Computational Homogenization of Architectured Materials

Architectured materials involve geometrically engineered distributions of microstructural phases at a scale comparable to the scale of the component, thus calling for new models in order to determine the effective properties of materials. The present chapter aims at providing such models, in the case of mechanical properties. As a matter of fact, one engineering challenge is to predict the effective properties of such materials; computational homogenization using finite element analysis is a powerful tool to do so. Homogenized behavior of architectured materials can thus be used in large structural computations, hence enabling the dissemination of architectured materials in the industry. Furthermore, computational homogenization is the basis for computational topology optimization which will give rise to the next generation of architectured materials. This chapter covers the computational homogenization of periodic architectured materials in elasticity and plasticity, as well as the homogenization and representativity of random architectured materials

Effect of reinforcement shape on physical properties and representative volume element of particles-reinforced composites: Statistical and numerical approaches

International audienceWe are considering the effect of the particle shape on the effective elastic properties and representative volume element of two-phase composites. In this work, microstructures with ellipsoidal and spherical particles are considered. Three dimensional particles are randomly generated for different volume fractions without any contact between neighbouring spheres according to Poisson process. The used analysis is based on numerical homogenization approaches by finite element method and morphological characterization of microstructures by random fields. The effects of various parameters such as particles volume fraction, contrast in phase properties and particles shape were identified. The statistical methods are introduced and then coupled with numerical simulations. The notion of statistically representative volume, named the deterministic representative volume element (RVE), is used. The variation of this RVE as a function of particles volume fraction for heterogeneous materials is presented. These variations suggest us to identify the morphological distribution of particles which is more anisotropic and which needs a large RVE size

Random versus periodic microstructures for elasticity of fibers reinforced composites

International audienceHomogenization of effective elastic properties of fiber reinforced composites frequently supposed periodic arrangement of fibers because such microstructures allow analytical or low computational cost integrations. Hexagonal frame was often preferred than square one which is strongly anisotropic. In practical situations those periodical microstructures are not realistic. Real microstructures are often random or if they are periodic their boundaries don't fit with the periodic scheme. We studied with the help of finite elements samples that exhibit hexagonal arrangement of fibers embedded in a random distribution. Characteristic length scales of hexagonal area were extracted from observation of stress maps. Principal results are a short scale in which bulk and shear stresses become structured. On the other hand we nether reached a size large enough to observe local stress maps similar to those produced by a periodic model

Prenatal diagnosis of de novo unbalanced translocation 8p;21q using subtelomeric probes

WOS: 000241446600007PubMed ID: 17100200We report an unbalanced translocation involving chromosomes 8 and 21 in a fetus showing ultrasonographic abnormalities in the second trimester of pregnancy. A 41-year-old pregnant woman, gravida 1 para 0, was referred to the Genetics Clinic at the 16th week of gestation because of advanced maternal age and fetal pelvicaliectasis on ultrasonographic examination. Pregnancy had occurred following ICSI treatment. After genetic counseling amniocentesis was performed. Fetal karyotype analysis revealed a 46,XY,8p+ karyotype. Ultrasonographic examination was repeated at the 20(th) week of gestation and showed intrauterine growth retardation, ventriculomegaly, cerebellar structural abnormality and pelvicaliectasis. Chromosomes of both parents were normal. Molecular cytogenetic studies (FISH) using chromosome-specific subtelomere probes showed a terminal deletion of 8p and trisomy of the 21q subtelomeric region. Further analysis with Down Syndrome specific region probes revealed two signals. The couple decided to terminate the pregnancy. This is the first prenatally diagnosed case of unbalanced t(8p;21q) of de novo origin

Indications for referral of Turner's syndrome cases diagnosed prenatally

We performed a retrospective study of 17 Turner's syndrome (TS) cases who were diagnosed prenatally in our Genetic Diagnostic Centre, Alsancak-Izmir, Turkey, during the period 2000-2005. The indications for prenatal diagnosis, ultra-sonographic findings and demographic data of the mothers were evaluated from patient records. The most frequent indications for prenatal diagnostic intervention were cystic hygroma (6/17) and hydrops fetalis (4/17). Other indications were advanced maternal age, abnormal triple test [alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (Estriol)] levels in the diagnosis of Down's syndrome and fetal growth retardation. A 45,X non-mosaic karyotype (14/17) was detected in 14 of these cases, while three showed mosaicism with the following karyotypes: 45,XO/46,XX, 45,XO/46,XY and 45,XO/46,X,del (X)(q21;qter), respectively

ETUDE CO MPARATIVE ENTRE DEUX MODELES DE PROTHESES DE HANCHE

Résumé:Le but majeur de cette étude est de faire une comparaison  entre deux modèles de PTH ; la première avec une seule mobilité et la deuxième avec double mobilité et on a trouvé que le premier modèle donne le minimum de frottement par contre le deuxième modèle donne une contrainte de frottement importan

Indications for referral of Turner's syndrome cases diagnosed prenatally

We performed a retrospective study of 17 Turner's syndrome (TS) cases who were diagnosed prenatally in our Genetic Diagnostic Centre, Alsancak-Izmir, Turkey, during the period 2000-2005. The indications for prenatal diagnosis, ultra-sonographic findings and demographic data of the mothers were evaluated from patient records. The most frequent indications for prenatal diagnostic intervention were cystic hygroma (6/17) and hydrops fetalis (4/17). Other indications were advanced maternal age, abnormal triple test [alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (Estriol)] levels in the diagnosis of Down's syndrome and fetal growth retardation. A 45,X non-mosaic karyotype (14/17) was detected in 14 of these cases, while three showed mosaicism with the following karyotypes: 45,XO/46,XX, 45,XO/46,XY and 45,XO/46,X,del (X)(q21;qter), respectively