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

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

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Adhesive elastic contact of rough surfaces with power-law axisymmetric asperities / Lefeng Wang in Transactions of the ASME . Journal of tribology, Vol. 134 N° 3 (Juillet 2012)  

Public ISBD [article]  inTransactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 05 p. Titre : Adhesive elastic contact of rough surfaces with power-law axisymmetric asperities Type de document : texte imprimé Auteurs : Lefeng Wang, Auteur ; Weibin Rong, Auteur ; Bing Shao, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : tribology Langues : Anglais (eng) Mots-clés : adhesive contact  surface roughless  axisymetric asperities  power-law shape Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The contact model for rough surfaces with power-law axisymmetric asperities in the presence of adhesion is developed. The extended JKR adhesive contact model for power-law axisymmetric asperities, denoted as JKR-n, developed by Zheng and Yu (2007,“Using the Dugdale Approximation to Match a Specific Interaction in the Adhesive Contact of Elastic Objects,” J. Colloid Interface Sci., 310, pp. 27–34) is utilized to investigate the adhesive contact of rough surfaces. The JKR-n adhesive contact model generalizes the most adopted JKR model for spherical objects of n = 2. This work compares the effect of surface roughness on the adhesion force for rough surfaces with various power-law axisymmetric asperities. It is found that shapes of the asperities influence the pull-off forces greatly during the separation of rough surfaces. A general adhesion parameter that includes the shape index of asperities is proposed, and it can be used to characterize the adhesion performance of rough surfaces. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE9000134000003 [...] [article] Adhesive elastic contact of rough surfaces with power-law axisymmetric asperities [texte imprimé] / Lefeng Wang, Auteur ; Weibin Rong, Auteur ; Bing Shao, Auteur . - 2012 . - 05 p. tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 134 N° 3 (Juillet 2012) . - 05 p. Mots-clés : adhesive contact  surface roughless  axisymetric asperities  power-law shape Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The contact model for rough surfaces with power-law axisymmetric asperities in the presence of adhesion is developed. The extended JKR adhesive contact model for power-law axisymmetric asperities, denoted as JKR-n, developed by Zheng and Yu (2007,“Using the Dugdale Approximation to Match a Specific Interaction in the Adhesive Contact of Elastic Objects,” J. Colloid Interface Sci., 310, pp. 27–34) is utilized to investigate the adhesive contact of rough surfaces. The JKR-n adhesive contact model generalizes the most adopted JKR model for spherical objects of n = 2. This work compares the effect of surface roughness on the adhesion force for rough surfaces with various power-law axisymmetric asperities. It is found that shapes of the asperities influence the pull-off forces greatly during the separation of rough surfaces. A general adhesion parameter that includes the shape index of asperities is proposed, and it can be used to characterize the adhesion performance of rough surfaces. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE9000134000003 [...]

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Aeration in lubrication with application to drag torque reduction / Aphale, Chinar R. in Transactions of the ASME . Journal of tribology, Vol. 133 N° 3 (Juillet 2011)  

Public ISBD [article]  inTransactions of the ASME . Journal of tribology > Vol. 133 N° 3 (Juillet 2011) . - 07 p. Titre : Aeration in lubrication with application to drag torque reduction Type de document : texte imprimé Auteurs : Aphale, Chinar R., Auteur ; Schultz, William W., Auteur ; Ceccio, Steven L., Auteur Année de publication : 2012 Article en page(s) : 07 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Contact angle Discs (structures) Drag reduction Fluids Inclusions Lubricating oils Lubrication Plates Surface tension Two-phase flow Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The aeration of an oil film flowing between the faces of two closely spaced circular plates (one stationary, and one rotating) is examined experimentally, numerically, and with an improved lubrication model. The gap between the plates is small compared to their radii, making lubrication theory appropriate for modeling the flow. However, standard lubrication boundary conditions suggested by Reynolds (1886, "On the Theory of Lubrication and its Application to Mr. Beauchamp Tower's Experiments, Including an Experimental Determination of the Viscosity of Olive Oil," Philos. Trans. R. Soc. London, 177, pp. 157-234) of p = 0 and pn = 0 (Dirichlet and Neumann conditions on pressure) at the gas-liquid interface do not allow for the inclusion of a contact line model, a phenomenon that is important in the inception of aeration. Hence, the standard theory does not adequately predict the experimentally observed onset of aeration. In the present work, we modify the Neumann boundary condition to include both interfacial tension effects and the dynamics of the interface contact angle. The resulting one-dimensional Cartesian two-phase model is formulated to incorporate the prescribed contact line condition and tracks the interface shape and its motion. This model is then implemented in an axisymmetric, two-dimensional model of the rotating disk flow and used to predict the onset of aeration for varying surface tension and static contact angles. The results of the modified lubrication model are compared with experimental observations and with a numerical computation of the aerating flow using a volume of fluid method. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Aeration in lubrication with application to drag torque reduction [texte imprimé] / Aphale, Chinar R., Auteur ; Schultz, William W., Auteur ; Ceccio, Steven L., Auteur . - 2012 . - 07 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 3 (Juillet 2011) . - 07 p. Mots-clés : Contact angle Discs (structures) Drag reduction Fluids Inclusions Lubricating oils Lubrication Plates Surface tension Two-phase flow Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The aeration of an oil film flowing between the faces of two closely spaced circular plates (one stationary, and one rotating) is examined experimentally, numerically, and with an improved lubrication model. The gap between the plates is small compared to their radii, making lubrication theory appropriate for modeling the flow. However, standard lubrication boundary conditions suggested by Reynolds (1886, "On the Theory of Lubrication and its Application to Mr. Beauchamp Tower's Experiments, Including an Experimental Determination of the Viscosity of Olive Oil," Philos. Trans. R. Soc. London, 177, pp. 157-234) of p = 0 and pn = 0 (Dirichlet and Neumann conditions on pressure) at the gas-liquid interface do not allow for the inclusion of a contact line model, a phenomenon that is important in the inception of aeration. Hence, the standard theory does not adequately predict the experimentally observed onset of aeration. In the present work, we modify the Neumann boundary condition to include both interfacial tension effects and the dynamics of the interface contact angle. The resulting one-dimensional Cartesian two-phase model is formulated to incorporate the prescribed contact line condition and tracks the interface shape and its motion. This model is then implemented in an axisymmetric, two-dimensional model of the rotating disk flow and used to predict the onset of aeration for varying surface tension and static contact angles. The results of the modified lubrication model are compared with experimental observations and with a numerical computation of the aerating flow using a volume of fluid method. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]

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Air cycle combined heating and cooling for the food industry / A.M. Foster in International journal of refrigeration, Vol. 34 N° 5 (Août 2011)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 34 N° 5 (Août 2011) . - pp. 1296-1304 Titre : Air cycle combined heating and cooling for the food industry Titre original : Cycle à air utilisé pour le chauffage et le refroidissement dans l'industrie agro-alimentaire Type de document : texte imprimé Auteurs : A.M. Foster, Auteur ; T. Brown, Auteur ; A.J. Gigiel, Auteur Année de publication : 2011 Article en page(s) : pp. 1296-1304 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Brayton Cooking Cooling Centrifugal compressor Food COP Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the food industry there is often a need to both cook and cool food. Heating and cooling processes are rarely directly linked due to heat from refrigeration processes being insufficient to cook food. Therefore cooling and cooking is usually provided by separate pieces of equipment. This paper presents an air cycle system where the hot air was used for heating and the cold air used for fast freezing. The apparatus used a bootstrap unit developed for aircraft air conditioning which was unable to run at the low temperature required for food freezing, so a parallel compressor was added to enable the system to operate at the low temperature required for food freezing. This approach allowed temperatures as low as −140 °C and as high as 234 °C. The system cooked and froze beef burgers, and at the same time heated water up to 98 °C. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071100079X [article] Air cycle combined heating and cooling for the food industry = Cycle à air utilisé pour le chauffage et le refroidissement dans l'industrie agro-alimentaire [texte imprimé] / A.M. Foster, Auteur ; T. Brown, Auteur ; A.J. Gigiel, Auteur . - 2011 . - pp. 1296-1304. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 5 (Août 2011) . - pp. 1296-1304 Mots-clés : Brayton Cooking Cooling Centrifugal compressor Food COP Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the food industry there is often a need to both cook and cool food. Heating and cooling processes are rarely directly linked due to heat from refrigeration processes being insufficient to cook food. Therefore cooling and cooking is usually provided by separate pieces of equipment. This paper presents an air cycle system where the hot air was used for heating and the cold air used for fast freezing. The apparatus used a bootstrap unit developed for aircraft air conditioning which was unable to run at the low temperature required for food freezing, so a parallel compressor was added to enable the system to operate at the low temperature required for food freezing. This approach allowed temperatures as low as −140 °C and as high as 234 °C. The system cooked and froze beef burgers, and at the same time heated water up to 98 °C. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071100079X

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Air infiltration in domestic refrigerators / Clito Afonso in International journal of refrigeration, Vol. 33 N° 4 (Juin 2010)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 33 N° 4 (Juin 2010) . - pp. 856-867 Titre : Air infiltration in domestic refrigerators : The influence of the magnetic seals conservation Titre original : Infıltration d'air dans les réfrigérateurs domestiques: influence de l'état des joints magnétiques Type de document : texte imprimé Auteurs : Clito Afonso, Auteur ; Manuel Castro, Auteur Année de publication : 2010 Article en page(s) : pp. 856-867 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Domestic refrigerator Review Seals Process Measurement Infiltration Air Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : One component of the heat exchange rate in domestic refrigerators/freezers and of the other all types of refrigeration stores is the air infiltration due to the air exchange rate between inside and outside of the store trough the magnetic seals of the doors. Due to their use (opening and closing the doors) they become leaky with the time. So, it is necessary to know to measure them in a proper way in order to be able to quantify which percentage of the energy consumption of the compressor is used to overcome the air infiltration rate. In this work the tracer gas technique was used for the measurement of the air infiltration rate in a household double door commercial refrigerator. Through several tests carried out it was possible to analyse the influence of the magnetic seal conservation condition on the air exchange rates of the refrigerator. It was concluded that the air infiltration rates were strongly dependent on the door seals conservation conditions. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700709002849 [article] Air infiltration in domestic refrigerators = Infıltration d'air dans les réfrigérateurs domestiques: influence de l'état des joints magnétiques : The influence of the magnetic seals conservation [texte imprimé] / Clito Afonso, Auteur ; Manuel Castro, Auteur . - 2010 . - pp. 856-867. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 4 (Juin 2010) . - pp. 856-867 Mots-clés : Domestic refrigerator Review Seals Process Measurement Infiltration Air Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : One component of the heat exchange rate in domestic refrigerators/freezers and of the other all types of refrigeration stores is the air infiltration due to the air exchange rate between inside and outside of the store trough the magnetic seals of the doors. Due to their use (opening and closing the doors) they become leaky with the time. So, it is necessary to know to measure them in a proper way in order to be able to quantify which percentage of the energy consumption of the compressor is used to overcome the air infiltration rate. In this work the tracer gas technique was used for the measurement of the air infiltration rate in a household double door commercial refrigerator. Through several tests carried out it was possible to analyse the influence of the magnetic seal conservation condition on the air exchange rates of the refrigerator. It was concluded that the air infiltration rates were strongly dependent on the door seals conservation conditions. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700709002849

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Air-side heat transfer and pressure drop characteristics of accelerated flow evaporators / Paulo J. Waltrich in International journal of refrigeration, Vol. 34 N° 2 (Mars 2011)  

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Air-side heat transfer characteristics of spiral-type circular fin-tube heat exchangers / Mooyeon Lee in International journal of refrigeration, Vol. 33 N° 2 (Mars 2010)  

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Air-side performance of a parallel-flow parallel-fin (PF2) heat exchanger in sequential frosting / Ping Zhang in International journal of refrigeration, Vol. 33 N° 6 (Septembre 2010)  

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Ammonia–water desorption heat and mass transfer in microchannel devices / Matthew D. Determan in International journal of refrigeration, Vol. 34 N° 5 (Août 2011)  

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An air-standard cycle and a thermodynamic perspective on operational limits of Ranque–Hilsh or vortex tubes / José Roberto Simões-Moreira in International journal of refrigeration, Vol. 33 N° 4 (Juin 2010)  

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An analytical complete model of tilting-pad journal bearing considering pivot stiffness and damping / Zhiyong Yan in Transactions of the ASME . Journal of tribology, Vol. 133 N° 1 (Janvier 2011)  

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An analytical model for the basic design calculations of journal bearings / R. K. Naffin in Transactions of the ASME . Journal of tribology, Vol. 132 N° 2 (Avril 2010)  

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An analytical prediction for performance and optimum design analysis of porous fins / Balaram Kundu in International journal of refrigeration, Vol. 34 N° 1 (Janvier 2011)  

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An application of dimensional analysis to entropy-wear relationship / Hisham A Abdel-Aal in Transactions of the ASME . Journal of tribology, Vol. 134 N° 3 (Juillet 2012)  

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An application of the extended corresponding states model to thermodynamic property calculations for trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) / Ryo Akasaka in International journal of refrigeration, Vol. 33 N° 5 (Août 2010)  

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