Publications

2023

• Microstructure, Mechanical Properties, and Thermal Stability of Al-Al2O3 Nanocomposites Consolidated by ECAP or SPS from Milled Powders
  
  • Lacour-Gogny-Goubert Antoine
  • Doquet Véronique
  • Novelli Marc
  • Tanguy Alexandre
  • Hallais Simon
  • Bourgon Julie
  • Villeroy Benjamin
  • Massion Roxane
  Metals, MDPI, 2023, 13 (5), pp.825. Ultrafine-grained Al matrix nanocomposites, reinforced with Al2O3 nanoparticles, were produced from milled powders, either by equal channel angular pressing (ECAP), at room or high temperature, with or without back pressure, or by spark plasma sintering (SPS). Their microstructures, mechanical properties (compression, hardness, and sliding wear), and thermal stabilities (thermally induced softening and cracking) were compared, and the advantages and limitations of each process discussed on a scientific but also practical point of view. For the most successful set of process parameters, the yield stress in compression reached 380 MPa, the hardness, HV = 139, remained stable up to 500 °C, and the resistance to sliding wear was comparable to that of Al 5083, and better than that of Al 7075-T6. While the samples consolidated at high temperatures (by ECAP or SPS) showed a good thermal stability, those consolidated by ECAP at room temperature were prone to thermally induced softening and cracking, which was related to trapped and pressurized gases. (10.3390/met13050825)
  DOI : 10.3390/met13050825
• Mechanical Response of Metal Solenoids Subjected to Electric Currents
  
  • Elliott R.
  • Triantafyllidis N.
  Journal of Elasticity, Springer Verlag, 2023, 154 (1-4), pp.407-419. (10.1007/s10659-023-10015-y)
  DOI : 10.1007/s10659-023-10015-y
• Computer-aided generation, 3D-printing and experimental study of porous and composite materials
  
  • Hooshmand Ahoor Zahra
  , 2023. The present study deals with computer-aided design, 3D-printing, large strain numerical simulation, and experimental testing of random geometries with focus on porous materials. In particular, we attempt to assess the effect of random porous features on the mechanical response at large strain by comparing the response of well-chosen random and periodic porous geometries. We first investigate the computer-aided design process of a variety of porous geometries including random polydisperse porous materials with spherical and ellipsoidal voids, standard eroded Voronoi geometries, hexagonal honeycombs, and TPMS structures. In addition, we propose a novel computer-aided design strategy to obtain a new type of random Voronoi-type porous materials called M-Voronoi (from mechanically grown) with smooth void shapes and variable intervoid ligament sizes that can reach very low relative densities. This is achieved via a numerical, large strain, nonlinear elastic, void growth mechanical process. The proposed M-Voronoi method is general and can be applied to create both two and three-dimensional random geometries and allows the formation of isotropic or anisotropic materials. The void growth process is a consequence of mass conservation and the incompressibility of the surrounding nonlinear elastic matrix phase and the final achieved relative density may be analytically estimated in terms of the determinant of the applied deformation gradient. The extremely low densities in the M-Voronoi geometries are achieved through an intermediate remesh step in the virtual fabrication process. For this purpose, we developed a versatile and general remeshing algorithm based on the geometry reconstruction of an orphan mesh that can handle arbitrarily complex meshes, including those that contain voids or multiple phases. Moreover, the studied random geometries are general to model seamlessly a wide range of composites involving particles, multi-phase, and even polycrystals with finite interfaces under mechanical or coupled loads (e.g. magneto-electro mechanical, etc.).In the next part of the study, we fabricate the designed porous materials with a polymer 3D-printer via PolyJet technology and a UV-curable resin called TangoBlack which is a highly viscous soft polymer with brittle fracture. Meanwhile, the viscous behavior of TangoBlack is studied under uniaxial tensile, loading-unloading, and relaxation tests on a new proposed specimen geometry and is subsequently characterized by a nonlinear rubber viscoelastic model for incompressible isotropic elastomers. We then use this material to 3D-print the designed two-dimensional porous materials with square representative geometries and isotropic/anisotropic features in terms of void size and realization. The mechanical response of the fabricated porous materials is experimentally investigated by testing them under uniaxial large strain compression and low strain rates. We show that the randomness of the proposed M-Voronoi geometries and their non-uniform intervoid ligament size leads to enhanced mechanical properties at large compressive strains with no apparent peak-stress and strong hardening well before densification, while they become very close to random eroded Voronoi geometries at low densities.In the last part of this study, we investigate numerically the mechanical properties of the three-dimensional random porous geometries consisting of M-Voronoi, polydisperse porous materials with spherical voids, and classical TPMS-like geometries. The simulations are performed at large strains under compression loading while considering the matrix an elastic-perfectly plastic material without hardening. We observe enhanced plastic flow stress in the geometries with random topologies as opposed to the TPMS periodic structures. This behavior is explained by noting that deformation localizes in geometries with a periodic pattern, contrary to the random geometries which exhibit a rather diffused localization.
• Aligned Nanofibrous Net Deposited Perpendicularly on Microridges Supports Endothelium Formation and Promotes the Structural Maturation of hiPSC-Derived Cardiomyocytes
  
  • Tian Feng
  • Yin Linlin
  • Lin Peiran
  • Liu Yurong
  • Wang Wenlong
  • Chen Yong
  • Tang Yadong
  ACS Applied Materials & Interfaces, Washington, D.C. : American Chemical Society, 2023, 15 (14), pp.17518-17531. Cell alignment widely exists in various in vivo tissues and also plays an essential role in the construction of in vitro models, such as vascular endothelial and myocardial models. Recently, microscale and nanoscale hierarchical topographical structures have been drawing increasing attention for engineering in vitro cell alignment. In the present study, we fabricated a micro-/nanohierarchical substrate based on soft lithography and electrospinning to assess the synergetic effect of both the aligned nanofibrous topographical guidance and the off-ground culture environment provided by the substrate on the endothelium formation and the maturation of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The morphology, proliferation, and barrier formation of human umbilical vein endothelial cells (HUVECs) as well as the alignment, cardiac-specific proteins, and maturity-related gene expression of hiPSC-CMs on the aligned-nanofiber/microridge (AN-MR) substrate were studied. Compared with the glass slide and the single-aligned nanofiber substrate, the AN-MR substrate enhanced the proliferation, alignment, and cell–cell interaction of HUVECs and improved the length of the sarcomere and maturation-related gene expression of hiPSC-CMs. Finally, the response of hiPSC-CMs on different substrates to two typical cardiac drugs (isoproterenol and E-4031) was tested and analyzed, showing that the hiPSC-CMs on AN-MR substrates were more resistant to drugs than those in other groups, which was related to the higher maturity of the cells. Overall, the proposed micro-/nanohierarchical substrate supports the in vitro endothelium formation and enhances the maturation of hiPSC-CMs, which show great potential to be applied in the construction of in vitro models and tissue engineering. (10.1021/acsami.2c22551)
  DOI : 10.1021/acsami.2c22551
• Caractériser l’extrême localisation de la plasticité dans les verres métalliques par l’essai de compression diamétrale
  
  • Bernard Cédric
  • Hin Sovannara
  • Charleux Ludovic
  • Roux Émile
  • Yokoyama Yoshihiko
  • Tanguy Alexandre
  • Keryvin Vincent
  , 2023. Les verres métalliques sont des alliages amorphes possédant des propriétés mécaniques exceptionnelles : très hautes limite élastique, dureté et capacité de stockage d’énergie élastique. On parle de verres métalliques massifs (VMM) lorsque les bruts, obtenus habituellement par trempe, dépassent le centimètre d’épaisseur. Dépourvus de réseau cristallin, les VMM ne sont pas soumis au mécanisme de mouvement de dislocations qui régit habituellement la plasticité dans les métaux. A température ambiante, les déformations plastiques se localisent dans un réseau de bandes de cisaillement (BdC) très fines (jusqu’à ~20 nm) où elles peuvent atteindre des niveaux extrêmement élevés. Sous sollicitations uniaxiales, ces BdC se propagent rapidement à travers la section et mènent rapidement à la rupture de la structure, comportement qui constitue d’ailleurs le principal point faible des verres métalliques. Toutefois, pour certaines sollicitations moins conventionnelles favorisant l’apparition d’une plasticité confinée, ils peuvent adopter un comportement fortement ductile à l’échelle macroscopique. L’essai de compression diamétrale est un moyen d’y parvenir. L’essai de compression diamétrale a pour particularité de solliciter une l’éprouvette cylindrique dont l’axe de révolution est normal à la direction du chargement, autrement dit, les plateaux s’appuient sur deux génératrices diamétralement opposées. Les deux faces planes sont, quant à elles, libres et facilement observables, ce qui facilite la mesure de champ in situ. Une technique expérimentale innovante basée sur un essai de compression diamétral réalisé dans la chambre d’un microscope électronique à balayage (MEB) couplé à une analyse de corrélation d’images micrographiques a permis de déterminer le champ de déplacement d’une des faces de l’éprouvette avec une résolution de 5μm/pixel. Les cartes de déformation ainsi obtenues donnent accès avec une précision inédite aux valeurs extrêmes des déformations localisées dans les BdC. L’analyse qualitative et quantitatives des motifs dessinés au cours de l’essai par les BdC émergeant à la surface de l’éprouvette permet de mieux comprendre les phénomènes impliqués dans la déformation plastique des VMM à l’échelle microscopique tels que la création et la propagation des BdC, mais aussi leurs interactions mutuelles. Finalement, un modèle original de plasticité, le modèle compartimenté, construit à partir de lois de comportement simples mais distribuées aléatoirement sur le maillage a été utilisé dans une simulation éléments finis de l’essai. Les résultats numériques montrent que ce modèle est capable de reproduire la réponse macroscopique du VMM, le développement des BdC dans l’éprouvette à l’échelle microscopique, mais aussi les mécanismes d’interaction complexes qui se produisent entre les BdC au cours de l’essai.
• Curing-dependent thermo-viscoelastic and shrinkage behaviour of photopolymers
  
  • Sekmen Kubra
  • Rehbein Thomas
  • Johlitz Michael
  • Lion Alexander
  • Constantinescu Andrei
  Mechanics of Materials, Elsevier, 2023, 179, pp.104566. This study investigates the influence of curing on the thermo-viscoelastic properties and chemical shrinkage of a commercially available photopolymer resin used in SLA and DLP 3D printing and presents a modelling approach for predicting material properties. UV rheometer and DMA measurements were performed to investigate the viscoelastic properties of the photopolymer material as a function of temperature, degree of cure, and frequency. Time–temperature and time-cure superposition principles were applied to the experimental results. In addition, the chemical shrinkage behaviour was studied by the UV rheometer as a function of the degree of cure and temperature, and a model equation was proposed based on these parameters. Our experimental findings have led to the development of constitutive equations for the complete material behaviour. (10.1016/j.mechmat.2023.104566)
  DOI : 10.1016/j.mechmat.2023.104566
• Comparison of optimization parametrizations for regional lung compliance estimation using personalized pulmonary poromechanical modeling
  
  • Laville Colin
  • Fetita Catalin
  • Gille Thomas
  • Brillet Pierre-Yves
  • Nunes Hilario
  • Bernaudin Jean-François
  • Genet Martin
  Biomechanics and Modeling in Mechanobiology, Springer Verlag, 2023, 22, pp.1541–1554. Interstitial lung diseases, such as idiopathic pulmonary fibrosis (IPF) or post-COVID-19 pulmonary fibrosis, are progressive and severe diseases characterized by an irreversible scarring of interstitial tissues that affects lung function. Despite many efforts, these diseases remain poorly understood and poorly treated. In this paper, we propose an automated method for the estimation of personalized regional lung compliances based on a poromechanical model of the lung. The model is personalized by integrating routine clinical imaging data-namely computed tomography images taken at two breathing levels in order to reproduce the breathing kinematic-notably through an inverse problem with fully personalized boundary conditions that is solved to estimate patient-specific regional lung compliances. A new parametrization of the inverse problem is introduced in this paper, based on the combined estimation of a personalized breathing pressure in addition to material parameters, improving the robustness and consistency of estimation results. The method is applied to three IPF patients and one post-COVID-19 patient. This personalized model could help better understand the role of mechanics in pulmonary remodeling due to fibrosis; moreover, patient-specific regional lung compliances could be used as an objective and quantitative biomarker for improved diagnosis and treatment follow up for various interstitial lung diseases. (10.1007/s10237-023-01691-9)
  DOI : 10.1007/s10237-023-01691-9
• Strain and damage analysis using high resolution digital image correlation in the stir zone of an AA6061-AA7075 dissimilar friction stir weld
  
  • Dimov Nicolas
  • Weisz-Patrault Daniel
  • Tanguy Alexandre
  • Sapanathan Thaneshan
  • Benoist Julien
  • Charkaluk Eric
  • Simar Aude
  Materials Today Communications, Elsevier, 2023, 34, pp.105359. This work focuses on the strain and damage analysis of a micro tensile experiment of a AA6061-AA7075 dissimilar friction stir weld. Scanning electron microscopy combined with high resolution digital image correlation has been performed at two different scales to analyse strain fields and damage in the AA6061-AA7075 mixed region of the stir zone. Local alloy composition was identified as the critical parameter affecting the meso-scale strain distribution. At a finer scale, intermetallic particles also lead to strain localization within each individual alloy. (10.1016/j.mtcomm.2023.105359)
  DOI : 10.1016/j.mtcomm.2023.105359
• Using Data from job seekers, job offers and past hirings to learn a Job Recommender System: the VADORE Project
  
  • Bied Guillaume
  • Nathan Solal
  • Perennes Elia
  • Gaillac Christophe
  • Caillou Philippe
  • Crépon Bruno
  • Sebag Michèle
  , 2023. The Vador Project started in 2018 between the French Public Employment Service Pole Emploi, computer scientists from Paris Saclay and economist from CREST. The project aims to learn a new recommender system from past hirings and job seekers and offers data. We will present both the past, current and futur research and technical challenges faced by the projects and its contributions.
• Analysis of cone-like singularities in twisted elastic ribbons
  
  • Audoly Basile
  • van der Heijden G.H.M.
  Journal of the Mechanics and Physics of Solids, Elsevier, 2023, 171, pp.105131. Twisting a thin elastic ribbon is known to produce a localised deformation pattern resembling a cone whose tip is located on the edge of the ribbon. Using the theory of inextensional ribbons, we present a matched asymptotic analysis of these singularities for ribbons whose width-to-length ratio w/ℓ ≪ 1 is small. An inner layer solution is derived from the finite-w Wunderlich model and captures the fast, local variations of the bending and twisting strains in the neighbourhood of the cone-like region; it is universal up to a load intensity factor. The outer solution is given by the zero-w Sadowsky model. Based on this analysis, we propose a new standalone ribbon model that combines the Sadowsky equations with jump conditions providing a coarse-grained description of cone-like singularities, and give a self-contained variational derivation of this model. Applications to the Möbius band and to an end-loaded open ribbon are presented. Overall, the new model delivers highly accurate approximations to the solutions of the Wunderlich model in the limit w ≪ ℓ while avoiding the numerical difficulties associated with cone-like singularities. (10.1016/j.jmps.2022.105131)
  DOI : 10.1016/j.jmps.2022.105131
• Intense shear band plasticity in metallic glass as revealed by a diametral compression test
  
  • Bernard C.
  • Hin S.
  • Charleux Ludovic
  • Roux Émile
  • Yokoyama Y.
  • Tanguy Alexandre
  • Keryvin V.
  Materials Science and Engineering: A, Elsevier, 2023, 864, pp.144533. Shear band initiation, development and mutual interaction are studied in a Zr 55 Cu 30 Al 10 Ni 5 metallic glass by means of an innovative experimental technique associating diametral compression test (or Brazilian test), scanning electron microscopy and digital image correlation analysis. The intense strain occurring in shear bands and the deformation map of their overall pattern are both estimated with a high resolution (∼ 5 μm/pixel), offering a better understanding of the phenomenon. Finite element simulations based on a new and original plasticity model, the compartmentalized model, makes it possible to reproduce the shear band development observed experimentally, as well as the interlocking mechanism occurring between the shear bands. (10.1016/j.msea.2022.144533)
  DOI : 10.1016/j.msea.2022.144533
• Recommendations on "Grey-Zone Publishers
  
  • Blanqui Frédéric
  • Canteaut Anne
  • Jong Hidde De
  • Imperiale Sébastien
  • Mitton Nathalie
  • Pallez Guillaume
  • Pennec Xavier
  • Rival Xavier
  • Thirion Bertrand
  , 2023, pp.1-3. Recommendations from the Inria Evaluation Commiteee, adopted on January 25, 2023, on several publishers, notably MDPI and Frontiers, that have significantly increased their presence in the fields of computer science and mathematics, areas where they were absent in the past. Their presence raises a number of questions, often troubling evaluators and jury members.
• Recommandations sur les « éditeurs de la zone grise »
  
  • Blanqui Frédéric
  • Canteaut Anne
  • de Jong Hidde
  • Imperiale Sébastien
  • Mitton Nathalie
  • Pallez Guillaume
  • Pennec Xavier
  • Rival Xavier
  • Thirion Bertrand
  , 2023, pp.1-3. Recommandations de la Commission d'Évaluation Inria, adoptées le 25 janvier 2023, sur certains éditeurs, notamment MDPI et Frontiers, qui prennent depuis quelques années une place significative dans les domaines de l'informatique et des mathématiques, disciplines où ils étaient absents par le passé.
• Numerical solver for the modelling of guided waves propagation under stress condition in the context of SHM applications.
  
  • Dalmora Andre
  • Imperiale Alexandre
  • Imperiale Sébastien
  • Moireau Philippe
  , 2023. In leading-edge industrial applications, assessing structure integrity is an important aspect of safety requirements. Structural Health Monitoring (SHM) proposes to use sensors and signal processing units in situ. One of the most attractive SHM techniques is ultrasonic guided waves. Guided waves propagate on large distances and interact with defects in the structure making damage detection possible. Modelling and simulation can be helpful tools for the design or the reliability assessment of SHM solutions. The currently available models developed for that purpose do not take into account the effect of operational conditions such as internal stresses. These conditions can modify wave propagation and therefore affect the interpretation of recorded signals. The objective of this work is to propose a model and associated numerical methods for elastic wave propagation in an arbitrarily deformed medium. Any hyperelastic constitutive law can be considered. As the structures considered are usually thin, we avoid shear-locking by using a shell formulation to solve the quasi-static problem representing the effects of structure loading. The computed displacement is then fed into a spectral elements method (SEM) kernel to solve the time-domain linearized 3D elastodynamics problem representing the wave propagation. We validate our model for an isotropic aluminium plate under tensile forces. Additionally to the direct modelling, we aim at using these tools within inversion loops to reconstruct the prestresses by means of ultrasonic transducers measurements.
• Microrheology and structural quantification of hypercoagulable clots
  
  • Wolff-Trombini Laura
  • Ceripa Adrien
  • Moreau Julien
  • Galinat Hubert
  • James Chloé
  • Westbrook Nathalie
  • Allain Jean-Marc
  Biomedical optics express, Optical Society of America - OSA Publishing, 2023, 14 (8), pp.4179-4189. We propose a combination of microrheological and structural characterizations of fibrin networks to study blood hypercoagulability. Fibrin is the central element of coagulation as its polymerization creates the network of fibers in which platelets and red blood cells are included. This is a controlled process via cascades between various coagulation factors. An alteration in the concentrations of coagulation factors and inhibitors will lead to hypocoagulation or hypercoagulation. These changes in the conditions of polymerization of fibrin lead to the formation of networks with different architectures and thus modify its mechanical behavior. We have performed microrheology by recording Brownian motion of microbeads caught in the network of clots. The structure was quantified under the same polymerization conditions with confocal microscopy images. We have tested our approach by adding fibrinogen to the plasma, which leads to a stiffer, denser network with shorter fibers. The addition of coagulation Factor VIII at 400% induces the same correlated trend between a denser network and a higher modulus. This comparative approach is promising for the study of other conditions altering clot formation and may lead to a new diagnosis approach for hypercoagulability. (10.1364/BOE.492669)
  DOI : 10.1364/BOE.492669
• A synchrotron transmission X-ray microscopy study on precipitate evolution during solid-state thermal cycling of a stainless steel
  
  • Gaudez S.
  • Ben Haj Slama M.
  • Heripre E.
  • Yedra L.
  • Scheel M.
  • Hallais S.
  • Upadhyay M.V.
  Additive Manufacturing, Elsevier, 2023, 73, pp.103692. During additive manufacturing of stainless steels, sub-micron sized oxide (i.e., MnSiO3 , SiO2 , and CrMn2O4) and non-oxide (i.e., sulfide, in particular MnS, and possibly carbides, phosphides and nitrides) precipitates form during solidification. But do they evolve during the subsequent solid-state thermal cycling (SSTC) until the end of the printing process? A recent study on subjecting thin-film lamellae extracted from an additively manufactured stainless steel to heating-cooling treatments inside a transmission electron microscope (TEM) confirmed that precipitate composition can indeed evolve during SSTC. However, that study could not provide any conclusive evidence on precipitate volume fraction, density, and size evolution. In this work, we have quantified these changes using a novel experimental procedure combining (i) micropillar extraction from an additively manufactured stainless steel, (ii) subjecting them to different SSTC (including annealing) inside a TEM, (iii) performing synchrotron transmission X-ray microscopy to identify precipitates, and (iv) using a machine learning model to segment precipitates and quantify precipitate volume fraction, density, and size. Comparing these quantities before and after each SSTC/annealing sequence reveals that new oxides nucleated during rapid SSTC with high maximum temperature. However, during slow SSTC with high maximum temperature and annealing, precipitates dissolve because of oxygen evaporation during SSTC inside the TEM. A new empirical relationship correlating precipitate sizes and cooling rates is proposed. It is in good agreement with data collected from conventional casting, directed energy deposition, and powder bed fusion processes. (10.1016/j.addma.2023.103692)
  DOI : 10.1016/j.addma.2023.103692
• Numerical estimation via remeshing and analytical modeling of nonlinear elastic composites comprising a large volume fraction of randomly distributed spherical particles or voids
  
  • Luo H.
  • Hooshmand-Ahoor Z.
  • Danas K.
  • Diani J.
  European Journal of Mechanics - A/Solids, Elsevier, 2023, pp.105076. We investigate numerically via finite element (FE) simulations and analytically the nonlinear behavior of a soft matrix comprising a large volume fraction (up to 55%) of monodisperse spherical inclusions, which can be either rigid particles or voids. To address the issue of severe mesh distortion at large strains, we employ a successive remeshing and solution mapping technique that allows us to achieve a large macroscopic deformation, with the maximum attained stretch being at least two to three times when compared to that without remeshing. A general algorithm allowing to read complex arbitrary particle geometries is proposed and implemented allowing to remesh a finitely strained domain with randomly distributed inclusions of arbitrary shape. The present simulation results for a neo-Hookean elastic matrix filled with rigid particles show that the nonlinear stress-stretch uniaxial tension response can be well approximated by a neo-Hookean material with an effective shear modulus that depends on the volume fraction of the inclusions. Additionally, a study of the number of particles demonstrates that sixty four monodisperse spheres is a good compromise to reach accurate results for large deformations and maintain a reasonable cpu-time. The FE data serve as a powerful assessment tool for analytical homogenization models. Newly developed and existing models for small and large strains are proposed and assessed, respectively, for both rigid particles and voids. These results fill the gap for large volume fractions of inclusions and serve as a reference for the homogenization of the microstructures of interest. (10.1016/j.euromechsol.2023.105076)
  DOI : 10.1016/j.euromechsol.2023.105076
• Sliding wear resistance and residual stresses of parts repaired by laser metal deposition
  
  • Zurcher Théo
  • Serrano-Munoz Itziar
  • Mishurova Tatiana
  • Faria Guilherme Abreu
  • Degener Sebastian
  • Fridrici Vincent
  • Charkaluk Eric
  • Bruno Giovanni
  Journal of Materials Science, Springer Verlag, 2023. Large temperature gradients inherent to additive manufacturing (AM) processes induce large residual stress (RS) in the final part. Because RS can influence the tribological properties, this study focuses on the relationship between wear sliding properties and RS in IN718 coatings. Such coatings were deposited with a Laser Metal Deposition (LMD) machine using to two different scanning strategies. The wear resistance and RS state of two types of samples were investigated after surface milling. RS were measured before and after tests on a reciprocating sliding test apparatus. Two different X-ray diffraction techniques were employed to measure the surface and subsurface state RS: Laboratory Energy Dispersive X-ray Diffraction (LEDXD) and Synchrotron X-ray Energy Dispersive Diffraction (SXEDD). Due to the milling process, coatings show similar depth distributions of RS from 22 µm to 92 µm depth, but exhibit different magnitudes depending on the scanning strategy used. Reciprocating sliding wear tests induced high compressive residual stresses that erased the initial RS state. However, a similar wear behavior was observed in the two samples, which possess similar texture and microstructure. This demonstrates that the influence of RS on wear resistance is a second-order effect. Nevertheless, it was observed that RS can still impact the wear performance at the early testing stages of the repaired parts. (10.1007/s10853-023-09129-4)
  DOI : 10.1007/s10853-023-09129-4
• A direct method for cyclic crystal plasticity with application to high-cycle fatigue
  
  • Echerradi Insaf
  • Weisz-Patrault Daniel
  • Peigney Michaël
  , 2023. The prediction of fatigue in materials and structures is usually based on experimental Wohler curves, relating the number of cycles to failure to the amplitude of the applied cyclic loading. Those curves show some scattering due notably to the variability of the microstructure. Predicting fatigue lifetime can thus be seen as a statistical problem that depends on microstructural descriptors. This paper paves the way to a probabilistic approach for quantitatively linking crystallographic and morphological texture data to fatigue lifetime prediction. In more detail, a simplified mesoscopic model is constructed for calculating the evolution of an elastic-plastic polycrystal with a prescribed texture. That model is limited to high cycle fatigue, corresponding to cyclic loadings of sufficiently low amplitude for plasticity to be mainly confined to few well-separated grains. The model obtained takes details of the texture into account, i.e. the distribution, shape and orientation of the individual grains. It relies on analytical formula and is mesh-free. A comparison with full-field finite element simulation shows that the proposed model leads to satisfactory results in regard to its complexity. In the case of cyclic loading, we show that the model presented leads to a direct method for calculating the asymptotic values of the plastic slips (and cumulated plastic slips) reached in each grain when the number of cycles grows to infinity. We show how that direct approach can be used for upscaling a local failure criterion to the mesoscopic scale and performing probabilistic analysis. (10.1007/978-3-031-29122-7_9)
  DOI : 10.1007/978-3-031-29122-7_9
• Theory of Plasticity and Strain Hardening of Glassy Polymers
  
  • Merlette Thomas C.
  • Hem Jeirome
  • Crauste-Thibierge Caroline
  • Ciliberto Sergio
  • Clement Florence
  • Sotta Paul
  • Long Didier R
  Macromolecules, American Chemical Society, 2023, 56 (16), pp.6510-6526. (10.1021/acs.macromol.3c00526)
  DOI : 10.1021/acs.macromol.3c00526
• Time-synchronization of interventional cardiovascular magnetic resonance data using a biomechanical model for pressure-volume loop analysis
  
  • Gusseva Maria
  • Castellanos Daniel
  • Greer Joshua
  • Hussein Mohamed
  • Hasbani Keren
  • Greil Gerald
  • Reddy Surendranath
  • Hussain Mohammad
  • Chapelle Dominique
  • Chabiniok Radomir
  Journal of Magnetic Resonance Imaging, Wiley-Blackwell, 2023, 57 (1), pp.320-323. (10.1002/jmri.28216)
  DOI : 10.1002/jmri.28216
• A biomechanics-based parametrized cardiac end-diastolic pressure–volume relationship for accurate patient-specific calibration and estimation
  
  • Chapelle Dominique
  • Le Gall Arthur
  Scientific Reports, Nature Publishing Group, 2023, 13, pp.9. A simple power law has been proposed in the pioneering work of Klotz et al. (Am J Physiol Heart Circ Physiol 291(1):H403–H412, 2006) to approximate the end-diastolic pressure–volume relationship of the left cardiac ventricle, with limited inter-individual variability provided the volume is adequately normalized. Nevertheless, we use here a biomechanical model to investigate the sources of the remaining data dispersion observed in the normalized space, and we show that variations of the parameters of the biomechanical model realistically account for a substantial part of this dispersion. We therefore propose an alternative law based on the biomechanical model that embeds some intrinsic physical parameters, which directly enables personalization capabilities, and paves the way for related estimation approaches. (10.1038/s41598-023-38196-5)
  DOI : 10.1038/s41598-023-38196-5
• Using Population Based Kalman Estimator to Model COVID-19 Epidemic in France: Estimating the Effects of Non-Pharmaceutical Interventions on the Dynamics of Epidemic
  
  • Collin Annabelle
  • Hejblum Boris P.
  • Vignals Carole
  • Lehot Laurent
  • Thiébaut Rodolphe
  • Moireau Philippe
  • Prague Mélanie
  The international journal of biostatistics, De Gruyter, 2023. In response to the ongoing COVID-19 pandemic caused by SARS-CoV-2, governments are taking a wide range of non-pharmaceutical interventions (NPI). These measures include interventions as stringent as strict lockdown but also school closure, bar and restaurant closure, curfews and barrier gestures i.e . social distancing. Disentangling the effectiveness of each NPI is crucial to inform response to future outbreaks. To this end, we first develop a multi-level estimation of the French COVID-19 epidemic over a period of one year. We rely on a global extended Susceptible-Infectious-Recovered (SIR) mechanistic model of the infection including a dynamical (over time) transmission rate containing a Wiener process accounting for modeling error. Random effects are integrated following an innovative population approach based on a Kalman-type filter where the log-likelihood functional couples data across French regions. We then fit the estimated time-varying transmission rate using a regression model depending on NPI, while accounting for vaccination coverage, apparition of variants of concern (VoC) and seasonal weather conditions. We show that all NPI considered have an independent significant effect on the transmission rate. We additionally demonstrate a strong effect from weather conditions which decrease transmission during the summer period, and also estimate increased transmissibility of VoCs. (10.1515/ijb-2022-0087)
  DOI : 10.1515/ijb-2022-0087
• From domain decomposition to model reduction for Large nonlinear structures
  
  • Leturcq Bertrand
  • Le Tallec Patrick
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2023, 351 (S1), pp.1-17. The numerical simulation of multiscale and multiphysics problems requires efficient tools for spatial localization and model reduction. A general strategy combining Domain Decomposition and Nonuniform Transformation Field Analysis (NTFA) is proposed herein for the simulation of nuclear fuel assemblies at the scale of a full nuclear reactor. The model at subdomain level solves the full elastic problem but with a reduced nonlinear loading, based on simplified boundary conditions, reduced creep flow rules, projected sign preserving contact conditions, and a NTFA like reduced friction law to get the evolution of each slipping mode. With this loading reduction, the local solution can be explicitly obtained from a small set of precomputed elementary elastic solutions. The numerical tests indicate that considerable cost reduction (a factor of 50 to 1000) can be achieved while preserving engineering accuracy (10.5802/crmeca.168)
  DOI : 10.5802/crmeca.168
• Discrete-time formulations as time discretization strategies in data assimilation
  
  • Moireau Philippe
  , 2023, 2, pp.297-339. Data assimilation combines control theory and scientific computing to propose a set of methods for coupling dynamic models and data sequences for estimation and prediction in all engineering domains. Data assimilation naturally raises the question of how the developed control and optimization methods interact with the discretization of the underlying physical models, in particular their temporal discretization. We would like to present here some of the best known techniques developed for discrete-time models, which are essentially based on a mechanism involving model prediction on the one hand and data correction on the other. We show that they can be considered as specific discretizations of the data assimilation strategies proposed for continuous-time models in the sense of a discretization-and-then-control approach. This paradigm justifies the stability of these prediction-correction schemes, paving the way for convergence properties and justifying their popularity in practice. (10.1016/bs.hna.2022.11.005)
  DOI : 10.1016/bs.hna.2022.11.005