Multiscale (analytical and computational) models have been developed based on a thermodynamic variational principle (TVP) to model sintering and eventual mudcracking in thermal barrier coatings (TBCs) made using the electron beam physical vapour deposition (EB-PVD) process. It is assumed that the sintering occurs by interfacial diffusion at local contacts between columns and driven by changes in interface free energy and elastic stored energy of the coating. The models link diffusional processes at the scale of contacting feathery columns with the macroscopic deformation and sintering response. In service, the columns can come into contact and sinter together. As sintering progresses there is a build up of strain energy in the system which reduces the driving force for sintering and leads to either complete or incomplete sintering of the TBC depending on the magnitude of effective modulus (E) of the coating. By seeding the coating with initial imperfections, different types of behaviour are observed depending on the value of E and the spacing between imperfections. For compliant coatings, the response is insensitive to the presence of imperfections and the coating fully sinters. At higher values of E, strain energy is released by the development of intercolumnar cracks in the coating, which can propagate to the interface with the TGO (thermally grown oxide), deflect into the interface and propagate, leading to spallation of regions of the coating and loss of thermal protection. It is observed that cracks develop at initial imperfections in the structure. The greater the spacing between imperfections the faster the development of cracks at these locations. If a TBC contains a distribution of imperfections there is progressive formation of cracks, with the average spacing decreasing with time, after an initial incubation period. The crack density eventually saturates to a constant value, which depends on the mechanical properties of the TBC. Initially, a crack spacing, CS, in the range 1.5H ≤ CS ≤ 3H has been predicted based on trapezoidal contact models. Here H is the thickness of the coating. Crack spacing predicted using this model is consistent in the lower range of experimentally observed crack spacing. However, axisymmetric contact models predict a crack spacing, CS, in the range 4H ≤ CS ≤ 8H, which is in good agreement with experimentally observed crack spacing range 3H ≤ CS ≤ 10H reported in the literature. Compared to the trapezoidal contact models, axisymmetric contact models more accurately predict the sintering response.

L’évolution des propriétés d’adhérence dépend de la nature de l’adhésion entre le mortier et son support, mais également des conditions environnementales auxquelles l’ouvrage est exposé. Les mortiers de façade sont intrinsèquement soumis au séchage. Ce phénomène tend a priori à réduire la résistance du lien entre les matériaux par la limitation du développement de l’adhésion et par la création de contraintes de traction et de cisaillement.Ces dernières peuvent conduire à la fissuration voire à la désolidarisation du mortier.L’objectif de cette thèse est de comprendre les phénomènes initiateurs de cette fissuration et d’évaluer son impact sur l’adhérence. Le couplage entre hydratation et séchage, le dosage en éther de cellulose et la rugosité du support sont les principaux paramètres étudiés. Les dispositifs expérimentaux développés au cours de ces travaux mises en place révèlent que ces trois paramètres influencent significativement la fissuration des mortiers. Aucun lien clair n’a cependant pu être mis en évidence entre fissuration et adhérence. / The quality of adherence between a coating mortar and its substrate, such as building front wall, depends on environmental conditions. Especially, the restraint of the drying shrinkage of the mortar by the substrate usually results in tensile stresses. This could lead to cracking or even debonding. The main objective of the present PhD dissertation is to study the cracking phenomenon due to restrained drying shrinkage and its impact on the failure of the mortar/substrate system. The interaction between cement hydration and drying, the content of cellulose ether (used as chemical admixture) and the substrate roughness are the main studied parameters. For this purpose, several original experimental devices were developed. In particular, cracking was investigated with digital image correlation. The three studied parameters appeared to influence significantly the adherence and cracking. However, no clear relation between cracking and adherence could be emphasized.

Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-02-23T19:40:28Z No. of bitstreams: 0 / Made available in DSpace on 2015-02-23T19:40:28Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

La transmission sociale de comportements chez les animaux non humains fait l'objet de nombreuses recherches en psychologie ou en biologie. Dans une perspective didactique de type anthropologique, nous montrons que certains comportements chimpanzés qualifiés de culturels par les primatologues sont comparables à ce que nous qualifions d'oeuvres en didactique. A ce titre, leur transmission peut faire l'objet d'une lecture didactique. Reprenant des données recueillies en primatologie, nous proposons une analyse didactique de l'action conjointe du jeune chimpanzé et de sa mère considérés comme des sujets institutionnels, relativement à l'oeuvre "cassage de noix". Le logiciel Transana nous a permis de procéder à plusieurs types d'analyses : 1/ analyses par tranche d'âge 2/ analyses par « action / succession d'actions » 3/ mise en évidence de biographèmes. Ayant décrit ce que font, à chaque tranche âge, les jeunes primates et leur mère, nous montrons que l'âge du petit chimpanzé constitue un déterminant des formes de l'action didactique. A partir des normes révélées par l'analyse par âge, nous avons identifié des épisodes dans lesquels les petits chimpanzés sortaient de la norme et où leur rapport au cassage de noix évoluait. Nous avons alors réalisé une étude de ces épisodes en les considérant comme des biographèmes que nous avons situé dans la biographie didactique des sujets observés. Les analyses transversales de certaines actions ayant un fort effet du point de vue de l'apprentissage nous conduisent à supposer que la nature et la forme de l'action didactique est influencée par d'autres déterminants, notamment le sexe du petit et le fait que la mère soit ou non primipare. / The social transmission of non-human animal behaviors has been studied by many psychologists or biologists. Adopting the anthropological viewpoint of the comparative approaches in didactics, we study the learning of nut-craking by young chimpanzees in Taï. This behavior described as "cultural" by primatologists are comparable to what didaticians call "oeuvres". In this respect, this object can be subjected to a didactic analysis. Using the data collected by primatologists, we offer a didactic analysis of the joint action of young chimpanzees and their mother (looked upon as institutional subjects) relating to nut-craking. The Transana software we used enabled us to carry out several types of analyses : 1/ longitudinal analyses by age group ; 2/ cross-sectional analyses by « action/sequence of actions » ; 3/ the highlighting of biographemes. Having described what young primates and their mother do in the course of each age group, we demonstrate that the chimpanzees' age constitues a determinant of the form of didactic action . Our method for studying the nut-craking learning process among wild chimpanzees applies for all acculturation situations. Using the norms the age analysis revealed, we identify episods called "biographems" in which young chimpanzees we can observe that their relation to nut-cracking evolved and located those biographems within the didactic biography of the subjects we observed. Since the cross-sectional analyses of certain actions had a strong effect in terms of learning, we assume that the nature and form of didactic action is influenced by other determinants, in particular the young chimpanzee's sexe and whether the mother is primiparous or not.