weight loss decrease with adding oil to water. It was also found that the variation of fractal dimension versus concentration of oil-in-water emulsions has a general trend that does not depend on magnification factor. The cavitation erosion behavior and mechanism for water and o/w emulsions has been studied. It was found that the predominant failure mode was fatigue for water and o/w emulsions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Fractal analysis of cavitation eroded surface in dilute emulsions [texte imprimé] / A. Abouel-Kasem, Auteur ; F. A. Alturki, Auteur ; S. M. Ahmed, Auteur . - 2012 . - 09 p. Triboblogy Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 09 p. Mots-clés : Emulsions  Fractals  Fracture  Stainless  steel  Water  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the present work, the topographical images of cavitation erosion surfaces at water and oil-in-water (o/w) emulsions were quantified using fractal analysis. The oil-in-water emulsion concentrations were 2, 5 and 10 wt. %, which are in the popular range used in hydraulic systems. The study showed that the variation of fractal dimension calculated from slope of linearized power spectral density for water and o/w emulsions can be used to characterize the cavitation intensity in similar manner to the weight loss. Both the fractal dimension and the weight loss decrease with adding oil to water. It was also found that the variation of fractal dimension versus concentration of oil-in-water emulsions has a general trend that does not depend on magnification factor. The cavitation erosion behavior and mechanism for water and o/w emulsions has been studied. It was found that the predominant failure mode was fatigue for water and o/w emulsions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Semi-analytical viscoelastic contact modeling of polymer-based materials / W. Wayne Chen in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 10 p. Titre : Semi-analytical viscoelastic contact modeling of polymer-based materials Type de document : texte imprimé Auteurs : W. Wayne Chen, Auteur ; Q. Jane Wang, Auteur ; Z. Huan, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Triboblogy Langues : Anglais (eng) Mots-clés : Conjugate  gradient  methods  Fast  Fourier  transforms  Indentation  Mechanical  contact  Polymers  Surface  roughness  Time-domain  analysis  Transient  analysis  Viscoelasticity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Contact of viscoelastic materials with complicated properties and surface topography require numerical solution approaches. This paper presents a 3-D semianalytical contact model for viscoelastic materials. With the hereditary integral operator and elastic-viscoelastic correspondence principle, surface displacement is expressed in terms of viscoelastic creep compliance and contact pressure distribution history in the course of a contact process. Through discretizing the contact equations in both spatial and temporal dimensions, a numerical algorithm based on the robust Conjugate Gradient method and Fast Fourier transform has been developed to solve the normal approach, contact pressure, and real contact area simultaneously. The transient contact analysis in the time domain is computationally expensive. The fast Fourier transform algorithm can help reduce the computation cost significantly. The comparisons of the new numerical results with an analytical viscoelastic contact solution for Maxwell materials and with an indentation test measurement reported in the literature has validated and demonstrated the accuracy of the proposed model. Moreover, the present model has been used to simulate the contact between a polymethyl methacrylate (PMMA) substrate and a rigid sphere driven by step, ramped, and harmonic normal loads. The validated model and numerical method can successfully compute the viscoelastic contact responses of polymer-based materials with time-dependent properties and surface roughness subjected to complicated loading profiles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Semi-analytical viscoelastic contact modeling of polymer-based materials [texte imprimé] / W. Wayne Chen, Auteur ; Q. Jane Wang, Auteur ; Z. Huan, Auteur . - 2012 . - 10 p. Triboblogy Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 10 p. Mots-clés : Conjugate  gradient  methods  Fast  Fourier  transforms  Indentation  Mechanical  contact  Polymers  Surface  roughness  Time-domain  analysis  Transient  analysis  Viscoelasticity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Contact of viscoelastic materials with complicated properties and surface topography require numerical solution approaches. This paper presents a 3-D semianalytical contact model for viscoelastic materials. With the hereditary integral operator and elastic-viscoelastic correspondence principle, surface displacement is expressed in terms of viscoelastic creep compliance and contact pressure distribution history in the course of a contact process. Through discretizing the contact equations in both spatial and temporal dimensions, a numerical algorithm based on the robust Conjugate Gradient method and Fast Fourier transform has been developed to solve the normal approach, contact pressure, and real contact area simultaneously. The transient contact analysis in the time domain is computationally expensive. The fast Fourier transform algorithm can help reduce the computation cost significantly. The comparisons of the new numerical results with an analytical viscoelastic contact solution for Maxwell materials and with an indentation test measurement reported in the literature has validated and demonstrated the accuracy of the proposed model. Moreover, the present model has been used to simulate the contact between a polymethyl methacrylate (PMMA) substrate and a rigid sphere driven by step, ramped, and harmonic normal loads. The validated model and numerical method can successfully compute the viscoelastic contact responses of polymer-based materials with time-dependent properties and surface roughness subjected to complicated loading profiles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Motion analysis of micropart in dry friction environment due to surface excitation considering microscale forces / M. Rizwan in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 12 p. Titre : Motion analysis of micropart in dry friction environment due to surface excitation considering microscale forces Type de document : texte imprimé Auteurs : M. Rizwan, Auteur ; P. S. Shiakolas, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Deformation  Friction  Mechanical  contact  Micromechanics  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This manuscript investigates the motion of a micropart on a dry nonlubricated controlled deformable surface considering the dynamically changing microforces while in contact with the surface. The motion analysis of a micropart on a flexible surface under controlled deformation is the first step to initiate feasibility of a micromanipulation device. At the micro/nanoscale, the surface force of attraction becomes more significant than the inertia force; thus motion analysis requires estimating and accommodating these forces in a dynamic model. The model considers microscale forces and surface roughness conditions (asperity deformation), while dynamically evaluating the friction coefficient and attraction force due to the dynamic asperity deformation as the micropart moves on a controlled deformation active surface. The parameters considered in the model include the micropart mass and size, the relative roughness between the micropart and surface, the surface and micropart material, and input actuator frequency, stroke, and deformation profile. The simulation results indicate that predictable micropart motion could be achieved but only within a certain range of input actuator frequencies. At lower frequencies no motion is possible while at higher frequencies the micropart detaches from the surface. The understanding of the effects of the microforces on the dynamic model and micropart motion would pave the way towards controlled micropart translocation and manipulation employing a flexible surface for microassembly or for processes requiring controlled micropart handling for heterogeneous microdevice mass production. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Motion analysis of micropart in dry friction environment due to surface excitation considering microscale forces [texte imprimé] / M. Rizwan, Auteur ; P. S. Shiakolas, Auteur . - 2012 . - 12 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 12 p. Mots-clés : Deformation  Friction  Mechanical  contact  Micromechanics  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This manuscript investigates the motion of a micropart on a dry nonlubricated controlled deformable surface considering the dynamically changing microforces while in contact with the surface. The motion analysis of a micropart on a flexible surface under controlled deformation is the first step to initiate feasibility of a micromanipulation device. At the micro/nanoscale, the surface force of attraction becomes more significant than the inertia force; thus motion analysis requires estimating and accommodating these forces in a dynamic model. The model considers microscale forces and surface roughness conditions (asperity deformation), while dynamically evaluating the friction coefficient and attraction force due to the dynamic asperity deformation as the micropart moves on a controlled deformation active surface. The parameters considered in the model include the micropart mass and size, the relative roughness between the micropart and surface, the surface and micropart material, and input actuator frequency, stroke, and deformation profile. The simulation results indicate that predictable micropart motion could be achieved but only within a certain range of input actuator frequencies. At lower frequencies no motion is possible while at higher frequencies the micropart detaches from the surface. The understanding of the effects of the microforces on the dynamic model and micropart motion would pave the way towards controlled micropart translocation and manipulation employing a flexible surface for microassembly or for processes requiring controlled micropart handling for heterogeneous microdevice mass production. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Coupling continuous and discontinuous descriptions to model first body deformation in third body flows / Hong-Phong Cao in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 07 p. Titre : Coupling continuous and discontinuous descriptions to model first body deformation in third body flows Type de document : texte imprimé Auteurs : Hong-Phong Cao, Auteur ; Mathieu Renouf, Auteur ; Frédéric Dubois, Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Deformation  Finite  element  analysis  Friction  Internal  stresses  Rheology  Velocity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The present paper proposes an extension of the classical discrete element method used to study third body flows. Based on the concept of the tribological triplet proposed by Godet and Berthier, the aim of this work is to enrich description, by accounting for the deformation of the first body and investigating its influence on third-body rheology. To achieve this, a novel hybrid approach that combines continuous and discontinuous descriptions is used. To illustrate the advantage of such modeling, comparisons with the classical approach, which considers the first body as rigid, are performed in terms of macroscopic friction coefficient and velocity and stress profiles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Coupling continuous and discontinuous descriptions to model first body deformation in third body flows [texte imprimé] / Hong-Phong Cao, Auteur ; Mathieu Renouf, Auteur ; Frédéric Dubois, Auteur . - 2012 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 07 p. Mots-clés : Deformation  Finite  element  analysis  Friction  Internal  stresses  Rheology  Velocity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The present paper proposes an extension of the classical discrete element method used to study third body flows. Based on the concept of the tribological triplet proposed by Godet and Berthier, the aim of this work is to enrich description, by accounting for the deformation of the first body and investigating its influence on third-body rheology. To achieve this, a novel hybrid approach that combines continuous and discontinuous descriptions is used. To illustrate the advantage of such modeling, comparisons with the classical approach, which considers the first body as rigid, are performed in terms of macroscopic friction coefficient and velocity and stress profiles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Improved wear resistance of dendrite composite eutectic Fe-B alloy / Licai Fu in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 05 p. Titre : Improved wear resistance of dendrite composite eutectic Fe-B alloy Type de document : texte imprimé Auteurs : Licai Fu, Auteur ; Jun Yang, Auteur ; Qinling Bi, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Dendrites  Eutectic  alloys  Friction  Oxidation  Wear  resistance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The dry-sliding tribological properties of the dendrite composite eutectic Fe-B alloys (Fe94.3B5.7, Fe75B25 Fe67B33) were studied comparatively with various sliding speeds. The friction coefficient of the Fe-B alloy changes slightly with the boron content. The wear rate of the Fe94.3B5.7 alloy with about 30 vol. % dendrite t-Fe2B is only one third of Fe75B25 alloy with 15 vol. % dendrite and Fe67B33 alloy with 90 vol. % dendrite in the high sliding speed. First, a hard t-Fe2B phase reduced the wear of the Fe-B alloy directly. Second, the compactly oxide layers resulting from oxidation of the alpha-Fe on the worn surfaces also decreases the wear rate of Fe-B alloys. On the whole, the wear rate of the Fe94.3B5.7 is lower than Fe67B33 and Fe75B25. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Improved wear resistance of dendrite composite eutectic Fe-B alloy [texte imprimé] / Licai Fu, Auteur ; Jun Yang, Auteur ; Qinling Bi, Auteur . - 2012 . - 05 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 05 p. Mots-clés : Dendrites  Eutectic  alloys  Friction  Oxidation  Wear  resistance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The dry-sliding tribological properties of the dendrite composite eutectic Fe-B alloys (Fe94.3B5.7, Fe75B25 Fe67B33) were studied comparatively with various sliding speeds. The friction coefficient of the Fe-B alloy changes slightly with the boron content. The wear rate of the Fe94.3B5.7 alloy with about 30 vol. % dendrite t-Fe2B is only one third of Fe75B25 alloy with 15 vol. % dendrite and Fe67B33 alloy with 90 vol. % dendrite in the high sliding speed. First, a hard t-Fe2B phase reduced the wear of the Fe-B alloy directly. Second, the compactly oxide layers resulting from oxidation of the alpha-Fe on the worn surfaces also decreases the wear rate of Fe-B alloys. On the whole, the wear rate of the Fe94.3B5.7 is lower than Fe67B33 and Fe75B25. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Tribological characteristics of deformed magnesium alloy AZ61 under dry conditions / Abdel-Wahab El-Morsy in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 08 p. Titre : Tribological characteristics of deformed magnesium alloy AZ61 under dry conditions Type de document : texte imprimé Auteurs : Abdel-Wahab El-Morsy, Auteur ; A. Abouel-Kasem, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Deformation  Drying  Extrusion  Fractals  Internal  stresses  Magnesium  alloys  Stainless  steel  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The wear behavior of deformed magnesium alloy AZ61 under dry conditions was evaluated. Two types of AZ61 alloy were used, extruded and rolled samples, to investigate the effect of deformation process on the wear behavior. The experiments were performed using a pin-on-ring type wear apparatus against a stainless-steel counterface under applied stresses in the range of 3–7 MPa, and within a sliding velocity range of 0.2–1.8 m/s. The topographical images of the eroded surfaces at different sliding velocity for extruded and rolled samples were quantified using fractal analysis. The results revealed that for all applied stress, the wear rates increased with increasing the sliding velocity of both samples. The wear rate of the rolled samples is greater than that of the extruded samples at the stress range from 3 to 5 MPa. However, when the stress is increased to 7 MPa the wear rate of the rolled samples is lower than that of the extruded samples. The variation of fractal value of slope of linearized power spectral density (PSD) with the sliding velocity is largely similar to the relationship between the wear rate and the sliding velocity. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Tribological characteristics of deformed magnesium alloy AZ61 under dry conditions [texte imprimé] / Abdel-Wahab El-Morsy, Auteur ; A. Abouel-Kasem, Auteur . - 2012 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 08 p. Mots-clés : Deformation  Drying  Extrusion  Fractals  Internal  stresses  Magnesium  alloys  Stainless  steel  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The wear behavior of deformed magnesium alloy AZ61 under dry conditions was evaluated. Two types of AZ61 alloy were used, extruded and rolled samples, to investigate the effect of deformation process on the wear behavior. The experiments were performed using a pin-on-ring type wear apparatus against a stainless-steel counterface under applied stresses in the range of 3–7 MPa, and within a sliding velocity range of 0.2–1.8 m/s. The topographical images of the eroded surfaces at different sliding velocity for extruded and rolled samples were quantified using fractal analysis. The results revealed that for all applied stress, the wear rates increased with increasing the sliding velocity of both samples. The wear rate of the rolled samples is greater than that of the extruded samples at the stress range from 3 to 5 MPa. However, when the stress is increased to 7 MPa the wear rate of the rolled samples is lower than that of the extruded samples. The variation of fractal value of slope of linearized power spectral density (PSD) with the sliding velocity is largely similar to the relationship between the wear rate and the sliding velocity. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Theoretical investigation of couple stress squeeze films in a curved circular geometry / Vimala Manivasakan in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 08 p. Titre : Theoretical investigation of couple stress squeeze films in a curved circular geometry Type de document : texte imprimé Auteurs : Vimala Manivasakan, Auteur ; Govindarajan Sumathi, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Discs  (structures)  Hydrodynamics  Laminar  flow  Lubrication  Non-Newtonian  flow Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A theoretical investigation of the laminar squeeze flow of a couple-stress fluid between a flat circular static disk and an axisymmetric curved circular moving disk has been carried out using modified lubrication theory and microcontinuum theory. The combined effects of fluid inertia forces, curvature of the disk and non-Newtonian couple stresses on the squeeze film behavior are investigated analytically. Each of these effects and their combinations show a significant enhancement in the squeeze film behavior, and these are studied through their effects on the squeeze film pressure and the load carrying capacity of the fluid film as a function of time. Two different forms of the gapwidth between the disks have been considered, and the results have been shown to be in good agreement with the existing literature. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Theoretical investigation of couple stress squeeze films in a curved circular geometry [texte imprimé] / Vimala Manivasakan, Auteur ; Govindarajan Sumathi, Auteur . - 2012 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 08 p. Mots-clés : Discs  (structures)  Hydrodynamics  Laminar  flow  Lubrication  Non-Newtonian  flow Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A theoretical investigation of the laminar squeeze flow of a couple-stress fluid between a flat circular static disk and an axisymmetric curved circular moving disk has been carried out using modified lubrication theory and microcontinuum theory. The combined effects of fluid inertia forces, curvature of the disk and non-Newtonian couple stresses on the squeeze film behavior are investigated analytically. Each of these effects and their combinations show a significant enhancement in the squeeze film behavior, and these are studied through their effects on the squeeze film pressure and the load carrying capacity of the fluid film as a function of time. Two different forms of the gapwidth between the disks have been considered, and the results have been shown to be in good agreement with the existing literature. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Geometry optimization of textured three-dimensional micro- thrust bearings / C. I. Papadopoulos in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 14 p. Titre : Geometry optimization of textured three-dimensional micro- thrust bearings Type de document : texte imprimé Auteurs : C. I. Papadopoulos, Auteur ; E. E. Efstathiou, Auteur ; P. G. Nikolakopoulos, Auteur Année de publication : 2012 Article en page(s) : 14 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Computational  fluid  dynamics  Friction  Genetic  algorithms  Machine  bearings  Micromotors  Minimisation  Navier-Stokes  equations  Numerical  analysis  Pareto  optimisation  Rotors  Stators  Texture Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as micro-channels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Geometry optimization of textured three-dimensional micro- thrust bearings [texte imprimé] / C. I. Papadopoulos, Auteur ; E. E. Efstathiou, Auteur ; P. G. Nikolakopoulos, Auteur . - 2012 . - 14 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 14 p. Mots-clés : Computational  fluid  dynamics  Friction  Genetic  algorithms  Machine  bearings  Micromotors  Minimisation  Navier-Stokes  equations  Numerical  analysis  Pareto  optimisation  Rotors  Stators  Texture Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as micro-channels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Contaminant migration in the vicinity of a grease lubricated bearing seal contact / P. Baart in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 08 p. Titre : Contaminant migration in the vicinity of a grease lubricated bearing seal contact Type de document : texte imprimé Auteurs : P. Baart, Auteur ; P. M. Lugt, Auteur ; B. Prakash, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Greases  Lubricating  oils  Organic  compounds  Probability  Rolling  bearings  Sealing  materials  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Lubricating grease is commonly used for lubricating “sealed and greased for life” rolling element bearings. This grease also provides an additional sealing function to protect the bearing against ingress of contaminants. In this work the sealing function of lubricating grease in the vicinity of the seal lip contact has been studied experimentally by measuring the migration of spherical fluorescent contaminant particles in the vicinity of the contact, as a function of shaft speed and lubricant type. The experimental results reveal that in some greases contaminant particles migrate towards the sealing contact where the shear rate reaches its highest value. However, for other greases, Newtonian base oils, and elastic fluids, this is not necessarily the case and contaminant particles consistently migrate away from the sealing contact. Various physical phenomena have been investigated to explain the difference in migration behavior. It is concluded that migration towards the sealing contact is driven by the viscosity gradient and migration away from the sealing contact is related to the Weissenberg number. The sealing function of grease in the vicinity of the sealing contact is due to the migration of contaminant particles. The migration reduces the probability of particles to reach the sealing and bearing contacts. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Contaminant migration in the vicinity of a grease lubricated bearing seal contact [texte imprimé] / P. Baart, Auteur ; P. M. Lugt, Auteur ; B. Prakash, Auteur . - 2012 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 08 p. Mots-clés : Greases  Lubricating  oils  Organic  compounds  Probability  Rolling  bearings  Sealing  materials  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Lubricating grease is commonly used for lubricating “sealed and greased for life” rolling element bearings. This grease also provides an additional sealing function to protect the bearing against ingress of contaminants. In this work the sealing function of lubricating grease in the vicinity of the seal lip contact has been studied experimentally by measuring the migration of spherical fluorescent contaminant particles in the vicinity of the contact, as a function of shaft speed and lubricant type. The experimental results reveal that in some greases contaminant particles migrate towards the sealing contact where the shear rate reaches its highest value. However, for other greases, Newtonian base oils, and elastic fluids, this is not necessarily the case and contaminant particles consistently migrate away from the sealing contact. Various physical phenomena have been investigated to explain the difference in migration behavior. It is concluded that migration towards the sealing contact is driven by the viscosity gradient and migration away from the sealing contact is related to the Weissenberg number. The sealing function of grease in the vicinity of the sealing contact is due to the migration of contaminant particles. The migration reduces the probability of particles to reach the sealing and bearing contacts. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

A boundary lubrication friction model sensitive to detailed engine oil formulation in an automotive cam/follower interface / Rupesh Roshan in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 09 p. Titre : A boundary lubrication friction model sensitive to detailed engine oil formulation in an automotive cam/follower interface Type de document : texte imprimé Auteurs : Rupesh Roshan, Auteur ; Martin Priest, Auteur ; Anne Neville, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Automotive  components  Engines  Friction  Lubricating  oils  Lubrication  Molybdenum  compounds  Organic  compounds  Regression  analysis  Steel  Valves  Zinc  compounds Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Theoretical studies have shown that in severe operating conditions, valve train friction losses are significant and have an adverse effect on fuel efficiency. However, recent studies have shown that existing valve train friction models do not reliably predict friction in boundary and mixed lubrication conditions and are not sensitive to lubricant chemistry. In these conditions, the friction losses depend on the tribological performance of tribofilms formed as a result of surface–lubricant additive interactions. In this study, key tribological parameters were extracted from a direct acting tappet type Ford Zetec SE (Sigma) valve train, and controlled experiments were performed in a block-on-ring tribometer under conditions representative of boundary lubrication in a cam and follower contact. Friction was recorded for the tribofilms formed by molybdenum dithiocarbamate (MoDTC), zinc dialkyldithiophosphate (ZDDP), detergent (calcium sulfonate), and dispersant (polyisobutylene succinimide) additives in an ester-containing synthetic polyalphaolefin (PAO) base oil on AISI E52100 steel components. A multiple linear regression technique was used to obtain a friction model in boundary lubrication from the friction data taken from the block-on-ring tribometer tests. The model was developed empirically as a function of the ZDDP, MoDTC, detergent, and dispersant concentration in the oil and the temperature and sliding speed. The resulting friction model is sensitive to lubricant chemistry in boundary lubrication. The tribofilm friction model showed sensitivity to the ZDDP–MoDTC, MoDTC–dispersant, MoDTC–speed, ZDDP–temperature, detergent–temperature, and detergent–speed interactions. Friction decreases with an increase in the temperature for all ZDDP/MoDTC ratios, and oils containing detergent and dispersant showed high friction due to antagonistic interactions between MoDTC–detergent and MoDTC–dispersant additive combinations. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] A boundary lubrication friction model sensitive to detailed engine oil formulation in an automotive cam/follower interface [texte imprimé] / Rupesh Roshan, Auteur ; Martin Priest, Auteur ; Anne Neville, Auteur . - 2012 . - 09 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 09 p. Mots-clés : Automotive  components  Engines  Friction  Lubricating  oils  Lubrication  Molybdenum  compounds  Organic  compounds  Regression  analysis  Steel  Valves  Zinc  compounds Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Theoretical studies have shown that in severe operating conditions, valve train friction losses are significant and have an adverse effect on fuel efficiency. However, recent studies have shown that existing valve train friction models do not reliably predict friction in boundary and mixed lubrication conditions and are not sensitive to lubricant chemistry. In these conditions, the friction losses depend on the tribological performance of tribofilms formed as a result of surface–lubricant additive interactions. In this study, key tribological parameters were extracted from a direct acting tappet type Ford Zetec SE (Sigma) valve train, and controlled experiments were performed in a block-on-ring tribometer under conditions representative of boundary lubrication in a cam and follower contact. Friction was recorded for the tribofilms formed by molybdenum dithiocarbamate (MoDTC), zinc dialkyldithiophosphate (ZDDP), detergent (calcium sulfonate), and dispersant (polyisobutylene succinimide) additives in an ester-containing synthetic polyalphaolefin (PAO) base oil on AISI E52100 steel components. A multiple linear regression technique was used to obtain a friction model in boundary lubrication from the friction data taken from the block-on-ring tribometer tests. The model was developed empirically as a function of the ZDDP, MoDTC, detergent, and dispersant concentration in the oil and the temperature and sliding speed. The resulting friction model is sensitive to lubricant chemistry in boundary lubrication. The tribofilm friction model showed sensitivity to the ZDDP–MoDTC, MoDTC–dispersant, MoDTC–speed, ZDDP–temperature, detergent–temperature, and detergent–speed interactions. Friction decreases with an increase in the temperature for all ZDDP/MoDTC ratios, and oils containing detergent and dispersant showed high friction due to antagonistic interactions between MoDTC–detergent and MoDTC–dispersant additive combinations. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Identification of a friction model at the tool-chip-workpiece interface in dry machining of a AISI 1045 steel with a TiN coated carbide tool / Hamdi Ben Abdelali in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 11 p. Titre : Identification of a friction model at the tool-chip-workpiece interface in dry machining of a AISI 1045 steel with a TiN coated carbide tool Type de document : texte imprimé Auteurs : Hamdi Ben Abdelali, Auteur ; Cedric Courbon, Auteur ; Joël Rech, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Cutting  Friction  Machining  Numerical  analysis  Steel  Titanium  compounds  Tools  Velocity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The characterization of frictional phenomena at the tool-chip-workpiece interface in metal cutting remains a challenge. This paper aims at identifying a friction model and a heat partition model at this interface during the dry cutting of an AISI1045 steel with TiN coated carbide tools. A new tribometer, based on a modified pin-on-ring system, has been used in order to reach relevant values of pressures, temperatures, and sliding velocities. Additionally a 3D Arbitrary Lagrangian Eulerian model (A.L.E.) numerical model simulating the frictional test has been developed in order to extract local parameters around the spherical pin, such as average contact pressure, average local sliding velocity, and average contact temperature, from experimental macroscopic measurements. A large range of sliding velocities [0.083–5 m/s] has been investigated. It has been shown that friction coefficient and heat partition coefficient are mainly dependant on local sliding velocity at the interface. Three friction regimes have been identified. These experimental and numerical results provide a better understanding of the tribological phenomena along the tool-chip-workpiece interfaces in dry machining of an AISI 1045 steel with a TiN coated carbide tool. Finally a new friction model and heat partition model has been developed for implementation in a numerical cutting model. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Identification of a friction model at the tool-chip-workpiece interface in dry machining of a AISI 1045 steel with a TiN coated carbide tool [texte imprimé] / Hamdi Ben Abdelali, Auteur ; Cedric Courbon, Auteur ; Joël Rech, Auteur . - 2012 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 11 p. Mots-clés : Cutting  Friction  Machining  Numerical  analysis  Steel  Titanium  compounds  Tools  Velocity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The characterization of frictional phenomena at the tool-chip-workpiece interface in metal cutting remains a challenge. This paper aims at identifying a friction model and a heat partition model at this interface during the dry cutting of an AISI1045 steel with TiN coated carbide tools. A new tribometer, based on a modified pin-on-ring system, has been used in order to reach relevant values of pressures, temperatures, and sliding velocities. Additionally a 3D Arbitrary Lagrangian Eulerian model (A.L.E.) numerical model simulating the frictional test has been developed in order to extract local parameters around the spherical pin, such as average contact pressure, average local sliding velocity, and average contact temperature, from experimental macroscopic measurements. A large range of sliding velocities [0.083–5 m/s] has been investigated. It has been shown that friction coefficient and heat partition coefficient are mainly dependant on local sliding velocity at the interface. Three friction regimes have been identified. These experimental and numerical results provide a better understanding of the tribological phenomena along the tool-chip-workpiece interfaces in dry machining of an AISI 1045 steel with a TiN coated carbide tool. Finally a new friction model and heat partition model has been developed for implementation in a numerical cutting model. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

A 3D finite element study of fatigue life dispersion in rolling line contacts / Nick Weinzapfel in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 10 p. Titre : A 3D finite element study of fatigue life dispersion in rolling line contacts Type de document : texte imprimé Auteurs : Nick Weinzapfel, Auteur ; Farshid Sadeghi, Auteur ; Alexander Liebel, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Fatigue  cracks  Fatigue  testing  Grain  boundaries  Rolling  bearings  Steel Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Rolling contact fatigue of rolling element bearings is a statistical phenomenon that is strongly affected by the heterogeneous nature of the material microstructure. Heterogeneity in the microstructure is accompanied by randomly distributed weak points in the material that lead to scatter in the fatigue lives of an otherwise identical lot of rolling element bearings. Many life models for rolling contact fatigue are empirical and rely upon correlation with fatigue test data to characterize the dispersion of fatigue lives. Recently developed computational models of rolling contact fatigue bypass this requirement by explicitly considering the microstructure as a source of the variability. This work utilizes a similar approach but extends the analysis into a 3D framework. The bearing steel microstructure is modeled as randomly generated Voronoi tessellations wherein each cell represents a material grain and the boundaries between them constitute the weak planes in the material. Fatigue cracks initiate on the weak planes where oscillating shear stresses are the strongest. Finite element analysis is performed to determine the magnitude of the critical shear stress range and the depth where it occurs. These quantities exhibit random variation due to the microstructure topology which in turn results in scatter in the predicted fatigue lives. The model is used to assess the influence of (1) topological randomness in the microstructure, (2) heterogeneity in the distribution of material properties, and (3) the presence of inherent material flaws on relative fatigue lives. Neither topological randomness nor heterogeneous material properties alone account for the dispersion seen in actual bearing fatigue tests. However, a combination of both or the consideration of material flaws brings the model's predictions within empirically observed bounds. Examination of the critical shear stress ranges with respect to the grain boundaries where they occur reveals the orientation of weak planes most prone to failure in a three-dimensional sense that was not possible with previous models. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] A 3D finite element study of fatigue life dispersion in rolling line contacts [texte imprimé] / Nick Weinzapfel, Auteur ; Farshid Sadeghi, Auteur ; Alexander Liebel, Auteur . - 2012 . - 10 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 10 p. Mots-clés : Fatigue  cracks  Fatigue  testing  Grain  boundaries  Rolling  bearings  Steel Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Rolling contact fatigue of rolling element bearings is a statistical phenomenon that is strongly affected by the heterogeneous nature of the material microstructure. Heterogeneity in the microstructure is accompanied by randomly distributed weak points in the material that lead to scatter in the fatigue lives of an otherwise identical lot of rolling element bearings. Many life models for rolling contact fatigue are empirical and rely upon correlation with fatigue test data to characterize the dispersion of fatigue lives. Recently developed computational models of rolling contact fatigue bypass this requirement by explicitly considering the microstructure as a source of the variability. This work utilizes a similar approach but extends the analysis into a 3D framework. The bearing steel microstructure is modeled as randomly generated Voronoi tessellations wherein each cell represents a material grain and the boundaries between them constitute the weak planes in the material. Fatigue cracks initiate on the weak planes where oscillating shear stresses are the strongest. Finite element analysis is performed to determine the magnitude of the critical shear stress range and the depth where it occurs. These quantities exhibit random variation due to the microstructure topology which in turn results in scatter in the predicted fatigue lives. The model is used to assess the influence of (1) topological randomness in the microstructure, (2) heterogeneity in the distribution of material properties, and (3) the presence of inherent material flaws on relative fatigue lives. Neither topological randomness nor heterogeneous material properties alone account for the dispersion seen in actual bearing fatigue tests. However, a combination of both or the consideration of material flaws brings the model's predictions within empirically observed bounds. Examination of the critical shear stress ranges with respect to the grain boundaries where they occur reveals the orientation of weak planes most prone to failure in a three-dimensional sense that was not possible with previous models. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

A deterministic mixed lubrication model for mechanical seals / Christophe Minet in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 11. p. Titre : A deterministic mixed lubrication model for mechanical seals Type de document : texte imprimé Auteurs : Christophe Minet, Auteur ; Noël Brunetière, Auteur ; Bernard Tournerie, Auteur Année de publication : 2012 Article en page(s) : 11. p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Cavitation  Flow  simulation  Hydrodynamics  Lubrication  Mechanical  contact  Poiseuille  flow  Rough  surfaces  Sealing  materials  Seals  (stoppers)  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Mechanical seals are commonly used in industrial applications. The main purpose of these components is to ensure the sealing of rotating shafts. Their optimal point of operation is obtained at the boundary between the mixed and hydrodynamic lubrication regimes. However, papers focused on this particular aspect in face seals are rather scarce compared with those dealing with other popular sealing devices. The present study thus proposes a numerical flow model of mixed lubrication in mechanical face seals. It achieves this by evaluating the influence of roughness on the performance of the seal. The choice of a deterministic approach has been made, this being justified by a review of the literature. A numerical model for the generation of random rough surfaces has been used prior to the flow model in order to give an accurate description of the surface roughness. The model takes cavitation effects into account and considers Hertzian asperity contact. Results for the model, including Stribeck curves, are presented as a function of the duty parameter. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] A deterministic mixed lubrication model for mechanical seals [texte imprimé] / Christophe Minet, Auteur ; Noël Brunetière, Auteur ; Bernard Tournerie, Auteur . - 2012 . - 11. p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 11. p. Mots-clés : Cavitation  Flow  simulation  Hydrodynamics  Lubrication  Mechanical  contact  Poiseuille  flow  Rough  surfaces  Sealing  materials  Seals  (stoppers)  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Mechanical seals are commonly used in industrial applications. The main purpose of these components is to ensure the sealing of rotating shafts. Their optimal point of operation is obtained at the boundary between the mixed and hydrodynamic lubrication regimes. However, papers focused on this particular aspect in face seals are rather scarce compared with those dealing with other popular sealing devices. The present study thus proposes a numerical flow model of mixed lubrication in mechanical face seals. It achieves this by evaluating the influence of roughness on the performance of the seal. The choice of a deterministic approach has been made, this being justified by a review of the literature. A numerical model for the generation of random rough surfaces has been used prior to the flow model in order to give an accurate description of the surface roughness. The model takes cavitation effects into account and considers Hertzian asperity contact. Results for the model, including Stribeck curves, are presented as a function of the duty parameter. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Contact mechanisms of transfer layered surface during sliding wear of amorphous carbon film / X. Fan in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 10 p. Titre : Contact mechanisms of transfer layered surface during sliding wear of amorphous carbon film Type de document : texte imprimé Auteurs : X. Fan, Auteur ; D. F. Diao, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Amorphous  semiconductors  Carbon  Cyclotron  resonance  Finite  element  analysis  Scanning  electron  microscopy  Shear  strength  Silicon  compounds  Sliding  friction  Wear  X-ray  chemical  analysis Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The contact mechanisms of a transfer layered surface during sliding wear of a Si3N4 ball against the amorphous carbon film were investigated. In this study, amorphous carbon films were deposited by electron cyclotron resonance plasma sputtering technique. The dependence of friction coefficient and wear life of the films on transfer layer was tested with pin-on-disk tribometer. Wear tracks and the transfer layered surfaces at different friction coefficient stages were observed with scanning electron microscope and measured with energy dispersive spectrometer In order to clarify the contact mechanisms of a transfer layered surface, three contact models of initial high friction coefficient stage without transfer layer (state I), transfer layer forming stage with friction coefficient decreasing (state II), and transfer layered surface stable sliding stage with low friction coefficient (state III) were proposed, and the contact stresses (normal stress, shear stress, von Mises stress) of the three contact states were calculated by using finite element analysis. The results demonstrated that a transfer layer formed at the contact interface and gradually decreased the maximum contact stresses, which contributed to the long wear life of amorphous carbon films. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Contact mechanisms of transfer layered surface during sliding wear of amorphous carbon film [texte imprimé] / X. Fan, Auteur ; D. F. Diao, Auteur . - 2012 . - 10 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 10 p. Mots-clés : Amorphous  semiconductors  Carbon  Cyclotron  resonance  Finite  element  analysis  Scanning  electron  microscopy  Shear  strength  Silicon  compounds  Sliding  friction  Wear  X-ray  chemical  analysis Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The contact mechanisms of a transfer layered surface during sliding wear of a Si3N4 ball against the amorphous carbon film were investigated. In this study, amorphous carbon films were deposited by electron cyclotron resonance plasma sputtering technique. The dependence of friction coefficient and wear life of the films on transfer layer was tested with pin-on-disk tribometer. Wear tracks and the transfer layered surfaces at different friction coefficient stages were observed with scanning electron microscope and measured with energy dispersive spectrometer In order to clarify the contact mechanisms of a transfer layered surface, three contact models of initial high friction coefficient stage without transfer layer (state I), transfer layer forming stage with friction coefficient decreasing (state II), and transfer layered surface stable sliding stage with low friction coefficient (state III) were proposed, and the contact stresses (normal stress, shear stress, von Mises stress) of the three contact states were calculated by using finite element analysis. The results demonstrated that a transfer layer formed at the contact interface and gradually decreased the maximum contact stresses, which contributed to the long wear life of amorphous carbon films. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Detailed state of the art review for the different online/inline oil analysis techniques in context of wind turbine gearboxes / Andrew Hamilton in Transactions of the ASME . Journal of tribology, Vol. 133 N° 4 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 18 p. Titre : Detailed state of the art review for the different online/inline oil analysis techniques in context of wind turbine gearboxes Type de document : texte imprimé Auteurs : Andrew Hamilton, Auteur ; Francis Quail, Auteur Année de publication : 2012 Article en page(s) : 18 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Condition  monitoring  Fluorescence  Fourier  transform  spectra  Gears  Infrared  spectra  Lubricating  oils  Maintenance  engineering  Photoacoustic  spectra  Sensors  Wind  power  Wind  turbines Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The main driver behind developing advanced condition monitoring (CM) systems for the wind energy industry is the delivery of improved asset management regarding the operation and maintenance of the gearbox and other wind turbine components and systems. Current gearbox CM systems mainly detect faults by identifying ferrous materials, water, and air within oil by changes in certain properties such as electrical fields. In order to detect oil degradation and identify particles, more advanced devices are required to allow a better maintenance regime to be established. Current technologies available specifically for this purpose include Fourier transform infrared (FTIR) spectroscopy and ferrography. There are also several technologies that have not yet been or have been recently applied to CM problems. After reviewing the current state of the art, it is recommended that a combination of sensors would be used that analyze different characteristics of the oil. The information individually would not be highly accurate but combined it is fully expected that greater accuracy can be obtained. The technologies that are suitable in terms of cost, size, accuracy, and development are online ferrography, selective fluorescence spectroscopy, scattering measurements, FTIR, photoacoustic spectroscopy, and solid state viscometers. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Detailed state of the art review for the different online/inline oil analysis techniques in context of wind turbine gearboxes [texte imprimé] / Andrew Hamilton, Auteur ; Francis Quail, Auteur . - 2012 . - 18 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 4 (Octobre 2011) . - 18 p. Mots-clés : Condition  monitoring  Fluorescence  Fourier  transform  spectra  Gears  Infrared  spectra  Lubricating  oils  Maintenance  engineering  Photoacoustic  spectra  Sensors  Wind  power  Wind  turbines Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The main driver behind developing advanced condition monitoring (CM) systems for the wind energy industry is the delivery of improved asset management regarding the operation and maintenance of the gearbox and other wind turbine components and systems. Current gearbox CM systems mainly detect faults by identifying ferrous materials, water, and air within oil by changes in certain properties such as electrical fields. In order to detect oil degradation and identify particles, more advanced devices are required to allow a better maintenance regime to be established. Current technologies available specifically for this purpose include Fourier transform infrared (FTIR) spectroscopy and ferrography. There are also several technologies that have not yet been or have been recently applied to CM problems. After reviewing the current state of the art, it is recommended that a combination of sensors would be used that analyze different characteristics of the oil. The information individually would not be highly accurate but combined it is fully expected that greater accuracy can be obtained. The technologies that are suitable in terms of cost, size, accuracy, and development are online ferrography, selective fluorescence spectroscopy, scattering measurements, FTIR, photoacoustic spectroscopy, and solid state viscometers. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

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