Showing results 21 to 37 of 37
 Comparative analysis of the lubricating power between a pure mineral oil and biodegradable oils of the same mean iso grade; Bozet, Jean-Luc  in Dowson, D.; Taylor, C. M.; Childs, T. H. C. (Eds.) et al Lubricants and lubrication : proceedings of the 21th Leeds-Lyon symposium on tribology held at the Institute of Tribology , University of Leeds U.K., 6th-9th September 1994 (1995) n this paper, we compare the viscosimetric and tribological properties of some vegetable oils and one synthetic ester with a pure mineral oil. The viscosimetric characteristics of lubricants show that ... [more ▼] n this paper, we compare the viscosimetric and tribological properties of some vegetable oils and one synthetic ester with a pure mineral oil. The viscosimetric characteristics of lubricants show that both vegetable oils and ester have a higher viscosity index than mineral oil. The test results show that all tested oils have a somewhat dilatant behaviour.The oiliness, antiwear and extreme pressure properties of lubricants have been studied respectively with a Stribeck machine and a four-ball machine. We have noted the following: On the four-ball machine, extreme pressure results expressed in terms of pressure wear index and mean hertz load show that the higher performance is obtained with the vegetable oils. Extreme pressure results expressed in terms of weld load, do not show a big difference between the tested oils. Antiwear results expressed in terms of wear scar show that die highest performances are obtained with vegetable oils. On the Stribeck machine, oiliness results expressed in terms of friction coefficient indicate that: in the regime of fluid lubrication, tested oils have me same behaviour; in die boundary lubrication regime, both vegetable oils and synthetic, ester have a better response uian mineral oil. [less ▲] Detailed reference viewed: 15 (2 ULg)Caractérisation du frottement sous forte accélération et forte charge; Bozet, Jean-Luc ; in Actes des Journees internationales francophones de la Societe Tribologique de France (1995), 1 Detailed reference viewed: 13 (0 ULg)Influences physico-chimiques sur le comportement tribologique des résines polyimides; Bozet, Jean-Luc in Matériaux et Techniques (1995), (n° 5-6,), 43-48 Physical and chemical properties vary with temperature. In a sliding contact between a pair of materials, high speeds can provoke a rise of the temperature of these materials due to the heat produced by ... [more ▼] Physical and chemical properties vary with temperature. In a sliding contact between a pair of materials, high speeds can provoke a rise of the temperature of these materials due to the heat produced by friction. Consequently, the increase of temperature can modify physical and chemical properties affecting their tribological behaviour. Tribological tests performed on polyimide resins sliding against austenitic stainless steel indicate that there is a friction transition which is temperature dependent. A wear transition accompanying the friction transition was not observed. The tests were performed during a research campaign developed in order to investigate the behaviour of some pairs of materials which can be used in a tightness or a bearing function for valves in aerospace applications. [less ▲] Detailed reference viewed: 7 (0 ULg)Développement d'un boîtier d'essai dédié à l'expérimentation d'un roulement à billes noyé dans l'oxygène liquideBozet, Jean-Luc ; Germain, Albert ; in Mécanique Industrielle et Matériaux (1994, December), 47(5), 463-467 Les roulements à billes de la turbopompe alimentant un moteur fusée cryotechnique en oxygène liquide sont des organes mécaniques dont la définition est délicate. Pour le compte de l'Agence Spatiale ... [more ▼] Les roulements à billes de la turbopompe alimentant un moteur fusée cryotechnique en oxygène liquide sont des organes mécaniques dont la définition est délicate. Pour le compte de l'Agence Spatiale Européenne (E.S.A.), sous la responsabilité de la Société Européenne de Propulsion (S.E.P.) et la maîtrise d'œuvre du Centre National d'Etudes Spatiales (C.N.ES.-France), un programme de caractérisation expérimentale du fonctionnement de ces roulements a conduit une association de plusieurs laboratoires de l'Université de Liège à réaliser un banc d'essai spécifique. Grâce à la pneumatique, le concept mécanique retenu permet de solliciter le roulement à éprouver par des charges radiales et/ou axiales variables en cours d'essai. Ce concept mécanique, la nature et la régulation des fluides nécessaires au bon fonctionnement du banc, la conduite informatique d'un essai ainsi que la mesure des paramètres physiques utiles à la quantification des performances du roulement noyé dans l'oxygène liquide font l'objet de développements ci-après. Parmi ces paramètres physiques, on dénombre la température de la bague intérieure du roulement. Cette température s'avère décisive pour détecter rapidement les signes précurseurs de la dégradation du roulement soumis à des conditions précises de charges, de débit d'oxygène liquide sous pression et de vitesse de rotation. [less ▲] Detailed reference viewed: 18 (2 ULg)Analyse surfométrique de phénomènes tribologiques : dégradation des surfaces fonctionnellesBozet, Jean-Luc ; Scientific conference (1994, November) Detailed reference viewed: 3 (0 ULg)La tribologie, une spécialité liégeoiseBozet, Jean-Luc in Athena (1994), 97 Detailed reference viewed: 10 (1 ULg)The regularity of the friction coefficient : different means of characterizationBozet, Jean-Luc ; in Proc. 6th International Congress on Tribology (1994), 5 Detailed reference viewed: 3 (0 ULg)Numerical solutions on non steady-state conditions of lubrication in internal combustion engine bearing; Bozet, Jean-Luc in Proc. 6th International Congress on Tribology (1994), 4 Detailed reference viewed: 3 (0 ULg)Influence de la force centrifuge sur la tenue mécanique des éléments d'un roulement à billes à gorges profondesBozet, Jean-Luc Conference (1994) Detailed reference viewed: 5 (0 ULg)Tests de capacité de charge des roulements ayant subi des traitements de surfaceBozet, Jean-Luc Scientific conference (1993) Detailed reference viewed: 4 (0 ULg)Tribological behaviour of fluorinated and polyimide resins sliding against a metallic surface in liquid nitrogenBozet, Jean-Luc ; in Proc. 5th European Space Mechanisms and Tribology Symposium (1993) In a cryogenic fluid, the sliding of polymers over a metallic surface is governed by adhesion more than by deformation phenomena. Polyimide resins and fluorinated resins submerged into a cryogenic fluid ... [more ▼] In a cryogenic fluid, the sliding of polymers over a metallic surface is governed by adhesion more than by deformation phenomena. Polyimide resins and fluorinated resins submerged into a cryogenic fluid exhibit a noticeable increase of hardness which induces a decrease of the friction coefficient and of the wear rate compared to a sliding process performed in ambient air. The decrease of wear and friction coefficient is linked to adhesive and deformation phenomena. For fluorinated resins a cold flow is observed. This behavior is illustrated and quantified from test results. Polychlorotrifluorethylene and polyimide resins are characterized. [less ▲] Detailed reference viewed: 26 (0 ULg)TYPE OF WEAR FOR THE PAIR TI6A14V/PCTFE IN AMBIENT AIR AND IN LIQUID-NITROGENBozet, Jean-Luc in Wear (1993), 162(Part B), 1025-1028 In the development of large, high pressure valves for cryotechnic rocket engines, the Tribology Department of the University of Liege had the opportunity to evaluate the pair Ti6Al4V ... [more ▼] In the development of large, high pressure valves for cryotechnic rocket engines, the Tribology Department of the University of Liege had the opportunity to evaluate the pair Ti6Al4V/polychlorotrifluoroethylene (PCTFE) on a pin-on-disk tribometer in ambient air and liquid nitrogen with the contact pressure and sliding speed ranging, respectively, from 3 to 9 MPa and 0.03 to 0.05 m s-1. Because of the affinity of titanium for halogen elements, such as chlorine and fluorine, which are both present in PCTFE, we noticed the formation of an abrasive compound made of chlorine, fluorine, titanium and aluminium. These elements were detected by electron microscopy. In both environments the heat produced during sliding is responsible for the decomposition of the PCTFE. The surface of the polymer is softened by the heat and embedded abrasive particles then scratch the sliding track of the Ti6Al4V disk. This abrasiveness is confirmed with a three-dimensional stylus profilometer used on the Ti6Al4V disks. The low temperature and neutrality of liquid nitrogen hardly inhibit the decomposition of the polymer. This is related to the poor thermal conductivity of both titanium and PCTFE: the heat produced at the contact is fully available for the chemical reaction between the chlorine, fluorine and titanium, all the more so since this reaction requires little energy to take place. A better understanding of the wear behaviour of the pair PCTFE/Ti6Al4V in both air and liquid nitrogen should lead to the development of a surface treatment which prevents the formation of abrasive particles. We could then use titanium alloys as bulk materials for sliding parts in cryogenic valves and, because of the low specific mass of titanium, could benefit from the subsequent weight reduction. [less ▲] Detailed reference viewed: 11 (0 ULg) Comportement à grande vitesse des roulements à billes à gorges profondes chargés radialementDebongnie, Jean-François ; Bozet, Jean-Luc Conference (1993) Première étape d'une étude du comportement des roulements à billes à grande vitesse. Detailed reference viewed: 66 (10 ULg)Essai tribologiques : utilités et limites; La maîtrise du frottement secBozet, Jean-Luc in European Journal of Mechanical Engineering = Revue Européenne de mécanique = Europees Tijdschrift voor Mechanica (1992), 36(3), 87-194 Detailed reference viewed: 11 (0 ULg)Utilisation des fichiers de mesure d'état de surface 3D par un logiciel d'analyse d'imagesBozet, Jean-Luc ; Pirard, Eric Scientific conference (1992) Detailed reference viewed: 5 (1 ULg)La tribologie et ses applications spatialesBozet, Jean-Luc Scientific conference (1991) Detailed reference viewed: 6 (0 ULg)Tribological problems related to cryotechnic valves of the VULCAIN Engine; ; Bozet, Jean-Luc in 1er colloque Matériaux Vulcain (1990) Detailed reference viewed: 26 (0 ULg)
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