Publications

2025

• Magnetic‐Driven Viscous Mechanisms in Ultra‐Soft Magnetorheological Elastomers Offer History‐Dependent Actuation with Reprogrammability Options
  
  • Gonzalez‐saiz Ernesto
  • Lopez‐donaire Maria Luisa
  • Gutiérrez Lucía
  • Danas Kostas
  • Garcia‐gonzalez Daniel
  Advanced Science, Wiley Open Access, 2025, e06790. This work elucidates an important open question in the field of mechanically soft magnetorheological elastomers (MREs): how microstructural rearrangements during magnetic actuation modulate their viscoelastic behavior. Experimental assays are provided on mechanically confined and very soft MREs that, under magnetic actuation, show an order of magnitude increase in relaxation times compared to purely mechanical cases. It is demonstrated that such a modulation in the viscous response can be tuned by the amplitude and actuation rate of the magnetic stimuli, and is intrinsically linked to microstructural rearrangements of the magnetic particles. Motivated by these experimental observations, magnetic actuation protocols are conceived to enable mechanical responses in soft materials with force-memory. Specifically, due to the magnetically induced long-term viscous relaxation, one can induce magnetic-driven yielding by introducing material hardening during cycling loading. This mechanical memory of the MRE can be subsequently removed by releasing the magnetic stimuli for 1 h, resetting the material performance and its microstructural state. These mechanisms are deeply understood by a combination of different experimental approaches and a new theoretical magneto-mechanical continuum model. The results reported herein respond to unraveled fundamental questions in soft MREs, and provide a game-changing concept for designing a new branch of soft sensor-actuator and reservoir computing systems. (10.1002/advs.202506790)
  DOI : 10.1002/advs.202506790
• Left heart hemodynamics simulations with fluid-structure interaction and reduced valve modeling
  
  • Ruz Oscar
  • Diaz Jérôme
  • Vidrascu Marina
  • Moireau Philippe
  • Chapelle Dominique
  • Fernández Miguel Angel
  International Journal for Numerical Methods in Biomedical Engineering, John Wiley and Sons, 2025, 41 (9), pp.e70088. The combination of reduced models of cardiac valve dynamics with a one-way kinematic uncoupling of blood flow and electromechanics is a widespread approach for reducing the complexity of cardiac hemodynamics simulations. This comes however with a number of shortcomings: artificial pressure oscillations, missing isovolumetric phases and valve laws without precise continuous formulation. This paper is aimed at overcoming these three difficulties while still mitigating computational cost. A novel reduced model of valve dynamics is proposed in which unidirectional flow is enforced in a mathematically sound fashion. Artificial pressure oscillations are overcome by considering a fluid-structure interaction model, which couples bi-ventricular electromechanics and blood flow in the left cavities. The interface coupling is solved in a partitioned fashion via an unconditionally stable loosely coupled scheme. A priori energy estimates are derived for both the continuous coupled problem and its numerical approximation. The benefits and limitations of the proposed approaches are illustrated in a comprehensive numerical study. (10.1002/cnm.70088)
  DOI : 10.1002/cnm.70088
• Effect of Dissolved Oxygen and Temperature on Oxidation and Stress Corrosion Cracking of 316L Stainless Steel in Nuclear Primary Environment
  
  • Fayolle Charles
  • Guerre Catherine
  • Duhamel Cecilie
  • Crépin Jérôme
  • Nguejio Josiane
  • Rousseau Matthias
  • De Curières Ian
  , 2025, pp.1-15. The effects of dissolved oxygen and temperature on oxidation and stress corrosion cracking (SCC) were investigated by exposing 316L coupons and Slow Strain Rate Tensile Tests (SSRT) specimens in simulated primary water at 290°C and 320°C in both hydrogenated and oxygenated environments. A duplex oxide layer has been observed on all specimens, with a continuous inner layer and an outer layer composed of crystallites. Oxide thickness on coupons is maximum at 320°C in the range [290°C, 340°C] in hydrogenated environment, and is minimum at the same temperature in oxygenated environment. Intergranular oxidation penetrations were numerous in hydrogenated environment and are rare or absent in oxygenated environment. In SSRT, the material is less susceptible to SCC in oxygenated environment at 320°C. No SCC cracks were found at 290°C in hydrogenated environment. The susceptibility to both oxidation and SCC in this environment increases within the range [290°C, 340°C].
• Finite strain micro-poro-mechanics: Formulation and compared analysis with macro-poro-mechanics
  
  • Manoochehrtayebi Mahdi
  • Genet Martin
  • Bel-Brunon Aline
  International Journal of Solids and Structures, Elsevier, 2025, 317, pp.113354. Porous materials are ubiquitous in nature -notably living tissues, which often undergo large deformations and engineering applications. Poromechanics is an established theory to model the response of such materials; however, it is limited in its description of microscale phenomena, and structure-properties relationships. In this paper, we propose a microscopic poromechanical model based on a novel formulation of the micro-poro-mechanics problem, which allows to compute the response of any porous periodic microstructure to any loading involving fluid pressure, macroscopic strain, and/or macroscopic stress. We systematically compare the global response of our micro-model to macro-poromechanics, in both the infinitesimal and finite strain settings, and investigate in particular three mechanisms, namely solid compressibility, strain-pressure coupling and deviatoric-volumetric strain coupling. We notably illustrate how the micro-model can be used to derive macroscopic parameters, and how these parameters depend on microscopic features like pore shape, porosity, material properties, etc. This modeling framework will be the basis for powerful micro-poro-mechanical models of various materials and tissues, where pore-scale phenomena can be incorporated explicitly. (10.1016/j.ijsolstr.2025.113354)
  DOI : 10.1016/j.ijsolstr.2025.113354
• X-Ray tomography analysis of damage in synthetic polycrystalline rock salt : effect of confining pressure, brine and strain rate
  
  • Du Nina
  , 2025. Green hydrogen, produced from renewable energysources, is considered as a promising energy vector. Its large-scale storage in deep salt caverns is a potential solution toface the time gap between the energy production and its use.Indeed, rock salt is a rock with low porosity, low permeabi-lity and is inert to hydrogen. Salt caverns have already beenin use for seasonal storage of hydrocarbons. However, theintermittency of renewable energy sources means that injec-tion/withdrawal cycles have to be more frequent. Previous stu-dies have highlighted the coexistence of intra-crystalline andinter-crystalline deformation mechanisms, leading to micro-cracking of the material from the early stages of the plasticdeformation. The aim of the present work is to extend theseanalyses to triaxial loading conditions, which are more repre-sentative of the operating conditions in salt caverns, with anobservation of the evolution of porosity and micro-cracking in-side the samples. The study is performed on synthetic ma-terial with controlled microstructure, in which the grain sizeis suited to in situ mechanical testing means. Samples withdifferent brine contents can be produced with the elaborationprocesses using NaCl powder pressing that have been im-plemented. This enables the study of the effect of humidityon the activation of damage micro-mechanisms. The micro-structure of the obtained material is characterised with opticaland electronic microscopy and with EBSD. An in situ triaxialmachine, that has been modified for the needs of the study,allows us to observe the development of micro-cracks at dif-ferent confining pressures using laboratory and synchrotronX-Ray computed micro-tomography at a high imaging resolu-tion. The high flux of the synchrotron radiation enables shor-ter scan durations compared to the ones in laboratory, so thatseveral combination of confining pressures and loading ratescould have been tested on dry and wet samples. Under thetesting conditions considered, the viscoplastic deformation ofsalt is accompanied by diffuse grain boundary micro-cracking,indicating that mechanisms at the interfaces of grains are ne-cessary mechanisms to accommodate the local plastic incom-patibilities between neighbouring grains, even under signifi-cant confinements, representative of the lithostatic pressureof many salt caverns. An increase of the confinement andthe presence of brine seem to reduce the development of themicro-crack network. This suggests that dissolution precipita-tion mechanisms could be active and serve as local accom-modation mechanisms or operate as healing mechanisms.
• A gradient plasticity model for porous metals with random spheroidal voids: Theory and applications
  
  • Xenos S
  • Danas K
  • Aravas N
  Mechanics of Materials, Elsevier, 2025, 208, pp.105413. This work deals with the development of a rate-independent, implicit gradient plasticity model for porous metallic materials comprising microstructures with an isotropic distribution of randomly oriented spheroidal voids. We take into account void shape effects via a single constant, the void aspect ratio, which can be used as a calibration parameter for the model. The non-local formulation introduces a characteristic material length, which serves as a regularization parameter and can be estimated by association to a microstructural dimension of the material at hand. The mathematical character of the resulting non-local problem and the conditions for loss of ellipticity are carefully examined. We show, both analytically and numerically, that the proposed model retains the elliptic properties of the governing equations and can provide mesh-independent numerical solutions in the post-bifurcation (softening) regime. This analysis also indicates that the critical localization strain is an increasing function of the void shape. Implementation of the model in the finite element software ABAQUS allows to investigate the effects of the various parameters through the numerical simulation of industrially relevant problems such as the cup-and-cone fracture of cylindrical bars and the Charpy V-notch test. By revisiting the first Sandia Fracture Challenge, we showcase the capability of the model to sufficiently reproduce real-world experimental results while maintaining a manageable number of calibrated parameters. (10.1016/j.mechmat.2025.105413)
  DOI : 10.1016/j.mechmat.2025.105413
• Inter-granular damage in experimentally deformed rock-salt investigated by X-ray micro-tomography: confining pressure and brine effects
  
  • Du Nina
  • Bornert Michel
  • Dimanov Alexandre
  • Aimedieu Patrick
  • Blanco-Martín Laura
  • Jiménez-Camargo Jubier
  Journal of Structural Geology, Elsevier, 2025, 199, pp.105488. We have investigated the mechanical behaviour of synthetic rock-salt during compression tests using in situ X-ray micro computed tomography (XR-μCT). Samples were deformed under controlled strain rate in an X-ray semi-transparent triaxial cell adapted to X-ray tomography. We were interested in the development of micro damage in relation to the stress state and the presence or absence of brine. For that purpose, we produced by powder compaction in œdometric cells two types of materials with different amounts of water. One is considered “laboratory dry” and the other is considered “water saturated”. Both materials exhibit similar mean grain size (c.a. 200 μm). Both types of samples were deformed at uniaxial and triaxial conditions (15 MPa confining pressure), at room temperature and constant displacement rate (1 μm/s). The results show that the dominant damage mechanisms correspond to the progressive development of diffuse inter-granular micro-cracking. This can be explained by the strong anisotropy in the crystal plasticity of NaCl, which results in local plastic strain incompatibilities between neighboring grains in the polycrystalline rock-salt. Conversely, the development of micro-crack damage is strongly reduced by both confining pressure and presence of brine. Natural Leine rock salt samples bearing inter-crystalline brine and tested under similar conditions show similar trends as regards inter-granular micro-damage. We suggest that the development of inter-granular micro-cracking is suppressed or retarded in the presence of brine thanks to dissolution-precipitation processes, which in addition to the well-known healing effect may also reduce the local plastic strain incompatibilities. (10.1016/j.jsg.2025.105488)
  DOI : 10.1016/j.jsg.2025.105488
• Volumetric strain measurements in human cornea : characterization of deswelling, inflation responses and stromal striae microstructures
  
  • Wu Qian
  , 2025. The human cornea, as the eye's outermost transparent layer, plays a vital role in its refractive power. The geometry of the cornea is crucial, as any irregularities can affect its function and visual performance.The stroma makes up about 90% of the cornea's thickness and mainly determines its mechanical properties due to its highly organized collagen structure. Stroma striae, vertical lines in the posterior cornea, can be observed in both healthy and pathological corneas, but they appear morefrequently and are more pronounced in patients with pathologies such as keratoconus.In this thesis, we primarily focus on the biomechanics of the healthy human cornea. Our interest lies in understanding the mechanical properties of the cornea and how they relate to its microstructure. To this end, we coupled Optical Coherence Tomography (OCT) with mechanical testing. Our findings reveal that the cornea exhibits both anisotropy and heterogeniety, particularly in the thickness. We also discovered that stromal striae are fold-like structures at the microscale, and regions containing these striae exhibit greater deformation perpendicular to their orientation compared to the neighboring areas. At an even finer scale, observed using Second Harmonic Generation (SHG) microscopy, we found that this deformation correlates with changes in collagen orientation. Additionally, we observed that the cornea is highly sensitive to its surrouding environment due to its porosity and its osmotic equilibrium with external conditions. This presents challenges for corneal deswelling procedures aimed at restoring physiological thickness and hydration. To address this, we proposed an optimized protocol for effective corneal deswelling.
• Automatically generated cardiovascular digital twin in critical care: a proof of concept study
  
  • Kimmig François
  • Le Gall Arthur
  • Windsor Camille
  • Vallée Fabrice
  • Chapelle Dominique
  • Moireau Philippe
  , 2025. This proof of concept study demonstrates the capabilities of a virtually automatically generated digital twin framework for enhancing hemodynamic monitoring in critical care. By combining a deterministic cardiovascular model with patient-specific data through data assimilation techniques, the digital twin can act as a data denoiser, reconstruct physiological waveforms that are typically unavailable in critical care settings and generate clinically relevant biomarkers. Validation was performed using real data from patients under general anesthesia. The proposed framework efficient calibration and ability to follow the patient's state over time supports the possibility of real-time bedside applications. (10.1007/978-3-031-94562-5_35)
  DOI : 10.1007/978-3-031-94562-5_35
• 3D-Shell Electromechanical Modeling of the Left Atrium
  
  • Ruz Oscar
  • Vidrascu Marina
  • Chapelle Dominique
  • Fernández Miguel Angel
  , 2025, 15672. The thin-walled nature of the atrial wall can lead to numerical locking issues when using 3D models discretized with standard finite elements. In order to circumvent these issues, we introduce a comprehensive electromechanical model of the left atrium based on a 3D-shell formulation. The model integrates both the passive and active components of the atrial tissue, while blood flow and the mitral valve dynamics are described in a lumped parameter fashion. The resulting model is discretized with a finite element approach specifically designed to mitigate numerical locking. The effectiveness of the proposed approach is evaluated by comparing the numerical results with biomarkers reported in the literature, in the case of both healthy and pathological conditions. (10.1007/978-3-031-94559-5_5)
  DOI : 10.1007/978-3-031-94559-5_5
• Fast mesoscopic model of plasticity in polycrystals to compute probabilistic S–N curves in high cycle fatigue
  
  • Echerradi Insaf
  • Weisz-Patrault Daniel
  • Peigney Michael
  International Journal of Solids and Structures, Elsevier, 2025, 315 (1), pp.113348. High cycle fatigue in polycrystals is mostly governed by deterministic laws such as crystal plasticity, but also depends on probabilistic properties, such as random defects and crystallographic and morphological textures, which result in significant scatter of fatigue lifetime at the macroscopic scale. Thus, modeling fatigue phenomena so that the probabilistic density function of failure is anticipated, would be useful especially for very high cycle fatigue involving up to 10 9 cycles. To do so, the grain structure with crystal orientations should be considered in full field computations, which usually involve prohibitive computation cost therefore hindering numerical exploration of statistical distribution of fatigue failures.<p>This paper therefore consists of developing a very fast full field mesoscopic model of polycrystals subjected to crystal plasticity during cyclic loading based on energy minimization techniques. As a result, the uniform plastic slip in each grain is obtained in the form of a relatively simple recursive formula, which guarantees short computation time even for very high cycle fatigue. The proposed approach has been validated against a classical crystal plasticity finite element model in 2D, and satisfying agreement is observed. In addition the model has been applied in combination with classical fatigue criteria to rapidly compute the fatigue lifetime and then derive probabilistic S-N curves, hence creating a substantial link between crystallographic and morphological textures on the one hand, and fatigue lifetime estimations on the other hand.</p> (10.1016/j.ijsolstr.2025.113348)
  DOI : 10.1016/j.ijsolstr.2025.113348
• Motion tracking with Finite Elements Meshes and Image Models
  
  • Álvarez-Barrientos Felipe
  • Škardová Kateřina
  • Genet Martin
  , 2025, LNCS-15672, pp.367-377. Motion tracking plays an important role in many domains including biomedical and mechanical engineering. Numerous methods have been proposed in the literature. While recent machine learning-based approaches provide fairly robust and accurate results, classical methods -combining statistical analysis of image intensity with a model of the underlying motion- remain widely used, as they offer greater control over the obtained results. Such approaches may handle highly complex motions; however, any artifact in the images (e.g., partial voluming, local decrease of signal-to-noise ratio or even local signal void), may drastically affect the tracking. In order to reduce the impact of such artifacts, this paper extends a recently proposed motion tracking approach that relies on both a geometrical model of the tracked object and a model of the images themselves. The problem is thus formulated in terms of finding the displacement of the object such that the generated images, obtained with the image model, best match the acquired images. That way, if any artifact is present in the acquired images but also well represented in the image model, precise motion information can still be recovered from the acquired images. The performance of the proposed method is illustrated on tagged magnetic resonance images, for which acquired images are usually low-resolution, generating significant partial voluming. A simple model of such images is formulated. The method is applied to 2D synthetically generated image series representing various kinematics, with resolutions as low as those found in in vivo acquisitions, and compared to a classical tracking method. In order to avoid computing the cost function gradient, a derivative-free algorithm is used to solve the optimization problem. On the considered examples, the proposed method performs better than the classical tracking method. (10.1007/978-3-031-94559-5_33)
  DOI : 10.1007/978-3-031-94559-5_33
• Upscaling transformation plasticity using full field fast Fourier transform simulations of polycrystals undergoing phase transformations under applied loads
  
  • Hussain Shahul Hameed Nambiyankulam
  • Weisz-Patrault Daniel
  • Appolaire Benoît
  • Denis Sabine
  • Settefrati Amico
  International Journal of Solids and Structures, Elsevier, 2025, 315, pp.113337. Transformation plasticity has been intensively studied because of its significant impact on various industrial fabrication and forming processes. The widely used analytical macroscopic models are based on idealized microstructures and strong assumptions. Such models predict linear (or weakly non-linear) dependence between the transformation plastic strain rate and the applied load, whereas experimental evidence shows that this dependence becomes highly non-linear when the applied stress becomes non-negligible with respect to the macroscopic yield stress. Such a non-linear response is not fully understood especially for phase transformations arising at high temperatures for which the product phase is often softer than the parent phase, and involving visco-plastic behavior.<p>Therefore to overcome this difficulty, the first key contribution of this paper is to exhibit the detailed mechanisms leading to transformation plasticity in steels undergoing austenite to ferrite phase transformation at high temperature and to explain the non-linear dependence between the transformation plastic strain and the applied load. To do so, full-field simulations of visco-plastic polycrystalline aggregates undergoing phase transformations under applied load are performed. In addition, the second key contribution consists in upscaling the outcomes obtained at the scale of the polycrystal into a macroscopic statistical model, that can be used for large simulations of industrial processes. To do so, a database of computations with various initial microstructures, grain shape distributions, and applied loads have been performed, and used to derive the macroscopic statistical model. Of course, to create such a database, a relatively short computation time should be obtained for the full-field simulations, which is achieved by using a fast Fourier transform-based algorithm. Numerical results showed that the combination of two different mechanisms may explain the non-linear behavior of transformation plasticity with respect to the applied load. Moreover, the upscaled statistical model has been tested on full field simulations not included in the database and a good agreement was observed.</p> (10.1016/j.ijsolstr.2025.113337)
  DOI : 10.1016/j.ijsolstr.2025.113337
• Volumetric mechanical properties of soft tissues measured by optical coherence tomography: application to corneal heterogeneity
  
  • Giraudet Chloé
  • Wu Qian
  • Allain Jean-Marc
  Journal of the mechanical behavior of biomedical materials, Elsevier, 2025, 169, pp.107078. Biological tissues have complex mechanical properties, which are deeply related to their function. It is thus needed to quantify the volumetric displacements induced by mechanical load, rather than only surface displacements. In this article, we propose to use Optical Coherence Tomography as a simple and fast method to quantify the volumetric deformation of the cornea under pressure. Indeed, the cornea plays a key role in vision, and any mechanical defect can impact the eye as it is under the intraocular pressure. Our observations show that, in the tangential direction, the cornea deforms more in the posterior than in the anterior region. In the depth direction, we observed a strong compression, with depth-dependent heterogeneity, delineating three distinct regions. This strong compression can be explained only by important outward water fluxes. Our study shows the complexity of human corneal mechanics, highlighting the need of adequate volumetric measure to characterize its strong anisotropy and depth-dependent behavior. (10.1016/j.jmbbm.2025.107078)
  DOI : 10.1016/j.jmbbm.2025.107078
• PlastiNN: A physics-informed neural network architecture for real-time finite strain elasto-plastic simulations
  
  • Lesueur Louis
  • Weisz-Patrault Daniel
  • Thorin Anders
  , 2025. Complex fabrication and forming processes operating under finite strains could benefit significantly from optimization loops, which are often hindered by the prohibitive computational costs of process modeling. Neural networks present a promising solution to accelerate numerical predictions, thereby enabling such optimizations. Furthermore, processes like forging, which involve substantial inherent variability, often require manual process control. Neural networks could provide real-time predictions that would greatly assist in decision-making. Although recursive neural networks have been applied in mechanics, their use in modeling elasto-plastic behavior at finite strains remains underexplored. This paper introduces a neural network architecture that incorporates physical principles by emulating the classical decomposition of elasticity prediction and plastic correction. This approach results in faster training times and more accurate predictions. Additionally, the network can accommodate a series of successive loads on the workpiece, which is critical for the targeted applications. The effectiveness of this strategy is validated through 1D, 2D, and 3D simulations, ranging from challenging toy applications to more realistic industrial test cases, highlighting the potential of the proposed neural network architecture for modeling elastic-plastic behavior at finite strains in engineering processes. The databases that were used in this work are openly accessible, for other researchers to compare.
• Fixing non-positive energies in higher-order homogenization
  
  • Thbaut Manon
  • Audoly Basile
  • Lestringant Claire
  Journal of the Mechanics and Physics of Solids, Elsevier, 2025, pp.106168. Energy functionals produced by second-order homogenization of periodic elastic structures commonly feature negative gradient moduli. We show that this undesirable property is caused by the truncation of the energy expansion in powers of the small scale separation parameter. By revisiting Cholesky's LDLT decomposition, we propose an alternative truncation method that restores positivity while preserving the order of accuracy. We illustrate this method on a variety of periodic structures, both continuous and discrete, and derive compact analytical expressions of the homogenized energy that are positive and accurate to second order. The method can also cure the energy functionals produced by second-order dimension reduction, which suffer similar non-positivity issues. It naturally extends beyond second order. (10.1016/j.jmps.2025.106168)
  DOI : 10.1016/j.jmps.2025.106168
• Clavier à dynamique contrôlée pour pianos numériques
  
  • Boutillon Xavier
  • Chichignoud Jérémie
  • Lamy Raphaël
  • Somma Antonio
  , 2025. Le toucher des meilleurs pianos numériques est obtenu par l'insertion dans l'instrument de mécanismes pratiquement identiques au mécanisme traditionnel. D'autres dispositifs, dits "à toucher lourd", comportant le plus souvent un pseudo-marteau, sont utilisés, mais leur rendu haptique est généralement considéré comme insuffisamment réaliste par rapport à la référence que constitue le mécanisme de clavier de piano à queue. Nous proposons un dispositif où le mouvement de la touche du piano numérique est capté lors du jeu et utilisé par un micro-contrôleur pour calculer la force qui serait opposée au doigt du pianiste par le mécanisme traditionnel. Cette force, corrigée de l'effet intrinsèque de la touche du piano numérique, est appliquée à cette touche par un actuateur commandé en temps réel par le micro-contrôleur. Le dispositif est paramétrable, en particulier suivant les valeurs que l'on souhaite donner aux principaux éléments du mécanisme traditionnel imité. Le projet ClaviDyC est financé par la Satt Paris-Saclay.
• Gabriel Weinreich, aux multiples facettes
  
  • Boutillon Xavier
  , 2025. Peu de chercheurs ont leur nom, et au moins une partie de leurs travaux, connus de sans doute tous les chercheurs en acoustique musicale, et probablement de la grande majorité des curieux de ce domaine ; Gabriel Weinreich est l'un d'eux. Pour ceux qui l'ont connu, le souvenir de sa pensée originale, mais sans ostentation, reste durablement associé à la fois à la vigueur de ses apports scientifiques et à la chaleur de sa générosité personnelle. À ceux qui n'ont pas eu la chance de le rencontrer personnellement, il ne sera peut-être pas indifférent d'entendre évoquer quelques souvenirs symptomatiques de cette originalité de pensée, dans les registres tout à la fois scientifique, religieux, musical, relationnel, professoral, informatique, linguistique, esthétique, automobile, historique.
• The role of pianistic movement idiosyncrasies in musical interpretation
  
  • Somma Antonio
  • Roudet Jeanne
  • Fabre Benoît
  , 2025. The physical function of a musician’s movement is to exert mechanical work on the instrument, thereby controlling sound production. Different movement profiles can result in the same displacement at the musician-instrument interface, producing an identical sound. Additionally, movement has a cognitive function, embodying the meaning the musician attributes to the sound—that is, its expressivity. Each musician thus develops a personal movement strategy that combines these two functions. Research on instrumental performance often focuses on shared movement features rather than individual-specific ones, typically examining their relationship to sound control physiology or to the formal structure of the score. Our study adopts a complementary approach, linking movement specificities to interpretive singularities. Two pianists, engaged in a historically informed approach, were interviewed about their technique. Thematic analysis shed light on the pianists’ verbalized gesture strategies as embodiment of their individual aesthetic frameworks. Specificities in their gesture strategies were highlighted. The same pianists then performed the same piece on a historical piano. Upper-limb movements and audio recordings were analyzed to determine their interpretive choices as well as movement idiosyncrasies. Verbalized gesture strategies, interpretive choices, and movement idiosyncrasies were compared, revealing the inherently expressive nature of the movements performed.
• Clavier à toucher versatile pour instruments numériques
  
  • Somma Antonio
  • Boutillon Xavier
  , 2025. Les instruments de musique traditionnels à clavier − clavicorde, clavecin, orgue, pianoforte, piano moderne, etc. − présentent une grande diversité de touchers aux musiciens. Sur le plan perceptif, un instrument à clavier est considéré ici comme l’association d’un toucher et de l’ensemble des sons générés par l’instrument. La diversité des touchers reflète celle des dispositifs associés au clavier qui permettent de générer le son ou d’en commander l’obtention. Ces dispositifs sont le plus souvent purement mécaniques et passifs, mais parfois électriques. Depuis des dizaines d’années, des instruments où le son est produit électriquement se sont développés, souvent dans l’objectif d’imiter les instruments traditionnels, le piano en particulier. Certains de ces instruments sont devenus des standards, indépendamment de leur succès ou non dans l’imitation d’un instrument traditionnel. Notre projet de «Clavier à toucher versatile pour instruments numériques» vise à offrir aux claviéristes, au sens le plus large, un clavier dont ils puissent choisir le toucher en référence à celui d’un instrument connu, l’adapter à leurs préférences, ou régler ce toucher à partir de caractéristiques proposées. Notre dispositif associe la mesure du mouvement de la touche, le calcul en temps réel du rendu haptique par un micro-contrôleur et l’actionnement par un dispositif actif. En raison de ses particularités, l’imitation du mécanisme du piano à queue fait l’objet d’une réalisation spécifique, présentée dans une communication séparée. Le projet <i>ClaDyVers</i> est soutenu par l’Institut polytechnique de Paris.
• Residual stress control in large format polylactic acid additive manufacturing via fast thermomechanical simulation and in-operando imaging techniques
  
  • Viano Rafaël
  • Demont Léo
  • Margerit Pierre
  • Mesnil Romain
  • Caron Jean-François
  • Weisz-Patrault Daniel
  , 2025. Polymer-based Large Format Additive Manufacturing (LFAM) is an extrusion-based technology utilizing a robotic arm-mounted nozzle to deposit large-diameter polymer beads from heated polymer pellets. However, technical challenges arise due to slower cooling rates and heat accumulation, significant deformation that should be accounted for updating the nozzle path, as well as the development of residual stresses from thermo-chemical shrinkage leading to debonding. To overcome these challenges, the study proposes to combine recent and fast thermal and mechanical approaches. This computationally efficient digital twin of the process is validated experimentally on a thin-wall structure using polylactic acid as a feedstock material. To do so, anisotropic material properties are characterized, and in-operando temperature and displacement field measurements are performed using an infrared thermal camera and backward Digital Image Correlation techniques. Numerical results are in satisfying agreement with experimental data. The validated digital twin is then utilized to characterize the effect of process parameters on the number of layers above the glass transition temperature, the formation of residual stresses and the position offset between the top surface of the structure and the nozzle. This paper presents a fast numerical tool to better design fabrication conditions and improve the quality and fabricability of LFAM-produced parts.
• High-vacuum laser treatments enhance strength, ductility and fatigue limit of additively manufactured stainless steel
  
  • Santos Macías Juan Guillermo
  • Chen Kewei
  • Tanguy Alexandre
  • Isac Nathalie
  • Vallet Maxime
  • Cornet Louis
  • Michel Vincent
  • Upadhyay Manas Vijay
  , 2025, pp.114064. Post-process laser scanning under high vacuum is proposed as a non-isothermal heat treatment to simultaneously refine the intragranular microstructure near the surface and reduce surface roughness, while also preventing oxidation, in order to enhance the overall mechanical response of an alloy. This treatment is performed using laser spot sizes and scan speeds that produce higher temperature gradients and faster heating/cooling rates than those encountered during manufacturing. The effectiveness of this approach is demonstrated on laser-based direct energy deposited (LDED) 316L stainless steel using parameters similar to those used in laser-based powder bed fusion (LPBF). High vacuum (< 0.1 Pa) lasering is conducted inside a newly integrated continuous-wave laser and scanning electron microscope (CW Laser-SEM). The treatments result in an order-of-magnitude reduction in microsegregation cell and dislocation structure sizes, as well as in the surface roughness of LDED 316L. For a parameter set in which the laser penetrates 14% of the total depth (7% each on the two widest surfaces of dogbone-shaped samples), significant improvements are obtained in yield strength (31.11%), ductility (14.2%), and fatigue limit (25%). The proposed approach has tremendous potential to alter the microstructure and improve the mechanical response of both additively and conventionally manufactured alloys. (10.1016/j.matdes.2025.114064)
  DOI : 10.1016/j.matdes.2025.114064
• Modèle mécanique rapide multi-fils pour la fabrication additive à base de cordons
  
  • Preumont Laurane
  , 2025. La fabrication additive à base de cordons repose sur le dépôt successif de fils de matière caractérisés par un rapport d'aspect singulier : leur longueur dépasse de plusieurs ordres de grandeur leur section millimétrique. Si cette géométrie suggère naturellement une modélisation unidimensionnelle, la superposition des cordons crée un solide tridimensionnel au comportement mécanique complexe, notamment en raison des gradients thermiques inhérents au procédé.Pour prédire les déformations lors de la fabrication, la simulation numérique est indispensable. L'approche conventionnelle par éléments finis 3D nécessite un maillage très fin, générant des temps de calcul prohibitifs pour les pièces réelles, particulièrement en optimisation où de nombreuses itérations sont requises.Cette thèse vise à développer une stratégie de modélisation rapide des procédés additifs permettant d'évaluer l'état de contrainte des pièces pour limiter les déformations. L'originalité réside dans le développement du modèle QuadWire qui, plutôt que de raffiner le maillage 3D, propose une description enrichie du cordon comme structure unidimensionnelle à quatre particules par point matériel. Cette cinématique capture la complexité des états mécaniques 3D tout en réduisant significativement les degrés de liberté.Le chargement est appliqué via des déformations libres calculées par un logiciel thermique rapide. Le comportement élastique s'inscrit dans le cadre des matériaux standards généralisés, permettant des extensions futures. Les paramètres sont identifiés par comparaison avec un modèle 3D raffiné.Le manuscrit comprend trois parties principales précédées de rappels théoriques sur la modélisation multiparticulaire, l'optimisation sous contrainte et l'état de l'art en simulation de fabrication additive. Les fondements théoriques du modèle QuadWire sont d'abord présentés, en justifiant tous les choix axiomatiques qui mènent aux efforts généralisés, puis les équations d'équilibre sont établies par le principe des puissances virtuelles. L'implémentation numérique aux éléments finis linéaires est ensuite détaillée, démontrant des gains significatifs en degrés de liberté. Enfin, deux chapitres d'optimisation traitent de l'identification des paramètres matériau et du développement d'un schéma d'optimisation pour la contre-déformée.Les contributions principales concernent le développement théorique du modèle, son implémentation modulaire en accès libre, et ses applications pratiques en optimisation de forme sous contrainte. Cette approche innovante permet de réduire significativement les temps de calcul tout en maintenant une précision satisfaisante. La diffusion du code en accès libre favorisera ses futurs développements.
• Theory of Bauschinger and Some Other Memory Effects in Glassy Polymers
  
  • Merlette Thomas C
  • Clément Florence
  • Sotta Paul
  • Long Didier R
  Macromolecules, American Chemical Society, 2025, 58 (6), pp.3298-3320. We proposed recently that the strain hardening of glassy polymers is attributed to the increase of free energy barriers for α-relaxation as a consequence of local orientation of Kuhn segments during the course of deformation. As the chains have been signicantly oriented at the Kuhn segments scale, the contribution of Kuhn segments orientation to free energy barriers may become large and may then overcompensate the decrease of free energy barriers due to the increasing stress, the latter being responsible for yield and the onset of plastic ow. We show that the slow relaxation of Kuhn segments orientation explains the various memory eects observed in the strain hardening regime and generically named Bauschinger eect. It explains the fact that the stress-strain curve of a second deformation after some waiting time at some point in the strain hardening regime rejoins the reference curve, and that a yield stress is present for this second deformation. Indeed, the degrees of freedom which control the free energy barriers associated to yield relax on the time scale of the experiment, whereas Kuhn segments orientations, that is the degrees of freedom which control the free energy barriers associated to plastic ow in the strain hardening regime, relax slowly. We calculate the evolution of the relaxation time distributions, as well as that of the dominant relaxation time and of the Kuhn segments orientations, during successive deformations (tractiontraction, traction-compression, compression-traction, compression-compression). These predictions could be tested experimentally. (10.1021/acs.macromol.4c01745)
  DOI : 10.1021/acs.macromol.4c01745
• Estimating elastic and thermal contributions to lattice strains from operando X-ray diffraction measurements using fast simulations
  
  • Gaudez S.
  • Weisz-Patrault D.
  • Abdesselam K.A.
  • Gharbi H.
  • Honkimäki V.
  • van Petegem S.
  • Upadhyay M.V.
  Additive Manufacturing, Elsevier, 2025, 101, pp.104674. Lattice strains obtained from operando synchrotron X-ray diffraction measurements during metal additive manufacturing are being increasingly used to estimate temperature evolution during the process. At the minimum, these transient lattice strains have contributions from thermal and elastic strains. Temperature estimates from lattice strains have thus far been extracted assuming that elastic strains are negligible in comparison to thermal strains at high temperatures when the heat source is close to the probed region. However, such an assumption may not only lead to inaccuracies in estimating temperature but also fail to correctly estimate the non-negligible stress evolution occurring at moderate to low temperatures as the heat source moves away. Numerical simulations can be used to predict lattice strains but these predictions are necessarily different from experimental measures.<p>This work proposes an experimentally corrected numerical approach to improve simulation predictions. It involves first using a recently developed fast numerical thermomechanics model to predict lattice strains. Then, the predicted thermal and elastic strains are corrected using a minimization procedure under the strict constraint that the predicted lattice strains are strictly equal to the measured ones, thus improving the original estimates. This strategy is demonstrated for operando synchrotron X-ray diffraction measurements during directed energy deposition of a thin wall made from 316L stainless steel, which exhibits negligible solid-state phase transformations. Following validation, the corrected thermal and elastic strains are used to estimate temperature and stress evolution and study the difference in temperature and heating/cooling rate prediction caused by neglecting elastic strains.</p> (10.1016/j.addma.2025.104674)
  DOI : 10.1016/j.addma.2025.104674