Influences des hétérogénéité élastoplastiques sur les contraintes du deuxième ordre dans les polycristaux métalliques mono- et biphasés : calculs autocohérents - mesures par diffraction X

The aim of this work is to study influences of elastoplastic heterogeneities on microscopic stress and strain fields in one - and two phased polycrystals. Local stresses and strains are calculated owing to the self consistant scheme of cinematic integral equation linking local and global strains. Elastic strain calculations allow to show second order stresses and to simulate perfectly X-ray diffraction experiments on isotropic materials and materials with crystallographic and morphologic texture. Parallel calculations and diffraction experiments after tensile plastic déformations show that the model is able to predict residual stresses and their evolution during plastic straining, and their influences on X-ray diffraction experiments. The simple model based on the problem of an inclusion in a matrix allows to explain qualitatively the splitting of X-ray diffraction curves after surface machining in multiphased materials, and to link it to the morphology of the constituents for global homogeneous strainsCe travail propose une étude de l'influence des hétérogénéités élastoplastiques sur les champs de contraintes et déformations microscopiques dans les polycristaux mono-et biphasés. Les grandeurs locales sont calculées à l'aide de l'approximation autocohérente de l'équation intégrale cinématique reliant grandeurs locales et globales. Le calcul des déformations dans le domaine élastique permet de mettre en évidence l'origine des contraintes du deuxième ordre et de simuler de facon parfaite les courbes de mesure par diffraction des rayons X pour des matériaux isotropes et présentant des textures cristallographiques et morphologiques. Les calculs et les mesures de diffraction menés en parallèle pour des déformations plastiques en traction simple montrent que le modèle est également capable de prédire les contraintes résiduelles, leurs évolutions et leurs influences sur les courbes de diffraction. Le modèle simple de l'inclusion dans une matrice permet d'expliquer qualitativement le dédoublement des courbes de diffraction de matériaux multiphasés lié à des traitements de surface, mais également de le relier à la morphologie des constituants pour des déformations macrohomogène

Determination of elastoplastic properties of TiO2 thin films deposited on dual phase stainless steel using nanoindentation tests

International audienceIn recent years, the extraction of mechanical behaviour of thin films by nanoindentation using sharp indenter geometry has been extensively studied. This work investigates the mechanical properties of TiO2 thin film (1 µm thickness) deposited by spin coating on dual phase Duplex stainless steel and glass substrates. Experiments are carried out with different sharp triangular pyramids (a Cube corner and a Berkovich indenter) using a commercial Nano Indenter® XP apparatus. The substrate effect has been counteracted and an inverse method proposed in literature for bulk material has been adapted to assess the elastoplastic parameters of the tested thin film directly from estimation of the hardness and elastic modulus values determined experimentally. This experimental method, coupled with two dimensional finite elements modelling, allows the determination of the mechanical behaviour of the film over the Duplex steel

Finite Element Analysis and Characterization of a New Low Modulus Titanium Alloy Used in Two THA Designs

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De Novo Pathogenic Variants in N-cadherin Cause a Syndromic Neurodevelopmental Disorder with Corpus Callosum, Axon, Cardiac, Ocular, and Genital Defects

International audienceCadherins constitute a family of transmembrane proteins that mediate calcium-dependent cell-cell adhesion. The extracellular domain of cadherins consists of extracellular cadherin (EC) domains, separated by calcium binding sites. The EC interacts with other cadherin molecules in cis and in trans to mechanically hold apposing cell surfaces together. CDH2 encodes N-cadherin, whose essential roles in neural development include neuronal migration and axon pathfinding. However, CDH2 has not yet been linked to a Mendelian neurodevelopmental disorder. Here, we report de novo heterozygous pathogenic variants (seven missense, two frameshift) in CDH2 in nine individuals with a syndromic neurodevelopmental disorder characterized by global developmental delay and/or intellectual disability, variable axon pathfinding defects (corpus callosum agenesis or hypoplasia, mirror movements, Duane anomaly), and ocular, cardiac, and genital anomalies. All seven missense variants (c.1057G>A [p.Asp353Asn]; c.1789G>A [p.Asp597Asn]; c.1789G>T [p.Asp597Tyr]; c.1802A>C [p.Asn601Thr]; c.1839C>G [p.Cys613Trp]; c.1880A>G [p.Asp627Gly]; c.2027A>G [p.Tyr676Cys]) result in substitution of highly conserved residues, and six of seven cluster within EC domains 4 and 5. Four of the substitutions affect the calcium-binding site in the EC4-EC5 interdomain. We show that cells expressing these variants in the EC4-EC5 domains have a defect in cell-cell adhesion; this defect includes impaired binding in trans with N-cadherin-WT expressed on apposing cells. The two frameshift variants (c.2563_2564delCT [p.Leu855Valfs∗4]; c.2564_2567dupTGTT [p.Leu856Phefs∗5]) are predicted to lead to a truncated cytoplasmic domain. Our study demonstrates that de novo heterozygous variants in CDH2 impair the adhesive activity of N-cadherin, resulting in a multisystemic developmental disorder, that could be named ACOG syndrome (agenesis of corpus callosum, axon pathfinding, cardiac, ocular, and genital defects)