Publications

2021

• Review of “A damage criterion based on energy balance for an isotropic cohesive zone model”
  
  • Chrysochoos André
  • Daridon Loïc
  • Renouf Mathieu
  • Marigo Jean-Jacques
  • Brassart Laurence
  , 2021.
• Morphological instabilities of vicinal surfaces during epitaxial growth
  
  • Benoit-Maréchal Lucas
  , 2021. The study of step dynamics on vicinal surfaces is a long-standing problem in crystal growth, dating back to the seminal work of Burton, Cabrera, and Frank (BCF) in 1951. On these surfaces, the crystal grows by step flow, i.e., by propagation of the atomic steps, which may develop instabilities breaking the regularly spaced, straight-step initial configuration. Step bunching corresponds to situations where steps coalesce together resulting in an alternating pattern of bunches and wide atomic terraces, and step meandering to situations where the initially straight steps exhibit a distinct waviness.Using nonequilibrium thermodynamics and the formalism of configurational forces, we derive a generalized Gibbs-Thomson relation for the step chemical potential which natively accounts for the contribution of the elastic bulk and incorporates the necessary coupling between the diffusion fields on adjacent terraces (the chemical effect). This leads to a free-boundary problem that generalizes the BCF model for the governing equations of step flow where full account is taken of the dynamics terms. In doing so, we circumvent the quasistatic approximation that prevails in the existing literature.Through comprehensive numerical simulations, scaling laws governing the coarsening behaviour of step bunches are identified. Taking the discrete-to-continuum limit of the step-flow equations leads to a nonlinear partial differential equation that describes the macroscopic evolution of the surface profile, from which we recover the numerically obtained scaling laws. Importantly, we demonstrate that the chemical and dynamical effects can account for the onset of step bunching and for the scaling laws experimentally observed in the coarsening regime.In the context of a general stability analysis, we discuss the influence on step bunching and step meandering of all the mechanisms independently, as well as their interplay, and we demonstrate the significant impact of the chemical and dynamical effects on stability, even in the slow deposition/evaporation regime where the dynamics were deemed negligible. Consequently, we set forth the possible coexistence of bunching and meandering, in contrast with the BCF model which predicts that the two instabilities are mutually exclusive.In light of these findings, we show that the chemical and dynamical effects offer interesting alternative explanations to account for the step instabilities observed in some experiments, notably in the setting of electromigration under extreme deposition flux for which we correctly predict the unexplained step pairing instability. A full accounting of the stability reversals observed on Si(111) under electromigration remains an open problem as the chemical and dynamical effects do not modify the stability dependence on the direction of the current.
• Altered Aortic Hemodynamics and Relative Pressure in Patients with Dilated Cardiomyopathy
  
  • Marlevi David
  • Mariscal-Harana Jorge
  • Burris Nicholas
  • Sotelo Julio
  • Ruijsink Bram
  • Hadjicharalambous Myrianthi
  • Asner Liya
  • Sammut Eva
  • Chabiniok Radomir
  • Uribe Sergio
  • Winter Reidar
  • Lamata Pablo
  • Alastruey Jordi
  • Nordsletten David
  Journal of Cardiovascular Translational Research, Springer, 2021. Ventricular-vascular interaction is central in the adaptation to cardiovascular disease. However, cardiomyopathy patients are predominantly monitored using cardiac biomarkers. The aim of this study is therefore to explore aortic function in dilated cardiomyopathy (DCM). Fourteen idiopathic DCM patients and 16 controls underwent cardiac magnetic resonance imaging, with aortic relative pressure derived using physics-based image processing and a virtual cohort utilized to assess the impact of cardiovascular properties on aortic behaviour. Subjects with reduced left ventricular systolic function had significantly reduced aortic relative pressure, increased aortic stiffness, and significantly delayed time-to-pressure peak duration. From the virtual cohort, aortic stiffness and aortic volumetric size were identified as key determinants of aortic relative pressure. As such, this study shows how advanced flow imaging and aortic hemodynamic evaluation could provide novel insights into the manifestation of DCM, with signs of both altered aortic structure and function derived in DCM using our proposed imaging protocol. (10.1007/s12265-021-10181-1)
  DOI : 10.1007/s12265-021-10181-1
• Simple deformation measures for Discrete elastic rods and ribbons
  
  • Korner K
  • Audoly Basile
  • Bhattacharya K
  Proceedings of the Royal Society of London. Series A, Mathematical and physical sciences, Royal Society, The, 2021, 4477 (2256). The Discrete elastic rod method (Bergou et al., 2008) is a numerical method for simulating slender elastic bodies. It works by representing the centerline as a polygonal chain, attaching two perpendicular directors to each segment, and defining discrete stretching, bending and twisting deformation measures and a discrete strain energy. Here, we investigate an alternative formulation of this model based on a simpler definition of the discrete deformation measures. Both formulations are equally consistent with the continuous rod model. Simple formulas for the first and second gradients of the discrete deformation measures are derived, making it easy to calculate the Hessian of the discrete strain energy. A few numerical illustrations are given. The approach is also extended to inextensible ribbons described by the Wunderlich model, and both the developability constraint and the dependence of the energy on the strain gradients are handled naturally. (10.1098/rspa.2021.0561)
  DOI : 10.1098/rspa.2021.0561
• Temperature- and degree of cure-dependent viscoelastic properties of photopolymer resins used in digital light processing
  
  • Rehbein Thomas
  • Johlitz Michael
  • Lion Alexander
  • Sekmen Kubra
  • Constantinescu Andrei
  Progress in Additive Manufacturing, Springer Verlag, 2021, 6 (4), pp.743-756. Abstract In the present paper, the degree of cure-dependent viscoelastic properties of a commercial photopolymer resin (Loctite® 3D 3830) used in digital light processing (DLP) 3D printing are investigated experimentally and described by suitable model equations. To do this, tests are carried out both on the liquid resin and printed specimens under various conditions. The experimental methods include photo-DSC, UV rheometry, and dynamic mechanical analysis. A commercial digital light processing (DLP) printer (Loctite® EQ PR10.1) is used for the printing of the samples. Model equations are proposed to describe the behavior of the material during and after the printing process. For the representation of the degree of cure depending on temperature and light intensity, the one-dimensional differential equation proposed in a previous paper is extended to capture a temperature-dependent threshold value. The change of the viscoelastic properties during crosslinking is captured macroscopically by time-temperature and time-cure superposition principles. The parameters of the model equations are identified using nonlinear optimization algorithms. A good representation of the experimental data is achieved by the proposed model equations. The findings of this paper help users in additive manufacturing of photopolymers to predict the material properties depending on the degree of cure and temperature of printed components. (10.1007/s40964-021-00194-2)
  DOI : 10.1007/s40964-021-00194-2
• Prediction of Ventricular Mechanics After Pulmonary Valve Replacement in Tetralogy of Fallot by Biomechanical Modeling: A Step Towards Precision Healthcare
  
  • Gusseva Maria
  • Hussain Tarique
  • Hancock Friesen Camille
  • Greil Gerald
  • Chapelle Dominique
  • Chabiniok Radomir
  Annals of Biomedical Engineering, Springer Verlag, 2021, 49 (12), pp.3339-3348. (10.1007/s10439-021-02895-9)
  DOI : 10.1007/s10439-021-02895-9
• Design of thin micro-architectured panels with extension-bending coupling effects using topology optimization
  
  • Agnelli Filippo
  • Nika Grigor
  • Constantinescu Andrei
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2021, 391, pp.114496. We design the micro-architecture of thin elastic panels to control their macroscopic behavior, accounting simultaneously for in-plane stiffness, out-of-plane stiffness and the extension-bending coupling effects. Our topology optimization method combines inverse homogenization, the Hadamard shape derivative and a level set method in the diffuse interface context to systematically capture within the unit cell the optimal micro-architecture. The efficiency of the solution method is illustrated through four numerical examples where the designed shape yields an important extension-bending coupling. The deformation responses under tensile loading is assessed numerically both on the complete periodic panel and on its homogenised twin plate. The results demonstrate that the simultaneous control of the inplane, out-of-plane and their coupled behavior enables to shift a flat panel into a dome or a saddle shaped structure. Moreover, the obtained unit cells are elementary blocks to create directly 3D printable objects with shape-morphing capabilities. (10.1016/j.cma.2021.114496)
  DOI : 10.1016/j.cma.2021.114496
• Analysis Of Real-Life Multi-Input Loading Histories For The Reliable Design Of Vehicle Chassis
  
  • Baroux Emilien
  • Delattre Benoit
  • Constantinescu Andrei
  • Pamphile Patrick
  • Raoult Ida
  , 2021. In order to reliably design automotive structures, engineers need to determine and justify validation conditions and levels. These must stem from a thorough knowledge of structural damage induced by service loading conditions. From multi-input variable amplitude loading histories applied on a car's wheel axles, we propose a multidimensional pseudo-damage description for the design of car chassis weak points. We present a multivariate description of client loading histories. We use it in a statistical analysis of a labelled measurement campaign to explain the heterogeneity of car driver profiles. Finally, we explore the question of complex load damage reconstruction using proving ground reference loads.
• A convenient formulation of Sadowsky model for elastic ribbons
  
  • Audoly Basile
  • Neukirch Sébastien
  Proceedings of the Royal Society of London. Series A, Mathematical and physical sciences, Royal Society, The, 2021, 477 (2256), pp.20210548. Elastic ribbons are elastic structures whose length-to-width and width-to-thickness aspectratios are both large. Sadowsky proposed a one-dimensional model for ribbons featuring a nonlinear constitutive relation for bending and twisting: it brings in both rich behaviors and numerical difficulties. By discarding non-physical solutions to this constitutive relation, we show that it can be inverted; this simplifies the system of differential equations governing the equilibrium of ribbons. Based on the inverted form, we propose a natural regularization of the constitutive law that eases the treatment of singularities often encountered in ribbons. We illustrate the approach with the classical problem of the equilibrium of a Möbius ribbon, and compare our findings to the predictions of the Wunderlich model. Overall, our approach provides a simple method for simulating the statics and the dynamics of elastic ribbons. (10.1098/rspa.2021.0561)
  DOI : 10.1098/rspa.2021.0561
• In-silico study of accuracy and precision of left-ventricular strain quantification from 3D tagged MRI
  
  • Berberoğlu Ezgi
  • Stoeck Christian T
  • Moireau Philippe
  • Kozerke Sebastian
  • Genet Martin
  PLoS ONE, Public Library of Science, 2021, 16 (11), pp.e0258965. Cardiac Magnetic Resonance Imaging (MRI) allows quantifying myocardial tissue deformation and strain based on the tagging principle. In this work, we investigate accuracy and precision of strain quantification from synthetic 3D tagged MRI using equilibrated warping. To this end, synthetic biomechanical left-ventricular tagged MRI data with varying tag distance, spatial resolution and signal-to-noise ratio (SNR) were generated and processed to quantify errors in radial, circumferential and longitudinal strains relative to ground truth. Results reveal that radial strain is more sensitive to image resolution and noise than the other strain components. The study also shows robustness of quantifying circumferential and longitudinal strain in the presence of geometrical inconsistencies of 3D tagged data. In conclusion, our study points to the need for higher-resolution 3D tagged MRI than currently available in practice in order to achieve sufficient accuracy of radial strain quantification. (10.1371/journal.pone.0258965)
  DOI : 10.1371/journal.pone.0258965
• Association of Carpal Tunnel Syndrome in Diabetes Patient
  
  • Jaganath K
  • Kumar Arun
  • Kumar Sathish
  • Raj K. Nithish
  • Sundaram P. Sanmuga
  Journal of Pharmaceutical Research International, Hooghly: Sciencedomain International, 2021, 33 (48A), pp.41-45. Objective: The objective of our study was to determine Prevalence of carpel tunnel syndrome among diabetic patients and the significant association between carpel tunnel syndrome and diabetes mellitus. Materials and Methods: Study was conducted on 250 patients at Saveetha medical college and hospital. Study was conducted after getting proper ISE approval. Subjects were selected according to inclusion and exclusive criteria's. For every study subject after getting consent demographic information, past medical history of Diabetes such as type, duration, any associated complication (diabetic neuropathy, retinopathy, etc.), medication, and lifestyle modification were obtained via a self-reporting structured questionnaire and confirmed by the subject's medical record. For every subject, clinical tests such as Tinel's test and Phalen test were performed and nerve conduction study was used for diagnose carpal tunnel syndrome among the subjects who were showing positive clinical test. All data collected were entered into the standardized database and statistic analysis was calculated. Results: After analysing the data collected on association between carpel tunnel syndrome and a diabetes patient. Conclusion: It implies that there is a significant relationship between carpal tunnel syndrome and diabetes patients.
• Biomechanical Modeling to Inform Pulmonary Valve Replacement in Tetralogy of Fallot Patients after Complete Repair
  
  • Gusseva Maria
  • Hussain Tarique
  • Friesen Camille Hancock
  • Moireau Philippe
  • Tandon Animesh
  • Patte Cécile
  • Genet Martin
  • Hasbani Keren
  • Greil Gerald
  • Chapelle Dominique
  • Chabiniok Radomir
  Canadian Journal of Cardiology, Elsevier, 2021, 37, pp.1798-1807. Background: A biomechanical model of the heart can be used to incorporate multiple data sources (ECG, imaging, invasive hemodynamics). The purpose of this study was to use this approach in a cohort of tetralogy of Fallot patients after complete repair (rTOF) to assess comparative influences of residual right ventricular outflow tract obstruction (RVOTO) and pulmonary regurgitation on ventricular health. Methods: 20 rTOF patients who underwent percutaneous pulmonary valve replacement (PVR) and cardiovascular magnetic resonance (CMR) were included in this retrospective study. Biomechanical models specific to individual patient and physiology (pre- and post-PVR) were created and utilized to estimate the RV myocardial contractility. The ability of models to capture post-PVR changes of RV end-diastolic volume (EDV) and effective flow in pulmonary artery (Qeff) was also compared to expected values. Results: RV contractility pre-PVR (65±17 kPa, mean ± SD) was increased in rTOF patients in comparison to normal RV (39-45 kPa) (p<0.05). The contractility decreased significantly in all patients post-PVR (p<0.05). Patients with predominantly RVOTO demonstrated greater reduction in contractility (median decrease 35%) post-PVR than those with predominant pulmonary regurgitation (median decrease 12%). The model simulated post-PVR decreased EDV for majority and suggested an increase of Qeff –both in line with published data. Conclusions: This study uses a biomechanical model to synthesize multiple clinical inputs and give an insight into RV health. Individualized modeling allows us to predict the RV response to PVR. Initial data suggest that residual RVOTO imposes greater ventricular work than isolated pulmonary regurgitation. (10.1016/j.cjca.2021.06.018)
  DOI : 10.1016/j.cjca.2021.06.018
• MAESSTRO 1.0.0
  
  • Elie Benjamin
  • Cotté Benjamin
  • Boutillon Xavier
  • Chauvat Nicolas
  • Laxalde Denis
  • Bessou Frank
  • Nhu Viet-Hung
  • Trévisan Benjamin
  , 2021. MAESSTRO is a software for sound synthesis of piano tones based on a complete vibroacoustic modeling of the piano. The main goal is to provide piano makers a set of tools that allow them to predict the acoustic impacts of structural modifications of piano soundboards on the resulting sounds. The interest of the physical modeling that drives the numerical computations embedded in the software is to be able to reproduce the vibroacoustics of the piano in a realistic fashion: the acoustic variations between tones produced by different pianos faithfully reflect their structural differences. For that purpose, MAESSTRO gathers and coordinates several numerical and physical models that numerically simulate all of the physical phenomena involved in the production of piano tones, from the hammer impulsion upto the acoustic radiation. MAESSTRO includes several functionalities which are the following * entering the geometry and the materials of the virtual soundboard thanks to a Graphical User Interface (GUI), * feeding MAESSTRO with MIDI files to be synthesized, * simulating numerically the physical phenomena involved in the production of piano tones, * post-processing the software outputs, * creating audio files of synthesized piano tones. The package contains three subpackages : * maesstro-ihm contains the source codes of the GUI, implemented in TypeScript * maesstro-matlab is a Matlab toolbox that contains the source codes for the computation of the modal basis of the soundboard, including an automatic mesh generator using GMSH. Matlab is only needed to modify the source files and generate updated executables. In order to launch the executables, only Matlab Runtime is needed * maesstro-python contains the python modules which is used to call the different modules via a command line interface
• On the design of 3D printable architectured sheets
  
  • Agnelli Filippo
  , 2021. The aim of this thesis is to design and mechanically characterize periodic architectural materials, with a focus on the case of thin sheets. These solids are characterized by their micro-architecture, obtained by periodically repeating elementary meshes, which confer exceptional macroscopic properties. The advances in 3D printing techniques offer the possibility to manufacture micro architectures of ever more complex shapes, opening the way to new possibilities related to their design. The study is placed within the framework of materials with elastic linear behaviours and is based upon asymptotic homogenization, and topology optimization with the level set method. The first part deals with the systematic design cycle of thin architectured sheets exhibiting a negative Poisson's ratio. After fixing the target elastic properties, the final configuration of the micro-architecture is obtained by solving the inverse problem with topology optimization algorithms. Architectured sheets specimens are fabricated and mechanically loaded in tension and shear. A multi-scale analysis method using digital image correlation makes it possible to identify the in-plane mechanisms of deformation. These experimental analyses, supplemented by finite element simulations, make it possible to evaluate the effects of geometric non-linearities and manufacturing imperfections on the structural response. The second part is devoted to the study of composite panels, featuring an extension-bending coupling mechanism, which can be harnessed to manufacture panels that change shape. These panels were first build as a network of undulated ribbons, parametrised by b-splines, and more recently using topology optimization method adapted to plates. In both cases, the elastic properties are estimated using the generalized Kirchhoff-Love thin plate models. Simultaneous control of in-plane, out-of-plane and coupling behaviour enable to morph flat structures into dome- or saddle shapes under the action of in-plane loading. Experimental tests with point-like boundary highlights exceptional out of plane displacement.
• Coupling data measured in operating theatre with patient-specific biomechanical model of heart and vessels to augment haemodynamic monitoring of patients undergoing general anaesthesia
  
  • Le Gall Arthur
  , 2021. Haemodynamic evaluation of anaesthetised patients in operating theatre or in intensive care units can be challenging. Indeed, monitoring devices can be inaccurate and/or invasive. Physicians have to evaluate the usefulness of the information given by the monitor, and its potential harms linked to its invasiveness before implementing the technique. Modelling methods may be an interesting alternative to improve the risk/benefit balance for the patients.Biomechanical modelling of heart and vessels as presented in this PhD thesis, when turned into patient-specific regime using patients' data measured in operating theatre, can allow simulation of cardiovascular physiology, including pressure-volume relationships through the cardiac cycle.In 45 patients undergoing general anaesthesia, we analysed the haemodynamic profile in terms of cardiac bioenergetics or ventricular arterial coupling, and we were able to evaluate the effects of Noradrenaline administered for 16 hypotensive patients, on cardiac efficiency, using pressure-volume loops estimated from a patient-specific biomechanical model.Our approach is original as it is based on a rigorous cardiovascular physiological description and on continuum mechanics theory allowing physical and physiological interpretation of the modelling results.This PhD thesis presents also original methods for model calibration, from limited data availability. We developed a passive constitutive law (end-diastolic pressure-volume relationship -- EDPVR) estimation method which reunites the biomechanical approach, usually difficult to implement in clinical settings, and the phenomenological approach, more efficient but less rigorous.We also explored the potentials of a time-varying elastance model, derived from the full biomechanical model. We demonstrated that for reasonable variation ranges, the time-varying elastance model could be used as a surrogate for the biomechanical model. This approach improves the computational time and resources, allowing to consider the transfer of our approach in real-time monitoring conditions.This PhD thesis is a proof of concept of the coupling between biomechanical modelling of heart and vessels and data measured in operating theatre to augment cardiovascular monitoring in anaesthetised patients. This is also the first step toward transfer of the method from bench to bedside.
• Right-left ventricular shape variations in tetralogy of Fallot: associations with pulmonary regurgitation
  
  • Mauger Charlène A
  • Govil Sachin
  • Chabiniok Radomir
  • Gilbert Kathleen
  • Hegde Sanjeet
  • Hussain Tarique
  • Mcculloch Andrew D
  • Occleshaw Christopher J
  • Omens Jeffrey
  • Perry James C
  • Pushparajah Kuberan
  • Suinesiaputra Avan
  • Zhong Liang
  • Young Alistair A
  Journal of Cardiovascular Magnetic Resonance, BioMed Central : Elsevier, 2021, 23 (1). Abstract Background Relationships between right ventricular (RV) and left ventricular (LV) shape and function may be useful in determining optimal timing for pulmonary valve replacement in patients with repaired tetralogy of Fallot (rTOF). However, these are multivariate and difficult to quantify. We aimed to quantify variations in biventricular shape associated with pulmonary regurgitant volume (PRV) in rTOF using a biventricular atlas. Methods In this cross-sectional retrospective study, a biventricular shape model was customized to cardiovascular magnetic resonance (CMR) images from 88 rTOF patients (median age 16, inter-quartile range 11.8–24.3 years). Morphometric scores quantifying biventricular shape at end-diastole and end-systole were computed using principal component analysis. Multivariate linear regression was used to quantify biventricular shape associations with PRV, corrected for age, sex, height, and weight. Regional associations were confirmed by univariate correlations with distances and angles computed from the models, as well as global systolic strains computed from changes in arc length from end-diastole to end-systole. Results PRV was significantly associated with 5 biventricular morphometric scores, independent of covariates, and accounted for 12.3% of total shape variation (p < 0.05). Increasing PRV was associated with RV dilation and basal bulging, in conjunction with decreased LV septal-lateral dimension (LV flattening) and systolic septal motion towards the RV (all p < 0.05). Increased global RV radial, longitudinal, circumferential and LV radial systolic strains were significantly associated with increased PRV (all p < 0.05). Conclusion A biventricular atlas of rTOF patients quantified multivariate relationships between left–right ventricular morphometry and wall motion with pulmonary regurgitation. Regional RV dilation, LV reduction, LV septal-lateral flattening and increased RV strain were all associated with increased pulmonary regurgitant volume. Morphometric scores provide simple metrics linking mechanisms for structural and functional alteration with important clinical indices. (10.1186/s12968-021-00780-x)
  DOI : 10.1186/s12968-021-00780-x
• Deformation of aluminum in situ SEM and full field measurements by digital image correlation: evidence of concomitant crystal slip and grain boundary sliding
  
  • Dimanov Alexandre
  • Sabbagh A El
  • Raphanel J
  • Bornert M
  • Thiên-Nga L
  • Hallais S
  • Tanguy A
  Materials Science and Engineering, Elsevier, 2021. Mechanical testing in situ scanning electron microscopy (SEM) has become a standard technique for multiscale micromechanical investigation of polycrystalline materials. Direct observation of developing strain heterogeneities allows identification of the active mechanisms and quantification of their respective contributions to the overall strain. We developed a novel experimental setup for thermomechanical testing in situ SEM, especially suited to full strain field measurements. These are based on digital image correlation (DIC), from the sample scale to the scales of the aggregate and the single grain. We present results obtained during simple compression, at controlled displacement rates and at temperatures up to 400°C, of nearly pure polycrystalline aluminum exhibiting randomly oriented coarse grains (ca. 300 m in size). Electron microlithography was applied to produce specific surface marking patterns appropriate for the different scales of interest. Full surface strain fields were obtained by digital image correlation (DIC) analysis. The localization patterns evidenced dominant crystal slip plasticity, but also substantial simultaneous and continuous activity of grain boundary sliding (GBS), the contribution of which increased with temperature. We therefore advocate that experiments such as these here presented are necessary to go beyond a description in terms of deformation mechanism maps, which attribute deformation to a single mechanism. (10.2139/ssrn.3922862)
  DOI : 10.2139/ssrn.3922862
• On chemical reaction planar fronts in an elastic–viscoelastic mechanical framework
  
  • Petrenko Svetlana
  • Freidin Alexander B
  • Charkaluk Eric
  Continuum Mechanics and Thermodynamics, Springer Verlag, 2021, 34, pp.137 - 163. A stress-affected chemical reaction front propagation is considered using the concept of a chemical affinity tensor. A reaction between an elastic solid constituent and a diffusing constituent, localized at the reaction front, is considered. As a result of the reaction, the elastic constituent transforms into viscoelastic one. The reaction is accompanied by volume expansion that in turn may result in stresses at the reaction front, which affect the front velocity through the normal component of the chemical affinity tensor. Considering a plane strain problem with a planar chemical reaction front propagation under uniaxial deformation, we focus on the studies of the reaction front kinetics in dependence on external strains and material parameters with the use of the notion of the equilibrium concentration. Then, stress relaxation behind the propagating reaction front is modeled. A standard linear solid model is used for the reaction product, and its particular cases are also considered. Analytical solutions are obtained which allow to study in explicit form the strain influence and material parameters on the front retardation or acceleration and stress relaxation. Keywords Mechanochemistry • Chemical affinity tensor • Reaction front kinetics • Stress relaxation • Standard linear solid model Communicated by Andreas Öchsner. (10.1007/s00161-021-01051-x)
  DOI : 10.1007/s00161-021-01051-x
• Coupling reduced-order blood flow and cardiac models through energy-consistent strategies: modeling and discretization
  
  • Manganotti Jessica
  • Caforio Federica
  • Kimmig François
  • Moireau Philippe
  • Imperiale Sébastien
  Advanced Modeling and Simulation in Engineering Sciences, Springer, 2021, 8. In this work we provide a novel energy-consistent formulation for the classical 1D formulation of blood flow in an arterial segment. The resulting reformulation is shown to be suitable for the coupling with a lumped (0D) model of the heart that incorporates a reduced formulation of the actin-myosin interaction. The coupling being consistent with energy balances, we provide a complete heart-circulation model compatible with thermodynamics hence stable numerically and informative physiologically. These latter two properties are verified by numerical experiments. (10.1186/s40323-021-00206-4)
  DOI : 10.1186/s40323-021-00206-4
• Mesure PeakForce-QNM AFM des rides de surface induites par photopolymérisation sur l'objet imprimé en 3D DLP
  
  • Sekmen Kübra
  • Chang Xuyang
  • Hallais Simon
  • Danas Kostas
  • Constantinescu Andrei
  , 2021.
• PeakForce-QNM AFM measurement of photopolymerization-induced surface wrinkles in 3D printed objects
  
  • Sekmen Kübra
  • Chang Xuyang
  • Hallais Simon
  • Danas Kostas
  • Constantinescu Andrei
  , 2021.
• Quantification of mechanofluorochromism at the macroscale via colorimetric analysis of controlled mechanical stimulation
  
  • Poggi Benjamin
  • Bodelot Laurence
  • Louis Marine
  • Métivier Rémi
  • Allain Clémence
  Journal of Materials Chemistry C, Royal Society of Chemistry, 2021, 9 (36), pp.12111-12117. Novel setup and analysis method have been designed to quantify the response of mechanofluorochromic compounds to compression or shearing stresses. (10.1039/d1tc02274a)
  DOI : 10.1039/d1tc02274a
• Chemo-mechanical couplings in inelastic solids : analytical solutions and application to oxidation
  
  • Petrenko Svetlana
  , 2021. In the last decades, a particular attention in solid mechanics has been devoted to the investigation of materials, whose structure changes due to chemical transformations , which induces strong couplings between chemistry, mechanics and physics. Such stress-assisted chemical reactions are relevant in various industrial and medical applications and in modern technologies like batteries charging/discharging cycles introducing volume changes and cracks in electrodes, oxidation processes in MEMS or metal-based composite materials, thermo- or photo-oxidation of polymers. It is thus necessary to take into account the influence of stress-strain state on chemical transformation in detail for predicting the lifetime and the behavior of structural elements under simultaneous thermomechanical and chemical effects. Such processes can be described using the two-phase reaction model, in which reaction is localized at the sharp interface- reaction front, and the diffusing reactant is transported to the reaction front through the transformed material. The work presented in this PhD thesis is based on a coupled chemo-mechanical continuum theory applied to particular geometries and constitutive relations in order to obtain analytical solutions compared to experiments results.In the first part of the work, using the thermodynamical approach based on the concept of chemical affinity tensor, a theoretical analysis is conducted in order to take into account inelastic effects (viscosity, plasticity) and the geometry of structural elements (plane, spherical and cylindrical) on the chemical front propagation. The reaction rate is defined by the normal component of the chemical affinity tensor, which is equal to the combination of chemical potentials. After defining equilibrium conditions, the influence of inelastic behaviour of the transformed material on the reaction rate is studied in details. Analytical expressions of stress relaxation behind the reaction front are developed in the viscoelastic case. The analytical solution for perfectly plastic transformed material is obtained and shows that even only due to chemical transformations, without any external loading, the material can plastify. The effect of the structure’s geometry on the chemical reaction propagation is studied for plane, spherical and cylindrical problems. It is also shown how the mechanical properties of initial and new material can impact chemical reaction evolutions.In the second part of the work, in order to validate this approach, high-temperature oxidation experiments for pure nickel wires and balls are conducted. The objective of such experiments is to study the kinetics of such a front at local scales and to compare the obtained results with analytical solutions. Such comparisons show how the rheological properties of materials and geometry of the considered body are important to predict the reaction front propagation. By combining these experiments with the analytical solutions, values for the diffusion coefficient and the chemical reaction constants are obtained.
• Effective Model for Elastic Waves in a Substrate Supporting an Array of Plates/Beams with Flexural and Longitudinal Resonances
  
  • Marigo Jean-Jacques
  • Pham Kim
  • Maurel Agnès
  • Guenneau Sébastien
  Journal of Elasticity, Springer Verlag, 2021, 146 (1), pp.143-177. (10.1007/s10659-021-09854-4)
  DOI : 10.1007/s10659-021-09854-4
• Rheology of partially molten plagioclase containing wetting silica-rich anhydrous melt abbreviated title: Rheology of partially molten plagioclase
  
  • Dimanov Alexandre
  , 2021. The present work explores the effects of melt chemistry on diffusion controlled creep of partially molten labradorite plagioclase (An 50) at anhydrous conditions. Using sol-gel and hot pressing techniques we produced: 1) nominally melt-free samples (Lab), with < 1 vol. % residual glass confined solely to multiple grain junctions; 2) SilLab1 and SilLab5 partially molten samples containing respectively 1 and 5 vol. % excess amorphous silica, resulting in partial melts wetting numerous grain boundaries as thin (< 10 nm) amorphous films. Energy dispersive X-ray analysis showed that the amorphous phases in Lab, SilLab1 and SilLab5 samples contained about ~ 70, ~ 85 and ~ 95 wt. % Si02, respectively. Infrared spectroscopy showed that the initial traces of water (~ 0.05 wt. %) were dried out by annealing in air above 1100°C. Uniaxial creep tests performed at 1100-1250°C and 3-60 MPa flow stresses showed dominantly linear viscous flow, with a strong grain size dependence indicating grain boundary sliding and diffusion control. Counter-intuitively strength and activation energy increased with the content of melts, but in accord with the silica content of the latter, that is with their polymerization state. Our results show that the kinetics of grain boundary diffusion controlled creep strongly depends on melt chemistry. Instead of acting as shortcut for diffusion, thin films of highly viscous amorphous phases may in turn considerably reduce grain boundary transport properties.