Comptes Rendus Mecanique最新文献

{"title":"Physico-chemical approach of polymer chemical ageing: a short review","authors":"E. Richaud","doi":"10.5802/crmeca.64","DOIUrl":"https://doi.org/10.5802/crmeca.64","url":null,"abstract":"Polymers are known to degrade in their use conditions, with the risk that their properties reach unacceptable level. This paper reviews the modeling of modifications occurring at molecular and architectural changes occurring during their chemical ageing, with the aim of predicting the physical (mechanical) properties, all values being linked by structure properties relationships.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"27 1","pages":"1-11"},"PeriodicalIF":0.8,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87977224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification methodology of a rate-sensitive constitutive law with mean field and full field modeling approaches for polycrystalline materials","authors":"Y. Charles, Chun-Lei Zhang, M. Gaspérini, B. Bacroix","doi":"10.5802/crmeca.56","DOIUrl":"https://doi.org/10.5802/crmeca.56","url":null,"abstract":"The present paper deals with the consideration of the rate-sensitivity mechanical behavior of metallic materials, in the framework of mean field and full field homogenization approaches. We re-examine the possibility of describing properly this rate sensitivity with a simple and widely used power law expressed at the level of the slip system, and we propose a methodology to accelerate the identification of the global material constitutive law for Finite Element (FE) simulations. For such an aim, simulations of a tensile test are conducted, using a simple homogenization model (the Taylor one, used in a relaxed constraint form) and an FE code (Abaqus), both using the same single-crystal rate-dependent constitutive law. It is shown that, provided that the identification of this law is performed with care and well adapted to the examined case (rate-sensitive or insensitive materials, static and/or dynamic ranges), the simple power law can be used to simulate the macroscopic behavior of polycrystalline aggregates in a wide range of strain rate (including both static and dynamic regimes) and strain-rate sensitivity values (up the rate-insensitive limit).","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"200 1","pages":"1-20"},"PeriodicalIF":0.8,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72837147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polycrystal thermo-elasticity revisited: theory and applications","authors":"C. Tomé, R. Lebensohn","doi":"10.5802/crmeca.18","DOIUrl":"https://doi.org/10.5802/crmeca.18","url":null,"abstract":"The self-consistent (SC) theory is the most commonly used mean-field homogenization method to estimate the mechanical response behavior of polycrystals based on the knowledge of the properties and orientation distribution of constituent single-crystal grains. The original elastic SC method can be extended to thermo-elasticity by adding a stress-free strain to an elastic constitutive relation that expresses stress as a linear function of strain. With the addition of this independent term, the problem remains linear. Although the thermo-elastic self-consistent (TESC) model has important theoretical implications for the development of self-consistent homogenization of non-linear polycrystals, in this paper, we focus on TESC applications to actual thermo-elastic problems involving non-cubic (i.e. thermally anisotropic) materials. To achieve this aim, we provide a thorough description of the TESC theory, which is followed by illustrative examples involving cooling of polycrystalline non-cubic metals. The TESC model allows studying the effect of crystallographic texture and single-crystal elastic and thermal anisotropy on the effective thermo-elastic response of the aggregate and on the internal stresses that develop at the local level.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"42 1","pages":"1-15"},"PeriodicalIF":0.8,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84718259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient simulation of single and poly-crystal plasticity based on the pencil glide mechanism","authors":"L. T. Le, K. Ammar, S. Forest","doi":"10.5802/crmeca.44","DOIUrl":"https://doi.org/10.5802/crmeca.44","url":null,"abstract":"The present work demonstrates that the pencil glide mechanism is a physically reliable and a computationally efficient model to simulate the nonlinear behaviour of b.c.c. single and polycrystals. For that purpose, the pencil glide extension of Schmid’s criterion used by Gilormini [1] is incorporated in a single crystal model and in a homogenized polycrystal model accounting for large elastoviscoplastic deformations. The response of the pencil glide model in terms of stress-strain curves and lattice rotation is compared to the prediction based on the consideration of all ({110}〈111〉+ {112}〈111〉) slip systems. In the case of α-iron single crystals both approaches are shown to accurately reproduce recent experimental results [2, 3]. The comparison is extended to α-iron polycrystals behaviour under tension, compression, rolling and simple shear loading conditions. The evolution of crystallographic textures obtained either based on pencil glide or using the 24 slip systems is analyzed and compared to classical experimental results from the literature. Limitations of the approach, especially in the case of simple shear textures, are also pointed out. The pencil glide approach can be viewed as a reduced order model enhancing computational efficiency of crystal plasticity simulations involving many slip mechanisms.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"85 1","pages":"1-30"},"PeriodicalIF":0.8,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84129049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphogenesis through elastic phase separation in a pneumatic surface","authors":"Emmanuel Si'efert, B. Roman","doi":"10.5802/crmeca.43","DOIUrl":"https://doi.org/10.5802/crmeca.43","url":null,"abstract":"We report a phenomenon of phase separation that relates in many aspects to Yves Couder's work: an inflatable architectured elastomer plate, expected to expand homogeneously in its plane, buckles instead widely out-of-plane into very complex shape when internal pressure is applied. We show that this morphogenetic pattern formation is due to a two-dimensional elastic phase separation, which induces incompatible patchy non-Euclidean reference metric.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"4 1 1","pages":"649-657"},"PeriodicalIF":0.8,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87534650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphogenetic processes: from leaves to embryos","authors":"L. Pauchard","doi":"10.5802/crmeca.33","DOIUrl":"https://doi.org/10.5802/crmeca.33","url":null,"abstract":"The present manuscript is devoted to two works related to the spontaneous formation of patterns in Nature: venation in leaves and evolution of embryos. Morphogenetic processes and growth-induced instability phenomena are modelled through analogue experiments. The organization of veins in leaves is similar to what is expected from growth in a tensorial stress field that governs the formation of fractures, while the change in the shape of embryos is related to the deformation of a shell-like membrane whose properties evolve with time. The approaches resulting from analogue experiments is a way to explore specific properties of the media at a macroscopic scale. Thus the manuscript aims to focus on the analogue experiments, their adaptability to reproduce specific patterns and the relation between both growth-induced instability and mechanical behaviour of the matter.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"40 1","pages":"637-648"},"PeriodicalIF":0.8,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74459822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Yves Couder: Putting mechanics back into the shoot apical meristem","authors":"J. Traas, O. Hamant","doi":"10.5802/crmeca.19","DOIUrl":"https://doi.org/10.5802/crmeca.19","url":null,"abstract":"In 2008, we published an article proposing that the microtubular cytoskeleton in plants use maximal tensile stress directions to guide organ growth [1]. Yves Couder was instrumental in that project. Here are some memories and prospects from this collaborative and interdisciplinary endeavor.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"168 1","pages":"679-684"},"PeriodicalIF":0.8,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84655478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the relation between apical growth, organ formation and cell wall mechanics across land plant species","authors":"A. Peaucelle","doi":"10.5802/crmeca.28","DOIUrl":"https://doi.org/10.5802/crmeca.28","url":null,"abstract":"The rapid cell growth that is associated with the formation of new lateral organs in the shoot apical meristem was linked to an increase in cell wall elasticity but not viscosity in the plant model Arabidopsis thaliana. To investigate the generality of this puzzling relationship, we explored in seven plant species, covering a wide diversity across land plants, the changes in mechanical properties of the cell walls that occur during organ formation. We show that, despite the considerable variation in cell wall composition among the species tested, a drop in cell wall stiffness systematically accompanied primordia formation. We also observed that meristem activity correlates with cell wall elasticity in three species. Thus it seems that cell wall elasticity and growth rate in the meristem are correlated across the land plants.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"215 1","pages":"685-692"},"PeriodicalIF":0.8,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79574170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shape dynamics of rotating polygons on the surface of liquid nitrogen in a Leidenfrost state","authors":"Jacob Bach, A. Duchesne, T. Bohr","doi":"10.5802/crmeca.24","DOIUrl":"https://doi.org/10.5802/crmeca.24","url":null,"abstract":"When liquid nitrogen is set into rotation in a warm pot, the surface, initially forming an axissymmetrical, toroidal shape, spontaneously re-structures into a series of rotating polygons with a diminishing number of corners, while slowing down. This spontaneous “ordering” occurs despite the violently turbulent and boiling state of the fluid. We show experimentally that these shapes are well-described as a sum of a few Fourier modes, and we present experimental results for the development of the frequencies and amplitudes of these wave-modes during the transient process. We compare our results with the theoretical results for the instabilities of a potential vortex flow and argue that the first polygon formed in the transient process should be described by this theory. The paper is dedicated to the memory of Yves Couder, colleague, friend and a life-long source of inspiration. Résumé. Dans cet article nous nous intéressons au cas d’un volume d’azote liquide en état de caléfaction mis en rotation dans un récipient cylindrique chauffé. La surface libre du liquide, initialement sous forme d’un tore axisymétrique, va se déstabiliser et se restructurer en une série de polygones tournants dont le nombre de côtés diminue à mesure que le liquide ralentit. Ce facettage apparaît spontanément alors même que le liquide connait une violente ébullition et un écoulement extrêmement turbulent. Nous démontrons expérimentalement que les formes observées peuvent être décrites par la combinaison d’un petit nombre de modes de Fourier et nous étudions l’évolution de ces modes en termes d’amplitude et de fréquence depuis le premier polygone visible jusqu’à la fin de la rotation du liquide. Nous comparons nos résultats expérimentaux avec un modèle théorique décrivant la perte de stabilité des écoulements de type vortex potentiel et nous soutenons que le premier polygone observable suite à la déstabilisation de la forme axisymétrique peut être décrit par ce modèle. Cet article est dédié à la mémoire d’Yves Couder qui fut pour nous un collègue, un ami et une intarissable source d’inspiration.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"39 1","pages":"457-473"},"PeriodicalIF":0.8,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87480046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental teaching — A tribute to Yves Couder by the example: stroboscopy and fluorescence lifetime with a fan","authors":"A. Eddi, Paul Baconnier, Matthieu Blons, Samuel Pautrel, S. Protière, E. Fort","doi":"10.5802/crmeca.39","DOIUrl":"https://doi.org/10.5802/crmeca.39","url":null,"abstract":"Yves Couder created “PhyExp” at Paris Diderot University in 80s. This undergraduate course was meant to introduce experimental physics to students through projects. This approach proved fruitful both for students and teachers and has been replicated Ecole Supérieure de Physique et Chimie Industrielles (ESPCI). As a tribute to Yves, we report here the results obtained during this course about a specific project, namely the measurement of fluorescence lifetimes using stroboscopy and a fan. We obtain quantitative measurements for both Europium and Terbium that are commonly used in fluorescent tubes and we further study the variation of the lifetime with temperature. Résumé. Durant les années 80, Yves Couder a introduit une nouvelle méthode d’enseignement à l’Université Paris Diderot à travers le module “PhyExp”. Au cours de projets expérimentaux, les étudiants découvraient des problèmes originaux de physique ainsi que les méthodes permettant d’y apporter des solutions. Ce module a été reproduit à l’Ecole Supérieure de Physique et Chimie Industrielles (ESPCI) depuis 2014. En forme d’hommage à l’approche d’Yves Couder, nous pésentons ici les résultats obtenus par un groupe d’étudiants dont le projet consistait à mesurer des temps de vie de fluorescence avec des moyens limités (un ventilateur et un spectromètre). En utilisant une méthode stroboscopique, nous avons pu obtenir des mesures quantitatives pour les raies visibles de l’Europium et du Terbium, deux éléments présents dans les tubes fluorescents. Nous avons également évalué la variation de ces temps de vie avec la température.","PeriodicalId":50997,"journal":{"name":"Comptes Rendus Mecanique","volume":"40 7","pages":"439-445"},"PeriodicalIF":0.8,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72368111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}