Publications

2022

• Mechanically-grown morphogenesis of Voronoi-type materials: Computer design, 3D-printing and experiments
  
  • Hooshmand-Ahoor Z.
  • Tarantino M.G.
  • Danas K.
  Mechanics of Materials, Elsevier, 2022, pp.104432. The present work introduces a novel and versatile computer-design and experimental strategy to obtain random Voronoi-type geometries, called M-Voronoi (from mechanically grown), with smooth void shapes and variable intervoid ligament sizes that can reach very low relative densities. This is achieved via a numerical, large strain, nonlinear elastic, void growth mechanical process. Originally small circular voids embedded in a cell of arbitrary shape (triangle, circle, rectangle, trapezoid) grow when subjected to displacement (Dirichlet) boundary conditions. The deformed voids evolve into smooth Voronoi-type geometrical shapes leading to macroscopic isotropy or anisotropy depending on the prescribed boundary conditions. The void growth process is a direct consequence of mass conservation and the incompressibility of the surrounding nonlinear elastic matrix phase and the final achieved relative density may be analytically estimated in terms of the determinant of the applied deformation gradient. In order to study the mechanical properties of the M-Voronoi materials, we focus on two-dimensional porous polymer square representative isotropic and anisotropic geometries in terms of void size and realization, which are 3D-printed and experimentally tested under uniaxial compression. For comparison, we also test random polydisperse porous materials with circular voids, standard eroded Voronoi geometries and hexagonal honeycombs. The first two are also isotropic while the latter are only isotropic in the linear elastic regime. We show that the randomness of the M-Voronoi geometry and their non-uniform intervoid ligament size leads to enhanced mechanical properties at large compressive strains with no apparent peak-stress and strong hardening well before densification. By comparing them with the hexagonal geometries, which tend to exhibit a peak-stress and a plateau-type response, we show that the hardening response of the M-Voronoi is mainly due to their geometrical characteristics and less due to the polymer hardening response. Anisotropic M-Voronoi are also produced and tested indicating that anisotropy only 1 enhances the initial stiffness along the longitudinal direction but instead leads to lower buckling loads and hardening rates than the corresponding isotropic M-Voronoi in the nonlinear regime. (10.1016/j.mechmat.2022.104432)
  DOI : 10.1016/j.mechmat.2022.104432
• Residual stresses in thin walled-structures manufactured by directed energy deposition: In-situ measurements, fast thermo-mechanical simulation and buckling
  
  • Weisz-Patrault Daniel
  • Margerit Pierre
  • Constantinescu Andrei
  Additive Manufacturing, Elsevier, 2022, 56, pp.102903. Manufacturing strains and subsequent residual stresses are key elements in the behavior of thin-walled structures, as they induce buckling, warping, and failure. This work proposes a combined experimental and numerical analysis of these features by investigating the additive manufacturing of a thin-walled structure using directed energy deposition. In-situ measurements of temperature and in plan displacement fields during fabrication are identified over the entire part and all along the process by using infrared and optical cameras. One novelty of this work is to determine the displacement field without stopping fabrication unlike most of the existing approaches, which significantly simplifies the monitoring of the process. In addition, a numerical modeling of the process has been developed to investigate the formation of residual stresses. One novelty of the proposed approach is to reach reasonably short computation time, by decoupling thermal and mechanical problems, which is interesting for parametric studies. Results are relevant, as the computed temperature and displacement fields are in good agreement with the in-situ measurements. A complementary buckling analysis also shows the ability of the model to predict when fabrication has to be stopped due to excessive out of plan deflection. The presented model can therefore be used as a tool to select suitable process parameters for a given part. (10.1016/j.addma.2022.102903)
  DOI : 10.1016/j.addma.2022.102903
• 3D deep convolutional neural network segmentation model for precipitate and porosity identification in synchrotron X-ray tomograms
  
  • Gaudez S.
  • Ben Haj Slama M.
  • Kaestner A.
  • Upadhyay Manas Vijay
  Journal of Synchrotron Radiation, International Union of Crystallography, 2022, 29 (5), pp.1232-1240. New developments at synchrotron beamlines and the ongoing upgrades of synchrotron facilities allow the possibility to study complex structures with a much better spatial and temporal resolution than ever before. However, the downside is that the data collected are also significantly larger (more than several terabytes) than ever before, and post-processing and analyzing these data is very challenging to perform manually. This issue can be solved by employing automated methods such as machine learning, which show significantly improved performance in data processing and image segmentation than manual methods. In this work, a 3D U-net deep convolutional neural network (DCNN) model with four layers and base-8 characteristic features has been developed to segment precipitates and porosities in synchrotron transmission X-ray micrograms. Transmission X-ray microscopy experiments were conducted on micropillars prepared from additively manufactured 316L steel to evaluate precipitate information. After training the 3D U-net DCNN model, it was used on unseen data and the prediction was compared with manual segmentation. A good agreement was found between both segmentations. An ablation study was performed and revealed that the proposed model showed better statistics than other models with lower numbers of layers and/or characteristic features. The proposed model is able to segment several hundreds of gigabytes of data in a few minutes and could be applied to other materials and tomography techniques. The code and the fitted weights are made available with this paper for any interested researcher to use for their needs (https://github.com/manasvupadhyay/erc-gamma-3D-DCNN). (10.1107/S1600577522006816)
  DOI : 10.1107/S1600577522006816
• Effect of microscopic properties on the homogenized linear poroelastic behavior of lung parenchyma
  
  • Manoochehrtayebi Mahdi
  • Bel-Brunon Aline
  • Genet Martin
  , 2022. In this work, a micro-poro-mechanical model is proposed in 2D with various levels of irregularity and porosity, as a first step toward lung micromechanical modeling. The homogenized behavior of the generated microstructures is computed to evaluate how irregularity and porosity affect the macroscopic poroelastic material parameters
• Personalized pulmonary poromechanics in health, idiopathic pulmonary fibrosis and CoViD-19
  
  • Laville Colin
  • Patte Cécile
  • Fetita Catalin
  • Brillet Pierre-Yves
  • Gille Thomas
  • Nunes Hilario
  • Bernaudin Jean-François
  • Chapelle Dominique
  • Genet Martin
  , 2022. This abstract briefly describes our recent lung poromechanical model, and its associated model personalization procedure based on routine clinical data (thoracic scanners at end-expiration and endinspiration). The final aim of the personalized modeling pipeline is to provide automatic and objective diagnosis tools for fibrosing interstitial lung diseases, in the form of estimated regional stiffness maps. Here we present early results on three idiopathic pulmonary fibrosis patients and one COVID-19 patient. In the presentation we will detail the impact of various parameters of the method.
• A generic numerical solver for modeling the influence of stress conditions on guided wave propagation for SHM applications.
  
  • Dalmora Andre
  • Imperiale Alexandre
  • Imperiale Sébastien
  • Moireau Philippe
  , 2022. In leading-edge industrial applications, assessing structure integrity is an important aspect of safety requirements. Structural Health Monitoring (SHM) proposes to use sensors and signal processing units in situ. One of the most attractive SHM techniques is ultrasonic guided waves. Guided waves propagate on large distances and interact with defects in the structure making damage detection possible. Modelling and simulation can be helpful tools for the design or the reliability assessment of SHM solutions. The currently available models developed for that purpose do not take into account the effect of operational conditions such as internal stresses. These conditions can modify wave propagation and therefore affect the interpretation of recorded signals. The objective of this work is to propose a model filling this gap, and to derive corresponding numerical methods for elastic wave propagation in an arbitrarily deformed medium. Any hyperelastic constitutive law can be considered. As the structures considered are usually thin, we avoid shear-locking by using a shell formulation to solve the quasi-static problem representing the effects of structure loading. The computed displacement is then fed into a spectral elements method (SEM) kernel to solve the time-domain linearized 3D elastodynamics problem representing the wave propagation. We validate our model for an isotropic aluminium plate under tensile forces. Additionally, we apply these numerical procedures to a realistic bending experiment of a steel pipe, illustrating the effects of stresses on ultrasonic guided wave propagation. (10.1115/QNDE2022-98682)
  DOI : 10.1115/QNDE2022-98682
• Material modelling of the photopolymers for additive manufacturing processes
  
  • Sekmen Kubra
  • Rehbein Thomas
  • Johlitz Michael
  • Lion Alexander
  • Constantinescu Andrei
  , 2022, pp.94-106. Ultraviolet (UV) curing of polymers is a key phenomenon for several additive manufacturing technologies. This contribution presents a model relating the process parameters of UV light intensity and temperature to the thermal and mechanical properties of the polymer and the experimental results used to calibrate the model. Moreover, photo-differential scanning calorimetry (photo-DSC) measurements are performed to investigate the crosslinking reaction and to model the degree of cure as a function of the light intensity and temperature. The viscoelastic properties are measured by UV rheometry and it is shown that the classical time-cure superposition principle can equally be applied to the experimental results. Complete curing and mechanical model equations are provided to describe the material behavior as a result of our experimental findings.
• Additive Manufacturing of Metal Alloys 1
  
  • Peyre Patrice
  • Charkaluk Eric
  , 2022 (1). (10.1002/9781394163380)
  DOI : 10.1002/9781394163380
• Oxidation and decarburization during dual phase steels annealing for the industrial galvanizing process
  
  • Blanchard Alexis
  • Ruscassier N.
  • Héripré Eva
  • Aubin Véronique
  • Giorgi M.-L.
  , 2022.
• Modélisation de l'éruption d'une cavité saline de stockage souterrain d'hydrogène
  
  • Djizanne Hippolyte
  • Brouard Benoit
  • Berest Pierre
  • Hevin Grégoire
  , 2022. Modélisation de l'éruption d'une cavité saline de stockage souterrain d'hydrogène
• Analyse multi-échelle de la déformation, de la localisation et de l'endommagement des carbonates poreux sous conditions de chargement triaxiales
  
  • Doré-Ossipyan Catherine
  • Sulem Jean
  • Bornert Michel
  • Dimanov Alexandre
  , 2022. Analyse multi-échelle de la déformation, de la localisation et de l'endommagement des carbonates poreux sous conditions de chargement triaxiales
• Reduced-order cylindrical model of the left ventricle
  
  • Diaz Jérôme
  • Genet Martin
  • Chapelle Dominique
  • Moireau Philippe
  , 2022. The heart is a complex organ at the crossroads of different physics such as electrophysiology, solid mechanics, fluid mechanics and their interactions. Based on a cylindrical assumption of the left ventricle geometry, our proposed reduced model aleviates the cost of full 3D models. It retains key cardiac indicators such as the ventricular torsion and the pressure-volume loop while conserving energy-preserving properties. This reduced-order cylindrical model could help the adoption of cardiac modeling in the clinic thanks to its reduced complexity and computational burden.
• Creep tests on salt samples performed at very small stresses
  
  • Berest Pierre
  • Gharbi Hakim
  • Jehanno Didier
  • Peach Colin
  • Brouard Benoit
  • Blanco Martín Laura
  , 2022.
• Multi-scale biomechanics of healthy and pathological cornea
  
  • Giraudet Chloé
  , 2022. The cornea is the external and transparent part of the eye and one of the essential tissues for vision. Indeed, it provides 2/3 of the optical power of the eye while resisting the daily intraocular pressure variations to which it is subjected. Keratoconus is an idiopathic corneal dystrophy characterized by an ectasia and a progressive thinning of the tissue in the area affected by the pathology. To date, there is no clear and identified origin of the disease. One of the hypotheses put forward is the change in geometry induced by repeated ocular friction.The mechanical properties of the cornea are linked to the very particular microstructure of its stroma made of a plywood of collagen lamellae and it has been clearly identified that this microstructure becomes disorganized in the case of keratoconus. Numerous mechanical models have been developed to take into account this microstructure, in healthy and pathological cases, however there is to date very little experimental data on the macroscopic mechanical response of the cornea to validate them.The objective of this thesis is therefore to characterize the corneal mechanics in order to better understand the onset of pathology. Three main questions are investigated: what are the mechanical parameters that influence the appearance of keratoconus? Can we measure the mechanical response of the healthy cornea to complete the data available in the literature? What is the mechanical response of the cornea to intraocular pressure after tansplantation?
• Some contributions to cardiac and pulmonary biomechanical modeling, simulation & estimation
  
  • Genet Martin
  , 2022.
• Magnetoresponsive Devices with Programmable Behavior Using a Customized Commercial Stereolithographic 3D Printer
  
  • Lantean Simone
  • Roppolo Ignazio
  • Sangermano Marco
  • Hayoun Marc
  • Dammak Hichem
  • Barrera Gabriele
  • Tiberto Paola
  • Pirri Candido Fabrizio
  • Bodelot Laurence
  • Rizza Giancarlo
  Advanced Materials Technologies, Wiley, 2022, pp.2200288. The revolution of 4D printing allows combining smart materials to additive processes to create behavioral objects able to respond to external stimuli, such as temperature, light, electrical or magnetic fields. Here, we used a modified commercial Digital Light Processing (DLP) 3D printer to obtain complex macroscopic remotely-controlled gear-based devices. The fabrication process is based on the printing of magneto-responsive polymers containing in situ selfassembled microstructures, i.e. composed of oriented chains of Fe3O4 nanoparticles. First, we demonstrate that we are able to print magneto-responsive hammer-like actuators with different stiffness allowing both pure rotation or/and bending motions. Then, we exploit microstructure to create a magneto-responsive gear. In particular, we showed that they can be successfully used to transfer torque to other gears, thereby converting a rotation movement into linear translation. Finally, we demonstrated that magneto-responsive gears can be also combined with other non-magnetic elements to create complex assemblies, such as gear-trains, linear actuators and grippers, that can be remotely controlled. (10.1002/admt.202200288)
  DOI : 10.1002/admt.202200288
• Viscoelastic behavior of filled silicone elastomers and influence of aging in inert and hermetic environment
  
  • Avila Torrado Martin
  • Constantinescu Andrei
  • Johlitz Michael
  • Lion Alexander
  Continuum Mechanics and Thermodynamics, Springer Verlag, 2022. This article presents a series of experimental investigations on the viscoelastic behavior of silica-filled and silver-filled silicone rubber on the unaged and aged states. The study of specific aging conditions relative to the electronics industry is proposed in this work, namely aging in a hermetic, initially inert atmosphere, at high temperatures. Viscoelastic properties of the materials are measured through DMA tests. Strain sweep tests are carried for the characterization of unaged materials, and frequency sweeps at ambient temperature are performed to characterize the aging-dependent behavior. As a result of the experimental studies, an aging-dependent generalized Maxwell model is proposed in an attempt to describe the evolution in the behavior of silicones due to aging. (10.1007/s00161-022-01112-9)
  DOI : 10.1007/s00161-022-01112-9
• Revisiting the influence of the scanning speed on surface topography and microstructure of IN718 thin walls in directed energy deposition additive manufacturing
  
  • Bréhier Michèle
  • Weisz-Patrault Daniel
  • Tournier Christophe
  , 2022, 108, pp.470-476. Controlling the mechanical properties of metallic parts produced by additive manufacturing remains challenging. The mechanical behavior of parts is mainly related to the microstructure, which depends on process parameters and manufacturing strategies. The scanning speed is one of the key parameters that can be modulated during the process (according to the kinematic behavior of the machine tool) in order to reach different microstructures. Thus, in this work, an experimental study in laser metal powder directed energy deposition is conducted to analyze the influence of the scanning speed on the macroscopic geometry, the surface topography, and the microstructure. To do so, a series of single-layer experiments has been conducted to establish an empirical relationship between the laser power, the powder flow-rate and the scanning speed on the one hand, and the layer height and width on the other hand. In addition, six multi-layer thin-walled structures have been produced for various laser powers and scanning speeds in order to determine an association with macroscopic features, topography and microstructure. This approach opens interesting long-term perspectives to better control microstructures in DED. (10.1016/j.procir.2022.03.074)
  DOI : 10.1016/j.procir.2022.03.074
• The Role of the Relative Fluid Velocity in an Objective Continuum Theory of Finite Strain Poroelasticity
  
  • Gil Ludovic
  • Jabbour Michel
  • Triantafyllidis Nicolas
  Journal of Elasticity, Springer Verlag, 2022, 150 (1), pp.151-196. (10.1007/s10659-022-09903-6)
  DOI : 10.1007/s10659-022-09903-6
• A new reduced order model to represent the creep induced fuel assembly bow in PWR cores
  
  • Leturcq Bertrand
  • Le Tallec Patrick
  • Pascal Serge
  • Fandeur Olivier
  • Lamorte Nicolas
  Nuclear Engineering and Design, Elsevier, 2022, 394, pp.111828. Progressive deformation of nuclear fuel assemblies that occurs during a succession of irradiation cycles within PWR is at the core of numerous interactions. Progresses in the study of this phenomenon resulted from more and more complex models. To date, in the more advanced models, a mechanical model is combined to a hydraulic model of the core to address the fluid-structure interaction. A complete mechanical model of the core is generally built with a simplified finite element representation of each assembly using beam or simpler elements. The simplifying approach is required due to the high complexity of the multi-body multi-physics calculations. In order to improve the representativeness of the core model without penalizing the computational cost of the coupled simulations, a new method of model order reduction is proposed. It is specially adapted to this context and borrows the concepts of NTFA non-linear homogenization. The theoretical foundations and the application to a slender structure are presented. First, the method is validated on a simple case with spatially homogeneous characteristics. Finally, the case of the creep response of a fuel assembly under realistic heterogeneous loads is demonstrated. (10.1016/j.nucengdes.2022.111828)
  DOI : 10.1016/j.nucengdes.2022.111828
• In-Situ Evolution of Calcite Twinning during Uniaxial Compression of Carrara Marble at Room Temperature
  
  • Parlangeau Camille
  • Dimanov Alexandre
  • Hallais Simon
  Geosciences, MDPI, 2022, 12 (6). (10.3390/geosciences12060233)
  DOI : 10.3390/geosciences12060233
• On the anisotropy of the myocardium
  
  • Genet Martin
  • Tueni Nicole
  • Allain Jean-Marc
  , 2022.
• A nonlinear kinetics phase-field model for ferroelectrics
  
  • Guin Laurent
  • Hennecart Louis
  • Kochmann Dennis
  , 2022. Ferroelectric ceramics exhibit a spontaneous electric polarization that can be reversed under the application of an electrical or mechanical loading. The method of choice to model the evolution of polarization domains are diffuse-interface models (also called phase-field models), most of them being based on the Allen-Cahn equation. The latter assumes, unlike experimental evidence, a linear relation between the velocity of domain walls and their conjugate driving force. In this work, we develop an alternative phase-field formulation that accounts for the non-linear kinetics of domain walls, an important feature with regards to rate effects in ferroelectrics.
• Optimisation de forme de poutres et plaques viscoélastiques en vibration libre
  
  • Joubert Antoni
  • Allaire Grégoire
  • Amstutz Samuel
  • Diani Julie
  , 2022.
• Analysis of fatigue crack growth under cyclic mode II + static biaxial compression
  
  • Zaid Mael
  • Bonnand Vincent
  • Chiaruttini Vincent
  • Pacou Didier
  • Doquet Véronique
  • Depouhon Pierre
  , 2022. Cracks initiated in gears by rolling contact fatigue are subjected to triaxial compression with cyclic shear. In order to determine the crack growth kinetics for such loading, cyclic shear tests with static biaxial compression were performed on bearing steel, and resulted in long cracks propagation in mode II, with many secondary branches which influences the crack growth rate. Simulations highlight the crack growth competition and the role of biaxial compression on the extensive coplanar growth observed experimentally.