Publications

2019

• Fast Mesoscopic Simulation Of Grain Growth And Macroscopic Modeling
  
  • Weisz-Patrault Daniel
  • Sakout Sofia
  • Ehrlacher Alain
  , 2019. The Orientated Tessellation Updating Method (OTUM) is a fast mesoscopic model of grain growth that has been published recently for a single phased metal without diffusion or segregation of alloying elements. It is based on tessellation techniques and simple linear algebra. On this basis, some ideas to develop an upscaling strategy are broached in this work. The aim is to develop a macroscopic model of grain growth whose state variables contain for each material point the statistical descriptors of the microstructure (e.g., disorientation, grain size and shape distributions). (10.1063/5.0026505)
  DOI : 10.1063/5.0026505
• Residual Strains In Directed Energy Deposition Additive Manufacturing
  
  • Weisz-Patrault Daniel
  , 2019. Recently, a fast macroscopic and semi-analytical thermal analysis of Laser Metal Powder Directed Energy Deposition (LMPDED) has been submitted to publication. The effect of various process parameters are taken into account as well as solidi-fication and solid-state phase transitions. One of the main advantage of the proposed approach is that the model is fast enough to simulate the entire process and perform parametric studies or optimization loops. Thus, residual strains induced by temperature variations and phase transitions are easily computed. In addition, transformation induced plasticity is also investigated. Within this framework, temperature control strategies can be optimized.
• Effective Constitutive Behavior of Heterogeneous Materials Comprising Bimodular Phases
  
  • Monaldo Elisabetta
  • Brach Stella
  • Kondo Djimédo
  • Vairo Giuseppe
  , 2020, pp.595-605. In this study, the effective mechanical response of porous and composite materials comprising bimodular phases is investigated via a computational approach. Proposed numerical results, obtained via an iterative finite-element scheme, highlight that the local bimodularity leads to a macroscopic constitutive response more complex than that of local phases. By considering different strain-based conditions, coupling effects between hydrostatic and deviatoric states are highlighted. An unconventional macroscale material response, driven by perturbative effects locally induced by pores or inclusions, is revealed. Accordingly, proposed indications suggest that bimodularity features could be exploited for designing novel microstructured materials for advanced applications. (10.1007/978-3-030-41057-5_49)
  DOI : 10.1007/978-3-030-41057-5_49
• Locally Resonant Materials for Energy Harvesting at Small Scale
  
  • Moscatelli Marco
  • Comi Claudia
  • Marigo Jean-Jacques
  , 2020, pp.606-626. (10.1007/978-3-030-41057-5_50)
  DOI : 10.1007/978-3-030-41057-5_50
• MAESSTRO: A sound synthesis framework for Computer-Aided Design of piano soundboards
  
  • Elie Benjamin
  • Boutillon Xavier
  • Chabassier Juliette
  • Ege Kerem
  • Laulagnet Bernard
  • Trévisan Benjamin
  • Cotté Benjamin
  • Chauvat Nicolas
  , 2019. The design of pianos is mainly based on empirical knowledge due to the lack of a simple tool that could predict sound changes induced by changes of the geometry and/or the mechanical properties of the soundboard. We present the framework of a program for the Computer-Aided Design of piano soundboards that is intended to bridge that gap by giving piano makers a tool to synthesize tones of virtual pianos. The sound synthesis is solely based on physical models of the instrument in playing situation. The calculation of the sound is split into several modules: computation of the modal basis of the stiffened soundboard, computation of the string dynamics, simulation of the soundboard dynamics excited by the string vibration, and calculation of the sound radiation. Reference tests of sound synthesis of real pianos as well as sound synthesis of modified pianos are used to assess our main objective, namely to reflect faithfully structural modifications in the produced sound, and thus to make this tool helpful for both piano makers and researchers of the musical acoustics community.
• Fast macroscopic thermal analysis for laser metal deposition. Application to multiphase steels
  
  • Weisz-Patrault Daniel
  , 2019. Recently, a simplified macroscopic and semi-analytical thermal analysis of Laser Metal Deposition (LMD) has been submitted to publication. The model is fast enough to simulate the entire process. The proposed approach enables to compute: temperature, solidification and solid-state phase transitions kinetics. Process parameters, substrate characteristics and heat sources due to the enthalpy change during phase transitions are taken into account as well as convection due to the carrying and shielding gas. The present work exploits the proposed model to investigate the influence of some process parameters in order to determine whether complex multiphase steels (such as high strength steels) could be controllably obtained by LMD. Indeed, material properties of such steels are not only a matter of chemical composition but also and mostly a matter of phase proportions in a multiphase mixture (austenite, ferrite, pearlite, bainite and martensite). Within this framework, temperature control strategies during the process are numerically tested for a simple cylindrical geometry.
• Advanced modelling of rate-dependent anisotropic Ti-6Al-4V titanium alloy for aeronautical applications
  
  • Ruiz de Sotto Miguel
  • Longère Patrice
  • Doquet Véronique
  • Papasidero Jessica
  , 2019.
• Characterization of fracture anisotropy in clayey rocks by Digital Image Correlation
  
  • Bonnelye Audrey
  • Gharbi Hakim
  • Dimanov Alexandre
  • Bornert Michel
  • Mezni Manel
  • Hallais Simon
  • Aimedieu Patrick
  • King Andrew
  • Connil Nathalie
  , 2019.
• Characterization of mechanical anisotropy in clayey rocks by Digital Image Correlation
  
  • Bonnelye Audrey
  • Gharbi Hakim
  • Dimanov Alexandre
  • Bornert Michel
  • Aimedieu Patrick
  • King Andrew
  • Conil Nathalie
  , 2019. Clayey rocks inherently present strong bedding anisotropy, which conditions their physical and mechanical properties. We applied 2D and 3D Digital Image Correlation techniques in order to characterize the mechanical behavior of Callovo-Oxfordian clayey rocks, subjected to uniaxial unconfined compression. We specifically focused on the initiation and the development of damage at the microscale with respect to the bedding anisotropy. We used crackfree cylindrical specimens with 8 mm in diameter and 16 mm in length. Aiming to concentrate stresses and trigger controlled initiation of damage, some of the specimens were drilled in order to produce a borehole perpendicularly to their axis. The bedding of the samples was oriented at 0°, 45° or 90° to the loading direction. During the uniaxial compression the samples were monitored by either optical microscopy, or by synchrotron X-ray computed tomography. For both situations we used specific types of axial loading machines, adapted to the different observation techniques. Optical monitoring allows for fast acquisition, but the tests realized under synchrotron X-ray investigation last several hours. In this case, the sample water content was preserved as close as possible to saturation by imposing 95 % relative humidity atmosphere in the deformation apparatus. In both cases the natural material contrasts allowed to assess respectively the development of the 2D or 3D strain fields by Digital Image Correlation and to track the damage initiation and evolution. Our first observation concerns the similarity of the 2D and 3D strain patterns. We further demonstrate the development of two types of superimposed strain fields. The first one relates to the classical sample geometry and the stress concentrator borehole. But, the second one clearly reflects the sample microstructural anisotropy and its strong influence of the bedding orientation on the micro-cracking propagation geometry.
• Heat transfer in salt caverns
  
  • Bérest Pierre
  International Journal of Rock Mechanics and Mining Sciences, Pergamon and Elsevier, 2019, 120, pp.82 - 95. (10.1016/j.ijrmms.2019.06.009)
  DOI : 10.1016/j.ijrmms.2019.06.009
• Fast simulation of grain growth based on Orientated Tessellation Updating Method
  
  • Weisz-Patrault Daniel
  • Sakout Sofia
  • Ehrlacher Alain
  , 2019. This work is part of a more general idea consisting in developing a macroscopic model of grain growth whose state variables contain for each material point the statistical descriptors of the microstructure (e.g., disorientation, grain size and shape distributions). The strategy is to determine macroscopic free energy and dissipation potentials on the basis of a large number of computations at the scale of the polycrystal. The aim is to determine enriched macroscopic evolution laws. For sake of simplicity, this contribution only deals with grain growth of a single phased metal without diffusion or segregation of alloying elements. In order to test this upscaling strategy it is necessary to establish a simulation tool at the scale of the polycrystal. It should be sufficiently simple and fast to enable a large number of simulations of various microstructures, even if it leads to neglect some phenomena occurring at this scale. Usual grain growth models relying on mobile finite element modeling, level set functions, phase field or molecular dynamics are too computationally costly to be used within the proposed framework. Therefore , this paper focuses on the development of a "toy" model. Tessellation techniques are usually used to approximate polycrystalline microstructures. Therefore, one can approximate the real evolution of the microstructure as a succession of tessellation approximations. It then becomes quite natural to attempt to establish the evolution law of the microstructure directly on the parameters defining the tessellation. The obtained model is very light in terms of computational cost and enables to compute a large number of evolutions within the framework of the proposed statistical upscaling method.
• Effective models for non-perfectly conducting thin coaxial cables
  
  • Beck Geoffrey
  • Imperiale Sebastien
  • Joly Patrick
  , 2019. Continuing past work on the modelling of coax-ial cables, we investigate the question of the modeling of non-perfectly conducting thin coax-ial cables. Starting from 3D Maxwell's equations , we derive, by asymptotic analysis with respect to the (small) transverse dimension of the cable, a simplified effective 1D model. This model involves a fractional time derivatives that accounts for the so-called skin effects in highly conducting regions.
• Growth and remodelling of living tissues: perspectives, challenges and opportunities
  
  • Ambrosi Davide
  • Ben Amar Martine
  • Cyron Christian
  • Desimone Antonio
  • Goriely Alain
  • Humphrey Jay
  • Kuhl Ellen
  Journal of the Royal Society Interface, the Royal Society, 2019, 16 (157), pp.20190233. One of the most remarkable differences between classical engineering materials and living matter is the ability of the latter to grow and remodel in response to diverse stimuli. The mechanical behaviour of living matter is governed not only by an elastic or viscoelastic response to loading on short time scales up to several minutes, but also by often crucial growth and remodelling responses on time scales from hours to months. Phenomena of growth and remodelling play important roles, for example during morphogenesis in early life as well as in homeostasis and pathogenesis in adult tissues, which often adapt to changes in their chemo-mechanical environment as a result of ageing, diseases, injury or surgical intervention. Mechano-regulated growth and remodelling are observed in various soft tissues, ranging from tendons and arteries to the eye and brain, but also in bone, lower organisms and plants. Understanding and predicting growth and remodelling of living systems is one of the most important challenges in biomechanics and mechanobiology. This article reviews the current state of growth and remodelling as it applies primarily to soft tissues, and provides a perspective on critical challenges and future directions. (10.1098/rsif.2019.0233)
  DOI : 10.1098/rsif.2019.0233
• Precise calibration of optical tweezers using interference in backscattered signal. Application to the micro rheology of blood clots
  
  • Westbrook Nathalie
  • Wolff Laura
  • Gillant Flavie
  • Moreau Julien
  • Allain Jean-Marc
  • Perronet Karen
  • Richly Maximilian
  • Alexandrou Antigoni
  , 2019.
• Reduction of a mechanical model dedicated to the study of assembly bow
  
  • Leturcq Bertrand
  • Pascal Serge
  • Le Tallec Patrick
  • Pacull Julien
  , 2019. In the pressure vessel of a PWR, the core is filled of up to 241 fuel assemblies. Under operation, they are subjected to irradiation growth, creeping, tightening relaxation and rod slipping. Combined with the hydraulic forces induced by the coolant flow, these phenomena lead to assembly lateral deformation. Between two operating cycles, when changing the assembly position in the core, this deformation may sometime create difficulties with regard to handling operations. In order to prevent this situation, it would be useful to simulate the thermomechanical behaviour of the core, taking into account the previously mentioned phenomena. For that purpose, we present a 3D modelling approach in which each fuel assembly is represented by a reduced model that uses shape functions for kinematics as well as internal variables. The constitutive equations are then expressed in the reduced basis by defining and coupling the modal thermodynamic forces. We finally analyse the accuracy and performance of that new method through a simple case.
• Conservative and entropy controlled remap for multi-material ALE simulations with space-staggered schemes
  
  • Marboeuf Alexis
  • Claisse Alexandra
  • Le Tallec Patrick
  Journal of Computational Physics, Elsevier, 2019, 390, pp.66-92. The remapping strategy is crucial in any Arbitrary Lagrangian-Eulerian (ALE) algorithm based on a Lagrange-plus-remap paradigm. This step is particularly challenging for space-staggered schemes since inconsistencies may appear between cell centered and node centered fields after remap if no special care is taken [1], [2], [3]. We propose here a space-staggered remapping strategy focusing on conservation properties and entropy control. The proposed algorithm conserves mass, total energy and respects the Second Law of Thermodynamics (for robustness) up to round-off errors. This is achieved at a low computational cost by introducing a consistent, explicit and local post processing of the linear momentum after remap. This new method is then analyzed showing that the strict momentum conservation is sacrificed. It is now conserved to the scheme's order, such as entropy. Other classical properties such that the “DeBar consistency” [4], the continuity with the Lagrangian step and the monotonicity are also discussed. This work is developed in the context of the intersection-based (or overlay-based) remap. Therefore, the rezoned mesh does not have to be close to the Lagrangian one and, even if it is not considered here, our study can be easily extended to rezoning strategies which modify the mesh connectivity. (10.1016/j.jcp.2019.04.017)
  DOI : 10.1016/j.jcp.2019.04.017
• Random 3D-printed isotropic composites with high volume fraction of pore-like polydisperse inclusions and near-optimal elastic stiffness
  
  • Tarantino M.G. G
  • Zerhouni O.
  • Danas K.
  Acta Materialia, Elsevier, 2019, 175, pp.331-340. Highly porous materials with random closed-cell architecture combine isotropy with high stiffness. Yet in practice, the complexity of their manufacturing limits the experimental exploration of these materials, for which studies of the elastic response remain to date mainly theoretical. In this study, we measure experimentally the elastic moduli of random closed-cell porous-like composites fabricated by 3D-printing. These materials contain a high volume fraction (up to 82 vol pct) of non-overlapping, polydisperse void-like spherical inclusions, which are randomly dispersed in a homogeneous polymer matrix. We first generate the virtual microstructures of these materials using a random sequential adsorption (RSA) algorithm, and then use numerical homogenization to compute the size of the material representative volume element (RVE). The latter is used to assemble the test samples, whereby the void-like inclusions are 3D-printed using a gel-like polymer with mechanical properties that are in high contrast with those of the base polymer thus behaving mechanically as pores. Experiments reveal that the proposed isotropic. (10.1016/j.actamat.2019.06.020)
  DOI : 10.1016/j.actamat.2019.06.020
• A unique combination of in-situ and multi-scale methodologies to analyze damage mechanisms of temper rolled zinc coating
  
  • Legendre Jean
  • Créac'Hcadec Romain
  • Tanguy A.
  • Hallais S.
  • Schmitt Jean-Hubert
  • Héripré E.
  • Gilbert Franck
  • Jacquet D.
  • Mataigne J.
  Materials Science and Engineering: A, Elsevier, 2019, 763, pp.138156. Coated sheets for car body are assembled by spot-welding and, more and more, by adhesive bonding. Thus, during life time, the coating endures stresses which can lead to the failure of the whole bonded assembly. The behavior of the zinc coating has then to be primarily studied during tension of flat samples. Several investigation techniques, including in-situ characterizations and 3D observations, are combined to observe and understand the damage mechanisms of the zinc coating during plastic deformation. A specific attention is paid to the influence of temper rolling which is usually applied on low-carbon steel sheets after annealing and hot-dip coating. Damage is mainly observed at the boundary of large zinc grains lying on the surface plateaus, non-deformed by rolling, and often nucleates at the defects due to dendritic zinc solidification. (10.1016/j.msea.2019.138156)
  DOI : 10.1016/j.msea.2019.138156
• Scattering of gravity waves by a periodically structured ridge of finite extent
  
  • Maurel Agnès
  • Pham Kim
  • Marigo Jean-Jacques
  Journal of Fluid Mechanics, Cambridge University Press (CUP), 2019, 871, pp.350-376. We study the propagation of water waves over a ridge structured at the subwavelength scale using homogenization techniques able to account for its finite extent. The calculations are conducted in the time domain considering the full three-dimensional problem to capture the effects of the evanescent field in the water channel over the structured ridge and at its boundaries. This provides an effective two-dimensional wave equation which is a classical result but also non-intuitive transmission conditions between the region of the ridge and the surrounding regions of constant immersion depth. Numerical results provide evidence that the scattering properties of a structured ridge can be strongly influenced by the evanescent fields, a fact which is accurately captured by the homogenized model. (10.1017/jfm.2019.259)
  DOI : 10.1017/jfm.2019.259
• Average-based Population Protocols : Explicit and Tight Bounds of the Convergence Time
  
  • Mocquard Yves
  • Robin Frédérique
  • Sericola Bruno
  • Anceaume Emmanuelle
  , 2019. The computational model of population protocols is a formalism that allows the analysis of properties emerging from simple and pairwise interactions among a very large number of anonymous finite-state agents. Among the different problems addressed in this model, average-based problems have been studied for the last few years. In these problems, agents start independently from each other with an initial integer state, and at each interaction with another agent, keep the average of their states as their new state. In this paper, using a well chosen stochastic coupling, we considerably improve upon existing results by providing explicit and tight bounds of the time required to converge to the solution of these problems. We apply these general results to the proportion problem, which consists for each agent to compute the proportion of agents that initially started in one predetermined state, and to the counting population size problem, which aims at estimating the size of the system. Both protocols are uniform, i.e., each agent's local algorithm for computing the outputs, given the inputs, does not require the knowledge of the number of agents. Numerical simulations illustrate our bounds of the convergence time, and show that these bounds are tight in the sense that among extensive simulations, numerous ones exactly fit with our bounds.
• Crystal slip and Grain Sliding: a two-stroke engine driving ductile localization
  
  • Dimanov Alexandre
  • Bornert Michel
  • Raphanel Jean
  • Bourcier Mathieu
  • Gaye Ababacar
  • Sabbagh Alexandre El
  • Héripré Eva
  • Ludwigl Wolfgang
  • King Andrew
  • Gharbi Hakim
  • Tanguy Alexandre
  • Hallais Simon
  , 2019. Viscoplastic properties of polycrystalline materials condition many aspects of our everyday life, as for example, hot forming and durability of metallic structures at high temperature, glacier flow, or plate tectonics powered by convection of Earth’s mantle rocks. In general, it is admitted that viscoplastic deformation of polycrystals is largely dominated by crystal slip plasticity (CSP). Interfacial mechanisms, as grain boundary sliding (GBS) are mostly invoked for superpastic behaviour, favoured at high temperatures, small grain sizes and low strain rates. However, numerous studies evidence that often both mechanisms coexist. Still, very few have focussed on their respective contributions to the global deformation process. Besides, the way these mechanisms interact remains unclear. These questions are the aim of the present work. We have studied the viscoplastic response to uniaxial compression of two different classes of annealed and un-textured polycrystalline CFC materials: ionic NaCl and Aluminium, characterized by coarse and equilibrated polygonal grains (ca. 300 m). Aiming specifically at the localization aspects and mechanisms identification, we realized 2D full strain field micromechanical characterization, based on in situ SEM multi-scale observations and digital image correlation (DIC). Additionally, NaCl samples were analysed by in situ synchrotron X-ray tomography, so that we obtained 3D full strain fields. Our results clearly show that for both materials CSP and GBS co-exist. Besides, their interactions are co-operative: CSP is undoubtedly the dominant strain cumulative mechanism. Though, GBS continuously acts as a secondary (but necessary) mechanism, allowing for accommodation of local grain-to-grain strain incompatibilities, resulting from the inherently anisotropic nature of crystal slip. Both mechanisms are absolutely necessary to ensure macroscopically homogeneous flow. For both materials, we show how a minor (but crucial) contribution of GBS allows the development of localization bands and ductile strain propagation throughout the microstructure
• Stratégie centrée sur les paramètres cliniques de microcirculation à la phase initiale du choc septique : ne négliger aucun outil
  
  • Le Gall Arthur
  • Bruckert Vincent
  • Barbar Saber Davide
  • Leone Marc
  • Singer Mervyn
  Anesthésie & Réanimation, Elsevier Masson, 2019, 5 (4), pp.241-243. (10.1016/j.anrea.2019.05.003)
  DOI : 10.1016/j.anrea.2019.05.003
• Constitutive modelling of anisotropic rate-dependent Ti-6Al-4V titanium alloy for aircraft fan blade design
  
  • Ruiz de Sotto Miguel
  • Longère Patrice
  • Doquet Véronique
  • Papasidero Jessica
  , 2019.
• High-order discrete fourier transform for the solution of the Poisson equation
  
  • Caforio Federica
  • Imperiale Sébastien
  SIAM Journal on Scientific Computing, Society for Industrial and Applied Mathematics, 2019, 41 (5), pp.A2747-A2771. The aim of this work is to propose a novel, fast, matrix-free solver for the Poisson problem discretised with High-Order Spectral Element Methods (HO-SEM). This method is based on the use of the Discrete Fourier Transform to reduce the problem to the inversion of the symbol of the operator in frequency space. The solver proposed is endowed with several properties. First, it preserves the efficiency of standard FFT algorithm; then, the matrix storage is minimised; a pseudo-explicit Singular Value Decomposition (SVD) is used for the inversion of the symbols; finally, it can be easily extended to multiple dimensions and non-periodic boundary conditions. In particular, due to the underlying HO-SEM discretisation, the multi-dimensional symbol of the operator can be efficiently computed from the one-dimensional symbol by tensorisation. (10.1137/18M1225410)
  DOI : 10.1137/18M1225410
• Mixed analytic/energetic approach for a sliding orthotropic hollow cylinder. Application to coil sagging
  
  • Weisz-Patrault Daniel
  • Gantier Maxime
  • Ehrlacher Alain
  International Journal of Solids and Structures, Elsevier, 2019. This paper deals with the numerical simulation of coil sagging. This problem arises within the framework of the steel making industry where strips are wound on themselves for storage. Coil sagging is a major defect that can occur for recent grades undergoing phase transitions during the coiling process. The detailed mechanisms leading to coil sagging are still not well understood, making this phenomenon very difficult to prevent. The coil is a multilayer hollow cylinder where sliding takes place at each interface and significantly contributes to the overall deformation. However, a detailed numerical simulation addressing the contact problem, considering both pressure and sliding is difficult to perform under non-axisymmetric conditions. This paper presents a simplified approach considering an orthotropic hollow cylinder instead of a multilayer coil. The anisotropy is due to contact roughness that tends to decrease the radial stiffness. The hollow cylinder is subjected to gravity and an eigenstrain representing thermal expansion, phase transitions and transformation induced plasticity. Sliding at each interface is taken into account through a continuous plastic-like shear strain that is determined through an energetic principle. The proposed solution relies on analytical developments so that computation time is compatible with parametric studies. Results are addressed in order to give a better understanding of mechanisms and conditions under which coil sagging occur. (10.1016/j.ijsolstr.2019.01.029)
  DOI : 10.1016/j.ijsolstr.2019.01.029