Influence of roughness on ZDDP tribofilm formation in boundary lubricated fretting

Influence of initial surface topography on tribofilm formation in ZDDP lubricated contact was analysed. A small displacement fretting tests with sinusoidal motion were carried out in classical sphere/plane configuration. A range of surfaces with different initial roughness were prepared by milling and grinding processes. Tests were carried out using variable displacement method where amplitude of imposed displacement was gradually increased after every 1000 cycles from 2 to 30 µm. The surfaces after tribological tests were measured by interferometric profiler. Main findings confirm that initial roughness has a significant influence on antiwear tribofilm formation in boundary lubricated contact. Tribofilm form faster and require less energy to activate in case of rough surface obtained by milling process than in case of smooth grinded surface. However, in contact lubricated by ZDDP additive a significant transfer of material occurred from plane to sphere specimen

Aciers Hadfield obtenus par dépôt laser. Propriétés mécaniques et tribologiques

Pour de nombreuses applications dans le secteur de la mécanique, il est nécessaire de disposer de matériaux combinant des propriétés mécaniques intéressantes et des résistances à l’usure élevées. Ceci n’est généralement possible que grâce à des traitements superficiels adaptés, en particulier grâce à la réalisation de dépôts possédant une composition et une microstructure appropriées. L’utilisation des lasers de puissance est l’une des méthodes possibles pour une telle réalisation. Si les revêtements de type céramique ou composites à matrice métallique sont des candidats intéressants dans certains cas, leur faible aptitude à la déformation plastique en limite l’usage. Dans la présente étude, des revêtements métalliques Fe-Mn-C (acier Hadfield) sont obtenus par injection de poudre sous faisceau laser, puis caractérisés, tant d’un point de vue microstructural que mécanique et tribologique.Directement après dépôt, les revêtements Hadfield sont sains, fortement adhérents au substrat (liaison de type métallurgique) et de structure austénitique; ils présentent des caractéristiques mécaniques assez bonnes : dureté : 350 HV, limite d’élasticité: σE = 1200 MPa, module de Young : E = 210 GPa. Mais l’intérêt principal réside :- d’une part dans le fait qu’ils sont très ductiles (des déformations relatives supérieures à 80% sont réalisables sans dommages importants) et que cette déformation plastique s’accompagne d’un phénomène de durcissement considérable (des duretés Vickers de l’ordre de 800 HV sont mesurées),- d’autre part dans le caractère réduit et différé de l’usure observée lors des essais d’usure induite par petits débattements (“fretting”), que les essais soient réalisés dans le domaine élastique ou dans le domaine plastique.Une expertise métallurgique permet d’attribuer ce comportement à la formation de macles dans un domaine donné de déformation

Outsiderness, Social Class, and Votes in the 2014 European Elections

Votes have for a long time been considered to be structured by class conflict. However, in the 2014 European elections, vote does not seem to be significantly structured by traditional class. Instead, contemporary European societies face the melting down of the traditional working class and an increasing dualism between labour market “insiders” and “outsiders”. How do these socio-economic changes translate into politics? Building on the emerging literature on outsiderness and a survey conducted after the European elections of 2014, this article shows that traditional class divides have a limited electoral impact and that the insider-outsider divide tends to have only “negative” effects, decreasing voting turnout as well as support for the major right wing parties. The best predictor of voting behaviour is the subjective assessment by the respondents of their social position and its upward or downward trajectory.Les votes ont longtemps été considérés comme structurés par les conflits de classe. Toutefois, lors des élections européennes de 2014, le vote ne semble pas significativement structuré par les classes sociales. Les sociétés post-industrielles sont au contraire confrontées au déclin de la classe ouvrière traditionnelle et au dualisme croissant sur le marché du travail entre individus protégés (insiders) et individus exposés (outsiders). Comment ces changements socio-économiques se traduisent-ils dans le champ politique ? À partir de la littérature émergente sur la précarité et des données d’un sondage conduit après les élections européennes de 2014, cet article montre que les clivages de classe traditionnels ont un impact limité sur les comportements électoraux et que la distinction entre insiders et outsiders a surtout des effets négatifs, accroissant l’abstention et diminuant le soutien aux grands partis de droite. Le meilleur facteur explicatif des votes est l’évaluation subjective par les répondants de leur position sociale et de sa trajectoire ascendante ou descendante

Outsiderness, Social Class, and Votes in the 2014 European Elections

Votes have for a long time been considered to be structured by class conflict. However, in the 2014 European elections, vote does not seem to be significantly structured by traditional class. Instead, contemporary European societies face the melting down of the traditional working class and an increasing dualism between labour market “insiders” and “outsiders”. How do these socio-economic changes translate into politics? Building on the emerging literature on outsiderness and a survey conducted after the European elections of 2014, this article shows that traditional class divides have a limited electoral impact and that the insider-outsider divide tends to have only “negative” effects, decreasing voting turnout as well as support for the major right wing parties. The best predictor of voting behaviour is the subjective assessment by the respondents of their social position and its upward or downward trajectory.Les votes ont longtemps été considérés comme structurés par les conflits de classe. Toutefois, lors des élections européennes de 2014, le vote ne semble pas significativement structuré par les classes sociales. Les sociétés post-industrielles sont au contraire confrontées au déclin de la classe ouvrière traditionnelle et au dualisme croissant sur le marché du travail entre individus protégés (insiders) et individus exposés (outsiders). Comment ces changements socio-économiques se traduisent-ils dans le champ politique ? À partir de la littérature émergente sur la précarité et des données d’un sondage conduit après les élections européennes de 2014, cet article montre que les clivages de classe traditionnels ont un impact limité sur les comportements électoraux et que la distinction entre insiders et outsiders a surtout des effets négatifs, accroissant l’abstention et diminuant le soutien aux grands partis de droite. Le meilleur facteur explicatif des votes est l’évaluation subjective par les répondants de leur position sociale et de sa trajectoire ascendante ou descendante

Living through Lockdown: Social Inequalities and Transformations during the COVID-19 Crisis in France

This working paper offers an overview of the first stage of the Coping with Covid (CoCo) project, which tracks the behaviors and attitudes of a representative panel of the French metropolitan population during the COVID-19 lockdown. We conducted five survey waves and administered daily journals of open-ended responses between April and June 2020 among a sample of 1,216 people from a pre-existing panel (ELIPSS). Earlier surveys of this sample allowed us to better contextualize changes that may have occurred during this unusual period. We outline four experiential dimensions during the lockdown period: relation to work, everyday activities and time use, self-assessed health and well-being, and the framing of the pandemic crisis. What we found follows traditional inequality patterns and also reveals some unexpected changes in social practices and attitudes

La France confinée: Anciennes et nouvelles inégalités

This chapter offers an overview of the first stage of the Coping with Covid (CoCo) project, which tracks the behaviors and attitudes of a representative panel of the French metropolitan population during the COVID-19 lockdown. We conducted five survey waves and administered daily journals of open-ended responses between April and June 2020 among a sample of 1,216 people from a pre-existing panel (ELIPSS). Earlier surveys of this sample allowed us to better contextualize changes that may have occurred during this unusual period. We outline four experiential dimensions during the lockdown period: relation to work, everyday activities and time use, self-assessed health and well-being, and the framing of the pandemic crisis. What we found follows traditional inequality patterns and also reveals some unexpected changes in social practices and attitudes

Fretting wear response of a nitrided 316L SS/304L SS interface: Effect of lithium/bore liquid environment

International audienceIn nuclear power plants (NPP), rod cluster control assembly (RCCA) tubes undergo impact under low-pressure contact against guides, leading to specific wear on the contact surfaces. To focus on this industrial issue, an experimental layout was designed to perform reciprocating fretting in different environments.A representative tube interface (nitrided AISI 316L)/plane (AISI 304L) was investigated in air and in a solution composed of 1000 ppm of bore and 130 ppm of lithium to be closed to a NPP primary water chemistry at atmospheric pressure and room temperature. Wear regimes were identified in terms of variation in parameters such as sliding amplitude (from ± 40 μm to ± 160 μm), normal loads (from 2 N/mm to 5 N/mm) and test duration (from 100,000 to 1.5 million cycles).Surface damage evolution was followed by 3D profilometry and several analyses (SEM, EDX, optical observation) were conducted on surfaces and cross-sections. Based on these results, fretting-wear mechanisms in the 304L SS plate and nitrided 316L SS tube were investigated. The first results in dry environment showed that, for δg⁎ ± 120 μm there was a U-shape. Thus, a W-shape morphology parameter Mw was defined, taking into account the third-body wear volume. Moreover, the worn surfaces of the plane were smoother in solution, and wear was no longer detected on the tube specimens. A modified energy wear approach was then implemented to quantify reciprocating fretting wear rate according to ambient conditions. Finally, two wear mechanisms are proposed