Forming Process Simulation for Fabrication Optimization in Areva Creusot Forge and Industeel

International audienceThe grain size of the austenitic stainless steel is an important issue for parts such as primary pipes in nuclear power plants and more globally for metal forming. Having tools which can predict at least the final grain size distribution for these materials is strongly required. It is in this frame that ACF worked for several years with other industrial and academic partners such as INDUSTEEL CRMC, Aubert & Duval, Ascometal, CEA Valduc and CEMEF Mines ParisTech on the simulation of the recrystallization (ReX) of 304L austenitic stainless steel. Recent developments allowed simulation in a full-field context of the static recrystallization (SRX) of 304L stainless steel including a crystal plasticity formulation in a finite element (FE) context in order to model precisely the grain deformation anisotropy. This crystal plasticity model includes a decomposition of the dislocation density in SSDs (Statistically Stored Dislocations) and GNDs (Geometrically Necessary Dislocations). Including the GNDs gave better results on the localization of the strain but also allowed to define more relevant nucleation criteria. During and after ReX, the grain growth phenomenon due to capillarity effects is also modelled. To take into account capillarity effects enables to reproduce precisely the final microstructure morphology (shape of the grains, equilibrium angles at multiple junctions...). This full-field approach gives very good results for the modelling of 304L stainless steel SRX. In parallel, at plants, forging and rolling processes need to be simulated in order to optimize fabrication sequences in terms of material distortion capability versus rheological properties of these materials and in terms of grain size with potential impact on ultrasonic inspection performance. In order to verify the process capability, a reduced ¼ scale component of 304L stainless steel primary pipes has been fabricated in a similar forging sequence. Study of the recrystallization aspect at different locations of the component was part of the objectives of the project. The paper gives a view of all combined approaches: theoretical approach by recrystallization modeling as well as simulation of forging and rolling sequences with Forge® software (coupled to a mean-field metallurgical model called Thermide) and fabrication of a reduced scale part with nozzles as a test before the fabrication of the final component

Introduction

Over a period of two centuries, Rabelais in his Pantagruel and Montesquieu in the Lettres persanes depicted the library of Saint-Victor as a world of clerics cut off from modern learning. Nevertheless, until the end of 18th century, the library remained a reference for the educated public.Recent studies of the mediaeval abbey and of Claude de Grandrue’s Catalogue have cast new light on the history of the library during its first three centuries. However, what became of its collections from the 16th century on, and its collection of printed books in particular, is still unknown. Some suggestions for future research based on documents that remain are discussed in the aim of widening the field of inquiry.À deux siècles de distance, Rabelais dans Pantagruel et Montesquieu dans les Lettres persanes ont dépeint la bibliothèque de Saint-Victor comme un monde de clercs repliés sur un savoir suranné. Pourtant, jusqu’à la fin du XVIIIe siècle, cette bibliothèque est demeurée une référence pour le public cultivé. L’historiographie du sujet montre que si le renouveau des études sur l’abbaye médiévale et les travaux autour du catalogue de Claude de Grandrue ont apporté un éclairage sur la vie de la bibliothèque au cours des trois premiers siècles de son existence, son histoire à partir du XVIe siècle, et en particulier celle de ses collections imprimées, demeure très lacunaire. Quelques pistes de réflexion sont envisagées pour élargir le champ de la recherche à partir des sources subsistantes

Laurence Mathey-Maille, Écritures du passé. Histoires des ducs de Normandie

«Comment interpréter la prétention de l’histoire quand elle construit son récit à reconstruire quelque chose du passé?». Cette question posée par Paul Ricoeur dans Temps et Récit (1985) est au cœur de la thèse de Lettres soutenue par Laurence Mathey-Maille et du livre qu’elle en a tiré. Afin d’apporter sa contribution au débat sur les rapports entre écriture et histoire, entre temps et récit, L. M.-M. a choisi comme pôle d’observation l’historiographie médiévale et plus particulièrement l’ex..

Association between urban environment and mental health in Brussels, Belgium

Background Mental health disorders appear as a growing problem in urban areas. While common mental health disorders are generally linked to demographic and socioeconomic factors, little is known about the interaction with the urban environment. With growing urbanization, more and more people are exposed to environmental stressors potentially contributing to increased stress and impairing mental health. It is therefore important to identify features of the urban environment that affect the mental health of city dwellers. The aim of this study was to define associations of combined long-term exposure to air pollution, noise, surrounding green at different scales, and building morphology with several dimensions of mental health in Brussels.MethodsResearch focuses on the inhabitants of the Brussels Capital Region older than 15years. The epidemiological study was carried out based on the linkage of data from the national health interview surveys (2008 and 2013) and specifically developed indicators describing each participant's surroundings in terms of air quality, noise, surrounding green, and building morphology. These data are based on the geographical coordinates of the participant's residence and processed using Geographical Information Systems (GIS). Mental health status was approached through several validated indicators: the Symptom Checklist-90-R subscales for depressive, anxiety and sleeping disorders and the 12-Item General Health Questionnaire for general well-being. For each mental health outcome, single and multi-exposure models were performed through multivariate logistic regressions.Results Our results suggest that traffic-related air pollution (black carbon, NO2, PM10) exposure was positively associated with higher odds of depressive disorders. No association between green surrounding, noise, building morphology and mental health could be demonstrated.Conclusions These findings have important implications because most of the Brussel's population resides in areas where particulate matters concentrations are above the World Health Organization guidelines. This suggests that policies aiming to reduce traffic related-air pollution could also reduce the burden of depressive disorders in Brussels

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure