Pierre Kerfriden, O. Allix, Pierre Gosselet,
The prediction of the quasi-static response of industrial laminate structures requires to use fine descriptions of the material, especially when debonding is involved. Even when modeled at the mesoscale, the computation of these structures results in very large numerical problems. In this paper, the exact mesoscale solution is sought using parallel iterative solvers. The LaTIn-based mixed domain decomposition method makes it very easy to handle the complex description of the structure; moreover ...
Tópico(s): Numerical methods in engineering
2009 - Springer Science+Business Media | Computational Mechanics
Maxime Blanchard, Olivier Allix, Pierre Gosselet, Geoffrey Desmeure,
The purpose of this paper is to extend the non-invasive global/local iterative coupling technique [15] to the case of large structures undergoing nonlinear time-dependent evolutions at all scales. It appears that, due to the use of legacy codes, the use of different time grids at the global and local levels is mandatory in order to reach a satisfying level of precision. In this paper two strategies are proposed and compared for elastoviscoplastic models. The questions of the precision and performance ...
Tópico(s): Vibration and Dynamic Analysis
2019 - Elsevier BV | Finite Elements in Analysis and Design
J. Hinojosa, O. Allix, Pierre‐Alain Guidault, Ph. Cresta,
The paper is focussed on the robustness of parallel computation in the case of buckling and post-buckling analyses. In the nonlinear context, domain decomposition methods are mainly used as a solver for the tangent problem solved at each iteration of a Newton–Raphson algorithm. In case of strongly nonlinear and heterogeneous problems as those encountered in buckling and post-buckling, this procedure may lead to severe difficulties regarding convergence and efficiency. The problem of convergence ...
Tópico(s): Composite Structure Analysis and Optimization
2014 - Elsevier BV | Advances in Engineering Software
Guillaume Guguin, Olivier Allix, Pierre Gosselet, Stéphane Guinard,
SUMMARY In order to simulate the mechanical behavior of large structures assembled from thin composite panels, we propose a coupling technique, which substitutes local 3D models for the global plate model in the critical zones where plate modeling is inadequate. The transition from 3D to 2D is based on stress and displacement distributions associated with Saint‐Venant problems, which are precalculated automatically for a simple 3D cell. The hybrid plate/3D model is obtained after convergence of ...
Tópico(s): Structural Analysis and Optimization
2014 - Wiley | International Journal for Numerical Methods in Engineering
Dominique Massiot, Robert J. Messinger, Sylvian Cadars, Michaël Deschamps, Valérie Montouillout, Nadia Pellerin, Emmanuel Véron, Mathieu Allix, Pierre Florian, Franck Fayon,
Unlike the long-range order of ideal crystalline structures, local order is an intrinsic characteristic of real materials and often serves as the key to the tuning of their properties and their final applications. Although researchers can easily assess local ordering using two-dimensional imaging techniques with resolution that approaches the atomic level, the diagnosis, description, and qualification of local order in three dimensions is much more challenging. Solid-state nuclear magnetic resonance ( ...
Tópico(s): Nuclear materials and radiation effects
2013 - American Chemical Society | Accounts of Chemical Research
Alberto J. Fernández–Carrión, Mathieu Allix, Pierre Florian, Matthew R. Suchomel, Ana Isabel Becerro,
High resolution synchrotron powder XRD, 89Y CPMG NMR, and 139La MAS NMR spectroscopy have been applied to eventually draw the phase diagram of the La2Si2O7–Y2Si2O7 system. The diagram presents a solid solubility region of G-(La,Y)2Si2O7, which extends to the La0.9Y1.1Si2O7 composition at any temperature of this study. Compositions richer in Y show two-phase domains, with G + α at T < 1450 °C and G + δ at T > 1450 °C. The Y-rich extreme is more complex, showing two solid solution regions of δ- and γ-(La,Y) ...
Tópico(s): Glass properties and applications
2012 - American Chemical Society | The Journal of Physical Chemistry C
Karin Saavedra, O. Allix, Pierre Gosselet,
SUMMARY This paper investigates a computational strategy for studying the interactions between multiple through‐the‐width delaminations and global or local buckling in composite laminates taking into account possible contact between the delaminated surfaces. To achieve an accurate prediction of the quasi‐static response, a very refined discretization of the structure is required, leading to the resolution of very large and highly nonlinear numerical problems. In this paper, a nonlinear finite element ...
Tópico(s): Advanced Mathematical Modeling in Engineering
2012 - Wiley | International Journal for Numerical Methods in Engineering
Luc Gendre, O. Allix, Pierre Gosselet,
Abstract This paper presents a two‐scale approximation of the Schur complement of a subdomain's stiffness matrix, obtained by combining local (i.e. element strips) and global (i.e. homogenized) contributions. This approximation is used in the context of a coupling strategy that is designed to embed local plasticity and geometric details into a small region of a large linear elastic structure; the strategy consists in creating a local model that contains the desired features of the concerned region ...
Tópico(s): Composite Structure Analysis and Optimization
2011 - Wiley | International Journal for Numerical Methods in Engineering
O. Allix, Pierre Kerfriden, Pierre Gosselet,
Abstract In quasi‐static non‐linear time‐dependent analysis, the choice of the time discretization is a complex issue. The most basic strategy consists in determining a value of the load increment that ensures the convergence of the solution with respect to time on the base of preliminary simulations. In more advanced applications, the load increments can be controlled for instance by prescribing the number of iterations of the non‐linear resolution procedure, or by using an arc‐length algorithm. ...
Tópico(s): Advanced Numerical Methods in Computational Mathematics
2010 - Wiley | International Journal for Numerical Methods in Engineering
Lionel Gendre, Olivier Allix, Pierre Gosselet, François Comte,
This paper introduces a computational strategy to solve structural problems featuring nonlinear phenomena that occur within a small area, while the rest of the structure retains a linear elastic behavior. Two finite element models are defined: a global linear model of the whole structure, and a local nonlinear "submodel" meant to replace the global model in the nonlinear area. An iterative coupling technique is then used to perform this replacement in an exact but non-intrusive way, which means the ...
Tópico(s): Advanced Numerical Methods in Computational Mathematics
2009 - Springer Science+Business Media | Computational Mechanics
Hong-Minh Nguyen, Olivier Allix, Pierre Feissel,
The motivation of the paper is to develop a method allowing us to make use, in the context of identification, of highly perturbed tests leading to non-reliable measurements. Such tests are not seldom especially when dealing with structural fracture in dynamics. We follow here the concept of the modified constitutive relation error (MCRE) [1] where error on the model and error on the experimental data are both introduced. A first paper was devoted to the extension of the MCRE method to transient elasticity [ ...
Tópico(s): Probabilistic and Robust Engineering Design
2008 - IOP Publishing | Inverse Problems
Olivier Allix, Pierre Feissel, H.M. Nguyen,
Abstract Purpose – To propose and develop an identification method of material parameters from dynamics test in the presence of extensively corrupted measurements. Design/methodology/approach – The method we propose, which is based on the use of the error in constitutive relation for identification problems in the framework of transient dynamics, leads to nonstandard wave propagation problems. For solving this numerical difficulty, we used the transition matrix method for short‐duration tests and the ...
Tópico(s): Ultrasonics and Acoustic Wave Propagation
2005 - Emerald Publishing Limited | Engineering Computations
Olivier Allix, Pierre Feissel, P. Thévenet,
This paper deals with the modeling of damage in laminates under dynamic loading. In the first part, the basic aspects of the model, which were developed in previous studies, are described. In the second part, we focus on current developments concerning the identification of the model using dynamic experiments. Since the applications are related to the design of composite crash absorbers, particular attention is given to the dissipation of energy.
Tópico(s): Structural Response to Dynamic Loads
2003 - Elsevier BV | Computers & Structures
Tópico(s): Numerical methods in engineering
1996 - Elsevier BV | Studies in applied mechanics
L. Daudeville, Olivier Allix, Pierre Ladevèze,
Delamination is a phenomenon which involves complex degradation of both layers and inter-laminar connections. To take into account these degradations, the composite laminate is modeled at a meso scale as a stacking of homogeneous layers connected by interfaces. Layers and interfaces may be damaged. Both onset of delamination and its propagation on a short distance are predicted. Two applications are presented, the numerical simulations are compared with experimental results: (i) delamination in the ...
Tópico(s): Ultrasonics and Acoustic Wave Propagation
1995 - Elsevier BV | Composites Engineering
O. Allix, Pierre Ladevèze, Alberto Corigliano,
Interlaminar fracture specimens are widely used for studying the interlaminar toughness of composite laminates. The goal of this paper is to analyse delamination specimens within the framework of a damage meso-modelling of composite laminates. In this type of modelling a laminate is described as a stacking sequence of homogeneous layers and interlaminar interfaces. The interface is assumed to be damageable in order to model the delamination phenomena. In the case of the propagation of a pre-existing ...
Tópico(s): Composite Structure Analysis and Optimization
1995 - Elsevier BV | Composite Structures
Olivier Allix, Pierre Ladevèze, Éric Vittecoq,
Tópico(s): Epoxy Resin Curing Processes
1994 - Elsevier BV | Composites Science and Technology
Olivier Allix, Pierre Ladevèze,
Delamination is a phenomenon which involves complex degradations of layers and interlaminar connections. In order to take these degradations into account, a laminate is modelled as a stacking sequence of homogeneous layers and interlaminar interfaces. The aim of this article is to focus on the interface modelling and first identification. The interface is a three-dimensional medium the thickness of which is negligible compared to the in-plane dimensions. Therefore it can be modelled as a two-dimensional ...
Tópico(s): Structural Health Monitoring Techniques
1992 - Elsevier BV | Composite Structures
Olivier Allix, Pierre Ladevèze, Daniel Gilletta, Roger Ohayon,
Abstract Damage generally refers to the more or less gradual development of micro‐voids and micro‐cracks. Damage mechanics is the modelling of these phenomena on a structural analysis scale. In this paper we first recall the non‐linear behaviour models we have developed to model composite laminates. Then we present two examples of implementations of such models in a structural analysis code in order to simulate the inner‐failure of a structure, or to study delamination initiation.
Tópico(s): Numerical methods in engineering
1989 - Wiley | International Journal for Numerical Methods in Engineering
Karin Saavedra, O. Allix, Pierre Gosselet, Jorge Hinojosa, Antoine Viard,
This paper is devoted to the study of a micro–macro LaTIn-based Domain Decomposition Method for which the partitioning, the geometry and the boundary conditions play a major role in the number of iterations to convergence and in the scalability. To confront these obstacles, an analysis of the macroscopic space and of the search direction–two parameters of the strategy–is proposed for traction, bending and buckling examples. Then, we propose a new search direction which takes into account the global ...
Tópico(s): Composite Material Mechanics
2017 - Elsevier BV | Computer Methods in Applied Mechanics and Engineering
Tuong Van Le Doan, Neil Bostrom, Alan K. Burnham, Robert Kleinberg, Andrew E. Pomerantz, Pierre Allix,
Oil shale is a petroleum source rock that has not undergone the natural processes required to convert its organic matter to oil and gas. However, oil shale kerogen can be converted artificially to liquid and gaseous hydrocarbons by pyrolysis. Heating oil shale in place (in situ) has a number of operational, economic, and environmental advantages over surface retorts, particularly when the shale is too deep to mine. This work describes experiments conducted at temperatures and pressures appropriate ...
Tópico(s): Atmospheric and Environmental Gas Dynamics
2013 - American Chemical Society | Energy & Fuels
Guillaume Guguin, Olivier Allix, Pierre Gosselet, Stéphane Guinard,
Most large engineering structures are described as assemblies of plates and shells and they are computed as such using adhoc Finite Element packages. In fact their computation in 3D would be much too costly. In this framework, the connections between the parts are often modeled by means of simplified tying models. In order to improve the reliability of such simulations, we propose to apply a non-intrusive technique so as to virtually substitute the simplified connectors by a precise 3D nonlinear ...
Tópico(s): Railway Engineering and Dynamics
2016 - Springer Science+Business Media | Advanced Modeling and Simulation in Engineering Sciences
Olivier Allix, Pierre Ladevèze,
Tópico(s): Composite Structure Analysis and Optimization
1992 - Polish Scientific Publishers PWN | Archives of Mechanics
Stacy Reeder, Robert Kleinberg, Badarinadh Vissapragada, M.L. Machlus, Michael Herron, Alan K. Burnham, Pierre Allix,
Tópico(s): Reservoir Engineering and Simulation Methods
2013 - | Petrophysics – The SPWLA Journal of Formation Evaluation and Reservoir Description
Maxence Wangermez, Olivier Allix, Pierre‐Alain Guidault, Oana Ciobanu, Christian Rey,
This paper proposes a coupling strategy between a homogeneous macroscopic description of a structure and a description at a lower scale of some local details. In order to facilitate its implementation in industrial software, an interface coupling technique using a separation between micro and macro quantities of the unknowns is proposed. The approach leads to local solutions equivalent to those that would be obtained by second-order homogenization techniques. Its interest is that it does not require ...
Tópico(s): Advanced Mathematical Modeling in Engineering
2020 - Elsevier BV | Computer Methods in Applied Mechanics and Engineering
Pierre Allix, Odile Legoux, Paul Robert,
Tópico(s): Geophysics and Gravity Measurements
1984 - EDP Sciences | BSGF – Earth Sciences Bulletin
Mathieu Allix, María D. Alba, Pierre Florian, Alberto J. Fernández–Carrión, Matthew R. Suchomel, Alberto Escudero, Emmanuelle Suard, Ana Isabel Becerro,
Although the structures of pure Sc 2 Si 2 O 7 and β-Y 2 Si 2 O 7 have been described in the literature using the C 2/ m space group, 29 Si magic angle spinning (MAS) NMR measurements of the intermediate members of the Sc 2 Si 2 O 7 –β-Y 2 Si 2 O 7 system indicate a lowering of the symmetry to the C 2 space group. Indeed, these compositions exhibit a unique Si crystallographic site and an Si—O—Si angle lower than 180°, incompatible with the C 2/ m space group. C 2 is the only possible alternative. ...
Tópico(s): Glass properties and applications
2011 - Wiley | Journal of Applied Crystallography
J. C. Gupta, O ALLIX, Pierre‐Alain Boucard, A. Fanget, Pierre‐Louis Héreil,
This paper deals with the dynamic behaviour up to fracture of a three-dimensional carbon/carbon composite (3D C/C). This study is conducted jointly by the LMT and the Centre d'Études de Gramat facilities, a research centre of the French weaponry administration. In the first part, a one and a half dimensional (1 1/2D) mesomodel dedicated to normal impact is described and used successfully. This model is build through the analysis of the one-dimensional wave propagation in the longitudinal yarns of ...
Tópico(s): Structural Response to Dynamic Loads
2004 - Elsevier BV | Composites Science and Technology
Anne‐Sophie Boureau, Béatrice Guyomarch, Pierre Gourdy, Ingrid Allix, Cédric Annweiler, Nathalie Cervantes, Guillaume Chapelet, Isabelle Delabrière, Sophie Guyonnet, Rachel Litke, Marc Paccalin, A. Penfornis, Pierre‐Jean Saulnier, Matthieu Wargny, Samy Hadjadj, Laure de Decker, Bertrand Cariou,
Abstract Background There is a lack of real‐life data regarding the frequency and predictive factors of hypoglycemia in older patients with type 2 diabetes (T2D). This study aimed to determine the frequency and predictors of hypoglycemia in older patients with insulin‐treated T2D. Methods This prospective multicenter study included 155 insulin‐treated T2D patients aged 75 years and older with ≥2 self‐monitoring of blood glucose (SMBG) daily controls. Participants underwent a geriatric and diabetic ...
Tópico(s): Hyperglycemia and glycemic control in critically ill and hospitalized patients
2023 - Wiley | Journal of the American Geriatrics Society
Olivier Allix, Michel Dommanget, Michel Gratton, Pierre‐Louis Héreil,
A method for the prediction of fracture under dynamic loading for small structures made of a 3D carbon/carbon composite is proposed. Owing to the length scale of the loading, the notion of homogenised material is meaningless and our choice then is to model, identify and compute the material at an intermediate or mesoscale (fibre-strands/matrix-blocks). The idea here is that, because of the small size of the meso scale, the previous description of the damage mechanisms should be valid even for high- ...
Tópico(s): High-Velocity Impact and Material Behavior
2001 - Elsevier BV | Composites Science and Technology