Identification of Local Lubrication Regimes on Textured Surfaces by 3D Roughness Curvature Radius

This paper proposes a new method of 3D roughness peaks curvature radius calculation and its application to tribological contact analysis as a characteristic signature of tribological contact. This method is introduced through the classical approach of calculation of radius of asperity in 2D. Actually, the proposed approach provides a generalization of Nowicki's method [ ], depending on horizontal lines intercepting the studied profile. Here, the basic idea consists in intercepting the rough surface by a horizontal plane and to calculate the cross section area without including “islands into islands”, i.e. the small peaks enclosed in bigger ones. Then, taking into account the maximal value of the height amplitude of the roughness included into this area, an appropriate algorithm is proposed, without requiring the classical hypothesis of derivability, which may be unstable when applied to engineering surfaces. This methodology is validated on simulated surfaces, and applied to engineering surfaces created experimentally, with a laboratory aluminium strip drawing process. The regions of the textured and lubricated specimens surface are analysed, and the results gives interesting prospects to qualitatively identify the local lubrication regimes: regions with high curvature radii correspond to severe contact (boundary/mixed lubrication regime) while regions with low curvature radii correspond to hydrodynamic lubrication regime

Récits d´insertion de jeunes et régimes de temporalité

Le texte revient sur l’analyse récemment republiée (Analyser les entretiens biographiques, Presses de Laval, 2004) d’un corpus d’entretiens de jeunes racontant leur insertion, en France, au début des années 90. Il ré-interroge ces entretiens sous l’angle des temporalités mises en œuvre dans les quatre types de discours qui sous-tendent ces récits. S’appuyant sur le concept de formes d’historicité issu de l’épistémologie de l’histoire (Kosselleck, Hartog...), il distingue quatre régimes de temporalités selon les relations des jeunes au passé, au présent et à l’avenir. Le régime utopique est de type eschatologique chez les jeunes qui dissocient totalement leur passé de galère et leur espoir de salut grâce à un Autrui puissant. Le régime passéiste est celui des récits de rêve de la petite entreprise indépendante, du métier ou de l’artisanat caractéristique du travail masculin d’hier. Le régime futuriste est celui des jeunes les plus favorisés énonçant un projet et les étapes de sa réalisation. Le régime présentiste est celui des jeunes femmes enfermées dans leurs rôles de salariées non qualifiées et sans carrière et de mères assujetties aux tâches domestiques. [Résumé éditeur

Radiometric dating (U/Th) of the lower marine terrace (Tyrrhenian, MIS 5.5) west of Nice (French Riviera). Morphological and neotectonic quantitative implications.

International audienceMeasurements of U/Th desequilibrium by mass spectrometry with a plasma source were used for the dating of shells collected on the lower marine terrace to the west of Nice. The dates obtained (131-132 ka) confirm that this terrace corresponds to the Tyrrhenian Age (M.I.S 5.5) and can be correlated with the level with Strombus bubonius located east of Nice. Thus, a profile of almost 70 kms can be restored with precision from altimetric measurements of the deposits and from sedimentological indicators of the sea-level. This profile passes from the tectonic foreland of Provence to the front of the Nice Alpine Range after skirting the Pliocene Var Basin. It thus crosses major structural limits. As expected, the deformation of the lower Tyrrhenian terrace, consists of a west-to-east uplift with two boundaries: 1/ the "Var Fault" located under the Pliocene Basin, and 2/ the border fault of the Nice Range. The restoration of the exact sea-level has enabled measurements to be taken of the vertical throws since the M.I.S. 5.5: although moderate, they are notable, especially the "Var Fault" which is located outside the Alpine zone. The Quaternary vertical displacement of this fault is due to the recent reactivation of an Oligocene normal system fault located under the Basin.Des mesures de déséquilibres U/Th par spectrométrie de masse à source plasma ont été utilisées à fins de datation sur des coquilles récoltées sur la basse terrasse marine à l'ouest de Nice. Les âges obtenues (131-132 ka) confirment que cette terrassse correspond au Tyrrhénien (stade isostopique 5.5) et peut être parfaitement corrélé avec le niveau à strombes situé à l'est de Nice. Ainsi un profil de près de 70 kms peut être reconstitué avec précision à partir de l'altimétrie des témoins intégrant des indicateurs sédimentologiques de niveau marin. Ce profil passe de l'avant-pays provençal au front de l'arc alpin de Nice après avoir longé le bassin pliocène du Var. Il franchit donc des limites structurales majeures. La déformation de la basse terrasse tyrrhénienne, comme attendu, est un soulèvement d'ouest en est avec deux seuils : 1/ l'" accident du Var " situé sous le bassin pliocène et 2/ l'accident bordure de l'arc de Nice, qui ont réjoué depuis le stade 5.5. Les rejets verticaux sont calibrés : quoique modérés ils sont notables, surtout pour l'" accident du Var " qui se situe en dehors du domaine alpin. Le rejet vertical quaternaire de cet accident est attribué à la réactivation récente d'anciennes failles normales situées sous le bassin

An Analysis of Electroplated cBN Grinding Wheel Wear and Conditioning during Creep Feed Grinding of Aeronautical Alloys

Cubic boron nitride (cBN), in addition to diamond, is one of the two superabrasives most commonly used for grinding hard materials such as ceramics or difficult-to-cut metal alloys such as nickel-based aeronautical alloys. In the manufacturing process of turbine parts, electroplated cBN wheels are commonly used under creep feed grinding (CFG) conditions for enhancing productivity. This type of wheel is used because of its chemical stability and high thermal conductivity in comparison with diamond, as it maintains its shape longer. However, these wheels only have one abrasive layer, for which wear may lead to vibration and thermal problems. The effect of wear can be partially solved through conditioning the wheel surface. Silicon carbide (SiC) stick conditioning is commonly used in the industry due to its simplicity and good results. Nevertheless, little work has been done on the understanding of this conditioning process for electroplated cBN wheels in terms of wheel topography and later wheel performance during CFG. This work is focused, firstly, on detecting the main wear type and proposing a manner for its measurement and, secondly, on analyzing the effect of the conditioning process in terms of topographical changes and power consumption during grinding before and after conditioning.The authors gratefully acknowledge the funding support received from the Spanish Ministry of Economy and Competitiveness and the FEDER operation program for funding the project "Optimizacion de procesos de acabado para componentes criticos de aerorreactores" (DPI2014-56137-C2-1-R)

Measurement of friction in a cold extrusion operation: Study by numerical simulation of four friction tests

International audienceThe measurement of friction in the industrial metal working operations is a complex problem because the friction test must impose at the tool/metal interface conditions similar to those in the industrial operations. So in the European Network VIF (Virtual Intelligent Forging), a workshop (WP3) was held to evaluate friction condition in cold forging by using numerical simulation and experimental methods. It was chosen an industrial cold extrusion operation, in which a low carbon steel bar, covered with phosphate layer and soap, was drawn, cropped and then formed by extrusion. In order to know the friction condition in this industrial extrusion operation, four kinds of friction tests, forward extrusion, double-cup extrusion, upsetting-sliding test and T-shape compression were carried out in four labs, IPU, DIMEG, LAMIH and CEMEF, respectively. In a first preliminary step we simulate the drawing and extrusion operations in order to estimate the contact conditions in extrusion along the container and the die surfaces. Then by numerical simulation we estimate the contact conditions in the friction tests and define the parameters of the tests which insure the better similarity with the industrial operation. In the next step experiments will be performed in order to compare the results of these various friction tests

Liquid lubrication in sheet metal forming at mesoscopic scale

The lubricant entrapment and escape phenomena in metal forming are studied experimentally as well as numerically. Experiments are carried out in strip reduction of aluminium sheet applying a transparent die to study the fluid flow between mesoscopic cavities. The numerical strategy is based on a weak fluid/structure coupling involving the Finite ElementMethod and analytical calculations. It allows to quantify the final shape of the lubricant pocket

Roughness Signature of Tribological Contact Calculated by a New Method of Peaks Curvature Radius Estimation on Fractal Surfaces

This paper proposes a new method of roughness peaks curvature radii calculation and its application to tribological contact analysis as characteristic signature of tribological contact. This method is introduced via the classical approach of the calculation of radius of asperity. In fact, the proposed approach provides a generalization to fractal profiles of the Nowicki's method [Nowicki B. Wear Vol.102, p.161-176, 1985] by introducing a fractal concept of curvature radii of surfaces, depending on the observation scale and also numerically depending on horizontal lines intercepted by the studied profile. It is then established the increasing of the dispersion of the measures of that lines with that of the corresponding radii and the dependence of calculated radii on the fractal dimension of the studied curve. Consequently, the notion of peak is mathematically reformulated. The efficiency of the proposed method was tested via simulations of fractal curves such as those described by Brownian motions. A new fractal function allowing the modelling of a large number of physical phenomena was also introduced, and one of the great applications developed in this paper consists in detecting the scale on which the measurement system introduces a smoothing artifact on the data measurement. New methodology is applied to analysis of tribological contact in metal forming process

Biological potential of jerusalem artichoke as a feedstock for food and pharmaceutical industries

Studies aimed to import pharmaceuticalproducts, as well as to strengthen the food security of the Republic of Belarus, are highly relevant. In this connection an universal culture of Jerusalem artichoke is of interest, the value of which is determined due to the possibility of its use in feed, food and pharmaceutical industries. The paper presents the productivity research of Jerusalem artichoke varieties with different growing seasons, the estimation of mineral composition of tubers, the content of inulin as the most valuable component of mentioned agricultural crops was determined

Miocene Depositional Systems and Hydrocarbon Resources: the Texas Coastal Plain

The Miocene Major Stratigraphic Unit (MSU) of the Texas Coastal Plain is an offlapping sedimentary sequence deposited over the continental platform constructed by Late Oligocene Frio progradation. These Miocene deposits have yielded nearly 3 billion bbl of oil and 7 trillion ft3 of gas. Correlations with mammalian and foraminifer zones indicate that the Miocene MSU and its updip equivalents, the Oakville and Lagarto Formations (Fleming Group), range in age from Early to Late Medial Miocene (22.5 to 12 m.y.a.). Downdip, the upper Heterostegina and Discorbis Zones of the Anahuac shale wedge are included as a part of the Miocene MSU. Regional subsurface study indicates division of the Miocene MSU into six principal depositional systems: the Cypress fluvial system and San Jacinto delta system, developed in the Houston Embayment; the Moulton streamplain and Indianola barrier-strandplain-lagoon system across the San Marcos Arch; and the Santa Cruz fluvial system and Rosita delta system located in the Rio Grande Embayment. Integration of regional studies of depositional systems, their facies suites, structural styles, and character of produced hydrocarbons permitted delineation of 10 hydrocarbon production-exploration plays. The play forms the basic analytical unit in characterization of hydrocarbon production histories, predictions of future discoveries, and the placement of potential resources in a geographic-stratigraphic context. The Miocene MSU lacks entirely, or contains only negligible volumes of thermally mature source rocks. Thus, all Miocene MSU hydrocarbons are exotic, having been derived either by upward migration from older formations, or by lateral, updip migration from offshore marine Miocene units. Based on three historical evaluation methods employed in this study, the Miocene MSU contains between 250 and 1360 million boe of undiscovered, conventionally producible hydrocarbons.Bureau of Economic Geolog