Dépouillements

Study of a brittle transparent disk under dry RCF conditions / Arthur Francisco in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 08 p. Titre : Study of a brittle transparent disk under dry RCF conditions Type de document : texte imprimé Auteurs : Arthur Francisco, Auteur ; Houssein Abbouchi, Auteur ; Bernard Villechaise, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Brittleness  Discs  (structures)  Fatigue  Mechanical  contact  Rolling  friction  Tensile  strength Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Despite the numerous experimental works on rolling contact fatigue, dealing with two-disk contacts, some phenomena still remain badly understood. Most of the test benches, used for that purpose, impose the rotational speeds to the disks: global slipping occurs and the tangential force is measured. Even if this configuration is found in some mechanical contacts, it does not reflect situations, where only microslipping occurs with high tangential loads. For these reasons, an original bench has been designed: a specimen disk rotates a braked stainless steel disk under a normal load N. The tangential load T, due to the braked disk, is set below the global slipping value; the specimen disks are transparent for the cracks observation and brittle to avoid any plasticity complication. A typical run consists in carrying out a succession of steps of increasing the number of cycles. Each step ends with several measurements on the cracks: their counting and their width and depth measurements. The results are divided in two categories: general observations and quantitative results. The most evident observation concerns the crack shape since it propagates along an ellipse on the contact path. Furthermore, the direction of propagation inside the disk is perpendicular to the surface. Lastly, a regular primary network of well-defined cracks is observed with cracks less marked. Concerning the effects of varying loads, the higher the T, the faster the cracks initiate and propagate because of a higher tensile stress state. However, these effects can be partly overridden by N beneath the contact path. As the disk material is brittle, the crack behavior is quite similar to the one observed on metallic specimens. Even if the results are obtained in an epoxy resin, a reasonable transposition is possible. The disk transparency makes it possible to quantify the cracks growth and to propose original 3D photographs of the cracks. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Study of a brittle transparent disk under dry RCF conditions [texte imprimé] / Arthur Francisco, Auteur ; Houssein Abbouchi, Auteur ; Bernard Villechaise, Auteur . - 2011 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 08 p. Mots-clés : Brittleness  Discs  (structures)  Fatigue  Mechanical  contact  Rolling  friction  Tensile  strength Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Despite the numerous experimental works on rolling contact fatigue, dealing with two-disk contacts, some phenomena still remain badly understood. Most of the test benches, used for that purpose, impose the rotational speeds to the disks: global slipping occurs and the tangential force is measured. Even if this configuration is found in some mechanical contacts, it does not reflect situations, where only microslipping occurs with high tangential loads. For these reasons, an original bench has been designed: a specimen disk rotates a braked stainless steel disk under a normal load N. The tangential load T, due to the braked disk, is set below the global slipping value; the specimen disks are transparent for the cracks observation and brittle to avoid any plasticity complication. A typical run consists in carrying out a succession of steps of increasing the number of cycles. Each step ends with several measurements on the cracks: their counting and their width and depth measurements. The results are divided in two categories: general observations and quantitative results. The most evident observation concerns the crack shape since it propagates along an ellipse on the contact path. Furthermore, the direction of propagation inside the disk is perpendicular to the surface. Lastly, a regular primary network of well-defined cracks is observed with cracks less marked. Concerning the effects of varying loads, the higher the T, the faster the cracks initiate and propagate because of a higher tensile stress state. However, these effects can be partly overridden by N beneath the contact path. As the disk material is brittle, the crack behavior is quite similar to the one observed on metallic specimens. Even if the results are obtained in an epoxy resin, a reasonable transposition is possible. The disk transparency makes it possible to quantify the cracks growth and to propose original 3D photographs of the cracks. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Effects of nanostructured additives on boundary lubrication for potential artificial joint applications / Alice Pendleton in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 05 p. Titre : Effects of nanostructured additives on boundary lubrication for potential artificial joint applications Type de document : texte imprimé Auteurs : Alice Pendleton, Auteur ; Prasenjit Kar, Auteur ; Subrata Kundu, Auteur Année de publication : 2011 Article en page(s) : 05 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Aluminium  alloys  Friction  Fullerenes  Lubrication  Nanoparticles  Titanium  alloys  Vanadium  alloys  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Water-based fluids containing nanostructured fullerene C60 and 18-crown ether-6 were investigated. The effects of those nanostructured additives on the tribological performance of titanium and its alloys as potential biomaterials were analyzed. Experimentally, tribology tests were conducted using a Ti–6Al–4V ball against a disk made of pure titanium as a simplified model of the material rubbing pair. Lubrication mechanisms were studied by comparing the nanostructures, viscosities, and frictions. Results showed that the fullerene C60 in deionized water provided the lowest viscosity and friction. Crown ether, on the other hand, provided high friction and shear. Our analysis indicated that the fullerene was weakly interacted with water compared with the crown ether, resulting in an extended low friction in the boundary lubrication regime. The crown ether required extra energy in order to slide or roll. This led to a high friction. This finding opens the possibilities for lubrication design and optimization for biological and engineering applications in general. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Effects of nanostructured additives on boundary lubrication for potential artificial joint applications [texte imprimé] / Alice Pendleton, Auteur ; Prasenjit Kar, Auteur ; Subrata Kundu, Auteur . - 2011 . - 05 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 05 p. Mots-clés : Aluminium  alloys  Friction  Fullerenes  Lubrication  Nanoparticles  Titanium  alloys  Vanadium  alloys  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Water-based fluids containing nanostructured fullerene C60 and 18-crown ether-6 were investigated. The effects of those nanostructured additives on the tribological performance of titanium and its alloys as potential biomaterials were analyzed. Experimentally, tribology tests were conducted using a Ti–6Al–4V ball against a disk made of pure titanium as a simplified model of the material rubbing pair. Lubrication mechanisms were studied by comparing the nanostructures, viscosities, and frictions. Results showed that the fullerene C60 in deionized water provided the lowest viscosity and friction. Crown ether, on the other hand, provided high friction and shear. Our analysis indicated that the fullerene was weakly interacted with water compared with the crown ether, resulting in an extended low friction in the boundary lubrication regime. The crown ether required extra energy in order to slide or roll. This led to a high friction. This finding opens the possibilities for lubrication design and optimization for biological and engineering applications in general. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Tribological behaviors of PTFE-based composites filled with nanoscale lamellar structure expanded graphite / Yu-lin Yang in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 07 p. Titre : Tribological behaviors of PTFE-based composites filled with nanoscale lamellar structure expanded graphite Type de document : texte imprimé Auteurs : Yu-lin Yang, Auteur ; Zhi-ning Jia, Auteur ; Jin-jiang Chen, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Field  emission  electron  microscopy  Filled  polymers  Friction  Graphite  Nanocomposites  Scanning  electron  microscopy  Surface  morphology  Wear  resistance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper provides a polytetrafluoroethylene (PTFE)/nano-EG solid self-lubricating composite that exhibits very low friction coefficient and wear rate. In present study, the influences of the content of expanded graphite with nanoscale lamellar structure (nano-EG) in PTFE/nano-EG composite, normal contact pressure, and sliding velocity on tribological properties were studied by using the MMU-5G friction and wear tester sliding against AISI-1045 steel. Meanwhile, the property of nano-EG was characterized by utilizing a field emission scanning electron microscope. Compared with that of pure PTFE, the addition of nano-EG into PTFE matrix effectively improved the antifriction and wear resistance properties of PTFE/nano-EG composite. The highest wear resistance was found for the PTFE/nano-EG composite filled with 15 wt % nano-EG. The morphologies of worn surface of the ANSI-1045 steel and composites were observed using a confocal laser scanning microscopy (CLSM) and a scanning electron microscope (SEM) to examine composite microstructures and to study modes of failure. The images of CLSM and SEM indicate that the property of transfer film generated on the surface of mating pair is likely responsible for the lower wear rate observed in these experiments. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Tribological behaviors of PTFE-based composites filled with nanoscale lamellar structure expanded graphite [texte imprimé] / Yu-lin Yang, Auteur ; Zhi-ning Jia, Auteur ; Jin-jiang Chen, Auteur . - 2011 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 07 p. Mots-clés : Field  emission  electron  microscopy  Filled  polymers  Friction  Graphite  Nanocomposites  Scanning  electron  microscopy  Surface  morphology  Wear  resistance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper provides a polytetrafluoroethylene (PTFE)/nano-EG solid self-lubricating composite that exhibits very low friction coefficient and wear rate. In present study, the influences of the content of expanded graphite with nanoscale lamellar structure (nano-EG) in PTFE/nano-EG composite, normal contact pressure, and sliding velocity on tribological properties were studied by using the MMU-5G friction and wear tester sliding against AISI-1045 steel. Meanwhile, the property of nano-EG was characterized by utilizing a field emission scanning electron microscope. Compared with that of pure PTFE, the addition of nano-EG into PTFE matrix effectively improved the antifriction and wear resistance properties of PTFE/nano-EG composite. The highest wear resistance was found for the PTFE/nano-EG composite filled with 15 wt % nano-EG. The morphologies of worn surface of the ANSI-1045 steel and composites were observed using a confocal laser scanning microscopy (CLSM) and a scanning electron microscope (SEM) to examine composite microstructures and to study modes of failure. The images of CLSM and SEM indicate that the property of transfer film generated on the surface of mating pair is likely responsible for the lower wear rate observed in these experiments. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Self lubricating composite coatings containing TiC–MnS or WC-MnS compounds prepared by the plasma transferred arc (PTA) technique / P. Skarvelis in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 08 p. Titre : Self lubricating composite coatings containing TiC–MnS or WC-MnS compounds prepared by the plasma transferred arc (PTA) technique Type de document : texte imprimé Auteurs : P. Skarvelis, Auteur ; G. D. Papadimitriou, Auteur ; M. Perraki, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Abrasion  Friction  Lubrication  Manganese  compounds  Particle  reinforced  composites  Titanium  compounds  Tungsten  compounds  Wear  resistance  Wear  resistant  coatings Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Composite coatings containing manganese sulphide as lubricating addition and enhanced with hard carbide particles (TiC, WC) were synthesized on a plain steel substrate using the plasma transferred arc technique. The coatings are well bonded to the substrate, have a thickness of about 1 mm, and are free of any visual defects. They consist mainly of a martensitic or ferritic matrix enhanced with titanium or tungsten carbides and a dispersion of MnS particles. The tribological properties of the composites are assessed using a pin-on-disk device. Both composites possess self lubricating properties, due to the formation of a thin layer of manganese sulphide on their wear tracks. The corresponding friction coefficients vary between 0.25 and 0.28, compared with 0.50–0.60 obtained from similar hard coatings without MnS addition. The wear rates are of the order of 10−5 mm3/m N and are two orders of magnitude lower than those obtained from the substrate material with MnS addition, but without the presence of hard enhancing particles. The wear regime is mild abrasion due to the combined action of both lubricating (MnS) and hard (TiC or WC) particles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Self lubricating composite coatings containing TiC–MnS or WC-MnS compounds prepared by the plasma transferred arc (PTA) technique [texte imprimé] / P. Skarvelis, Auteur ; G. D. Papadimitriou, Auteur ; M. Perraki, Auteur . - 2011 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 08 p. Mots-clés : Abrasion  Friction  Lubrication  Manganese  compounds  Particle  reinforced  composites  Titanium  compounds  Tungsten  compounds  Wear  resistance  Wear  resistant  coatings Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Composite coatings containing manganese sulphide as lubricating addition and enhanced with hard carbide particles (TiC, WC) were synthesized on a plain steel substrate using the plasma transferred arc technique. The coatings are well bonded to the substrate, have a thickness of about 1 mm, and are free of any visual defects. They consist mainly of a martensitic or ferritic matrix enhanced with titanium or tungsten carbides and a dispersion of MnS particles. The tribological properties of the composites are assessed using a pin-on-disk device. Both composites possess self lubricating properties, due to the formation of a thin layer of manganese sulphide on their wear tracks. The corresponding friction coefficients vary between 0.25 and 0.28, compared with 0.50–0.60 obtained from similar hard coatings without MnS addition. The wear rates are of the order of 10−5 mm3/m N and are two orders of magnitude lower than those obtained from the substrate material with MnS addition, but without the presence of hard enhancing particles. The wear regime is mild abrasion due to the combined action of both lubricating (MnS) and hard (TiC or WC) particles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Contact area and static friction of rough surfaces with high plasticity index / Li, L. in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 10 p. Titre : Contact area and static friction of rough surfaces with high plasticity index Type de document : texte imprimé Auteurs : Li, L., Auteur ; I. Etsion, Auteur ; F. E. Talke, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : plasticity  rough  surfaces  stiction Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A model for the contact area and static friction of nominally flat rough surfaces and rough spherical surfaces is presented. The model extends previously published models, which are limited to plasticity index values below 8, to higher plasticity index values by accounting for fully plastically deformed asperities based on finite element results by Jackson and Green [2005, “A Finite Element Study of Elasto-Plastic Hemispherical Contact Against a Rigid Flat,” Trans. ASME, J. Tribol., 127, pp. 343–354]. The present model also corrects some deficiencies of the earlier models at very small plasticity index values below 0.5. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Contact area and static friction of rough surfaces with high plasticity index [texte imprimé] / Li, L., Auteur ; I. Etsion, Auteur ; F. E. Talke, Auteur . - 2011 . - 10 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 10 p. Mots-clés : plasticity  rough  surfaces  stiction Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A model for the contact area and static friction of nominally flat rough surfaces and rough spherical surfaces is presented. The model extends previously published models, which are limited to plasticity index values below 8, to higher plasticity index values by accounting for fully plastically deformed asperities based on finite element results by Jackson and Green [2005, “A Finite Element Study of Elasto-Plastic Hemispherical Contact Against a Rigid Flat,” Trans. ASME, J. Tribol., 127, pp. 343–354]. The present model also corrects some deficiencies of the earlier models at very small plasticity index values below 0.5. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Plasto-elastohydrodynamic lubrication (PEHL) in point contacts / Ning Ren in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Titre : Plasto-elastohydrodynamic lubrication (PEHL) in point contacts Type de document : texte imprimé Auteurs : Ning Ren, Auteur ; Dong Zhu, Auteur ; W. W. Chen, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Lubrication  Mechanical  contact  Plastic  deformation  Surface  roughness  Work  hardening Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Elastohydrodynamic lubrication (EHL) is an important branch of the lubrication theory, describing lubrication mechanisms in nonconformal contacts widely found in many mechanical components such as various gears, rolling bearings, cams and followers, metal-rolling tools, traction drives, and continuous variable transmissions. These components often transmit substantial power under heavy loading conditions. Also, the roughness of machined surfaces is usually of the same order of magnitude as, or greater than, the estimated average EHL film thickness. Consequently, most components operate in mixed lubrication regime with significant asperity contacts. Due to very high pressure concentrated in small areas, resulted from either heavy external loading or severe asperity contacts, or often a combination of both, subsurface stresses may exceed the material yield limit, causing considerable plastic deformation, which may not only permanently change the surface profiles and contact geometry but also alter material properties through work hardening as well. In the present study, a three-dimensional plasto-elastohydrodynamic lubrication (PEHL) model has been developed by taking into account plastic deformation and material work-hardening. The effects of surface/subsurface plastic deformation on lubricant film thickness, surface pressure distribution, and subsurface stress field have been investigated. This paper briefly describes the newly developed PEHL model and presents preliminary results and observed basic behavior of the PEHL in smooth-surface point contacts, in comparison with those from corresponding EHL solutions under the same conditions. The results indicate that plastic deformation may greatly affect contact and lubrication characteristics, resulting in significant reductions in lubricant film thickness, peak surface pressure and maximum subsurface stresses. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Plasto-elastohydrodynamic lubrication (PEHL) in point contacts [texte imprimé] / Ning Ren, Auteur ; Dong Zhu, Auteur ; W. W. Chen, Auteur . - 2011 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Mots-clés : Lubrication  Mechanical  contact  Plastic  deformation  Surface  roughness  Work  hardening Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Elastohydrodynamic lubrication (EHL) is an important branch of the lubrication theory, describing lubrication mechanisms in nonconformal contacts widely found in many mechanical components such as various gears, rolling bearings, cams and followers, metal-rolling tools, traction drives, and continuous variable transmissions. These components often transmit substantial power under heavy loading conditions. Also, the roughness of machined surfaces is usually of the same order of magnitude as, or greater than, the estimated average EHL film thickness. Consequently, most components operate in mixed lubrication regime with significant asperity contacts. Due to very high pressure concentrated in small areas, resulted from either heavy external loading or severe asperity contacts, or often a combination of both, subsurface stresses may exceed the material yield limit, causing considerable plastic deformation, which may not only permanently change the surface profiles and contact geometry but also alter material properties through work hardening as well. In the present study, a three-dimensional plasto-elastohydrodynamic lubrication (PEHL) model has been developed by taking into account plastic deformation and material work-hardening. The effects of surface/subsurface plastic deformation on lubricant film thickness, surface pressure distribution, and subsurface stress field have been investigated. This paper briefly describes the newly developed PEHL model and presents preliminary results and observed basic behavior of the PEHL in smooth-surface point contacts, in comparison with those from corresponding EHL solutions under the same conditions. The results indicate that plastic deformation may greatly affect contact and lubrication characteristics, resulting in significant reductions in lubricant film thickness, peak surface pressure and maximum subsurface stresses. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Effect of thread and bearing friction coefficients on the self-loosening of preloaded countersunk-head bolts under periodic transverse excitation / Amro M. Zaki in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Titre : Effect of thread and bearing friction coefficients on the self-loosening of preloaded countersunk-head bolts under periodic transverse excitation Type de document : texte imprimé Auteurs : Amro M. Zaki, Auteur ; Sayed A. Nassar, Auteur ; Xianjie Yang, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Fasteners  Friction Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A nonlinear mathematical model is developed for studying the self-loosening behavior of preloaded countersunk threaded fasteners that are subjected to cyclic transverse loads. Torque components acting on the bolt are divided into pitch and resistance torque components; the net torque determines whether or not the bolt will rotate loose under the external excitation. The accumulation of the differential amount of loosening rotation increments is converted into the gradual loss of the bolt tension/clamp load. Although the loosening model incorporates several system variables, this study is focused on investigating the effect of thread and bearing friction coefficients on the loosening of fasteners with coarse and fine threads. Model prediction of the self-loosening behavior is experimentally validated. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Effect of thread and bearing friction coefficients on the self-loosening of preloaded countersunk-head bolts under periodic transverse excitation [texte imprimé] / Amro M. Zaki, Auteur ; Sayed A. Nassar, Auteur ; Xianjie Yang, Auteur . - 2011 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Mots-clés : Fasteners  Friction Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A nonlinear mathematical model is developed for studying the self-loosening behavior of preloaded countersunk threaded fasteners that are subjected to cyclic transverse loads. Torque components acting on the bolt are divided into pitch and resistance torque components; the net torque determines whether or not the bolt will rotate loose under the external excitation. The accumulation of the differential amount of loosening rotation increments is converted into the gradual loss of the bolt tension/clamp load. Although the loosening model incorporates several system variables, this study is focused on investigating the effect of thread and bearing friction coefficients on the loosening of fasteners with coarse and fine threads. Model prediction of the self-loosening behavior is experimentally validated. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Application of elastic-plastic static friction models to rough surfaces with asymmetric asperity distribution / Chul Hee Lee in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

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

Thermodynamic model of the metallic friction process / Maria Maciag in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 07 p. Titre : Thermodynamic model of the metallic friction process Type de document : texte imprimé Auteurs : Maria Maciag, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Cooling  Enthalpy  Friction  Large-scale  systems  Specific  heat  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : An energy model of stabilized friction and wear is presented. Heating of a definite mass of surface material to the flash point, in consideration of the mass's specific heat and wear, is assumed to provide the basis for thermal processes. An energy balance is presented in the form of a first law of thermodynamics formula for open systems. Two new magnitudes, referred to as complex systemic constants C and D, are developed and their physical meaning is interpreted. These complex systemic constants are subsequently employed to describe the tribological system. Among other magnitudes in the model, density of thermal dissipation and enthalpy flux, power density of mechanical dissipation, wear severity, and specific work of wear are described. Friction and wear testing results [Ciecieląg, 1994, “Energy Conditions of Metal Resistance to Tribological Wear,” Ph.D. thesis, Świetokrzyska Technical University, Kielce; Żurowski, 1996, “Energy Aspect of Increasing Wear-Resistance of Metals in the Process of Engineering Dry Friction,” Ph.D. thesis, Świetokrzyska Technical University, Kielce; Sadowski and Żurowski, 1992, “Thermodynamic Aspects of Metals' Wear-Resistance,” Tribology and Lubrication Engineering, 3, pp. 152–159] are employed to describe, in quantitative terms, selected tribological systems on the basis of the presented thermodynamic model. A method of determining the complex systemic constants C and D is developed. Specific work of wear, wear severity, probability of emergence of a flux of tribological wear products, and relation of worn mass to heated mass and flash temperature as functions of temperature are defined. This paper concludes with application, significance, and advantages of the complex systemic constants C and D, and phenomena arising in frictional contact between two metals. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Thermodynamic model of the metallic friction process [texte imprimé] / Maria Maciag, Auteur . - 2011 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 07 p. Mots-clés : Cooling  Enthalpy  Friction  Large-scale  systems  Specific  heat  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : An energy model of stabilized friction and wear is presented. Heating of a definite mass of surface material to the flash point, in consideration of the mass's specific heat and wear, is assumed to provide the basis for thermal processes. An energy balance is presented in the form of a first law of thermodynamics formula for open systems. Two new magnitudes, referred to as complex systemic constants C and D, are developed and their physical meaning is interpreted. These complex systemic constants are subsequently employed to describe the tribological system. Among other magnitudes in the model, density of thermal dissipation and enthalpy flux, power density of mechanical dissipation, wear severity, and specific work of wear are described. Friction and wear testing results [Ciecieląg, 1994, “Energy Conditions of Metal Resistance to Tribological Wear,” Ph.D. thesis, Świetokrzyska Technical University, Kielce; Żurowski, 1996, “Energy Aspect of Increasing Wear-Resistance of Metals in the Process of Engineering Dry Friction,” Ph.D. thesis, Świetokrzyska Technical University, Kielce; Sadowski and Żurowski, 1992, “Thermodynamic Aspects of Metals' Wear-Resistance,” Tribology and Lubrication Engineering, 3, pp. 152–159] are employed to describe, in quantitative terms, selected tribological systems on the basis of the presented thermodynamic model. A method of determining the complex systemic constants C and D is developed. Specific work of wear, wear severity, probability of emergence of a flux of tribological wear products, and relation of worn mass to heated mass and flash temperature as functions of temperature are defined. This paper concludes with application, significance, and advantages of the complex systemic constants C and D, and phenomena arising in frictional contact between two metals. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Comparison between elastic foundation and contact force models in wear analysis of planar multibody system / Saad Mukras in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Titre : Comparison between elastic foundation and contact force models in wear analysis of planar multibody system Type de document : texte imprimé Auteurs : Saad Mukras, Auteur ; Kim, Nam H., Auteur ; Nathan A. Mauntler, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Damping  Elastic  hysteresis  Elasticity  Finite  element  analysis  Iterative  methods  Mechanical  contact  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this paper, two procedures to analyze planar multibody systems experiencing wear at a revolute joint are compared. In both procedures, the revolute joint of interest includes a clearance whose shape and size are dictated by wear. The procedures consist of coupled iterative analyses between a dynamic system analysis with nonideal joints and a wear prediction to determine the evolution of the joint clearance. In the first procedure, joint forces and contact pressures are estimated using the elastic foundation model with hysteresis damping via the dynamic analysis. In the second procedure, a contact force model with hysteresis damping is used to estimate the joint forces. In the latter case, however, the contact pressure is estimated using a finite element method (FEM). A comparison in performance of the two models is facilitated through the use of an experimental slider-crank mechanism in which wear is permitted to occur at one of the joints. It is observed that the two procedures provide similar estimates for the dynamic response and wear volumes but substantially different predictions on the wear profiles. Additionally, experimental results show that while predictions on the wear volume from both models are reasonably accurate, the FEM-based model produced more accurate predictions on the wear profile. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Comparison between elastic foundation and contact force models in wear analysis of planar multibody system [texte imprimé] / Saad Mukras, Auteur ; Kim, Nam H., Auteur ; Nathan A. Mauntler, Auteur . - 2011 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Mots-clés : Damping  Elastic  hysteresis  Elasticity  Finite  element  analysis  Iterative  methods  Mechanical  contact  Wear Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In this paper, two procedures to analyze planar multibody systems experiencing wear at a revolute joint are compared. In both procedures, the revolute joint of interest includes a clearance whose shape and size are dictated by wear. The procedures consist of coupled iterative analyses between a dynamic system analysis with nonideal joints and a wear prediction to determine the evolution of the joint clearance. In the first procedure, joint forces and contact pressures are estimated using the elastic foundation model with hysteresis damping via the dynamic analysis. In the second procedure, a contact force model with hysteresis damping is used to estimate the joint forces. In the latter case, however, the contact pressure is estimated using a finite element method (FEM). A comparison in performance of the two models is facilitated through the use of an experimental slider-crank mechanism in which wear is permitted to occur at one of the joints. It is observed that the two procedures provide similar estimates for the dynamic response and wear volumes but substantially different predictions on the wear profiles. Additionally, experimental results show that while predictions on the wear volume from both models are reasonably accurate, the FEM-based model produced more accurate predictions on the wear profile. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

On squeeze film damping in microsystems / Victor Marrero in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Titre : On squeeze film damping in microsystems Type de document : texte imprimé Auteurs : Victor Marrero, Auteur ; Diana-Andra Borca-Tasciuc, Auteur ; John Tichy, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Compressibility  Compressible  flow  Liquid  films  Lubrication  Micromechanical  devices Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Classical hydrodynamic lubrication theory has been one of the most successful and widely used theories in all of engineering and applied science. This theory predicts that the force resisting the squeezing of a fluid between two parallel plates is inversely proportional to the cube of the fluid thickness. However, recent reports on liquid squeeze film damping in microsystems appear to indicate that experimentally measured damping force is proportional to the inverse of the fluid thickness to the first power—a large fundamental discrepancy from classical theory. This paper investigates potential limitations of lubrication theory in microsystems by theoretical and computational methods. The governing equations for a Newtonian incompressible fluid are solved subject to two-dimensional, parallel surface squeezing by an open-source computational fluid dynamics program called parallel hierarchic adaptive stabilized transient analysis (PHASTA), and by a classical similarity solution technique. At low convective Reynolds numbers, the damping force is determined as a function of the ratio of a reference film thickness H to a reference direction B along the film. Good agreement with classical lubrication theory is found for aspect ratios H/B as high as 1 despite the fact that lubrication theory requires that this ratio be “small.” A similarity analysis shows that when instantaneous convective Reynolds number is of order 10–100 (a range present in experiment), calculated damping deviates significantly from lubrication theory. This suggests that nonlinearity associated with high Reynolds numbers could explain the experimentally observed discrepancy in damping force. Dynamic analysis of beams undergoing small vibrations in the presence of a liquid medium further supports this finding. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] On squeeze film damping in microsystems [texte imprimé] / Victor Marrero, Auteur ; Diana-Andra Borca-Tasciuc, Auteur ; John Tichy, Auteur . - 2011 . - 06 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Mots-clés : Compressibility  Compressible  flow  Liquid  films  Lubrication  Micromechanical  devices Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Classical hydrodynamic lubrication theory has been one of the most successful and widely used theories in all of engineering and applied science. This theory predicts that the force resisting the squeezing of a fluid between two parallel plates is inversely proportional to the cube of the fluid thickness. However, recent reports on liquid squeeze film damping in microsystems appear to indicate that experimentally measured damping force is proportional to the inverse of the fluid thickness to the first power—a large fundamental discrepancy from classical theory. This paper investigates potential limitations of lubrication theory in microsystems by theoretical and computational methods. The governing equations for a Newtonian incompressible fluid are solved subject to two-dimensional, parallel surface squeezing by an open-source computational fluid dynamics program called parallel hierarchic adaptive stabilized transient analysis (PHASTA), and by a classical similarity solution technique. At low convective Reynolds numbers, the damping force is determined as a function of the ratio of a reference film thickness H to a reference direction B along the film. Good agreement with classical lubrication theory is found for aspect ratios H/B as high as 1 despite the fact that lubrication theory requires that this ratio be “small.” A similarity analysis shows that when instantaneous convective Reynolds number is of order 10–100 (a range present in experiment), calculated damping deviates significantly from lubrication theory. This suggests that nonlinearity associated with high Reynolds numbers could explain the experimentally observed discrepancy in damping force. Dynamic analysis of beams undergoing small vibrations in the presence of a liquid medium further supports this finding. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Design and evaluation of damped air bearings at head-disk interface / Jianhua Li in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 13 p. Titre : Design and evaluation of damped air bearings at head-disk interface Type de document : texte imprimé Auteurs : Jianhua Li, Auteur ; Junguo Xu, Auteur ; Yuki Shimizu, Auteur Année de publication : 2011 Article en page(s) : 13 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Damping  Elastic  constants  Frequency  response  Machine  bearings  Magnetic  heads  Modal  analysis Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Perturbation and modal-analysis methods were employed to systematically study a damped slider's dynamic characteristics, including an air-bearing slider's stiffness, damping coefficient, frequency response to translation and wavy motion, natural frequencies, damping ratios, and modal shape-node line. We found that a design with grooves distributed on a trailing pad effectively improved the slider's damping ratio in the second pitch mode; however, parametric studies revealed that the damping ratio was dependent on the number of grooves, their depth, location, width, length, distribution, orientation, and types. A higher damping ratio could be obtained by optimizing these parameters. The femto slider we designed with distributed damped grooves on a trailing pad had a higher damping ratio in the second pitch mode, and hence, its responses in the second pitch mode were greatly reduced, which were clarified through simulation and an experiment. Some issues on air-bearing stiffness reduction and negative damping at low frequency and contamination and lube pickup on the damped grooves were also evaluated in the experiment. No degradation could be found in the damped slider. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Design and evaluation of damped air bearings at head-disk interface [texte imprimé] / Jianhua Li, Auteur ; Junguo Xu, Auteur ; Yuki Shimizu, Auteur . - 2011 . - 13 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 13 p. Mots-clés : Damping  Elastic  constants  Frequency  response  Machine  bearings  Magnetic  heads  Modal  analysis Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Perturbation and modal-analysis methods were employed to systematically study a damped slider's dynamic characteristics, including an air-bearing slider's stiffness, damping coefficient, frequency response to translation and wavy motion, natural frequencies, damping ratios, and modal shape-node line. We found that a design with grooves distributed on a trailing pad effectively improved the slider's damping ratio in the second pitch mode; however, parametric studies revealed that the damping ratio was dependent on the number of grooves, their depth, location, width, length, distribution, orientation, and types. A higher damping ratio could be obtained by optimizing these parameters. The femto slider we designed with distributed damped grooves on a trailing pad had a higher damping ratio in the second pitch mode, and hence, its responses in the second pitch mode were greatly reduced, which were clarified through simulation and an experiment. Some issues on air-bearing stiffness reduction and negative damping at low frequency and contamination and lube pickup on the damped grooves were also evaluated in the experiment. No degradation could be found in the damped slider. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Surface roughness effects on air bearing performance over a wide range of knudsen and wave numbers / James White in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 10 p. Titre : Surface roughness effects on air bearing performance over a wide range of knudsen and wave numbers Type de document : texte imprimé Auteurs : James White, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Knudsen  flow  Machine  bearings  Poiseuille  flow  Slip  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Design of a near contact air bearing interface such as that created by a recording head slider and data storage disk requires consideration of a lubrication equation that is appropriate for high Knudsen number flows. The Poiseuille flow database reported by Fukui and Kaneko, 1990 [“A Database for Interpolation of Poiseuille Flow Rates for High Knudsen Number Lubrication Problems,” ASME J. Tribol., 112, pp. 78–83] is appropriate over a wide range of Knudsen numbers and is used throughout the data storage industry for analysis of the low flying recording head slider air bearing. However, at such low clearances, the topography of the air bearing surfaces also comes into question, making it important to consider both rarefaction and surface roughness effects in the air bearing design. In order to simplify the air bearing analysis of rough surfaces, averaging techniques for the lubrication equation have been developed for situations where the number of roughness elements (or waves) is either much greater or much less than the gas bearing number. Between these two extremes there are currently no roughness averaging methods available. Although some analytical and numerical studies have been reported for continuum and first-order slip conditions with simple geometries, little or no results have appeared that include both surface roughness and high Knudsen number flows outside the limited ranges where surface averaging techniques are used. In order to better understand the influence of transverse surface roughness over a wide range of Knudsen numbers and the relationship of key parameters involved, this paper describes a primarily analytical air bearing study of a wide, rough surface slider bearing using the Poiseuille flow database reported by Fukui and Kaneko. The work is focused outside the limited ranges where current surface averaging methods for the lubrication equation are expected to be valid. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Surface roughness effects on air bearing performance over a wide range of knudsen and wave numbers [texte imprimé] / James White, Auteur . - 2011 . - 10 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 10 p. Mots-clés : Knudsen  flow  Machine  bearings  Poiseuille  flow  Slip  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Design of a near contact air bearing interface such as that created by a recording head slider and data storage disk requires consideration of a lubrication equation that is appropriate for high Knudsen number flows. The Poiseuille flow database reported by Fukui and Kaneko, 1990 [“A Database for Interpolation of Poiseuille Flow Rates for High Knudsen Number Lubrication Problems,” ASME J. Tribol., 112, pp. 78–83] is appropriate over a wide range of Knudsen numbers and is used throughout the data storage industry for analysis of the low flying recording head slider air bearing. However, at such low clearances, the topography of the air bearing surfaces also comes into question, making it important to consider both rarefaction and surface roughness effects in the air bearing design. In order to simplify the air bearing analysis of rough surfaces, averaging techniques for the lubrication equation have been developed for situations where the number of roughness elements (or waves) is either much greater or much less than the gas bearing number. Between these two extremes there are currently no roughness averaging methods available. Although some analytical and numerical studies have been reported for continuum and first-order slip conditions with simple geometries, little or no results have appeared that include both surface roughness and high Knudsen number flows outside the limited ranges where surface averaging techniques are used. In order to better understand the influence of transverse surface roughness over a wide range of Knudsen numbers and the relationship of key parameters involved, this paper describes a primarily analytical air bearing study of a wide, rough surface slider bearing using the Poiseuille flow database reported by Fukui and Kaneko. The work is focused outside the limited ranges where current surface averaging methods for the lubrication equation are expected to be valid. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

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

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

Feasibility of gas-expanded lubricants for increased energy efficiency in tilting-pad journal bearings / Andres Clarens in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 08 p. Titre : Feasibility of gas-expanded lubricants for increased energy efficiency in tilting-pad journal bearings Type de document : texte imprimé Auteurs : Andres Clarens, Auteur ; Amir Younan, Auteur ; Shibo Wang, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Cooling  Lubricants  Machine  bearings  Shafts  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Lubricants are necessary in tilting-pad journal bearings to ensure separation between solid surfaces and to dissipate heat. They are also responsible for much of the undesirable power losses that can occur through a bearing. Here, a novel method to reduce power losses in tilting-pad journal bearings is proposed in which the conventional lubricant is substituted by a binary mixture of synthetic lubricant and dissolved CO2. These gas-expanded lubricants (GELs) would be delivered to a reinforced bearing housing capable of withstanding modest pressures less than 10 MPa. For bearings subject to loads that are both variable and predictable, GELs could be used to adjust lubricant properties in real time. High-pressure lubricants, mostly gases, have already been explored in tilting-pad journal bearings as a means to accommodate higher shaft speeds while reducing power losses and eliminating the potential for thermal degradation of the lubricant. These gas-lubricated bearings have intrinsic limitations in terms of bearing size and load capacity. The proposed system would combine the loading capabilities of conventional lubricated bearings with the efficiency of gas-lubricated bearings. The liquid or supercritical CO2 serves as a low-viscosity and completely miscible additive to the lubricant that can be easily removed by purging the gas after releasing the pressure. In this way, the lubricant can be fully recycled, as in conventional systems, while controlling the lubricant properties dynamically by adding liquid or supercritical CO2. Lubricant properties of interest, such as viscosity, can be easily tuned by controlling the pressure inside the bearing housing. Experimental measurements of viscosity for mixtures of polyalkylene glycol (PAG)+CO2 at various compositions demonstrate that significant reductions in mixture viscosity can be achieved with relatively small additions of CO2. The measured parameters are used in a thermoelastohydrodynamic model of tilting-pad journal bearing performance to evaluate the bearing response to GELs. Model estimates of power loss, eccentricity ratio, and pad temperature suggest that bearings would respond quite favorably over a range of speed and preload conditions. Calculated power loss reductions of 20% are observed when compared with both a reference petroleum lubricant and PAG without CO2. Pad temperature is also maintained without significant increases in eccentricity ratio. Both power loss and pad temperature are directly correlated with PAG-CO2 composition, suggesting that these mixtures could be used as “smart” lubricants responsive to system operating conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Feasibility of gas-expanded lubricants for increased energy efficiency in tilting-pad journal bearings [texte imprimé] / Andres Clarens, Auteur ; Amir Younan, Auteur ; Shibo Wang, Auteur . - 2011 . - 08 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 08 p. Mots-clés : Cooling  Lubricants  Machine  bearings  Shafts  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Lubricants are necessary in tilting-pad journal bearings to ensure separation between solid surfaces and to dissipate heat. They are also responsible for much of the undesirable power losses that can occur through a bearing. Here, a novel method to reduce power losses in tilting-pad journal bearings is proposed in which the conventional lubricant is substituted by a binary mixture of synthetic lubricant and dissolved CO2. These gas-expanded lubricants (GELs) would be delivered to a reinforced bearing housing capable of withstanding modest pressures less than 10 MPa. For bearings subject to loads that are both variable and predictable, GELs could be used to adjust lubricant properties in real time. High-pressure lubricants, mostly gases, have already been explored in tilting-pad journal bearings as a means to accommodate higher shaft speeds while reducing power losses and eliminating the potential for thermal degradation of the lubricant. These gas-lubricated bearings have intrinsic limitations in terms of bearing size and load capacity. The proposed system would combine the loading capabilities of conventional lubricated bearings with the efficiency of gas-lubricated bearings. The liquid or supercritical CO2 serves as a low-viscosity and completely miscible additive to the lubricant that can be easily removed by purging the gas after releasing the pressure. In this way, the lubricant can be fully recycled, as in conventional systems, while controlling the lubricant properties dynamically by adding liquid or supercritical CO2. Lubricant properties of interest, such as viscosity, can be easily tuned by controlling the pressure inside the bearing housing. Experimental measurements of viscosity for mixtures of polyalkylene glycol (PAG)+CO2 at various compositions demonstrate that significant reductions in mixture viscosity can be achieved with relatively small additions of CO2. The measured parameters are used in a thermoelastohydrodynamic model of tilting-pad journal bearing performance to evaluate the bearing response to GELs. Model estimates of power loss, eccentricity ratio, and pad temperature suggest that bearings would respond quite favorably over a range of speed and preload conditions. Calculated power loss reductions of 20% are observed when compared with both a reference petroleum lubricant and PAG without CO2. Pad temperature is also maintained without significant increases in eccentricity ratio. Both power loss and pad temperature are directly correlated with PAG-CO2 composition, suggesting that these mixtures could be used as “smart” lubricants responsive to system operating conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Effect of friction modifiers and antiwear additives on the tribological performance of a hydrogenated DLC coating / T. Haque in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 13 p. Titre : Effect of friction modifiers and antiwear additives on the tribological performance of a hydrogenated DLC coating Type de document : texte imprimé Auteurs : T. Haque, Auteur ; A. Morina, Auteur ; A. Neville, Auteur Année de publication : 2011 Article en page(s) : 13 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Abrasion  Additives  Atomic  force  microscopy  Diamond-like  carbon  Durability  Friction  Hydrogen  Lubricating  oils  Lubrication  Organic  compounds  Raman  spectra  Scanning  electron  microscopy  Thin  films  Wear  resistant  coatings  X-ray  chemical  analysis  X-ray  photoelectron  spectra Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : There has been a lot of attention on the effect of lubricant additives on the friction at carbon coated surfaces. But only few papers have addressed the effect of additives on the durability of some diamondlike carbon DLC coatings. This paper presents a systematic study assessing the additive/additive and additive/surface interactions, and their influences on the durability of a low hydrogen-containing (15 at. % hydrogen) metal-free DLC coating (a-C:15H). In this study, lubricating oils containing a zinc dithiophosphate (ZDDP) antiwear additive and/or organomolybdenum friction modifiers (moly dimer and moly trimer) were used. Tribological tests were carried out in a pin-on-plate tribometer under boundary lubrication conditions. To understand the effect of additives, tribofilms formed on the wear tracks were analyzed using surface sensitive analytical techniques such as atomic force microscope, scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy. Results showed that the ZDDP formed a zinc phosphate containing an ultrathin antiwear tribofilm, which offered excellent durability/wear protection to the a-C:15H coating. However, the antiwear performance of this additive was compromised when it was used with moly dimer or moly trimer. Surface analysis revealed that unlike steel surfaces, MoS2 formed on the DLC surfaces had negligible influence on friction, while the low friction DLC wear debris had strong influence on friction. Abrasive wear was found to be the dominating wear mechanism in the cases when additives showed poor wear protection on the a-C:15H coating. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Effect of friction modifiers and antiwear additives on the tribological performance of a hydrogenated DLC coating [texte imprimé] / T. Haque, Auteur ; A. Morina, Auteur ; A. Neville, Auteur . - 2011 . - 13 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 13 p. Mots-clés : Abrasion  Additives  Atomic  force  microscopy  Diamond-like  carbon  Durability  Friction  Hydrogen  Lubricating  oils  Lubrication  Organic  compounds  Raman  spectra  Scanning  electron  microscopy  Thin  films  Wear  resistant  coatings  X-ray  chemical  analysis  X-ray  photoelectron  spectra Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : There has been a lot of attention on the effect of lubricant additives on the friction at carbon coated surfaces. But only few papers have addressed the effect of additives on the durability of some diamondlike carbon DLC coatings. This paper presents a systematic study assessing the additive/additive and additive/surface interactions, and their influences on the durability of a low hydrogen-containing (15 at. % hydrogen) metal-free DLC coating (a-C:15H). In this study, lubricating oils containing a zinc dithiophosphate (ZDDP) antiwear additive and/or organomolybdenum friction modifiers (moly dimer and moly trimer) were used. Tribological tests were carried out in a pin-on-plate tribometer under boundary lubrication conditions. To understand the effect of additives, tribofilms formed on the wear tracks were analyzed using surface sensitive analytical techniques such as atomic force microscope, scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy. Results showed that the ZDDP formed a zinc phosphate containing an ultrathin antiwear tribofilm, which offered excellent durability/wear protection to the a-C:15H coating. However, the antiwear performance of this additive was compromised when it was used with moly dimer or moly trimer. Surface analysis revealed that unlike steel surfaces, MoS2 formed on the DLC surfaces had negligible influence on friction, while the low friction DLC wear debris had strong influence on friction. Abrasive wear was found to be the dominating wear mechanism in the cases when additives showed poor wear protection on the a-C:15H coating. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

On the prediction of running-in behavior in mixed-lubrication line contact / Saleh Akbarzadeh in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Titre : On the prediction of running-in behavior in mixed-lubrication line contact Type de document : texte imprimé Auteurs : Saleh Akbarzadeh, Auteur ; M. M. Khonsari, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Desorption  Gaussian  distribution  Lubrication  Plastic  deformation  Rolling  friction  Sliding  friction  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A model is presented, which enables one to predict the running-in performance of the rolling/sliding surfaces subjected to mixed-lubrication line contact. The load-sharing concept was used, in which it is assumed that both the fluid film and the asperities contribute in carrying the imposed load. The plastic deformation of asperities during the running-in is taken into consideration. In the application of the load-sharing method, it is often assumed that asperity heights have a Gaussian distribution. This assumption has been relaxed in this model. Prediction results for the variation in the arithmetic average of asperity heights (Ra) during the running-in period for contact of two rollers are compared with published experimental data. Also presented are the results for the variation in wear volume, wear rate, and friction coefficient during the running-in period. The effect of surface pattern, speed, and load on the running-in behavior is studied. The steady-state wear rate for different surface patterns calculated from this model is compared with the wear rate predicted by the thermal desorption model, and the results are in agreement both in trend and magnitude. The effect of running-in on the Stribeck curve for different surface pattern is discussed. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] On the prediction of running-in behavior in mixed-lubrication line contact [texte imprimé] / Saleh Akbarzadeh, Auteur ; M. M. Khonsari, Auteur . - 2011 . - 11 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 11 p. Mots-clés : Desorption  Gaussian  distribution  Lubrication  Plastic  deformation  Rolling  friction  Sliding  friction  Surface  roughness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A model is presented, which enables one to predict the running-in performance of the rolling/sliding surfaces subjected to mixed-lubrication line contact. The load-sharing concept was used, in which it is assumed that both the fluid film and the asperities contribute in carrying the imposed load. The plastic deformation of asperities during the running-in is taken into consideration. In the application of the load-sharing method, it is often assumed that asperity heights have a Gaussian distribution. This assumption has been relaxed in this model. Prediction results for the variation in the arithmetic average of asperity heights (Ra) during the running-in period for contact of two rollers are compared with published experimental data. Also presented are the results for the variation in wear volume, wear rate, and friction coefficient during the running-in period. The effect of surface pattern, speed, and load on the running-in behavior is studied. The steady-state wear rate for different surface patterns calculated from this model is compared with the wear rate predicted by the thermal desorption model, and the results are in agreement both in trend and magnitude. The effect of running-in on the Stribeck curve for different surface pattern is discussed. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Identification of force coefficients in a squeeze film damper with a mechanical seal / Adolfo Delgado in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 07 p. Titre : Identification of force coefficients in a squeeze film damper with a mechanical seal : large contact force Type de document : texte imprimé Auteurs : Adolfo Delgado, Auteur ; Luis San Andrés, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Damping  Friction  Mechanical  contact  Rotors  Vibrations Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Squeeze film dampers (SFDs) aid to reduce excessive vibration levels due to rotor imbalance and to raise stability thresholds in rotor-bearing systems. SFDs commonly include end seals to increase their damping capability with a lesser lubricant flow. Seals also aid to reduce the occurrence of air ingestion/entrapment that severely reduces the damper forced performance. However, most conventional end seals do not completely eliminate lubricant side leakage, which limits their effectiveness to prevent air ingestion. A novel end seal arrangement incorporates a spring loaded, contacting mechanical seal that effectively prevents lubricant side leakage and air ingestion. The mechanically sealed damper is intended for use in power engines for unmanned aircraft vehicles. The test damper journal is 2.54 cm in length and 12.7 cm in diameter, with a radial clearance of 0.127 mm. Prior literature reports dynamic load tests on the seal-SFD and measurements of orbital motions to characterize the mechanical parameters of both the mechanical seal and squeeze film damper section. The test data to date include damper operation for a single contact load (90 N) closing the mechanical seal. Presently, measurements of damper dynamic load performance are conducted with a larger contact force (260 N). A nonlinear parameter identification method in the frequency domain determines simultaneously the squeeze film damping and inertia coefficients and the seal dry-friction force. The test results show that the system equivalent viscous damping coefficients are twice as large as those obtained earlier with the smaller contact force. On the other hand, as expected, the squeeze film damper coefficients are nearly identical for both test configurations. Predicted squeeze film damping coefficients, from an improved model that includes the flow in the damper feed and discharge grooves, correlate well with the test data for small and moderate orbit radii. The experimental fluid added mass coefficients are in par with the actual mass of the bearing housing and accurately predicted. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Identification of force coefficients in a squeeze film damper with a mechanical seal : large contact force [texte imprimé] / Adolfo Delgado, Auteur ; Luis San Andrés, Auteur . - 2011 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 07 p. Mots-clés : Damping  Friction  Mechanical  contact  Rotors  Vibrations Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Squeeze film dampers (SFDs) aid to reduce excessive vibration levels due to rotor imbalance and to raise stability thresholds in rotor-bearing systems. SFDs commonly include end seals to increase their damping capability with a lesser lubricant flow. Seals also aid to reduce the occurrence of air ingestion/entrapment that severely reduces the damper forced performance. However, most conventional end seals do not completely eliminate lubricant side leakage, which limits their effectiveness to prevent air ingestion. A novel end seal arrangement incorporates a spring loaded, contacting mechanical seal that effectively prevents lubricant side leakage and air ingestion. The mechanically sealed damper is intended for use in power engines for unmanned aircraft vehicles. The test damper journal is 2.54 cm in length and 12.7 cm in diameter, with a radial clearance of 0.127 mm. Prior literature reports dynamic load tests on the seal-SFD and measurements of orbital motions to characterize the mechanical parameters of both the mechanical seal and squeeze film damper section. The test data to date include damper operation for a single contact load (90 N) closing the mechanical seal. Presently, measurements of damper dynamic load performance are conducted with a larger contact force (260 N). A nonlinear parameter identification method in the frequency domain determines simultaneously the squeeze film damping and inertia coefficients and the seal dry-friction force. The test results show that the system equivalent viscous damping coefficients are twice as large as those obtained earlier with the smaller contact force. On the other hand, as expected, the squeeze film damper coefficients are nearly identical for both test configurations. Predicted squeeze film damping coefficients, from an improved model that includes the flow in the damper feed and discharge grooves, correlate well with the test data for small and moderate orbit radii. The experimental fluid added mass coefficients are in par with the actual mass of the bearing housing and accurately predicted. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

A model for improved prediction of force coefficients in grooved squeeze film dampers and oil seal rings / Adolfo Delgado in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 12 p. Titre : A model for improved prediction of force coefficients in grooved squeeze film dampers and oil seal rings Type de document : texte imprimé Auteurs : Adolfo Delgado, Auteur ; Luis San Andrés, Auteur Année de publication : 2011 Article en page(s) : 12 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Damping  Elastic  constants  Mechanical  stability  Rings  (structures)  Seals  (stoppers)  Shock  absorbers Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Squeeze film damper (SFD) designs typically implement supply grooves to ensure adequate lubricant flow into the film lands. Oil seal rings, of land film clearance c, also incorporate short and shallow grooves (length<=30c,depth<=15c) to reduce cross-coupled stiffnesses, thus promoting dynamic stability without a penalty in increased leakage. However, extensive experimental results in the archival literature demonstrate that grooves do not reduce the force coefficients as much as theory predicts. A common assumption is that deep grooves do not influence a damper or oil seal ring forced response. However, unexpected large added mass coefficients, not adequately predicted, appear to be common in many tested SFD and oil seal configurations. In the case of oil seals, experiments demonstrate that circumferential grooves do reduce cross-coupled stiffnesses but to a lesser extent than predictions would otherwise indicate. A linear fluid inertia bulk-flow model for analysis of the forced response of SFDs and oil seal configurations with multiple grooves is advanced. A perturbation analysis for small amplitude journal motions about a centered position yields zeroth and first-order flow equations at each flow region (lands and grooves). At a groove region, a groove effective depth deta, differing from its actual physical value, is derived from qualitative observations of the laminar flow pattern through annular cavities. The boundary conditions at the inlet and exit planes depend on the actual seal or SFD configuration. Integration of the resulting first-order pressure fields on the journal surface yields the force coefficients (stiffness, damping, and inertia). Current model predictions are in excellent agreement with published test force coefficients for a grooved SFD and a grooved oil seal. The results confirm that large added mass coefficients arise from the flow interactions between the feed/discharge grooves and film lands in the test elements. Furthermore, the predictions, benchmarking experimental data, corroborate that short length inner-land grooves in an oil seal do not isolate the pressure fields of adjacent film lands and hence contribute greatly to the forced response of the mechanical element. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] A model for improved prediction of force coefficients in grooved squeeze film dampers and oil seal rings [texte imprimé] / Adolfo Delgado, Auteur ; Luis San Andrés, Auteur . - 2011 . - 12 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 12 p. Mots-clés : Damping  Elastic  constants  Mechanical  stability  Rings  (structures)  Seals  (stoppers)  Shock  absorbers Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Squeeze film damper (SFD) designs typically implement supply grooves to ensure adequate lubricant flow into the film lands. Oil seal rings, of land film clearance c, also incorporate short and shallow grooves (length<=30c,depth<=15c) to reduce cross-coupled stiffnesses, thus promoting dynamic stability without a penalty in increased leakage. However, extensive experimental results in the archival literature demonstrate that grooves do not reduce the force coefficients as much as theory predicts. A common assumption is that deep grooves do not influence a damper or oil seal ring forced response. However, unexpected large added mass coefficients, not adequately predicted, appear to be common in many tested SFD and oil seal configurations. In the case of oil seals, experiments demonstrate that circumferential grooves do reduce cross-coupled stiffnesses but to a lesser extent than predictions would otherwise indicate. A linear fluid inertia bulk-flow model for analysis of the forced response of SFDs and oil seal configurations with multiple grooves is advanced. A perturbation analysis for small amplitude journal motions about a centered position yields zeroth and first-order flow equations at each flow region (lands and grooves). At a groove region, a groove effective depth deta, differing from its actual physical value, is derived from qualitative observations of the laminar flow pattern through annular cavities. The boundary conditions at the inlet and exit planes depend on the actual seal or SFD configuration. Integration of the resulting first-order pressure fields on the journal surface yields the force coefficients (stiffness, damping, and inertia). Current model predictions are in excellent agreement with published test force coefficients for a grooved SFD and a grooved oil seal. The results confirm that large added mass coefficients arise from the flow interactions between the feed/discharge grooves and film lands in the test elements. Furthermore, the predictions, benchmarking experimental data, corroborate that short length inner-land grooves in an oil seal do not isolate the pressure fields of adjacent film lands and hence contribute greatly to the forced response of the mechanical element. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Elastohydrodynamic line-contact of compressible shear thinning fluids with consideration of the surface roughness / J. Y. Jang in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Titre : Elastohydrodynamic line-contact of compressible shear thinning fluids with consideration of the surface roughness Type de document : texte imprimé Auteurs : J. Y. Jang, Auteur ; M. M. Khonsari, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Crystallographic  shear  Elastic  deformation  Hydrodynamics  Lubrication  Surface  roughness  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Applications involving highly loaded elastohydrodynamic lubrication (EHL), particularly when the lubricant experiences shear thinning, operating with small film thicknesses may necessitate consideration of surface asperities. A modified Reynolds equation with provision for surface roughness and shear thinning is treated to predict the pressure and surface asperity effect in an EHL line-contact. The unknown in the Reynolds equation is the hydrodynamic pressure instead of the total pressure to ensure that the pressure boundary condition at the outlet is properly posed. The Carreau viscosity model is used for characterizing the shear thinning behavior, Patir and Cheng flow factors for taking into the influence of roughness on the lubricating film, and Greenwood–Trip for determination of pressure at the asperity level. The modified Reynolds equation is solved for the hydrodynamic pressure instead of the total pressure with appropriately defined boundary conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Elastohydrodynamic line-contact of compressible shear thinning fluids with consideration of the surface roughness [texte imprimé] / J. Y. Jang, Auteur ; M. M. Khonsari, Auteur . - 2011 . - 06 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Mots-clés : Crystallographic  shear  Elastic  deformation  Hydrodynamics  Lubrication  Surface  roughness  Viscosity Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Applications involving highly loaded elastohydrodynamic lubrication (EHL), particularly when the lubricant experiences shear thinning, operating with small film thicknesses may necessitate consideration of surface asperities. A modified Reynolds equation with provision for surface roughness and shear thinning is treated to predict the pressure and surface asperity effect in an EHL line-contact. The unknown in the Reynolds equation is the hydrodynamic pressure instead of the total pressure to ensure that the pressure boundary condition at the outlet is properly posed. The Carreau viscosity model is used for characterizing the shear thinning behavior, Patir and Cheng flow factors for taking into the influence of roughness on the lubricating film, and Greenwood–Trip for determination of pressure at the asperity level. The modified Reynolds equation is solved for the hydrodynamic pressure instead of the total pressure with appropriately defined boundary conditions. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

An overview of the hardness differential required for abrasion / Giuseppe Pintaude in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 04 p. Titre : An overview of the hardness differential required for abrasion Type de document : texte imprimé Auteurs : Giuseppe Pintaude, Auteur Année de publication : 2011 Article en page(s) : 04 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Abrasion  Elastoplasticity  Hardness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper presents an overview of the hardness differential required for abrasion. Empirically, the abrasive must be at least 1.2 times harder than the worn surface if it is to produce a scratch. This value has been determined theoretically using slip-line field modeling, which assumes rigid-plastic mechanical behavior, an assumption that is inadequate for most abrasive particles. Two approaches using elastic-plastic models and three tribological pairs with similar ratios of abrasive hardness to worn material hardness were tested to gain an understanding of the hardness differential required for abrasion. The analysis showed that the ratios of the property of the abrasive to the property of the worn surface did not change with the model used when the mechanical behavior of the materials was similar. However, when the behavior of the materials was very dissimilar—as is often the case in abrasive processes—the ratios varied greatly depending on the model used, showing that there is a need for models to describe the hardness differential required for abrasion. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] An overview of the hardness differential required for abrasion [texte imprimé] / Giuseppe Pintaude, Auteur . - 2011 . - 04 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 04 p. Mots-clés : Abrasion  Elastoplasticity  Hardness Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : This paper presents an overview of the hardness differential required for abrasion. Empirically, the abrasive must be at least 1.2 times harder than the worn surface if it is to produce a scratch. This value has been determined theoretically using slip-line field modeling, which assumes rigid-plastic mechanical behavior, an assumption that is inadequate for most abrasive particles. Two approaches using elastic-plastic models and three tribological pairs with similar ratios of abrasive hardness to worn material hardness were tested to gain an understanding of the hardness differential required for abrasion. The analysis showed that the ratios of the property of the abrasive to the property of the worn surface did not change with the model used when the mechanical behavior of the materials was similar. However, when the behavior of the materials was very dissimilar—as is often the case in abrasive processes—the ratios varied greatly depending on the model used, showing that there is a need for models to describe the hardness differential required for abrasion. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Slurry pump impeller wear / Veselin Batalovic in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 05 p. Titre : Slurry pump impeller wear : testing Type de document : texte imprimé Auteurs : Veselin Batalovic, Auteur Année de publication : 2011 Article en page(s) : 05 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Impellers  Wear  Wear  testing Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Erosion wear is a process that accompanies the facility for hydraulic transportation of solids. Since the pump is one of the vital parts of this facility, the working life of the pump is conditioned by the amount of wear. The working life can be realized only if the parameters chosen, for the pump elements, slurry, and transport conditions, will provide economic transport with minimal wear. Testing is the most reliable method for acquiring valid data. The two issues that need to be solved while planning the testing process are the choice of valid similarity criteria (test-industrial facility) and data selection. After the theoretical analyses, technically acceptable similarity criteria are obtained. A group of data needs to be defined through the experiment. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Slurry pump impeller wear : testing [texte imprimé] / Veselin Batalovic, Auteur . - 2011 . - 05 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 05 p. Mots-clés : Impellers  Wear  Wear  testing Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Erosion wear is a process that accompanies the facility for hydraulic transportation of solids. Since the pump is one of the vital parts of this facility, the working life of the pump is conditioned by the amount of wear. The working life can be realized only if the parameters chosen, for the pump elements, slurry, and transport conditions, will provide economic transport with minimal wear. Testing is the most reliable method for acquiring valid data. The two issues that need to be solved while planning the testing process are the choice of valid similarity criteria (test-industrial facility) and data selection. After the theoretical analyses, technically acceptable similarity criteria are obtained. A group of data needs to be defined through the experiment. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Study of wear self-repair of steel 100Cr6 rubbed with lubricants modified with schiff base copper complex / Xinlei Gao in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 05 p. Titre : Study of wear self-repair of steel 100Cr6 rubbed with lubricants modified with schiff base copper complex Type de document : texte imprimé Auteurs : Xinlei Gao, Auteur ; Li Wu, Auteur ; Jian Li, Auteur Année de publication : 2011 Article en page(s) : 05 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Atomic  force  microscopy  Friction  Lubrication  Monolayers  Scanning  electron  microscopy  Steel  Voltammetry  (chemical  analysis)  Wear  X-ray  chemical  analysis  X-ray  photoelectron  spectra Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Preparation of a Cu (II) chelate of bis(salicylaldehyde)ethylenediamine was carried out directly in epoxidized rape oil via a water/oil microemulsion reactor. Detailed characterization of the friction of boundary lubrication produced by epoxidized rape oil with and without the Cu (II) chelate of bis(salicylaldehyde)ethylenediamine was performed in reciprocating sliding tests with a microtribometer. In the presence of a modification of the epoxidized rape oil with 2 wt % of the Cu (II) chelate of bis(salicylaldehyde)ethylenediamine, the friction coefficient decreased by 15%. The Cu (II) chelate of bis(salicylaldehyde)ethylenediamine served as the additive in the epoxidized rape oil and self-assembled on the surface of 100Cr6 steel. The self-assembled monolayer was detected with atomic force microscopy and scanning electron microscopy, and characterized with cyclic voltammetry. It was verified by energy dispersive spectroscopy and X-ray photoelectron spectroscopy analyses that steel/steel rubbing pairs underwent a selective transfer of organic substance and copper, as a result of lubrication with the modified lubricant. It indicated that the modification of epoxidized rape oil with Cu (II) chelate of bis(salicylaldehyde)ethylenediamine led to wear self-repair on the steel surface, with selective transfer of a film of organic substance and copper metal. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Study of wear self-repair of steel 100Cr6 rubbed with lubricants modified with schiff base copper complex [texte imprimé] / Xinlei Gao, Auteur ; Li Wu, Auteur ; Jian Li, Auteur . - 2011 . - 05 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 05 p. Mots-clés : Atomic  force  microscopy  Friction  Lubrication  Monolayers  Scanning  electron  microscopy  Steel  Voltammetry  (chemical  analysis)  Wear  X-ray  chemical  analysis  X-ray  photoelectron  spectra Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Preparation of a Cu (II) chelate of bis(salicylaldehyde)ethylenediamine was carried out directly in epoxidized rape oil via a water/oil microemulsion reactor. Detailed characterization of the friction of boundary lubrication produced by epoxidized rape oil with and without the Cu (II) chelate of bis(salicylaldehyde)ethylenediamine was performed in reciprocating sliding tests with a microtribometer. In the presence of a modification of the epoxidized rape oil with 2 wt % of the Cu (II) chelate of bis(salicylaldehyde)ethylenediamine, the friction coefficient decreased by 15%. The Cu (II) chelate of bis(salicylaldehyde)ethylenediamine served as the additive in the epoxidized rape oil and self-assembled on the surface of 100Cr6 steel. The self-assembled monolayer was detected with atomic force microscopy and scanning electron microscopy, and characterized with cyclic voltammetry. It was verified by energy dispersive spectroscopy and X-ray photoelectron spectroscopy analyses that steel/steel rubbing pairs underwent a selective transfer of organic substance and copper, as a result of lubrication with the modified lubricant. It indicated that the modification of epoxidized rape oil with Cu (II) chelate of bis(salicylaldehyde)ethylenediamine led to wear self-repair on the steel surface, with selective transfer of a film of organic substance and copper metal. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse