Publications

2022

• Blowout from a hydrogen storage cavern
  
  • Djizanne Hippolyte
  • Brouard Benoit
  • Bérest Pierre
  • Hévin Grégoire
  • Murillo Rueda Carlos
  , 2022. To prevent catastrophic climate change, Europe and the world must rapidly shift to low carbon and renewable energies. Hydrogen as an energy vector, provides viable solutions to replace polluting and carbon-emitting fossil fuels. Gaseous hydrogen can be stored in underground storage and coupled with the existing natural gas pipe networks. Storage in salt caverns was recognized to be the best suited technology to meet new energy system challenges. Hydrogen storage caverns are currently operated in the UK and in Texas. A preliminary risk analysis dedicated to underground hydrogen salt cavern highlights the importance of containment losses (leaks) but also of the formation of a gas cloud following a blowout whose ignition may generate dangerous phenomena such as jet fire, Unconfined Vapor Cloud Explosion (UVCE) or flashfire as well. A blowout is one of the major accidental scenarios likely to occur during the operation of a hydrogen underground storage in salt cavern. Blowout is an uncontrolled release of gas from well after pressure control systems have failed. Several examples of blowouts in gas storage caverns have been described in the literature, such as that in an ethane storage at Fort Saskatchewan, Canada (Alberta Energy and Utilities Board, 2002) or in a natural gas storage at Moss Bluff, Texas (Rittenhour and Heath, 2012), see Réveillère et al., 2017. This paper presents the modeling of the subterraneous and aerial parts of a blowout from a hydrogen storage cavern. In the first part of this article, the method presented in Bérest et al. (2013) is used to predict the duration of the eruption and the evolution of key thermodynamics parameters such as hydrogen temperature, pressure, velocity and density. Then these results are used to compute dispersion in the atmosphere of the hydrogen jet outflowing from the wellhead and to evaluate the effects of potential resulting phenomena on surrounding assets.
• Creep tests on salt samples performed at very small stresses
  
  • Berest Pierre
  • Gharbi Hakim
  • Gordeliy Elizabeta
  • Jehanno Didier
  • Peach Colin
  • Brouard Benoit
  • Blanco Martín Laura
  , 2022.
• Cyclic hardening/softening and deformation mechanisms of a twip steel under reversed loading
  
  • d'Hondt C.
  • Doquet V.
  • Couzinié J.P.
  Materialia, Elsevier, 2022, 22, pp.101421. Push-pull tests at fixed plastic strain amplitude or fixed stress amplitude were run on a TWIP steel, and followed by TEM observations, to analyze its cyclic behavior in relation with the deformation mechanisms. The kinematic and isotropic components of the flow stress were measured throughout the whole cyclic hardening/softening stages, and their evolution with the cumulated plastic strain was compared to those measured in tension. The rise of the internal stress was found responsible for the initial cyclic hardening, but this stress reached at most 50 % of the flow stress, as compared to nearly 70% in tension. Special constitutive equations were identified to capture these evolutions, as well as the transition from hardening to softening. Both components of the flow stress slightly decrease during the softening stage, whose origin is discussed, based on TEM observations at peak stress amplitude, or after softening. The present measurements and TEM observations, combined with those from a previous study of twinning/detwinning kinetics in push-pull on the same steel [29], suggest that under cyclic loading, mechanical twinning cannot be responsible for significant kinematic hardening of intragranular nature (or "dynamic Hall-Petch effect"), but rather contributes to a back stress of intergranular origin. (10.1016/j.mtla.2022.101421)
  DOI : 10.1016/j.mtla.2022.101421
• Multiscale mechanical model based on patient-specific geometry: application to early keratoconus development
  
  • Giraudet Chloé
  • Diaz Jérôme
  • Le Tallec Patrick
  • Allain Jean-Marc
  Journal of the mechanical behavior of biomedical materials, Elsevier, 2022, 129, pp.105121. Keratoconus is a pathology of the cornea associated with a tissue thinning and a weakening of its mechanical properties. However, it remains elusive which aspect is the leading cause of the disease. To investigate this question, we combined a multiscale model with a patient-geometry in order to simulate the mechanical response of healthy and pathological corneas under intraocular pressure. The constitutive behavior of the cornea is described through an energy function which takes into account the isotropic matrix of the cornea, the geometric structure of collagen lamellae and the quasi-incompressibility of the tissue. A micro-sphere description is implemented to take into account the typical features of the collagen lamellae as obtained experimentally, namely their orientation, their stiffness and their dispersion, as well as the their unfolding stretch, at which they start to provide a significant force. A set of reference parameters is obtained to fit experimental inflation data of the literature. We show that the most sensitive parameter is the unfolding stretch, as a small variation of this parameter induces a major change in the corneal apex displacement. The keratoconus case is then studied by separating the impact of the geometry and the one of the mechanics. We computed the evolution of the SimK (a clinical indicator of cornea curvature) and elevation maps: we were able to reproduce the reported changes of SimK with pressure only by a mechanical weakening, and not by a change in geomtry. More specifically, the weakening has to target the lamellae and not the matrix. The mechanical weakening leads to elevations close to early stage keratoconus, but our model lacks the remodeling component to couple the change in mechanics with changes in geometry. (10.1016/j.jmbbm.2022.105121)
  DOI : 10.1016/j.jmbbm.2022.105121
• Towards 4D Printing of Very Soft Heterogeneous Magnetoactive Layers for Morphing Surface Applications via Liquid Additive Manufacturing
  
  • Brusa da Costa Linn Lucas
  • Danas Kostas
  • Bodelot Laurence
  Polymers, MDPI, 2022, 14 (9), pp.1684. This work explores the use of liquid additive manufacturing (LAM) to print heterogeneous magnetoactive layers. A general method is proposed where, by studying the printing of pure silicone lines, the successful printing of closed shapes, open shapes, and a combination thereof, can be achieved while accounting for the continuous deposition that is specific to LAM. The results of this characterization are subsequently exploited for the printing of a heterogeneous layer composed of four magnetoactive discs embedded in a pure silicone square. Such a layer, when affixed to a softer silicone substrate, yields a system that produces truly three-dimensional surface patterns upon application of a magnetic field. Hence, this work demonstrates that LAM is a promising approach for the rapid 4D printing of morphing surfaces exhibiting 3D surface patterns that can be actuated remotely and reversibly via a magnetic field. Such heterogenous layers have a wide range of applications, ranging from haptics to camouflage to differential cell growth. (10.3390/polym14091684)
  DOI : 10.3390/polym14091684
• Remplacement de l'épicéa par une structure sandwich pour la fabrication des tables d'harmonie de piano à queue : une approche locale
  
  • Margerit Pierre
  • Ege Kerem
  • Caron Jean-François
  • Lebée Arthur
  • Boutillon Xavier
  • Paulello Stephen
  , 2022. On présente une démarche de remplacement de l’épicéa par une structure composite de type sandwich pour la facture de la table d’harmonie du piano à queue Stephen Paulello SP190//. Isolée, cette structure bicouche anisotrope et hétérogène pose un défi majeur concernant la reproduction de ses propriétés vibroacoustiques à l’aide de matériaux de synthèse. L’approche proposée met en œuvre une méthode d’identification récemment développée et utilisant le formalisme ondulatoire, par opposition au formalisme modal plus couramment employé. Cette méthodologie alternative permet notamment d’obtenir les surfaces de dispersion correspondant aux ondes de flexion dans la structure, caractéristique du comportement à reproduire. Le remplacement est donc basé sur ces descripteurs locaux, simplifiant grandement la démarche d’optimisation, faisant fi de la géométrie de la structure et des conditions aux limites appliquées. La démarche complète sera présentée, de la mesure de la réponse dynamique de la table témoin en épicéa à la réalisation de son jumeau en composite.
• Estimation for dynamical systems using a population-based Kalman filter – Applications in computational biology
  
  • Collin Annabelle
  • Prague Mélanie
  • Moireau Philippe
  MathematicS In Action, Société de Mathématiques Appliquées et Industrielles (SMAI), 2022. Estimation of dynamical systems - in particular, identification of their parameters - is fundamental in computational biology, e.g., pharmacology, virology, or epidemiology, to reconcile model runs with available measurements. Unfortunately, the mean and variance priors of the parameters must be chosen very appropriately to balance our distrust of the measurements when the data are sparse or corrupted by noise. Otherwise, the identification procedure fails. One option is to use repeated measurements collected in configurations with common priors - for example, with multiple subjects in a clinical trial or clusters in an epidemiological investigation. This shared information is beneficial and is typically modeled in statistics using nonlinear mixed-effects models. In this paper, we present a data assimilation method that is compatible with such a mixed-effects strategy without being compromised by the potential curse of dimensionality. We define population-based estimators through maximum likelihood estimation. We then develop an equivalent robust sequential estimator for large populations based on filtering theory that sequentially integrates data. Finally, we limit the computational complexity by defining a reduced-order version of this population-based Kalman filter that clusters subpopulations with common observational backgrounds. The performance of the resulting algorithm is evaluated against classical pharmacokinetics benchmarks. Finally, the versatility of the proposed method is tested in an epidemiological study using real data on the hospitalisation of COVID-19 patients in the regions and departments of France. (10.5802/msia.25)
  DOI : 10.5802/msia.25
• Combinaison d'éléments de coque et d'éléments finis spectraux transitoires pour les problèmes de propagation d'ondes guidées dans des structures déformées
  
  • Dalmora Andre Luiz
  • Imperiale Alexandre
  • Imperiale Sébastien
  • Moireau Philippe
  , 2022. Dans les applications industrielles de pointe, l'évaluation de l'intégrité des structures est un aspect important des exigences de sécurité. Cependant, l'application des méthodes classiques d'évaluation non destructive peut être coûteuse et entraîne généralement des interruptions d'activité. Pour surmonter ces difficultés, le Structural Health Monitoring(SHM) propose d'utiliser des capteurs et des unités de traitement du signal in situ. Les ondes ultrasonores guidées constituent l'un des moyens de mettre en œuvre les systèmes SHM. Elles peuvent être utilisées pour évaluer les caractéristiques internes du matériau, telles que ses propriétés/défauts. Ces systèmes SHM sont déjà mis en œuvre dans des applications industrielles, mais leur utilisation est limitée en raison des conditions environnementales et opérationnelles. Un exemple typique est celui des charges opérationnelles induisant de grandes déformations et par conséquent des contraintes internes qui entraînent des changements dans la propagation des ondes[1]. Pour interpréter les signaux mesurés dans ce contexte, il est important que les efforts de modélisation de la propagation des ondes prennent en compte ce phénomène. L'objectif de notre travail est de présenter un modèle, et les méthodes numériques correspondantes, pour la propagation élastique des ondes dans un milieu précontraint. Comme les structures considérées sont généralement minces, nous utilisons une formulation de coque[2] pour la mécanique nonlinéaire pour résoudre le problème statique, représentant les effets du chargement de la structure. Le déplacement calculé est ensuite introduit dans un noyau de la méthode des éléments spectraux(SFEM)[3] pour résoudre le problème élastodynamique linéarisé dans le domaine temporel, représentant la propagation des ondes
• Experimental investigation and material modelling of the photopolymers for DLP additive manufacturing process
  
  • Sekmen Kubra
  • Rehbein Thomas
  • Lion Alexander
  • Johlitz Michael
  • Constantinescu Andrei
  , 2022.
• Personalized pulmonary poromechanics in health and idiopathic pulmonary fibrosis
  
  • Genet Martin
  • Patte Cécile
  • Laville Colin
  • Chapelle Dominique
  • Fetita Catalin
  • Brillet Pierre Yves
  • Gille Thomas
  • Nunes Hilario
  • Bernaudin Jean-François
  , 2022. Lung biomechanics has been extensively studied by physiologists, experimentally as well as theoretically, laying the ground for our current fundamental understanding of the relationship between function and mechanical behavior. However, many questions remain, notably in the intricate coupling between the multiple parenchymal constituents. These fundamental questions represent real clinical challenges, as pulmonary diseases are an important health burden. Interstitial lung diseases, for instance, affect several million people globally. Idiopathic Pulmonary Fibrosis (IPF), notably, a progressive form of interstitial lung disease where some alveolar septa get thicker and stiffer while others get completely damaged, remains poorly understood, poorly diagnosed, and poorly treated. We recently developed a model of the lungs at the breathing time scale and the organ space scale, where the "solid" phase is composed of both tissue and blood while the fluid phase is the air. Several pulmonary-specific hypotheses have been formulated, notably that the end-inhalation and end-exhalation states are in static equilibrium. Moreover, specific boundary conditions are imposed on the lungs themselves, modeling the effect of diaphragm-induced loading and rib cage: a pressure applied on lung surface representing pleural pressure, and a frictionless contact with the moving thorax. Moreover, the constitutive behavior allows to reproduce the volumetric response of lungs to a change of pressure as observed in experimental data. The proposed model can be personalized using clinical data. From two 3D CT-scans, acquired at end-exhalation and at end-inhalation, we obtain a personalized geometry through image segmentation, a personalized porosity, personalized motion & boundary conditions through image registration. Such data allow also to personalize regional mechanical parameters by minimizing the discrepancy between measured and computed motion. We will present results based on control and patient data. Notably, we will show that the model and estimation procedure can quantify the regional tissue stiffening induced by idiopathic pulmonary fibrosis. Our results illustrate how our pulmonary poromechanical model can be used as a diagnosis tool in the clinic when it is personalized to a patient using clinical data acquired in standard protocols.
• Experimental and numerical study of the DLP 3D printed photopolymers
  
  • Sekmen Kubra
  • Weisz-Patrault Daniel
  • Constantinescu Andrei
  , 2022.
• Symmetry and Asymmetry in the Fluid Mechanical Sewing Machine
  
  • Ribe Neil
  • Brun Pierre-Thomas
  • Audoly Basile
  Symmetry, MDPI, 2022, 14 (4), pp.772. The ‘fluid mechanical sewing machine’ is a device in which a thin thread of viscous fluid falls onto a horizontal belt moving in its own plane, creating a rich variety of ‘stitch’ patterns depending on the fall height and the belt speed. This review article surveys the complex phenomenology of the patterns, their symmetries, and the mathematical models that have been used to understand them. The various patterns obey different symmetries that include (slightly imperfect) fore–aft symmetry relative to the direction of belt motion and invariance under reflection across a vertical plane containing the velocity vector of the belt, followed by a shift of one-half the wavelength. As the belt speed decreases, the first (Hopf) bifurcation is to a ‘meandering’ state whose frequency is equal to the frequency Ωc of steady coiling on a motionless surface. More complex patterns can be studied using direct numerical simulation via a novel ‘discrete viscous threads’ algorithm that yields the Fourier spectra of the longitudinal and transverse components of the motion of the contact point of the thread with the belt. The most intriguing case is the ‘alternating loops’ pattern, the spectra of which are dominated by the first five multiples of Ωc/3. A reduced (three-degrees-of-freedom) model succeeds in predicting the sequence of patterns observed as the belt speed decreases for relatively low fall heights for which inertia in the thread is negligible. Patterns that appear at greater fall heights seem to owe their existence to weakly nonlinear interaction between different ‘distributed pendulum’ modes of the quasi-vertical ‘tail’ of the thread. (10.3390/sym14040772)
  DOI : 10.3390/sym14040772
• Metamaterials for energy harvesting at small scale
  
  • Moscatelli Marco
  , 2022. The increasing demand of low-power energy-autonomous small electronic sensors and devices has propelled the emergence of energy harvesting technologies based on ambient vibrations, as a prominent area of interest for research.For an efficient harvesting of energy, it is required to develop systems that are able to convey and trap the vibrations (and the energy they carry with them) in a compactly-supported domain.Phononic crystals and periodic locally resonant materials, if properly designed, can be used to develop vibration-based energy harvesting systems, by exploiting the presence of band gaps in their spectrum, i.e. intervals of frequencies corresponding to attenuated waves.Using a mass-in-mass crystal, we first individuate the roles of the main parameters of the problem of wave propagation in these two classes of metamaterials. Then, we employ a two-scale homogenization technique to derive their effective behavior at a sub-wavelength scale. In particular, locally resonant materials are analyzed, being characterized by the presence of band gaps at a sub-wavelength regime.Aiming to focus the mechanical energy in a confined area at low frequencies, we introduce a cavity in locally resonant materials, acting as a defect of periodicity and resulting in the formation of localized modes at frequencies inside a band gap.We show that mechanical waves traveling through these defective metamaterials can be trapped in the defect, where the energy piles up and focus.In the final part of the manuscript, by employing a cable with periodically attached masses, we show how this system behaves as a metamaterial and we experimentally validate the attenuation and localization effects.Our results provide new insights on the dynamic behavior of defective periodic media to be used in energy harvesting systems, which makes this work relevant to both theoretical and practical fields.
• A quasi-static poromechanical model of the lungs
  
  • Patte Cécile
  • Genet Martin
  • Chapelle Dominique
  Biomechanics and Modeling in Mechanobiology, Springer Verlag, 2022, 21 (2), pp.527-551. The lung vital function of providing oxygen to the body heavily relies on its mechanical behavior, and the interaction with its complex environment. In particular, the large compliance and the porosity of the pulmonary tissue are critical for lung inflation and air inhalation, and the diaphragm, the pleura, the rib cage and intercostal muscles all play a role in delivering and controlling the breathing driving forces. In this paper, we introduce a novel poromechanical model of the lungs. The constitutive law is derived within a general poromechanics theory via the formulation of lung-specific assumptions, leading to a hyperelastic potential reproducing the volume response of the pulmonary mixture to a change of pressure. Moreover, physiological boundary conditions are formulated to account for the interaction of the lungs with their surroundings, including a following pressure and bilateral frictionless contact. A strategy is established to estimate the unloaded configuration from a given loaded state, with a particular focus on ensuring a positive porosity. Finally, we illustrate through several realistic examples the relevance of our model and its potential clinical applications. (10.1007/s10237-021-01547-0)
  DOI : 10.1007/s10237-021-01547-0
• Patient-specific cardiovascular biomechanical modeling to augment interpretation of clinical data and assist planning interventions for patients with congenital heart disease
  
  • Gusseva Maria
  , 2022. This PhD thesis is an interdisciplinary research that deals with applied biomechanical modeling of the cardiovascular system in patients with congenital heart diseases . The aim is to explore the potential of biomechanical modeling to assist in clinical decision-making.First, we explored the ability of a previously developed biomechanical model to augment the interpretation of clinical data for patients with tetralogy of Fallot after repair (rTOF) prior to and after pulmonary valve replacement (PVR). Patient-specific models of the right ventricle (RV) and pulmonary circulation were built for 20 subjects pre- and post-PVR using cardiovascular magnetic resonance (CMR) and pressure catheter data. These models were subjected to the effects of pulmonary valve (PV) regurgitation and/or RV outflow tract (RVOT) obstruction. The models provided patient-specific indices of myocardial contractility pre- and post-PVR. The results showed a decrease of contractility in all patients post-PVR. Patients with predominantly RVOT obstruction experienced a higher level of contractility decrease whereas ceasing the regurgitation itself did not lead to a significant reduction in contractility. After this detailed study of pathophysiology of the overloaded RVs pre- and post-PVR, we explored the ability of the model to predict the response of ventricular mechanics when progressively decreasing the afterload of the RVs in patients with rTOF. Pre-PVR patient-specific models were used and cessation of PV regurgitation and progressive decrease of RVOT resistance were assumed. The resulting in silico relationships between the contractility and RVOT resistance post-PVR appeared to be linear, and consistent with that given by the patient-specific post-PVR models.For patients with single-ventricle hearts undergoing CMR combined with a pressure catheter (as part of planning for complex surgery), the model was used to synchronize in time the catheter-pressure data and the ventricular volumes obtained by CMR. This model-assisted time-synchronization produces high quality P-V loops that yield more accurate indices of myocardial energetics (maximum value of time-varying elastance (E_max) and stroke work) and hence could be used to ameliorate the clinical interpretation.Finally, we compared the indices of E_max and maximum time derivative of ventricular pressure, max(dP/dt), when obtained directly from the clinical measurements vs. model-derived contractility and max(dP/dt). All data- and model-derived indices showed a good agreement. In addition, a potential application of model-derived max⁡(dP/dt) as a model-based data filter was emphasized.Overall, this thesis demonstrated (1) an ability of biomechanical modeling to provide additional mechanical indices of ventricular function and their evolution under different loading conditions, which has the potential to contribute into the planning of optimal therapy; (2) an application of the model to provide robust clinical data processing of a variety of data acquisition protocols; and (3) a correspondence of model-derived indices with clinically accepted surrogate measures of contractility. In conclusion, this thesis showed that biomechanical modeling could be deployed in a clinical environment to address various types of problems towards the delivery of personalized healthcare solutions.
• Impact of impaired cerebral blood flow autoregulation on electroencephalogram signals in adults undergoing propofol anaesthesia: a pilot study
  
  • Manquat Elsa
  • Ravaux Hugues
  • Kindermans Manuel
  • Joachim Jona
  • Serrano José
  • Touchard Cyril
  • Mateo Joaquim
  • Mebazaa Alexandre
  • Gayat Etienne
  • Vallée Fabrice
  • Cartailler Jérôme
  British Journal of Anaesthesia open, Oxford: Elsevier Ltd, 2022. Background: Cerebral autoregulation actively maintains cerebral blood flow over a range of MAPs. During general anaesthesia, this mechanism may not compensate for reductions in MAP leading to brain hypoperfusion. Cerebral autoregulation can be assessed using the mean flow index derived from Doppler measurements of average blood velocity in the middle cerebral artery, but this is impractical for routine monitoring within the operating room. Here, we investigate the possibility of using the EEG as a proxy measure for a loss of cerebral autoregulation, determined by the mean flow index. Methods: Thirty-six patients (57.5 [44.25; 66.5] yr; 38.9% women, non-emergency neuroradiology surgery) anaesthetised using propofol were prospectively studied. Continuous recordings of MAP, average blood velocity in the middle cerebral artery, EEG, and regional cerebral oxygen saturation were made. Poor cerebral autoregulation was defined as a mean flow index greater than 0.3. Results: Eighteen patients had preserved cerebral autoregulation, and 18 had altered cerebral autoregulation. The two groups had similar ages, MAPs, and average blood velocities in the middle cerebral artery. Patients with altered cerebral autoregulation exhibited a significantly slower alpha peak frequency (9. (10.1016/j.bjao.2022.100004)
  DOI : 10.1016/j.bjao.2022.100004
• Anisotropic, rate-dependent ductile fracture of Ti-6Al-4V alloy
  
  • Ruiz de Sotto Miguel
  • Doquet Véronique
  • Longère Patrice
  • Papasidero Jessica
  International Journal of Damage Mechanics, SAGE Publications, 2022, 31 (3), pp.374-402. An extensive experimental campaign was run to investigate the influence of the loading direction, stress state (triaxiality ratio ranging from-0.5 to 1), and strain rate (from 10-3 to 1.5x10 3 s-1) on the ductile fracture of Ti-6Al-4V titanium alloy. Microscopic and macroscopic observations provided some insight into the shear-driven or micro-voiding-controlled damage mechanisms prevailing at low and high triaxiality ratios, respectively. Numerical simulations were run to determine the local loading paths to fracture in terms of plastic strain as a function of stress triaxiality ratio and Lode parameter. The ductility was found to be anisotropic, but only weakly dependent on the strain rate in the considered range. The anisotropy in ductility was different in tension (maximum along DD) and in compression (maximum along ND). The fracture strain decreased with the absolute value of the triaxiality, with a maximum close to zero. No clear correlation with the Lode parameter was found. (10.1177/10567895211036491)
  DOI : 10.1177/10567895211036491
• A computational framework for magnetically hard and soft viscoelastic magnetorheological elastomers
  
  • Rambausek M.
  • Mukherjee D.
  • Danas K.
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2022, 391, pp.114500. This work deals with a comprehensive theoretical and numerical framework that allows the modeling of finite strain magnetorheological elastomers (MREs) comprising mechanically soft nonlinear elastic-viscoelastic polymer phases and magnetically hard (i.e. dissipative) or soft (i.e. purely energetic) magnetic phases. The framework is presented in a general manner and is implemented using the finite element method. Two software implementations are developed, one using FEniCS and the other in Abaqus. A detailed analysis of the numerical schemes used to model the surrounding air is made and their pros and cons are discussed. The proposed framework is used to simulate two model geometries that are directly relevant to recent applications of MREs. The first two-dimensional example simulates a mechanically soft beam consisting of a single wavy-chain of hard or soft magnetic particles. The beam is subjected to transverse magnetic actuation loads that induce important vertical deflections. Despite the overall small local strains in the beam, a significant viscoelastic effect is observed when high-rate magnetic fields are applied. A torque model for the particles is also used to analyze the beam geometry and is found to be in relatively good agreement with the rest of the approaches for small actuation fields. The second example discusses the rotation of a three-dimensional ellipsoid embedded in a cubic elastomer domain, while the ensemble lies inside a larger cubic air domain. Non-monotonic uniaxial and rotating magnetic fields are applied leading to complex, non-monotonic rotations of the ellipsoidal particle. The hard and soft magnetic cases exhibit significant differences, whereas viscoelasticity is found to induce strong coupling with the magnetization rotation but not with the dissipative magnetization amplitude. Extensive supplementary material provides all details of our implementations as well as animated visualization of results. (10.1016/j.cma.2021.114500)
  DOI : 10.1016/j.cma.2021.114500
• Nucleation of creases and folds in hyperelastic solids is not a local bifurcation
  
  • Pandurangi Shrinidhi
  • Akerson Andrew
  • Elliott Ryan
  • Healey Timothy
  • Triantafyllidis Nicolas
  Journal of the Mechanics and Physics of Solids, Elsevier, 2022, 160, pp.104749. (10.1016/j.jmps.2021.104749)
  DOI : 10.1016/j.jmps.2021.104749
• Ultrathin Ge epilayers on Si produced by low-temperature PECVD acting as virtual substrates for III-V / c-Si tandem solar cells
  
  • Ghosh Monalisa
  • Bulkin Pavel
  • Silva François
  • Johnson Erik
  • Florea Ileana
  • Funes-Hernando Daniel
  • Tanguy Alexandre
  • Renard Charles
  • Vaissiere Nicolas
  • Decobert Jean
  • García Iván
  • Rey-Stolle Ignacio
  • Roca i Cabarrocas Pere
  Solar Energy Materials and Solar Cells, Elsevier, 2022, 236, pp.111535. (10.1016/j.solmat.2021.111535)
  DOI : 10.1016/j.solmat.2021.111535
• Dislocation transport using a time-explicit Runge-Kutta discontinuous Galerkin finite element approach
  
  • Upadhyay Manas V
  • Bleyer Jérémy
  Modelling and Simulation in Materials Science and Engineering, IOP Publishing, 2022. A time-explicit Runge–Kutta discontinuous Galerkin (RKDG) finite element scheme is proposed to solve the dislocation transport initial boundary value problem in 3D. The dislocation density transport equation, which lies at the core of this problem, is a first-order unsteady-state advection–reaction-type hyperbolic partial differential equation; the DG approach is well suited to solve such equations that lack any diffusion terms. The development of the RKDG scheme follows the method of lines approach. First, a space semi-discretization is performed using the DG approach with upwinding to obtain a system of ordinary differential equations in time. Then, time discretization is performed using explicit RK schemes to solve this system. The 3D numerical implementation of the RKDG scheme is performed for the first-order (forward Euler), second-order and third-order RK methods using the strong stability preserving approach. These implementations provide (quasi-)optimal convergence rates for smooth solutions. A slope limiter is used to prevent spurious Gibbs oscillations arising from high-order space approximations (polynomial degree ⩾ 1) of rough solutions. A parametric study is performed to understand the influence of key parameters of the RKDG scheme on the stability of the solution predicted during a screw dislocation transport simulation. Then, annihilation of two oppositely signed screw dislocations and the expansion of a polygonal dislocation loop are simulated. The RKDG scheme is able to resolve the shock generated during dislocation annihilation without any spurious oscillations and predict the prismatic loop expansion with very low numerical diffusion. These results indicate that the proposed scheme is more robust and accurate in comparison to existing approaches based on the continuous Galerkin finite element method or the fast Fourier transform method. (10.1088/1361-651X/ac44a7)
  DOI : 10.1088/1361-651X/ac44a7
• La fabrication additive des alliages métalliques 2
  
  • Peyre Patrice
  • Charkaluk Eric
  , 2022.
• La fabrication additive des alliages métalliques 1
  
  • Peyre Patrice
  • Charkaluk Eric
  , 2022.
• Influence of a static torque on plasticity and asperity-induced closure effects during fatigue crack growth in bainitic steel cylinders loaded in push-pull
  
  • Petureau Louis
  • Doquet Véronique
  • Dieu Benjamin
  International Journal of Fatigue, Elsevier, 2022, 155, pp.106628. Mode I fatigue crack growth with a superimposed static torque was investigated in bainitic steel. The torque had little effect on crack growth kinetics and path. However, the nonsingular stress parallel to the crack front, and bending stresses due to eccentric crack growth triggered crack twisting, even in mode I. A progressive increase in crack sliding displacement was due to a rise in elastic torsional compliance, but also to plastic ratchetting at the crack tip, and to a progressive shearing of crack face asperities, which reduced the enhancement of roughness-induced closure by the torque, however shown to enhance plasticity-induced closure. (10.1016/j.ijfatigue.2021.106628)
  DOI : 10.1016/j.ijfatigue.2021.106628
• Subsidence above rock-salt cavities - Numerical and explicit evaluations
  
  • Quintanilha de Menezes J. E.
  • Nguyen Minh D.
  , 2001, pp.139-143. Subsidence is always a long-term effect from the exploration of natural gas storage cavities. The internal pressure being less than in situ pressure leads to cavity convergence with has economical consequences as well as possible outcomes on the surface. After reviewing the subsidence phenomenology, by identifying what can be observed at the surface, and its environmental and structural consequences, some empirical and analytical means of estimating its deformation values are referred. With more detail, a numerical application is presented which uses coupled boundary and finite elements for subsidence evaluation due to deep storage cavities. This lasts characteristic gives rise to large extensions of deformed zones towards the surface. A real case of a storage cavity field with subsidence measurements made for more than ten years is taken as example and some predictions are made on future subsidence and horizontal displacement. (10.1201/9781003078562-16)
  DOI : 10.1201/9781003078562-16