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Simulation of low energy impacts on composite structures is a key feature in aeronautics. Unfortunately they are very expensive: on the one side, the structures of interest have large dimensions and need fine volumic meshes (at least locally) in order to capture damages. On the other side small time steps are required to ensure the explicit algorithms stability which are commonly used in these kind of simulations [4]. Implicit algorithms are in fact rarely used in this situation because of the roughness of the solutions that leads to prohibitive expensive time steps or even to non convergence of Newtonlike iterative processes. It is also observed that rough phenomenons are localized in space and time (near the impacted zone). It may therefore be advantageous to adopt a multiscale space/time approach by splitting the structure into several substructures owning there own space/time discretization and their own integration schemes. The purpose of this decomposition is to take advantage of the specificities of both algorithms families: explicit scheme focuses on rough areas while smoother (actually linear) parts of the solutions are computed with larger time steps with an implicit scheme. We propose here an implementation of the Gravouil-Combescure method (GC) [1] by the mean of low intrusive coupling between the implicit finite element analysis (FEA) code Z-set and the explicit FEA code Europlexus. Simulations of low energy impacts on composite stiffened panels are presented. It is shown on this application that time step ratios up to 5000 can be reached. However, computations related to the explicit domain still remain a bottleneck in terms of cpu time.

L'observation des sports de nature : quelles méthodes, quels outils, quels résultats ? Actes du colloque du 29 au « à novembre 2001. Valence. Réseau des chercheurs et experts en sports de nature et de montagne

International audience; The present paper aims at showing that coupling the eXtended Finite Element Method with X-ray microtomography and 3D digital image correlation provides a very promising tool to assess the 3D behaviour of arbitrary shaped cracks and to perform comparisons of “experimental” and simulated” crack shapes during propagation [1]. At first, 3D X-ray microtomography enables one to get 3D pictures of the local density of solids. Image and/or volume correlations require a random texture. Exploiting the resolution of the acquisition device available at INSA Lyon, cast-iron samples containing a fatigue crack were selected to provide adequate (random) markers. The graphite nodules provide a random texture in the images (Fig. 1). A testing machine inside the tomograph allows for taking 3D pictures of the specimen during a tensile test. The crack is visible on the deformed picture of the specimen, see Fig. 1