Publications

2025

• The influence of grain crushing and pore collapse on the formation of faults
  
  • Collins-Craft Nicholas Anton
  • Stefanou Ioannis
  • Sulem Jean
  • Einav Itai
  , 2025. During an earthquake, slip occurs in a localised shear zone that features a heavily granulated fault core that can be characterised as a shear band. We study the formation of this fault core in a granular rock such as sandstone by developing a model of crushable granular media within the framework of Breakage Mechanics. This model accounts for the evolution of the grain size distribution, while also accounting for the co-evolution of the solid fraction. An enrichment with the Cosserat continuum allows for the model to predict finite-width shear bands. The model is then calibrated against experimental data taken from tests on Bentheim sandstone, and a parametric study of the mechanical parameters is conducted using linear stability analysis. We find that for deeply-buried rocks the shear bands have a compactive component, and the initial value of the solid fraction does not play a strong role in the initial band thickness, but can influence the rate of delocalisation of the band. Post-localisation behaviour is studied with the finite element method, which shows the formation of zones of dilation outside the band in addition to the compaction within the band. Using a modified Kozeny--Carman permeability law, it is shown that within the band the permeability reduces by several orders of magnitude, but can increase outside the band. Our results highlight the importance of modelling grain size and solid fraction evolution as they exert a controlling influence on hydromechanical properties that play an important role in fault formation and seismic slip. Document submitted to Journal of Geophysical Research: Solid Earth
• Resolved DEM-CFD coupling for wave-armour blocks interactions
  
  • Barcet Matthieu
  • Benguigui William
  • Laviéville Jérôme
  • Benoit Michel
  • Wachs Anthony
  • Fede Pascal
  • Bonometti Thomas
  Ocean Engineering, Elsevier, 2025, 337, pp.121865. The present work aims to tackle breakwater stability challenges through an innovative numerical deterministic method using a resolved DEM-CFD (Discrete Element Method—Computational Fluid Dynamics) strategy, which simulates the individual motions of armour units within a fluid solver. To achieve this, a coupling between a DEM code and a CFD code is implemented and validated. The fluids (air and water) are solved using a Eulerian–Eulerian CFD solver, and the contacts between blocks are solved using a DEM code. The solids are defined within the fluid solver using a discrete forcing approach and are therefore fully resolved. In this way, the fluid solver enables the prediction of object motions with complex shapes such as tetrapods. To couple the codes, forces exerted on the solids are calculated in the fluid solver and sent to the DEM solver. Then, contact and gravity forces are computed and added to the fluid forces. The DEM solver then computes the new positions and velocities of the bodies, which are retrieved by the fluid solver. An experimental study is performed on a fixed and instrumented idealized breakwater to evaluate the wave forces acting on a coastal structure. The experiments are then numerically reproduced to validate the numerical model. Simulations of the impact of solitary waves on a row of mobile isolated tetrapods laid on a horizontal berm are then performed using the DEM-CFD coupling. The importance of initial placement and friction parameters is investigated to show the sensitivity to these parameters. (10.1016/j.oceaneng.2025.121865)
  DOI : 10.1016/j.oceaneng.2025.121865
• Simulation de la fissuration par champ de phase : Analyse technique de l’initialisation et la propagation de fissures
  
  • Loiseau Flavien
  • Zembra Edgar
  • Henry Hervé
  • Lazarus Véronique
  , 2025. Cette étude propose d’étudier les bias numériques dans les simulations de la fissuration par champ de phase. Plus spécifiquement, elle examine l’influence du maillage sur la trajectoire de fissure. Un problème de référence basé sur un essai de Pure Shear avec fissure initiale excentrée est utilisé pour évaluer l’impact de la discrétisation spatiale sur la trajectoire de fissure prédite. Les simulations par champ de phase sont comparées à une solution de référence issue de la mécanique linéaire élastique de la rupture, vers laquelle elles convergent théoriquement. Les résultats montrent que les maillages structurés introduisent une anisotropie artificielle qui contraint la fissure à suivre une trajectoire dépen- dante du maillage. En revanche, les maillages non structurés permettent une prédiction plus fidèle de la trajectoire exponentielle attendue. En effet, le caractère désordonné du maillage réduit les effets d’ani- sotropie artificiels induits par la discrétisation. Ces observations mettent en évidence l’importance du choix du maillage dans les simulations de propagation de fissures. Des recommandations pratiques sont finalement proposées pour minimiser les biais numériques dans les simulations par champ de phase.
• Simulation de la fissuration par champ de phase: Analyse technique de l'initiation et la propagation de fissure
  
  • Loiseau Flavien
  • Zembra Edgar
  • Henry Hervé
  • Lazarus Veronique
  , 2025. Cette étude propose d’étudier les bias numériques dans les simulations de la fissuration par champ de phase. Plus spécifiquement, elle examine l’influence du maillage sur la trajectoire de fissure. Un problème de référence basé sur un essai de Pure Shear avec fissure initiale excentrée est utilisé pour évaluer l’impact de la discrétisation spatiale sur la trajectoire de fissure prédite. Les simulations par champ de phase sont comparées à une solution de référence issue de la mécanique linéaire élastique de la rupture, vers laquelle elles convergent théoriquement. Les résultats montrent que les maillages structurés introduisent une anisotropie artificielle qui contraint la fissure à suivre une trajectoire dépendante du maillage. En revanche, les maillages non structurés permettent une prédiction plus fidèle de la trajectoire exponentielle attendue. En effet, le caractère désordonné du maillage réduit les effets d’anisotropie artificiels induits par la discrétisation. Ces observations mettent en évidence l’importance du choix du maillage dans les simulations de propagation de fissures. Des recommandations pratiques sont f inalement proposées pour minimiser les biais numériques dans les simulations par champ de phase.
• A mixing length model for arbitrary geometry
  
  • Labarre V.
  • Josserand Christophe
  • Le Berre M.
  • Monchaux R.
  • Pastur L.
  • Pomeau Y.
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2025, 151 (2), pp.23001. Abstract We present a novel phenomenological model for the mixing length used in turbulence models. It accounts for the nonlocality of the Reynolds stress tensor without introducing transport or integral equations. It has however the advantage of naturally accounting for the object's geometry while satisfying the standard symmetries of the Navier-Stokes equations. We investigate the model for the classical channel and pipe flows to characterize its main findings. We calibrate the three model parameters to recover the damping in the viscous sub-layer, the log-law of the wall, and the outer region behaviors. Our model compares favorably to friction factor measurements in the pipe flow at high Reynolds numbers and provides analytical predictions of the mixing length for several canonical flows. (10.1209/0295-5075/adea91)
  DOI : 10.1209/0295-5075/adea91
• Implementation of a nonlinear controller in Phase-Locked Loop experiments for nonlinear structure identification
  
  • Chukwu Augustus
  • Stephan Cyrille
  • Touzé Cyril
  • Doaré Olivier
  Mechanical Systems and Signal Processing, Elsevier, 2025, 237, pp.113114. Experimental continuation methods are used to retrieve and identify nonlinear characteristics of vibrating structures. Among the available methods, Phase-Locked Loop (PLL) allows for an easy-to-implement yet efficient method to continue nonlinear solutions such as backbone curves or frequency response functions. The PLL automatically locks onto the prescribed phase and thanks to a linear (proportional-integral) controller, can stabilize unstable periodic orbits. However, the tuning of the different parameters to be used in such a loop are seldomly documented in the literature, which in turn might lead to long duration tests. To ease the tuning effort and reduce the experimenting time, a nonlinear controller is here proposed as a way to improve the efficacy of Phase-Locked Loop testing. Thanks to the proposed design, named NCPLL (Nonlinear Controller PLL), most of the parameters are tuned easily, while a rapid locking to the prescribed state is at hand. The nonlinear gain can be easily adapted to reach a locked state rapidly. The efficacy of the NCPLL is first demonstrated on simple numerical examples including nonlinear oscillators with smooth restoring forces and Coulomb friction, and a finite element beam model with localized nonlinearities. Then the method is deployed on two different experimental test rigs. First, the case of smooth nonlinearity is tackled thanks to a cantilever beam vibrating in the magnetic field created by two magnets. Finally, the case of friction is addressed by considering an assembled beam with friction joints. In all the tested cases, the NCPLL shows excellent performance, requiring minimal tuning efforts whilst leading to fast measurements. (10.1016/j.ymssp.2025.113114)
  DOI : 10.1016/j.ymssp.2025.113114
• Compressible multi-phase fast transients modeling with fluid-structure interaction
  
  • Daude Frédéric
  , 2025. In certain operating or accidental situations, some undesirable multi-phase fast-transient events can occur in the piping systems of nuclear power plants such as Pressurized Water Reactor (PWR). These phenomena are characterized by high pressure variations. The generated pressure waves propagate and induce significant mechanical loads on some components which could impact the operation and the safety of industrial installations. In addition, due to the high pressure variation, the pressure amplitude can fall to its saturation value leading to the generation of vapor. This has a significant influence on the pressure waves propagation. In order to obtain realistic and representative computations, it is necessary to consider compressible two-phase flow modeling. The coupling between the fluid and the deformable structures has also to be taken into account in order to satisfactorily represent the mechanical consequences on some sensitive components. Moreover, the speed of sound within a compressible two-phase flow is known to undergo high variations as well as the Mach number as a function of the vapor volume fraction. Numerical methods able to capture the different flow regimes (incompressible and compressible) are thus required. Furthermore, most of the mentioned multi-phase fast-transient events occur in piping systems. As a consequence, dedicated mathematical models and numerical methods have to be developed for the achievement of industrial studies. The research summarized in the present document deals with the different topics, mentioned previously.
• An alternative elastoplastic model for ductile fracture with graded plasticity
  
  • Pham Clémence
  • Maitournam Habibou
  • Stolz Claude
  • Seyedi Darius
  • Gourdin Cédric
  , 2024. The prediction of failure modes in metallic structures is a crucial step in the safety analysis of industrial components subjected to significant mechanical loads (e.g., nuclear power plant components, pipelines, etc.). To perform such analyses, it is essential to accurately simulate the propagation of a defect in the ductile regime, characterized by large plastic deformations before and during propagation. Predictive numerical simulation of ductile fracture remains an open scientific and technical challenge, despite significant progress in recent years. The so-called local approach to fracture is widely used to model ductile fracture; however, like all softening models, it exhibits dependency on spatial discretization. The objective of this work is to propose a robust approach for modeling and simulating ductile fracture at the structural scale. It introduces an elastoplastic model with a bounded gradient of accumulated plastic strain and an associated set of internal constraints. This method aims to eliminate mesh dependency, without increasing the number of degrees of freedom of the numerical problem as it can be the case for most of non-local models. So, the proposed model strives for fast and efficient numerical computations at the structural scale. The feasibility of this approach is demonstrated through the resolution of problems on simple geometries, such as cylinders or spheres made of composite elastoplastic materials. Tests on 316L steel specimens are also conducted to further validate the robustness of this method.
• Modelling of crack propagation in strongly anisotropic media using phase-field fracture and LEFM
  
  • Loiseau Flavien
  • Lazarus Véronique
  , 2025. The study of crack propagation in anisotropic media is becoming increasingly important in structural mechanics. Additive manufacturing processes, in particular, are being investigated for their capacity to produce custom parts and their potential to repair structures (Ngo et al., 2018). Understanding and modeling their mechanical degradation is crucial to ensure the safe application of 3D-printed materials. However, knowledge of crack propagation modeling in these materials still needs to be completed. The microstructure of anisotropic materials induces anisotropy in their fracture toughness, complicating the modeling process. While some models can qualitatively represent crack propagation in such materials, only a few quantitative studies are currently available. Previous studies (Corre & Lazarus, 2021; Zhai, 2023) have demonstrated that strongly anisotropic phase-field fracture models can effectively capture crack propagation in anisotropic media. Building on this foundation, this work further evaluates the capabilities of strongly anisotropic phase-field fracture models. In particular, we aim to investigate more complex propagation problems, such as cases involving crack path bifurcation. Simulations will be compared against Linear Elastic Fracture Mechanics results, using the Generalization of the Maximum Energy Release Rate to anisotropic media. References Corre, T., & Lazarus, V. (2021). Kinked crack paths in polycarbonate samples printed by fused deposition modelling using criss-cross patterns. International Journal of Fracture, 230(1), 19–31. https://doi.org/10.1007/s10704-021-00518-x Ngo, T. D., Kashani, A., Imbalzano, G., Nguyen, K. T. Q., & Hui, D. (2018). Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. Composites Part B: Engineering, 143, 172–196. https://doi.org/10.1016/j.compositesb.2018.02.012 Zhai, X. (2023). Crack propagation in elastic media with anisotropic fracture toughness: Experiments and phase-field modeling [PhD thesis].
• Calibration of non-local damage models from full-field measurements: Application to discrete element fields
  
  • Védrine Louis
  • Loiseau Flavien
  • Oliver-Leblond Cécile
  • Desmorat Rodrigue
  European Journal of Mechanics - A/Solids, Elsevier, 2025, 112, pp.105611. Continuous damage models are increasingly used in numerical simulations to design structures, but their local formulations are sensitive to mesh size and present localization of strains in an infinitely thin region. To overcome these problems non-local damage models and related regularization methods, have been developed introducing a characteristic/internal length, thus avoiding pathological mesh dependence. Those methods make the damage evolution depends on the mechanical quantities at the current material point (local) and its neighborhood (non-local). Existing approaches to calibrate the internal length use global quantities in the calibration process, although local data is now becoming accessible (e.g., using digital image correlation). In this study, we investigate the use of full-field displacement measurements and propose a new methodology for calibrating a non-local damage model based on local field measurements and we apply it to calibrate the Eikonal Non-local Gradient (ENL-G) approach from the measured strain and damage field. After detailing the calibration procedure, we then apply it on a simple ideal case. We illustrate, and analyze the robustness of the calibration procedure with respect to the choice of evolution law and measurement noise of the proposed calibration method. To confront the procedure to a more realistic case, we employed a 2D beam-particle model. This discrete model is first identified with respect to the size and shape effect based on one of the comprehensive experimental data sets available in the literature, including four shapes with three sizes each. Then, it is used to generate a “reference” evolution of the damage and strain fields in beams of different sizes subjected to uniaxial tension. The parameters of the discrete model used have been calibrated to represent the scale and size effects, giving a very good representation of the experiments. We also illustrate the evolution of non-local interactions in the Eikonal approach using Green functions. Finally, the application of the calibration procedure shows that it is possible to determine the internal length of the non-local problem studied as well as the damage evolution law and its parameters. The outcomes of this study contribute to shed light on a new methodology to identify non-local damage models based on full-field measurements, and call for experimental size effect campaign with displacement field. (10.1016/j.euromechsol.2025.105611)
  DOI : 10.1016/j.euromechsol.2025.105611
• Parametric study of turbulence ingestion noise for marine propellers
  
  • Lavanant Romain
  • Cotté Benjamin
  • Serre Gilles
  • Mercier Jean-François
  , 2025, pp.1851-1858. Hydrodynamic noise is an important component of the overall noise radiated by a ship, particularly at low frequencies where propeller noise could be dominant especially at high speed. This study proposes a simplified analytical solution of the phenomenon of spectral humps of propeller noise due to the interaction between a rotating propeller and an incident turbulent flow. The acoustic radiation is described by the Ffowcs-Williams and Hawkings analogy in the compact approximation. The inflow turbulence field is assumed to be homogeneous and isotropic and is modeled using a von Kármán spectrum. Experimental validation and comparison with more costly analytical solutions demonstrate the ability of the developed model to correctly capture the characteristics of the humps related to turbulence ingestion. From the results obtained, a parametric analysis enables us to define a criterion for the emergence and shape of turbulence ingestion humps according to the propeller advance ratio, improving the criterion proposed by Ffowcs-Williams and Hawkings in 1969. (10.61782/fa.2025.0670)
  DOI : 10.61782/fa.2025.0670
• Following the equilibrium path during crack propagation under quasi-static loads: linear elastic fracture mechanics and phase-field approaches.
  
  • Loiseau Flavien
  • Lazarus Véronique
  , 2025. The equilibrium path [1] of an elastic body with an initial crack represents the sequence of states (displacement and crack geometry) at which the crack propagation threshold is met under a specific quasi-static proportional loading sequence. Constructing this equilibrium path requires adjusting the load amplitude to maintain the crack at its propagation threshold throughout its progression. Following the equilibrium path yields stable, incremental crack propagation at the cost of neglecting dynamic effects arising during instabilities. Following the equilibrium path in numerical simulations (e.g., phase-field fracture models) ensures controlled, incremental crack propagation, with each crack increment minimizing energy (in contrast to minimizing energy over the entire crack path). This work proposes methodologies for determining the equilibrium path using the frameworks of Linear Elastic Fracture Mechanics (LEFM) and phase-field fracture models. It focuses on a single controlled load, but extensions to more complex loads will also be discussed. We first examine the analytical case of a finite elastic body with a known crack path. This simple example introduces the core principles of path-following methods in fracture mechanics, serving as a foundation for more complex scenarios. We then address cases where the crack path is unknown a priori, requiring adaptations of the methodology to integrate numerical tools for elastic solutions, Stress Intensity Factor (SIF) computation, and crack-propagation solutions. Finally, we present the determination of the equilibrium path using phase-field fracture models, employing an extension [2] of arc-length methods. REFERENCES [1] Riks, E. (1979). An incremental approach to the solution of snapping and buckling problems. International Journal of Solids and Structures, 15(7), 529–551. [2] Chen, Z., & Schreyer, H. L. (1991). Secant structural solution strategies under element constraint for incremental damage. Computer Methods in Applied Mechanics and Engineering, 90(1), 869–884.
• How to introduce an initial crack in phase field simulations to accurately predict the linear elastic fracture propagation threshold?
  
  • Loiseau Flavien
  • Lazarus Veronique
  Journal of Theoretical, Computational and Applied Mechanics, INRIA, 2025, pp.1-16. Variational phase field fracture models are now widely used to simulate crack propagation in structures. A critical aspect of these simulations is the correct determination of the propagation threshold of pre-existing cracks, as it highly relies on how the initial cracks are implemented. While prior studies briefly discuss initial crack implementation techniques, we present here a systematic investigation. Various techniques to introduce initial cracks in phase field fracture simulations are tested, from the crack explicit meshing to the replacement by a fully damaged phase field, including different variants for the boundary conditions. Our focus here is on phase field models aiming to approximate, in the $\Gamma$-convergence limit, Griffith quasi-static propagation in the framework of Linear Elastic Fracture Mechanics. Therefore, a sharp crack model from classic linear elastic fracture mechanics based on Griffith criterion is the reference in this work. To assess the different techniques to introduce initial cracks, we rely on path-following methods to compute the sharp crack and the phase field smeared crack solutions. The underlying idea is that path-following ensures staying at equilibrium at each instant so that any difference between phase field and sharp crack models can be attributed to numerical artifacts. Thus, by comparing the results from both models, we can provide practical recommendations for reliably incorporating initial cracks in phase field fracture simulations. The comparison shows that an improper initial crack implementation often requires the smeared crack to transition to a one-element-wide phase band to adequately represent a displacement jump along a crack. This transition increases the energy required to propagate the crack, leading to a significant overshoot in the force-displacement response. The take-home message is that to predict the propagation threshold accurately and avoid artificial toughening; the crack must be initialized either setting the phase field to its damage state over a one-element-wide band or meshing the crack explicitly as a one-element-wide slit and imposing the fully cracked state on the crack surface. (10.46298/jtcam.15198)
  DOI : 10.46298/jtcam.15198
• Path-following methods for quasi-static crack propagation simulated by variational phase field approach
  
  • Loiseau Flavien
  • Lazarus Veronique
  , 2025.
• Normal form analysis of nonlinear oscillator equations with automated arbitrary order expansions
  
  • de Figueiredo Stabile André
  • Touzé Cyril
  • Vizzaccaro Alessandra
  Journal of Theoretical, Computational and Applied Mechanics, INRIA, 2025. Arbitrary order expansions for the automatic reduction and solutions of nonlinear vibratory systems have been developed successfully within the realm of the direct parametrisation of invariant manifolds. Whereas the method has been used with high-order expansions and large dimensional systems, this article proposes to look at the same problem from the opposite point of view. By using low-dimensional systems, symbolic computations, analytical developments and numerical verifications, this contribution analyses the reduced dynamics appearing in cases where a single master mode is involved, reviewing typical scenarios in nonlinear vibrations: primary resonance, sub- and superharmonic resonances and parametric excitation. To achieve this task, the normal form style is preferentially used. A symbolic open-source package is also provided to generalise the presented results to other styles, higher orders, and different scenarios. It is shown how the low-order terms allow recovering the classical solutions given by perturbation methods, and how the automated expansions allow one to generalise the analysis to arbitrary orders. When analytical solutions are not tractable anymore, numerical solutions are employed to underline how converged solutions are at hand when the validity limit of the expansions is not reached. All the results presented in this paper can thus be used to better understand the nonlinear dynamical solutions occurring in nonlinear vibrations, as well as from a system identification perspective, since the normal form is the simplest dynamical system displaying a given resonance scenario. (10.46298/jtcam.13234)
  DOI : 10.46298/jtcam.13234
• Open Review of "Normal form analysis of nonlinear oscillator equations with automated arbitrary order expansions
  
  • de Figueiredo Stabile André
  • Touzé Cyril
  • Vizzaccaro Alessandra
  • Römer Ulrich
  • Raze Ghislain
  • Chaillat Stéphanie
  , 2025.
• Caractérisation expérimentale du bruit d’un drone en vol stationnaire en environnements réel et contrôlé
  
  • Cotté Benjamin
  • Simião Pitta Vinícius
  • Hoareau Damien
  • Beausse Yoann
  • Toralba Thibault
  • Doaré Olivier
  • Chapoutot Alexandre
  , 2025. La mesure du bruit des drones dans un environnement réaliste est importante afin d’évaluer leur impact sur les riverains, mais aussi pour comprendre les sources de bruit dominantes en fonction des opérations de vol et ainsi améliorer les outils de modélisation et de simulation du bruit. Cette caractérisation expérimentale est une tâche difficile à cause de la variabilité des conditions météorologiques en milieu extérieur, du bruit de fond, et du bruit du drone. En effet, les différentes hélices du drone voient leur vitesse de rotation varier indépendamment pour assurer la stabilité en vol. C’est pourquoi des mesures en environnement contrôlé comme des chambres anéchoïques sont également réalisées afin de diminuer la variabilité du bruit, même si la taille limitée de ces installations limitent les opérations de vol réalisables. L’objectif de cette étude est de comparer les mesures de bruit en chambre anéchoique et en environnement extérieur pour un drone quadricoptère de petite taille en vol stationnaire, afin de déterminer les similitudes et différences entre les deux types de mesures. Les mesures en chambre anéchoïque ont été réalisées sur une structure fixe, ce qui permet de caractériser les hélices soit de façon isolée, soit par paire soit pour l’ensemble des quatre hélices. Pour les mesures en milieu extérieur, six microphones placés sur des plate-formes rigides ont été utilisées, et des mesures en vol stationnaire à trois hauteurs ont été réalisées. Même si les signaux acoustiques mesurés en extérieur présentent une plus grande complexité, les mêmes composantes spectrales sont retrouvées dans les deux types d’environnement. En particulier, une forte émergence du bruit des moteurs à environ 18 fois la fréquence de passage des pales est observée.
• Haut-parleurs en élastomères diélectriques : modèle, simulation et expériences
  
  • Doaré Olivier
  • Garnell Emil
  • Rouby Corinne
  , 2025. Les élastomères diélectriques sont des matériaux actifs flexibles capables de grandes déformations sous charge électrique. Ils consistent en une fine membrane élastomère (généralement en silicone ou en acrylique), couverte des deux côtés par des électrodes flexibles et étirables. L'épaisseur totale est de l'ordre de 100 microns. Lorsqu'une tension électrique est appliquée entre les électrodes, la membrane se comprime et sa surface augmente de plus de 100 %. Ce principe de conversion électromécanique peut être utilisé pour produire des haut-parleurs. Une caractéristique intrinsèque des haut-parleurs à élastomère diélectrique est leur nature multiphysique. En effet, le mécanisme d'actionnement est lui-même un couplage entre l'électrostatique et la mécanique ; le diaphragme est très fin et léger, et donc lié à l'acoustique, car l'air est lourd par rapport à la membrane ; et enfin, la résistivité des électrodes crée un couplage entre l'électrodynamique et la mécanique. Un modèle multiphysique de haut-parleurs à élastomère diélectrique a été mis en œuvre pour optimiser leurs performances acoustiques, en termes de réponse en fréquence. Le modèle et sa mise en œuvre numérique seront présentés, ainsi que des validations expérimentales sur des prototypes construits.
• Asymptotic approaches for dealing with distorted crack geometries
  
  • Lazarus Véronique
  , 2025. A growing, albeit not predominant, way to contribute to the climate transition in the field of fracture mechanics is to refine predictions from damage tolerance approaches used to assess the durability and reliability of sensitive components such as those found in railway, aeronautics, aerospace or nuclear industries. If it can be certified that the reduced safety margins remain acceptable, the intervals between maintenance operations could be extended, and the replacement of defective parts delayed, thereby reducing the environmental footprint. The aim of Damage Tolerance Approaches is to ensure that the existence of unavoidable defects does not compromise safety. This involves considering the most unfavorable case of brittle fracture and determining the propagation of a preexisting crack under cyclic loading until the Griffith energy fracture threshold is reached. Currently, this is done using simplified, smoothed-out crack geometries, relying either on tabulated values or Finite Element Methods. Since meshing of the entire structure is required, the latter currently struggles to accurately account for the small-scale tortuosity of the crack geometry. This paper aims to show that asymptotic approaches are efficient alternatives to address this challenge. Various aspects of these approaches, along with selected applications, will be reviewed. In addition to supporting the reduction of safety margins, these approaches also help to ensure that small geometrical perturbations do not lead to unexpected catastrophic failure. Asymptotic methods aim to provide analytical formulas for the variation of stress intensity factors caused by small-scale crack shape perturbations. Several applications are presented including crack shape evolution, the influence of heterogeneities, and propagation in general mixed-mode I+II+III condition.
• Influence of the mesh on the crack path in phase-field fracture simulations
  
  • Loiseau Flavien
  • Zembra Edgar
  • Lazarus Veronique
  • Henry Hervé
  , 2025. Over the past 25 years, phase-field fracture models [1, 2] have become increasingly popular for modeling crack propagation. In particular, their (Γ-)convergence towards the Linear Elastic Fracture Mechanics (LEFM) provides strong theoretical foundations. Despite this popularity, limited research has been conducted on how spatial discretization (e.g., mesh size, structure, and element geometry) affects the predicted crack path. This study addresses this gap from the perspective of the mechanical engineering community. We employ a benchmark problem inspired by the Pure Shear test [3] (also called strip specimen), involving an infinite strip with an initial horizontal edge crack located above the specimen center and subjected to tensile loading. The crack path is expected to deviate towards the center of the specimen exponentially. This result has been recovered using an incremental crack propagation solver based on LEFM, which serves as our reference. Phase-field fracture simulations, performed using the Finite Element Method, are then carried out. Different meshes (varying mesh size, structured/unstructured, and element geometry) are used in the simulations to assess their influence on the crack path. The bias induced by the mesh is evaluated by comparing the phase field simulation results with the reference. The final goal of this study is to provide recommendations to avoid, or at least mitigate, any bias induced by spatial discretization.
• A thermodynamically consistent wear modeling approach based on damage accumulation
  
  • Caradec Quentin
  • Breuzé Matthieu
  • Stolz Claude
  • Maitournam Habibou
  European Journal of Mechanics - A/Solids, Elsevier, 2025, 111, pp.105583. Due to the diversity of mechanisms involved, wear is very complex to model. Wear models are mostly empirical, and they sometimes fail to accurately predict wear evolution. In this paper, a damage-based wear modeling approach is developed in the framework of continuum thermodynamics. The model is physically consistent and aims at accounting for the progressive accumulation of nearsurface degradation leading to material detachment. A thermodynamic driving force associated with wear is derived under the form of an energy release rate. Wear evolution is then driven by the accumulation of near-surface damage, and wear occurs when the surface damage value reaches a threshold. The damage evolution problem is treated using the thick level set approach, providing a non-local formulation for damage evolution. Numerical simulations are conducted on a fretting test case using the finite element method, and the results compared to those obtained with a classical friction energy wear law. (10.1016/j.euromechsol.2025.105583)
  DOI : 10.1016/j.euromechsol.2025.105583
• Numerical hydrodynamic characterization for the design of a lab-scale jet-loop reactor
  
  • Gueguen Ronny
  • Neau Hervé
  • Benguigui William
  • Billet Anne-Marie
  • Julcour-Lebigue Carine
  • Ansart Renaud
  Chemical Engineering Research and Design, Elsevier, 2025, 217, pp.399-415. The jet-loop reactor is a powerful tool for analyzing the kinetics of heterogeneous catalytic reactions due to its high mixing degree. Indeed, the high momentum gas flow injected within the loop induces a large gas recycling flow, minimizing concentration and temperature gradients. The purpose of this numerical study is to optimize the geometric features of the reactor (injection nozzle diameters and length, and outlet pipe diameter) to improve the gas recycle ratio. Its hydrodynamic behavior is predicted by using multi-fluid solver, with an immersed boundary method to model the injector and easily vary its geometry. The effects of the operating parameters such as the injection flowrate, the pressure and the temperature are also assessed. In addition, a residence time distribution analysis allows for the evaluation of the Péclet number as a function of the geometric and operating parameters of the reactor. Then, a zero-dimensional hydrodynamic model, based on a macroscopic momentum balance, is finally developed. After fitting specific terms thanks to separated numerical CFD simulations, it enables a rapid optimization of the reactor design and provides insights into its behavior. (10.1016/j.cherd.2025.04.019)
  DOI : 10.1016/j.cherd.2025.04.019
• Open Review of "How to introduce an initial crack in phase field simulations to accurately predict the linear elastic fracture propagation threshold?
  
  • Loiseau Flavien
  • Lazarus Veronique
  • Kanti Mandal Tushar
  • Nguyen Vinh Phu
  Journal of Theoretical, Computational and Applied Mechanics, INRIA, 2025. <div><p>We would like to thank both reviewers for their thoughtful and constructive feedback on our manuscript, "How to introduce an initial crack in phase-field simulations to accurately predict the linear elastic fracture propagation threshold?".</p><p>We appreciate the time and effort invested in evaluating</p></div> (10.46298/jtcam.15198)
  DOI : 10.46298/jtcam.15198
• ESA Sea Surface Salinity Climate Change Initiative (Sea_Surface_Salinity_cci): Weekly and monthly sea surface salinity products from L-band, v5.5
  
  • Boutin Jacqueline
  • Vergely Jean-Luc
  • Reul Nicolas
  • Catany Rafael
  • Jouanno J.
  • Martin Adrien
  • Rouffi Frederic
  • Bertino L.
  • Bonjean Fabrice
  • Corato Giovani
  • Gévaudan Manon
  • Guimbard Sebastien
  • Khvorostyanov Dimitry
  • Kolodziejczyk Nicolas
  • Matthews M.
  • Olivier Léa
  • Raj R.
  • Rémy E.
  • Reverdin Gilles
  • Supply Alexandre
  • Thouvenin-Masson Clovis
  • Vialard Jérome
  • Sabia R.
  • Mecklenberg S.
  , 2025. The European Space Agency (ESA) Sea Surface Salinity Climate Change Initiative (CCI) consortium has produced global, level 4, multi-sensor Sea Surface Salinity maps covering the 2010-2023 period. This dataset collection contains Sea Surface Salinity (SSS) v5.5 data at a spatial resolution of 50km and a time resolution of 1 week. It has been spatially sampled on a regular 0.25° grid and 1 day of time sampling. This product is also available on polar 25 km EASE-2 (Equal Area Scalable Earth) grid. A monthly product is also available, at a spatial resolution of 50 km and a time resolution of 1 month. It is spatially sampled on a 0.25° grid and 15 days of time sampling. This product is also available on polar 25km EASE-2 grid. In addition to salinity, information on uncertainties are provided. For more information, see the user guide and product documentation available on the Sea Surface Salinity CCI web page (10.5285/7294d93479654c139770f13fae4142d1)
  DOI : 10.5285/7294d93479654c139770f13fae4142d1
• Stress intensity factor determination along a kinked crack path by DIC analyses
  
  • Corre Thomas
  • Hild François
  • Lazarus Veronique
  International Journal of Fracture, Springer Verlag, 2025, 249, pp.42. Sharp kinks may be observed under shear loading or in materials containing weak directions, such as those produced by additive manufacturing. A better understanding of the fracture of these materials, both theoretically and experimentally, is required to deploy them in structural applications. This study focuses on the measurement of stress intensity factors (SIFs) around a sharp kink using digital image correlation (DIC). The performances of two DIC-based techniques, namely, integrated-DIC and post-processing of DIC-measured displacement fields, are assessed on a benchmark test using fused deposit modeling capabilities, and are compared to a reference finite element solution. It is shown that Williams' expansion remains valid on a large enough region around the crack to extract reliable SIFs even very close to the crack kink. Both techniques are very trustworthy, provided the SIF identification zone is carefully defined to exclude the kink zone of influence. (10.1007/s10704-025-00862-2)
  DOI : 10.1007/s10704-025-00862-2