Tribology of SiC/SiC Ceramic Matrix Composites in Liquid Oxygen in Relation to the Design of Hydrostatic Bearings

in Tribotest Journal (2003), 10(2), 105-115

This paper aims with the characterization of ceramic matrix composites for bearing applications in LOX. First, compatibility tests have been performed to assume the safety and feasibility of further ... [more ▼]

This paper aims with the characterization of ceramic matrix composites for bearing applications in LOX. First, compatibility tests have been performed to assume the safety and feasibility of further research operations. Then tribology tests were made on a pin-on-disc apparatus using LOX as working environment. The measurement of friction and wear allowed a comparison between different kinds of CMC and steel 440C materials. As a logical approach, a real geometry test rig is now being built up. The design of a hybrid journal bearing has been finished and the manufacturing of the rig components started. [less ▲]

La jamais contente : analyse technique d’un record", Le véhicule électrique et hybride performant et moins polluant

Scientific conference (2002)

Modelling of friction and wear for designing cryogenic valves

in Tribology International (2001), 34(4), 207-215

From a tribological point of view, the selection of materials for seals for valves of cryogenic rocket engines is a critical issue for the designer. Due to the lack of comprehensive information on this ... [more ▼]

From a tribological point of view, the selection of materials for seals for valves of cryogenic rocket engines is a critical issue for the designer. Due to the lack of comprehensive information on this topic. data have been obtained in the framework of research programmes. In the first step, two polymers potentially usable for sealing cryogenic fluids were identified, They were submitted to general test conditions to gain some fundamental understanding of their tribological behaviour when immersed in a cryogenic fluid. This fundamental understanding proved to be helpful for an efficient technical approach. This approach with the test conditions as close as possible to those met in real valves has been used in the second step. In order to obtain the best information with the minimum number of tests, the statistical method of Doehlert has been adopted. The use of such a method led to the construction of surface response for modelling friction and wear. These surfaces and their associated equation are directly and easily usable by the designer, This way of treating technical tribological problem is illustrated by an example. (C) 2001 Elsevier Science Ltd. All rights reserved. [less ▲]

100km/h en 1899 : la voiture électrique de Jenatzy

Scientific conference (2000)

Mechanical properties of Al/Al2O3 nanolaminated films: correlation to microstructure

in Surface & Coatings Technology (2000), 125(1-3), 196-200

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate ... [more ▼]

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate temperatures: T-s= 25 degrees C and T-s= -90 degrees C. The period thickness of multilayers was lowering from 40 to 2 nm. From nanoindentation measurements, it appears that the hardness of multilayers has an intermediate value between those of metal (Al) and ceramic (Al2O3). The tribological test was conducted by the pin-on-disc method. The T-s=25 degrees C deposited multilayers, as well as single films, demonstrated poor wear resistance. The best wear resistance was obtained for multilayers deposited at the lowest substrate temperature (T-s= -90 degrees C). The results are ill good agreement with structural characterization. X-ray reflectometry demonstrated that the multilayer character of Al/Al2O3 is more pronounced for T-s= -90 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved. [less ▲]

Tribologie en oxygène liquide

in Matériaux et techniques ”, SIRPE, numéro hors série, 38èmes Journées du cercle d’études des métaux (1999, December)

Design of an axial mechanical gas seal with self-acting lift geometry

in European Journal of Mechanical and Environmental Engineering [=EJMEE] (1998), 43(no4), 195-203

Cet article étudie le comportement d'un joint mécanique sans contact à faces radiales, doté d'un dispositif d'augmentation de portance. La répartition des pressions et des vitesses dans le film mince est ... [more ▼]

Cet article étudie le comportement d'un joint mécanique sans contact à faces radiales, doté d'un dispositif d'augmentation de portance. La répartition des pressions et des vitesses dans le film mince est établie grâce à l'équation de Reynolds résolue au moyen de différences finies. L'étude paramétrique des caractéristiques du joint est ensuite réalisée en vue d'en déduire des abaques de fonctionnement et, par la suite, une démarche cohérente de choix des dimensions. L'auteur présente donc tout d'abord le fonctionnement d'un joint mécanique à gaz et il en décrit la géométrie et les conditions de travail. Après avoir défini et justifié les hypothèses utilisées, il propose une mise en équation du problème et décrit le comportement du système d'étanchéité en régime au moyen des résultats obtenus. L'article présente finalement l'influence de la géométrie du joint et propose une méthode de dimensionnement. [less ▲]

Nanoindentation and scanning force microscopy as a novel method for the characterization of tribological transfer films

in Wear (1997), 212(1), 18-24

In conventional pin-on-disk testing of the tribological characteristics of two different materials in sliding contact, the main parameters of interest are notably the friction and wear properties of the ... [more ▼]

In conventional pin-on-disk testing of the tribological characteristics of two different materials in sliding contact, the main parameters of interest are notably the friction and wear properties of the material pair. However, when two bodies consisting of hard and soft materials respectively are subjected to such testing, the appearance of a transfer film, or third body, which can be a composite mixture of the two, is often observed. Until now the characterization of transfer films in terms of their mechanical properties has been hampered by their nonhomogeneous distribution across a tested surface, their small size, low thickness and the difficulty in accurately positioning a test probe such that the film properties can be measured independently from those of the substrate. In this paper a new method is introduced, consisting of nanoindentation and scanning force microscopy (SFM), which is capable of highly localized indentation testing of a specified sample site with high resolution imaging of the area prior to and after indentation. In this way the hardness and modulus of a transfer film can be obtained, as well as valuable surface topographical information concerning the material response to the indentation. Measurements are presented for the material pair A286/polyimide after testing on a pin-on-disk tribometer in ambient air and liquid nitrogen. Distinct variations in hardness between the transfer films and their contacting bodies have een observed and correlated to the wear behaviour and testing environment. (C) 1997 Elsevier Science S.A. [less ▲]

Tribology in Aerospace Propulsion Mechanisms

in Space Scientific Research in Belgium, vol. IV : Space Technology (1996), 4

The Assessment of vegetable oils as renewable environmentally acceptable lubricants

Scientific conference (1996)