Couplage non-intrusif: réanalyse locale et calcul haute performance

Le couplage non-intrusif permet de prendre en compte efficacement des modifications locales (non-linéarités, conditions limites, géométrie) dans un modèle initial linéaire pré-existant sans que ce dernier ne soit affecté. Ce concept est étendu au cas des non-linéarités apparaissant de manière généralisée à l’échelle globale. Dans ce cas un ensemble de patchs recouvre l’intégralité du domaine, et le couplage peut être assimilé à une méthode de décomposition de domaine non-linéaire s’appuyant sur un logiciel industriel séquentiel

Local enrichment of NURBS patches using a non-intrusive coupling strategy: Geometric details, local refinement, inclusion, fracture

International audienceIn this work, we apply a non-intrusive global/local coupling strategy for the modelling of local phenomena in a NURBS patch. The idea is to consider the NURBS patch to be enriched as the global model. This results in a simple, flexible strategy: first, the global NURBS patch remains unchanged, which completely eliminates the need for costly re-parametrization procedures (even if the local domain is expected to evolve); then, easy merging of a linear NURBS code with any other existing robust codes suitable for the modelling of complex local behaviour is possible. The price to pay is the number of iterations of the non-intrusive solver but we show that this can be strongly reduced by means of acceleration techniques. The main development for NURBS is to be able to handle non-conforming geometries. Only slight changes in the implementation process, including the setting up of suitable quadrature rules for the evaluation of the interface reaction forces, are made in response to this issue. A range of numerical examples in two-dimensional linear elasticity are given to demonstrate the performance of the proposed methodology and its significant potential to treat any case of local enrichment in a NURBS patch simply

Non-Intrusive model coupling: A flexible way to handle local geometric and mechanical details in FEA

Computer Aided Engineering (CAE) often involves structural mechanics analysis (most of the time using the finite element method). When dealing with nonlinear complex models on large 3D structures, the computational cost becomes prohibitive. In this paper, we present the recent developments linked to an innovative computing method: non-intrusive coupling. Such a method allows to efficiently taking into account local modifications on an initial existing model in a non-intrusive way: the previously computed analysis is left unchanged. Large scale linear models can thus be easily computed, then localised nonlinear complex models can be used to pinpoint the analysis where required on the structure. After a presentation of the scientific context and a description of non-intrusive coupling methods, we will present its application to crack growth simulation and parallel structure analysis

Local/global non-intrusive parallel coupling for large scale mechanical analysis

The permanent increase in available computing resources can achieve more and more ambitious numerical simulations (most of the time using the finite element method). When dealing with non-linear complex models on large 3D structures, the computational cost becomes prohibitive. In this paper, we present the recent developments linked to an innovative computing method: non-intrusive coupling. Such a method allows to efficiently take into account local modifiations on an initial existing model in a non-intrusive way: the previously computed analysis is left unchanged. Large scale linear models can thus be easily computed, then localised non-linear complex models can be used to pinpoint the analysis where required on the structure. After a presentation of the scientific context and a description of non-intrusive coupling methods, we will present its application to crack growth simulation and parallel structure analysis

3D digital image correlation applied to birdstrike tests

The development of new bird strike shielding materials for commercial aircrafts requires test campaigns. During these tests, measurement of the high speed deformation is needed to characterize and compare the mechanical response of the shielding samples and to correlate numerical simulations with experiments. In this work, 3D digital image correlation method is used with high speed (HSP) cameras to compute the displacement and strain fields on a large area (approximately 400mm wide) of the back side of impacted samples. Compromise on spatial resolution, frame rate of HSP camera and measurement error is discussed

Validation and Modeling of Aeronautical Composite Structures Subjected to Combined Loadings: the VERTEX Project. Part 1: Experimental Setup, FE-DIC Instrumentation and Procedures

The development and certification of aeronautical composite structures is still largely based on the pyramid of tests. This approach is extremely costly in terms of number of tests and design loops. Moreover, this is made up of uniaxial tests whereas the real structures are mostly subjected to combined forces. The aim of the collaborative research program "VERTEX" is to make progress towards Predictive Virtual Testing and to significantly reduce the development costs of aeronautical and space programs. In this first part, the specific methodology for multiaxial tests of aeronautical structures is presented. The concept of technical specimen and their size are justified. Then, the development of a specific test device is presented. Compression / traction, shear, internal pressure and any combination are possible. Since structural tests were complex to be instrumented, a specific method of field measurement was developed. It is based on multi-camera instrumentation and an original approach named Finite Element Stereo Digital Image Correlation (FE-SDIC). A mechanical regularization with the use of Finite Element (FE) of the optical field measurements allows to calculate the translation or rotation displacement field. Thus this measured field is used for boundary conditions of the VERTEX tests. The experimental procedure, the measurement methodologies and the calculation / test dialogue are validated on isotropic metal plates in this paper

La PGD au service de la mesure de champs cinématiques volumiques

La réponse mécanique des matériaux hétérogènes est étroitement liée à leur micro-structure. Dans cette situation, des mesures 2D peinent à fournir des informations suffisantes pour établir un lien cohérent avec les simulations (3D avec des conditions aux limites complexes à modéliser). Des essais micro-mécaniques associés à des mesures de champs sont aujourd’hui utilisés pour identifier des lois de comportement. La Corrélation d’Images Volumiques (CIV) [1] permet d’accéder à des mesures de champs de déplacement volumiques aux échelles souhaitées. Dans une approche globale de la CIV, l’utilisation de fonctions de forme éléments finis (EF) pour l’interpolation du champ de déplacement (EF-CIV) permet de plus un lien direct entre mesures et simulations, ce qui sera déterminant au stade de l’identification des paramètres constitutifs. Cependant, la large quantité de données liées à de telles mesures volumétriques (en utilisant des mailles raffinées et/ou des grandes régions d’intérêt) peut mener à un temps de calcul excessif. Pour éviter ce problème, ce travail propose d’utiliser la méthode Proper Generalized Decomposition (PGD) [2] au problème de CIV. Le champ de déplacement est alors approximé sous une forme séparée avec des produits de fonctions 1D, réduisant ainsi la complexité numérique [3]. De plus, une stratégie multigrille basée sur PGD est développée et employée pour initialiser l’algorithme. Des images synthétiques et réelles sont analysées. Les résultats montrent que la méthode proposée réduit le temps de calcul tandis qu’elle préserve les avantages d’une approche EF-CIV (incertitudes, lien essais/calculs). [1] B. Bay, T. Smith, D. Fyhrie, M. Saad, Digital volume correlation: three-dimensional strain mapping using X-ray tomography, Experimental Mechanics 39 (1999) 217–226. [2] A. Ammar, B. Mokdad, F. Chinesta, R. Keunings, A new family of solvers for some classes of multidimensional partial differential equations encountered in kinetic theory modeling of complex fluids., Journal of Non-Newtonian Fluid Mechanics 139 (2006) 153–176. [3] J.-C. Passieux, J.-N. Périé, High resolution digital image correlation using proper generalized decomposition: PGD-DIC., International Journal for Numerical Methods in Engineering 92 (2012) 531–55

Validation and modeling of aeronautical composite structures subjected to combined loadings: The VERTEX project. Part 2: Load envelopes for the assessment of panels with large notches

One of the important issues in the certification of composite aeronautical structures is large notches. In this paper, tests are carried out on technological specimens and under tensile, shear stresses and combined loadings using the VERTEX means presented in the first part of this publication. Strong interactions between postbuckling and propagation of cuts were observed. The FE-SDIC methodology developed specifically allows a first dialog between calculation / testing. The Discrete Ply Modeling method is able to compute the onset of failure of such complex tests. New tests responses called "envelop" are proposed and realized by following a load path that allows to validate the behavior of the notched structure for certification purposes. This methodology should eventually lead to a new vision of the tests pyramid by "Predictive Virtual Testing"

Residual error based adaptive mesh refinement with the non-intrusive patch algorithm

This paper deals with the introduction of mesh refinement techniques within the non-intrusive patch process. For this, an ad hoc residual based explicit error estimator is built, which is adapted to a multi-scale solution, associated with those non-intrusive mesh refinement technique. Moreover, to reduce the global cost of the process, one introduces an estimate of the convergence error of the non-intrusive algorithm, which allows to reduce the number of iterations. This method is discussed and illustrated in various numerical examples