Publications

2026

• High strain-rate failure mechanisms of additively manufactured IN718 Gyroid structures: Experiments and numerical insights
  
  • Weller Alexis
  • Querois Julie
  • Vallino Nicolas
  • Francart Charles
  • Forquin Pascal
  • Constantinescu Andrei
  International Journal of Impact Engineering, Elsevier, 2026, 218, pp.105826. (10.1016/j.ijimpeng.2026.105826)
  DOI : 10.1016/j.ijimpeng.2026.105826
• Longitudinal waves in two-dimensional quasi-periodic lattices
  
  • Comi Claudia
  • Moscatelli Marco
  • Marigo Jean-Jacques
  European Journal of Mechanics - A/Solids, Elsevier, 2026, 119, pp.106194. We study longitudinal wave propagation in a two-dimensional elastic lattice formed by parallel bars coupled by slender beams whose out-of-plane thickness is modulated according to an Aubry-André-Harper profile. This modulation can yield periodic or quasi-periodic architectures depending on the choice of the parameters. Starting from the continuous bar-beam model, we derive a discrete formulation and analyze the existence of bounded solutions and band-gaps as functions of the modulation amplitude and geometry. We provide analytical criteria for band-gap nucleation and explicit estimates of gap widths, and we show how quasiperiodicity can both create new gaps and shrink existing ones relative to the periodic case. The results offer new insights on the influence of quasi-periodicity in 2D elastic lattices. We show numerically how this class of structures can be exploited to achieve topological pumping of elastic waves. (10.1016/j.euromechsol.2026.106194)
  DOI : 10.1016/j.euromechsol.2026.106194
• A probabilistic framework for irreversible kinetics
  
  • Upadhyay Manas V
  , 2026. A probabilistic framework for irreversible kinetics is proposed in which a constrained path functional $\mathcal J$ encodes constitutive physics and observations on the admissible history space $\mathcal H_{\rm ad}$, while a discrete Gibbs-type measure proportional to $\exp(-\mathcal{J}/\Theta)$ assigns probabilities to a candidate set $\mathcal{H} \subseteq \mathcal{H}_{\rm ad}$. The framework unifies forward-in-time evolution and inverse inference, which differ only through observations and how they constrain admissible histories. The parameter $\Theta$ controls epistemic uncertainty, and the measure is interpreted as a Bayesian posterior over histories. Maximizing this posterior is equivalent to simultaneous minimization of $\mathcal{J}$ over $\mathcal{H}$, distinguishing the continuous minimizer $h_{\rm cont}$ over $\mathcal{H}_{\rm ad}$ from the discrete maximum a posteriori (MAP) history $h_{\rm MAP}$ over $\mathcal{H}$. As $\Theta\to0$, the posterior concentrates on the discrete MAP set. For generalized standard material(GSM)-type incremental energy--dissipation functionals, seven forward-in-time examples show that, despite using the same incremental functionals, causal GSM evolution is generally only incrementally optimal. When minimizers are unique, observations are absent, and $h_{\rm cont}\in\mathcal{H}$, the strict ordering $\mathcal{J}(h_{\rm cont}) = \mathcal{J}(h_{\rm MAP}) < \mathcal{J}(h_{\rm GSM})$ holds, showing that the GSM history does not minimize the cost of the entire history. Finally, an endpoint-conditioned inverse problem with nonconvex energy demonstrates the finite-$\Theta$ capability of the framework to infer unobserved states and quantify uncertainty over admissible histories.
• Comparative Evaluation of Camera Modules for Real-time Deep Learning-Based Detection of Tomato Plants and Weeds on a Raspberry Pi Platform
  
  • Sharma Apoorva
  • Kumar Arun
  • Sharma Hemant Kumar
  Archives of Current Research International, Sciencedomain International, 2026, 26 (8), pp.332-342. Aims: To evaluate and compare three camera modules, namely a USB webcam, a smartphone camera, and a Raspberry Pi Camera Module, for real-time detection of tomato plants and weeds, in order to identify the most suitable imaging sensor for deployment in a precision spraying system. Study Design: Comparative experimental evaluation of camera hardware under static and simulated dynamic field conditions. Place and Duration of Study: Department of Farm Machinery and Power Engineering, G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India, between July and September 2024. Methodology: A You Only Look Once (YOLO)11n object detection model, trained to identify tomato plants and weeds, was deployed on a Raspberry Pi 4B for real-time inference. Three imaging sensors, a 2-megapixel (MP) USB webcam, a 64 MP smartphone camera (POCO M4 Pro) interfaced via the DroidCam application over Wi-Fi, and a 5 MP Raspberry Pi Camera Module interfaced through the Camera Serial Interface (CSI), were evaluated under static conditions and under conveyor-simulated dynamic conditions at 1 km/h. The modules were compared on resolution, interface type, integration complexity, image quality, detection accuracy, processing latency, and power requirement. Results: The USB webcam exhibited poor image quality and a processing latency of 1250–1365 milliseconds (ms). The smartphone camera achieved the highest image quality and detection accuracy but showed a latency of approximately 2,000–3,000 ms due to Wi-Fi-based streaming. The Raspberry Pi Camera Module recorded the lowest latency (700–900 ms), moderate-to-high detection accuracy, and required no external power source, giving it the most favourable overall balance among the three sensors. Conclusion: Data transmission pathway, rather than sensor resolution alone, was the decisive factor determining real-time deployability. The Raspberry Pi Camera Module was accordingly selected for the final precision spraying prototype, and these findings offer practical guidance for imaging sensor selection in edge-deployed, real-time precision agriculture systems. (10.9734/acri/2026/v26i82061)
  DOI : 10.9734/acri/2026/v26i82061
• Mechanics of surface accretion with application to inelastic bodies
  
  • Nevenchannyy Yury
  • Jabbour Michel
  • Guin Laurent
  , 2026, pp.106788. We derive a continuum theory of surface accretion that allows for inelastic behavior, thus going beyond existing models for elastic growth. We employ a Lagrangian framework with a time-dependent arbitrary reference configuration and adopt a multiplicative decomposition of the deformation gradient to account for both inelastic and elastic strains arising at attachment and their subsequent evolution. In doing so, we formulate the governing equations and identify the additional boundary conditions required at the accreting boundary. The inelastic behavior is then specialized to isochoric, irrotational, and isotropic viscoplasticity. By solving examples with spherical symmetry, we first demonstrate that our framework recovers existing analytical solutions for elastic bodies, while making explicit the assumptions underlying them. Second, for viscoplastic bodies, we show that, unlike in the elastic case where the solution is rate-independent, the mass flux acts as a mechanical loading parameter that determines the interplay between material addition and stress relaxation. This is of particular relevance to growth of rate-dependent materials such as lithium-metal electrodes in solid-state batteries. (10.1016/j.jmps.2026.106788)
  DOI : 10.1016/j.jmps.2026.106788
• GreenMelt: Part-Scale Ultra-Fast Melt Pool Prediction in Laser Powder Bed Fusion Accounting for Latent Heat and Marangoni Convection
  
  • Weisz-Patrault Daniel
  , 2026. Predicting microstructure in Laser Powder Bed Fusion (LPBF) or laser surface scanning requires accurate thermal analysis-including melt pool shape resolution at the part scale-yet remains computationally prohibitive due to the coupling between macro-scale heat accumulation and mesoscale melt pool phenomena. Thermal history governs solidification microstructure, making its rapid and accurate prediction a prerequisite for process parameter optimization. In this work, we propose a two-scale thermal model, named GreenMelt, that fully couples a macroscopic module, capturing part-scale heat accumulation, with an ultra-fast mesoscopic module resolving the melt pool and especially the zone where solidification takes place. The approach is formulated using Green's functions supplemented by physically-based distributed heat sources that account for the principal nonlinearities of the problem: latent heat of solidification and vaporization, and temperature redistribution induced by Marangoni convection. The framework supports arbitrary laser scan paths and nonlinear thermal contributions without compromising computational efficiency. The temperature field in the melt pool for single-track experiments is computed in 1 to 10 seconds on a laptop, compared to 3.5 to 5.5 hours for equivalent Computational Fluid Dynamics (CFD) simulations. Good quantitative agreement is maintained, with an average relative error in the mushy zone below 3%. The model's capabilities are further demonstrated on a full three-dimensional LPBF numerical experiment, confirming its applicability at the part scale. This approach makes the rapid numerical optimization of process parameters -including laser power, velocity, and scan strategy -tractable, enabling fine control over microstructure and mechanical properties in industrial LPBF components.
• On the limits of the energetic coupling between field dislocation mechanics and phase field crystal
  
  • Graini Aymane
  • Viñals Jorge
  • Upadhyay Manas V
  , 2026. This paper investigates the energetic coupling between Field Dislocation Mechanics (FDM) and the Phase Field Crystal (PFC) model proposed in Phys. Rev. B 102, 064109, 2020. While FDM correctly solves the initial boundary value problem of a continuum body with dislocation fields, PFC captures the underlying crystallographic structure. The coupling, which penalizes the L 2 distance between elastic distortion from FDM and configurational distortion from PFC in the L 2 sense, had been proposed to reconcile dislocation mechanics with crystallography in a single continuum framework. Variational analysis reveals that the coupling term acts as a divergence-driven forcing in the phase-field evolution that matches only the compatible (curl-free) parts of the distortion fields. Consequently, its contributions are insensitive to the incompatible (divergence-free) elastic distortion carrying all the information on dislocation topology. Furthermore, the nature of the configurational distortion causes mechanical boundary conditions to be transmitted diffusively from FDM to PFC rather than elastically. Numerical simulations demonstrate that this coupling cannot prevent the unnatural core spreading in FDM. Finally, it is shown that even in the most general case, an energetic coupling suffers from the same drawbacks, which limits its ability to integrate dislocation mechanics with crystallography.
• Mechanical Cloaking of Halftoned Imagery
  
  • Martínez Jonàs
  • Brisard Sébastien
  • Danas Kostas
  • Garner Eric
  • Kumar Siddhant
  • Lefebvre Sylvain
  ACM Transactions on Graphics, Association for Computing Machinery, 2026, 45 (4). Cloaking objects with metamaterials has been extensively studied to hide internal objects across various physical properties, including optical, acoustic, and thermal. We explore a new direction in mechanical cloaking: halftoning an image using a porous structure that behaves like a uniform, linear, isotropic material and visually matches a target image. For an external observer, this creates the surprising effect where the object appears mechanically isotropic and homogeneous while its porous structure resembles a target image. We introduce a parametric class of porous structures suitable for this problem, as demonstrated by numerical experiments. The structures we define offer a wide range of visual contrasts, enabling effective halftoning while maintaining near isotropic effective mechanical properties. (10.1145/3811394)
  DOI : 10.1145/3811394
• Unraveling plastic strain localization in aluminum polycrystals by coupling of in situ high-resolution digital image correlation and crystal plasticity
  
  • Girault Florian
  • Toualbi Louise
  • Tanguy Alexandre
  • Ask Anna
  • Charkaluk Eric
  Mechanics of Materials, Elsevier, 2026, 217, pp.105645. This study investigates the localization of plastic deformation in a small-grain 7xxx-series aluminum polycrystal. A particular focus is placed on analyzing the contribution of certain key features of the microstructure in the onset of local plasticity. One of the strengths of this study is the use of diverse experimental and numerical approaches. Particular attention was given to the methodological aspects of these approaches, which are used both for statistical and local analyses. A nanometric speckle pattern was used to track the intra-granular deformations of tensile specimens using high-resolution digital image correlation (HRDIC). These deformations were then correlated with relevant microstructure data. In parallel, a crystal plasticity model was implemented. Its purpose was to complete the experimental results and provide additional data inaccessible with DIC. A very weak correlation between plastic activity and crystallographic grain-averaged data was demonstrated, even for the Schmid factor. This shows the significance of the polycrystal effect due to the interactions between neighbor grains. Intermetallics exhibit a hard and brittle behavior, which triggers strain localization in their vicinity. However, particle clusters do not manifest any specific behavior. In addition, the experimental maps showed deformation concentrations near grain boundaries, of which the most deformed ones were detected using a machine learning procedure. The associated deformation mechanisms were numerically investigated, and it was shown that most grain boundaries can lead to stress and/or strain localization, even those featuring a good slip compatibility. (10.1016/j.mechmat.2026.105645)
  DOI : 10.1016/j.mechmat.2026.105645
• Modélisation à double porosité d'une microstructure à trois phases pour la perfusion pulmonaire
  
  • Xiao Haotian
  • Genet Martin
  , 2026. Modélisation à double porosité d'une microstructure à trois phases pour la perfusion pulmonaire
• NN-PGD for surrogate modeling of PDEs on parametrized domains
  
  • Škardová Kateřina
  • Daby-Seesaram Alexandre
  • Genet Martin
  , 2026. This work presents an extension of the Neural Network-Proper Generalised Decomposition (NN-PGD) framework for constructing surrogate models of PDEs defined on parametrized domains. Using a mapping onto a reference domain, the method allows a single model to provide solutions across a range of geometries. The framework combines the PGD with physics-informed training, enabling the modes to be learned directly from the governing equations. The approach is demonstrated on a 2D linear elasticity problem on a parametrized hexagonal domain.
• Data-driven reduced modeling of pleural pressure
  
  • Álvarez-Barrientos Felipe
  • Herszkowicz Quentin
  • Duwat Adrien
  • Fetita Catalin
  • Maître Xavier
  • Rodriguez Dima
  • Genet Martin
  , 2026. Pulmonary digital twins could enhance clinical diagnosis and treatment, but still rely on simplified boundary conditions for mechanical simulations. To address this, we build a pleural pressure model based on dynamic MRI using a poromechanical approach. Higher-order SVD is applied to pressure estimates from 10 volunteers to extract distinct spatial and temporal modes and quantify their separability. This reduced-order model identifies common patterns across subjects, potentially related to physiological variables, supporting the development of more realistic boundary conditions.
• Modélisation biomécanique des muscles extra-oculaires appliqué à un modèle optique
  
  • Bonnafé Julien
  • Allain Jean-Marc
  • Rio David
  , 2026. Nous développons un modèle éléments finis de l’œil, incluant le globe oculaire, les muscles extra-oculaires, le nerf optique et la graisse orbitale, afin d’analyser les efforts mécaniques lors de mouvements oculaires. Nous utilisons un modèle de Hill pour les muscles. Notre modèle inclut des contraintes internes (pression intraoculaire...). Au travers d’une géométrie simplifiée, nous montrons l’importance des contraintes internes et de la prise en compte de la graisse pour reproduire des mouvements réalistes de l’œil, et leurs conséquences sur la réfraction.
• A class of optimal virtual fields for inverse problems in elasticity
  
  • Chibli Nagham
  • Genet Martin
  • Imperiale Sébastien
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2026, 354 (G1), pp.417-449. This work addresses the identification of nonhomogeneous constitutive parameters from full-field measurements in both linear and nonlinear elasticity, considering incompressible as well as compressible materials. The inverse identification procedure relies on the Virtual Fields Method (VFM), which is based on the principle of virtual work with specifically chosen virtual fields. We propose an optimal class of virtual fields, designed to optimize the reconstruction stability with respect to measurement noise. A series of numerical experiments illustrate the effectiveness of the proposed approach. The method exhibits moderate sensitivity to measurement noise and remains robust even when the boundary conditions are only partially known. (10.5802/crmeca.361)
  DOI : 10.5802/crmeca.361
• Homogenizing elastic lattices with mechanisms
  
  • Audoly Basile
  • Lestringant Claire
  • Nassar Hussein
  European Journal of Mechanics - A/Solids, Elsevier, 2026, 117, pp.105956. We propose an asymptotic method for homogenizing periodic elastic lattices that works in the presence of mechanisms, both of the macroscopic type (strain-producing modes) and of the microscopic type (internal modes). When a microscopic mechanism is present, the unit-cell problem produced by classical homogenization is singular. It can be fixed by including the amplitude~$\theta (\mathbf{X})$ of the mechanism as an additional macroscopic degree of freedom (enrichment variable) contributing to the effective energy via its gradient $\nabla \theta (\mathbf{X})$. When a macroscopic mechanism is present, homogenization delivers a degenerate effective energy at leading order, which can be regularized by accounting for the strain gradient. We introduce an asymptotic second-order homogenization scheme that integrates these two features: it delivers an effective energy capturing both the strain-gradient effect $\nabla \mathbf{\varepsilon} (\mathbf{X})$ relevant to macroscopic mechanisms, and the $\nabla \theta (\mathbf{X})$ regularization relevant to microscopic mechanisms, if any is present. The versatility of the approach is illustrated with a selection of lattices displaying a variety of effective behaviors. It follows a unified pattern that leads to a classification of these effective behaviors. Whereas the procedure delivers known effective models for elastic lattices without mechanisms, it can generate novel effective models for lattices possessing mechanisms. (10.1016/j.euromechsol.2025.105956)
  DOI : 10.1016/j.euromechsol.2025.105956
• Experimental Investigation of Rock Salt Rheology Under Multiple Load Paths Applied in the Laboratory and in Salt Mines
  
  • Blanco-Martín Laura
  • Jiménez Camargo Jubier Alonso
  • Gharbi Hakim
  • Dimanov Alexandre
  • Bornert Michel
  • Brouard Benoit
  Rock Mechanics and Rock Engineering, Springer Verlag, 2026. An extensive experimental program on rock salt comprising short-term and long-term tests has been performed on samples from the same origin and prepared and preconditioned using the same protocols. The main targets are to investigate the thermo-mechanical response of rock salt under different load paths and to produce a large database on which constitutive models can be formulated and calibrated. A total of 17 tests have been conducted, including four uniaxial experiments. Temperatures range between 8 and 60 °C, and some tests last more than 2 years. The experiments cover a differential stress range relevant for underground applications. Deviators within 0.2−4.5 MPa have been investigated through uniaxial creep experiments in salt mines to take advantage of very stable ambient conditions (particularly, temperature and relative humidity). Deviators up to 35 MPa have been investigated through confined experiments in the laboratory. Additionally, a cross-check quasi-uniaxial test (confinement of 0.2 MPa) has been performed in the laboratory under conditions similar to those of the mine, and proves that experiments in both settings can be combined to extend the range of investigated stresses. However, uniaxially loaded samples show higher strain rates than confined samples. X-Ray computed tomography suggests more micro-fracturing during the former. The results obtained under confined conditions are consistent and confirm the different stress dependency of the creep rate under low and high deviators. A modified Lemaitre model is used to analyze the results. Next steps include microstructural investigations to gain insight into the dominant deformation mechanisms under different thermo-mechanical loads, allowing for more predictive constitutive models. (10.1007/s00603-026-05496-x)
  DOI : 10.1007/s00603-026-05496-x
• On the accuracy of 2D microstructure simulations to predict formation of intergranular residual mechanical fields during rapid laser-metal interactions
  
  • Mohanan Nikhil
  • Chadwick Alexander F
  • Samaei Arash
  • Bleyer Jérémy
  • Helfer Thomas
  • Wagner Gregory J
  • Voorhees Peter W
  • Upadhyay Manas V
  , 2026. The extent to which a three-dimensional extrusion of a two-dimensional microstructure (2DM) can reproduce the thermomechanical response of a fully three-dimensional microstructure (3DM) is investigated. A multi-physics numerical framework coupling computational thermal fluid dynamics (CFD), phase-field (PF) solidification, and thermo-elasto-viscoplastic finite element (TEVP-FE) modeling is employed to simulate a single laser line scan on a 316L stainless steel substrate. The temperature evolution obtained from CFD and the final microstructure predicted by PF simulations are used to perform two TEVP-FE simulations that differ only in the representation of the microstructure: 2DM and 3DM. Residual stresses, plastic strains, and Nye's tensor are compared at both local and statistical levels. The 2DM approximation captures the overall spatial evolution trends and the order of magnitude of residual stresses, but it does not reproduce the localization of shear stresses, plastic strains, and Nye's tensor, which is strongly influenced by the 3D grain morphology. Nevertheless, comparison of grain surface-averaged quantities on the lasered surface shows that the intergranular mechanical fields predicted by 2DM and 3DM match well in magnitudes and evolution trends. These results quantify the advantages and limitations of 2D microstructure approximations and provide guidance on the model complexity required for predicting intergranular mechanical fields at local and statistical levels.
• Stability of time stepping methods for discontinuous Galerkin discretizations of Friedrichs' systems
  
  • Imperiale Sébastien
  • Joly Patrick
  • Rodríguez Jerónimo
  , 2025. In this work we study new various energy-based theoretical results on the stability of s-stages, s-th order explicit Runge-Kutta integrators as well as a modified leap-frog scheme applied to discontinuous Galerkin discretizations of transient linear symmetric hyperbolic Friedrichs' systems. We restrict the present study to conservative systems and Cauchy problems.
• Continuous microstructure variations with graded properties in directed energy deposition
  
  • Bréhier Michèle
  • Weisz-Patrault Daniel
  • Tournier Christophe
  Additive Manufacturing Letters, Elsevier, 2026, 17, pp.100372. <div><p>Directed energy deposition additive manufacturing is a versatile technique for fabricating complex geometries, where precise control of process parameters is crucial for tailoring microstructure and part properties. Microstructure control strategies usually involve variation of material composition (i.e., functionally graded materials) or interlayer time delay. However, the obtained microstructures are usually uniform in the print direction and exhibit sharp transitions from one layer to the next in the build direction. This paper targets continuous microstructural variation by exploiting active cooling strategies to control cooling conditions. To do so, the scanning speed is continuously varied, necessitating accommodating the bead size variations with non-standard trajectory generation based on a phenomenological law. The proposed strategy is demonstrated on thin-wall structures made of IN718 using a powder-based laser directed energy deposition. The results reveal a continuous microstructural transition along the print direction, characterized by two distinct microstructural regimes with markedly different morphological features and crystallographic textures. This demonstrates the capability of scanning speed modulation to engineer heterogeneous microstructures within a single component, offering insights into tailoring material properties for specific engineering applications.</p></div> (10.1016/j.addlet.2026.100372)
  DOI : 10.1016/j.addlet.2026.100372
• Controlling pattern formation via magnetic field at the surface of magneto-active elastomer structures
  
  • Selvam Vignesh
  , 2026. Magnetorheological elastomers (MREs) are smart composite materials composed of magnetizable particles embedded in an elastomeric matrix. They respond readily and reversibly to applied magnetic fields through magneto-induced deformations or surface instabilities driven by coupled magneto-mechanical stresses and magnetic interactions. In layered MRE film–substrate systems, such instabilities can be triggered by mechanical, magnetic, or combined loading, leading to surface morphologies ranging from periodic wrinkling to more complex crinkling patterns. Despite extensive experimental and numerical efforts, these phenomena have so far been mostly limited to uniform films, resulting in 2.5D patterns with restricted tunability. However, achieving fully three-dimensional surface morphologies in uniform films requires large magnetic fields, while instability is often confined to narrow ranges of mechanical loading. This work aims to overcome these limitations by enabling controllable, targeted three-dimensional surface patterns through the introduction of heterogeneous magneto-mechanical properties in MRE films, made possible by advanced fabrication techniques.To achieve these objectives, an active mixing method for MRE inks is developed and implemented in a direct ink writing process using a dynamic helical mixer. This represents the first application of active mixing to MREs. This integrated approach provides a reliable and repeatable route to print heterogeneous MRE films with well-controlled geometry, uniformity, and rheological properties. Concurrently, a 3D numerical model is established to accurately capture surface pattern evolution under magnetic fields. This model employs a framework capable of reproducing magnetization, magnetostriction, and mechanical behavior across a broad spectrum of magnetic fields. Material properties are identified experimentally, and three-dimensional surface profiles are measured using stereo digital image correlation, enabling validation of the numerical model.Using this integrated experimental and numerical approach, this study systematically investigates surface pattern evolution in heterogeneous MRE film–substrate systems. The influence of film heterogeneity on the onset and transformation of surface patterns is examined, revealing new strategies for controlling complex three-dimensional morphologies via magnetic fields. Overall, the findings demonstrate that the combination of heterogeneous film design, additive manufacturing, and advanced modeling substantially expands the range of achievable shape transformations in MRE-based systems, thereby enabling new opportunities for adaptive surfaces and reconfigurable soft devices.
• Microscale Architected Materials for Elastic Waveguiding: Fabrication and Dynamic Characterization across Length and Time Scales
  
  • Kannan Vignesh
  • Dorn Charles
  • Drechsler Ute
  • Kochmann Dennis
  Physical Review X, American Physical Society, 2026, 16 (1), pp.011047. We present an experimental protocol for the fabrication and characterization of scalable microarchitected elastic waveguides. Using silicon microfabrication techniques, we develop free-standing 2D truss-based architected waveguides with a maximum diameter of 80 mm, unit cells size of 100 μ m , and minimum beam width of 5 μ m , thus achieving scale separation. To characterize elastic wave propagation, we introduce a custom-built scanning optical pump-probe experiment that enables contactless excitation of elastic wave modes and full spatiotemporal reconstruction of wave propagation across hundreds of unit cells with subunit cell resolution. Results on periodic architectures show excellent agreement with finite element simulations and equivalent experimental data at larger length scales. Motivated by scalable computational inverse design, we fabricate a specific example of a spatially graded waveguide and demonstrate its ability to guide elastic waves along an arbitrary predesigned path. (10.1103/21w4-zn1s)
  DOI : 10.1103/21w4-zn1s
• Locally implicit and stabilized explicit time schemes for transient visco-elastic wave propagation problems
  
  • Vasanthan Vinduja
  • Imperiale Alexandre
  • Imperiale Sébastien
  Journal of Numerical Mathematics, De Gruyter, 2026. In the context of numerical methods for time-domain wave propagation problems, combining high-order lumped finite elements with an explicit time scheme is a popular approach for either inviscid or visco-elastic models. This strategy has proven to be efficient in numerous cases. However, when dealing with non-uniform meshes or high-contrast materials, the stability condition on the time step becomes drastically stringent. One can encounter such configurations when meshing unfortunate CAD input le, e.g. when dealing with heterogeneous materials where neighboring heterogeneities produce very small elements in-between them, or when considering materials with high and localized wave velocities. To address efficiently these configurations, we propose to adapt the locally implicit and stabilized leapfrog methods to the Kelvin-Voigt, Maxwell and Zener visco-elastic models. We prove using energy arguments that the global stability condition of these schemes can be much more favorable compared to a fully-explicit scheme, decreasing the number of iterations for a fixed time window. We illustrate our approaches with 2D and 3D numerical test cases related to ultrasonic non-destructive testing experiments. (10.1515/jnma-2025-0044)
  DOI : 10.1515/jnma-2025-0044
• A projection scheme for an incompressible soft material poromechanics model
  
  • Barré Mathieu
  • Grandmont Céline
  • Moireau Philippe
  IMA Journal of Numerical Analysis, Oxford University Press (OUP), 2026. In this work, we propose and analyse a new scheme to discretize the linearized version of a rather general poromechanics model adapted to biological tissues perfusion. This model, which is related to – albeit different from – Biot equations, involves unsteady solid and fluid momentum balance equations that are further coupled through an incompressibility constraint, a pore pressure and permeability terms. The key feature of the scheme is to decouple the solid, fluid and pressure unknowns at each time step by means of a projection method, composed of a prediction and a correction step. We perform a complete stability analysis of the scheme depending on the implicit or explicit treatment of friction and pressure in the prediction step. Several boundary conditions are considered, including conditions coupling the solid and fluid phases on the boundary that are imposed at the discrete level using a Robin-Robin method. In the case of Dirichlet boundary conditions, we also provide a fully discrete error estimate as long as a discrete inf-sup condition is satisfied. The scheme properties and robustness with respect to physical parameters are illustrated by numerical experiments. Finally, its computational performance is compared with that of a monolithic approach.
• Stamps for Pattern Applications for DIC or Markers Tracking
  
  • Diani J.
  • Geraud G.
  • Coq A.
  • Kuzyara V.
  Experimental Techniques, Society for Experimental Mechanics, 2026. Digital image correlation requires a surface pattern to monitor deformation, and while spray paint is widely used for this purpose, it suffers from drawbacks such as limited reproducibility and poor control over speckle characteristics. This study aims to develop stamps to apply patterns with greater consistency and control, and to demonstrate that such pattern speckle performs comparably to traditional spray paint speckle. For that purpose, speckles were applied to polymer surfaces using two techniques, ink stamping of circular dots and conventional spray painting. Their quality was first evaluated through numerical assessments, followed by digital image correlation analyses under both small and large strains. Small-strain behavior was studied using synthetically deformed images based on sinusoidal displacements, while large-strain performance was assessed via uniaxial stretching of a holed elastomer sample. Both speckle application methods yielded similar results in terms of image correlation accuracy and robustness across deformation scales proving that the produced stamps offer a viable alternative to spray paint, providing significant advantages in terms of control, reproducibility, and customizability of the speckle pattern, without compromising performance. (10.1007/s40799-026-00875-z)
  DOI : 10.1007/s40799-026-00875-z
• Graded phononic metamaterials based on scalable microfabrication and design
  
  • Dorn Charles
  • Kannan Vignesh
  • Drechsler Ute
  • Kochmann Dennis
  Nature Communications, Nature Publishing Group, 2026, 17 (1), pp.3192. Abstract Metamaterials’ engineered internal structures enable customized material properties beyond those found in nature, such as the capability to guide, attenuate, and focus waves at will. Phononic metamaterials aim to manipulate mechanical waves, with broad applications in acoustics, elastodynamics and structural vibrations. A key bottleneck in the advancement of phononic metamaterials is their scalability beyond tens of unit cells per spatial dimension, which equally affects their design, simulation, and fabrication. Here, we present a framework for scalable inverse design of spatially graded phononic metamaterials for elastic wave guiding, together with a scalable microfabrication method. This framework enables the design and realization of complex waveguides including hundreds of thousands of unit cells, potentially extendable to millions with no change in protocol. Scalable designs are optimized with a ray tracing model for waves in spatially graded beam lattices and fabricated by photolithography and etching of silicon wafers, to create free-standing microarchitected films. Wave guiding is demonstrated experimentally by using pulsed laser excitation and interferometric displacement measurements. Broadband wave guiding is demonstrated, indicating the promise of our scalable design and fabrication methods for on-chip elastic wave manipulation. (10.1038/s41467-026-69888-x)
  DOI : 10.1038/s41467-026-69888-x