Combined effects of anisotropy and tension-compression asymmetry on the torsional response of AZ31 Mg

In this paper it is demonstrated that only by accounting for the combined effects of anisotropy and tension-compression asymmetry at polycrystal level, it is possible to explain and accurately predict the room-temperature torsional response of a strongly textured AZ31 Mg material. This is shown by using two modeling frameworks, namely: a viscoplastic self-consistent (VPSC) polycrystal model, and a macroscopic plasticity model based on an yield criterion, developed by Cazacu et al. (2006), that accounts for both orthotropy and tension-compression asymmetry in plastic flow. It is shown that unlike Hill's (1948) criterion, the latter macroscopic criterion quantitatively predicts the experimental results, namely: that the sample with axial direction along the rolling direction contracts, while the sample with axial direction along the normal direction elongates. Moreover, it is demonstrated that these experimentally observed axial strain effects can be quantitatively predicted with the VPSC polycrystal model, only if both slip and twinning are considered operational at single crystal level. On the other hand, if it is assumed that the plastic deformation is fully accommodated by crystallographic slip, the axial strains predicted by VPSC are very close with that predicted with Hill (1948) criterion, which largely underestimates the measured axial strain in the rolling direction, and predicts zero axial strain in the normal direction. (C) 2015 Elsevier Ltd. All rights reserved.X111513Ysciescopu

Letalitatea prin tuberculoză în imsp Spitalul Clinic Municipal de Ftiziopneumologie mun. Chişinău

Catedra Pneumoftiziologie USMF „Nicolae Testemiţanu”, Institutul de Ftiziopneumologie „Chiril Draganiuc”, IMSP SCMF, ChişinăuThe aim of the survey was to study the frequence, structure and the reasons of the deaths through tuberculosis in the PMSI MCHP Chisinau during three periods of time. The mortality through tuberculosis in the IInd and IIIrd period has increased fi ve times in comparison of the fi rst period. The lethality in the hospital has increased from 6,8% in the Ist period, till 38,2% in the second period and 55,0% in the IIIrd period. It is stated an enormous increase of the deaths through tuberculosis from 51,2%, 81,7% till 88, 5% and a decrease through other diseases (48,8%, 18,3%, 11,5%). The rate of the new reasons of dead people is 1/3 among those analysed, but the period of the hospitalization until death is the most increased one during the fi rst 10 days till one month with a tendency of increase in the II-nd and III-rd period. Scopul acestui studiu a fost studierea frecvenţei, structurii şi cauzelor deceselor prin tuberculoză în IMSP SCMF Chişinău în trei perioade de timp. Mortalitatea prin tuberculoza în perioada II şi III a crescut de 5 ori relativ cu I perioadă. Letalitatea în staţionar a crescut de la 6,8% în I perioadă, la 38,2% în a II şi 55,0% în a III perioadă. Se atestă o majorare evidentă a deceselor din contul tuberculozei de la 51,2%, 81,7% la 88,5% respectiv şi o descreş- tere prin alte boli (48,8%, 18,3%, 11,5%). Rata cazurilor noi la decedaţi constituie 1/3 din persoanele analizate, iar durata spitalizării pînă la deces este cea mai înaltă în primele 10 zile şi pînă la o lună, avînd o tendinţă de creştere în perioadele II şi III comparativ cu prima

Hardy's inequality for functions vanishing on a part of the boundary

We develop a geometric framework for Hardy's inequality on a bounded domain when the functions do vanish only on a closed portion of the boundary.Comment: 26 pages, 2 figures, includes several improvements in Sections 6-8 allowing to relax the assumptions in the main results. Final version published at http://link.springer.com/article/10.1007%2Fs11118-015-9463-

Creating Conditions for Harnessing the Potential of Transitions to Agroecology in Europe and Requirements for Policy | Création de conditions pour exploiter le potentiel des transitions vers l'agroécologie en Europe et exigences des politiques | Schaffung von Bedingungen für die Nutzung des agrarökologischen Potenzials in Europa und Anforderungen an die Politik

The European Union’s Farm-to-Fork Strategy sets out its ambitions and approach to how European’s value food sustainability, and the accompanying opportunities for improving the environment as well as the lifestyles and health of EU citizens. It identifies the role of agroecological approaches in primary production as one of the means by which these ambitions can be achieved, through new knowledge and innovations in land management and supply chains. This article concludes the Special Issue on the EU Horizon 2020 projects LIFT and UNISECO, synthesising requirements for the realisation of transitions to agroecology in Europe. It reports the key needs identified of developing human capital, partnerships, cooperation and social capital, access to data and tools, and the links between these needs and relevant EU and national level policies.Les systèmes alimentaires doivent être réorientés pour mieux prendre en compte les interactions avec l’environnement, l’économie, la santé et la société. Les transitions vers des pratiques et des systèmes agricoles agroécologiques peuvent relier les domaines de l’action publique et permettre d'atteindre des objectifs environnementaux, économiques et sociaux. Ces transitions fournissent une perspective pour examiner les politiques, les pratiques et les comportements des acteurs des systèmes agricoles et des chaînes de valeur, l’identifi cation des obstacles à l'adoption et les domaines d’action publique auxquels ils contribuent ou qui présentent des lacunes. Le développement du capital social et humain et de structures de gouvernance qui permettent les transitions vers l’agroécologie est la clé de leurs chances de succès. L’éducation et l’apprentissage tout au long de la carrière sont essentiels pour développer les connaissances et les compétences des jeunes générations de gestionnaires fonciers et d’autres acteurs des chaînes de valeur, tout au long de leur carrière. Le résultat recherché est une compréhension partagée des avantages des pratiques et des systèmes agroécologiques, créant des opportunités pour rééquilibrer les politiques vers la neutralité climatique, inverser la perte de biodiversité et renforcer les droits des citoyens. Pour concrétiser ces opportunités, les politiques et stratégies doivent être cohérentes à tous les niveaux territoriaux et systémiques, et adaptées au lieu, au système, aux personnes et aux étapes des transitions. Dans l’ensemble, elles devraient être conçus pour garantir que tous les citoyens bénéfi cient des transitions vers des systèmes agricoles agroécologiques, sur le long terme, et que personne ni aucun lieu ne soit désavantagé par les processus de changement ou les résultats escomptés.Die Lebensmittelsysteme müssen neu ausgerichtet werden, um den Wechselwirkungen zwischen der Umwelt, der Wirtschaft, der Gesundheit und der Gesellschaft stärker Rechnung zu tragen. Die Umstellung auf agrarökologische Anbaumethoden und - systeme kann die Politikbereiche miteinander verbinden und zur Erreichung ökologischer, wirtschaftlicher und sozialer Ziele beitragen. Sie bieten einen Ansatzpunkt für die Überprüfung der Politik, der Praxis und der Verhaltensweisen der Akteure in landwirtschaftlichen Systemen und Wertschöpfungsketten. Des Weiteren helfen sie bei der Ermittlung von Umsetzungsbarrieren und von Politikbereichen, zu denen sie beitragen oder in denen es Lücken gibt. Die Entwicklung von Sozial- und Humankapital sowie von Governance- Strukturen – die den Übergang zur Agrarökologie ermöglichen – sind ein wesentlicher Erfolgsfaktor. Bildung und lebenslanges Lernen sind ein zentraler Baustein, um die Kenntnisse und Fähigkeiten der jüngeren Generationen von Landwirten und Landwirtinnen und anderen Akteuren in den Wertschöpfungsketten zu entwickeln. Das angestrebte Ergebnis ist ein gemeinsames Verständnis über die Vorteile agrarökologischer Praktiken und Systeme. Dieses schafft Möglichkeiten für eine Neuausrichtung der Politik im Hinblick auf Klimaneutralität, Umkehrung des Verlusts der biologischen Vielfalt und Stärkung der Rechte der Bürger. Zur Verwirklichung der Möglichkeiten, sollten Politiken und Strategien über territoriale und Systemebenen hinweg kohärent und auf Ort, System, Menschen und Phasen des Übergangs zugeschnitten sein. Insgesamt sollten sie so konzipiert sein, dass alle Bürgerinnen und Bürger langfristig von der Umstellung auf agrarökologische Bewirtschaftungssysteme profi tieren und dass niemand oder kein Ort durch den Veränderungsprozess oder das angestrebte Ergebnis benachteiligt wird

Comparing faceted and smoothed tool surface descriptions in sheet metal forming simulation

This study deals with different tool surface description methods used in the finite element analysis of sheet metal forming processes. The description of arbitrarily-shaped tool surfaces using the traditional linear finite elements is compared with two distinct smooth surface description approaches: (i) Bézier patches obtained from the ComputerAided Design model and (ii) smoothing the finite element mesh using Nagata patches. The contact search algorithm is presented for each approach, exploiting its special features in order to ensure an accurate and efficient contact detection. The influence of the tool modelling accuracy on the numerical results is analysed using two sheet forming examples, the unconstrained cylindrical bending and the reverse deep drawing of a cylindrical cup. Smoothing the contact surfaces with Nagata patches allows creating more accurate tool models, both in terms of shape and normal vectors, when compared with the conventional linear finite element mesh. The computational efficiency is evaluated in this study through the total number of increments and the required CPU time. The mesh refinement in the faceted description approach is not effective in terms of computational efficiency due to large discontinuities in the normal vector field across facets, even when adopting fine meshes.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) via the projects PTDC/EME-TME/118420/2010 and PEst-C/EME/ UI0285/2013 and by FEDER funds through the program COMPETE – Programa Operacional Factores de Competitividade, under the project CENTRO-07-0224-FEDER-002001 (MT4MOBI). The first author is also grateful to the FCT for the PhD grant SFRH/BD/69140/2010.info:eu-repo/semantics/publishedVersio

Identification of plastic constitutive parameters at large deformations from three dimensional displacement fields

The aim of this paper is to provide a general procedure to extract the constitutive parameters of a plasticity model starting from displacement measurements and using the Virtual Fields Method. This is a classical inverse problem which has been already investigated in the literature, however several new features are developed here. First of all the procedure applies to a general three-dimensional displacement field which leads to large plastic deformations, no assumptions are made such as plane stress or plane strain although only pressure-independent plasticity is considered. Moreover the equilibrium equation is written in terms of the deviatoric stress tensor that can be directly computed from the strain field without iterations. Thanks to this, the identification routine is much faster compared to other inverse methods such as finite element updating. The proposed method can be a valid tool to study complex phenomena which involve severe plastic deformation and where the state of stress is completely triaxial, e.g. strain localization or necking occurrence. The procedure has been validated using a three dimensional displacement field obtained from a simulated experiment. The main potentialities as well as a first sensitivity study on the influence of measurement errors are illustrated

Numerical and experimental analysis of wrinkling during the cup drawing of an AA5042 aluminium alloy

The recent trend to reduce the thickness of metallic sheets used in forming processes strongly increases the likelihood of the occurrence of wrinkling. Thus, in order to obtain defect-free components, the prediction of this kind of defect becomes extremely important in the tool design and selection of process parameters. In this study, the sheet metal forming process proposed as a benchmark in the Numisheet 2014 conference is selected to analyse the influence of the tool geometry on wrinkling behaviour, as well as the reliability of the developed numerical model. The side-wall wrinkling during the deep drawing process of a cylindrical cup in AA5042 aluminium alloy is investigated through finite element simulation and experimental measurements. The material plastic anisotropy is modelled with an advanced yield criterion beyond the isotropic (von Mises) material behaviour. The results show that the shape of the wrinkles predicted by the numerical model is strongly affected by the finite element mesh used in the blank discretization. The accurate modelling of the plastic anisotropy of the aluminium alloy yields numerical results that are in good agreement with the experiments, particularly the shape and location of the wrinkles. The predicted punch force evolution is strongly influenced by the friction coefficient used in the model. Moreover, the two punch geometries provide drawn cups with different wrinkle waves, mainly differing in amplitude.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) under project PTDC/EMS-TEC/1805/2012. The first author is also grateful to the FCT for the Postdoctoral grant SFRH/BPD/101334/2014 and P.D. Barros is grateful to the FCT for the PhD Grant SFRH/BD/98545/2013info:eu-repo/semantics/publishedVersio

Modeling plastic anisotropy and strength differential effects in metallic materials

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