Yves Rémond | Université de Strasbourg (original) (raw)

Papers by Yves Rémond

Высокомолекулярные соединения. Серия А, 2008

High-level radioactive waste (HLW) vitrification is a manufacturing process designed to dispose o... more High-level radioactive waste (HLW) vitrification is a manufacturing process designed to dispose of nuclear energy fission products over long-term timescales. We studied and modeled the thermomechanical phenomena occurring during the processing of the glass blocks, e.g. during their solidification and their cooling down. The thermomechanical modeling takes place in 3D FEM simulations. The relaxations of the borosilicate glass are to be taken into account through scripted algorithms. They allow us to describe accurately the evolution of the glass properties over its phase transition (the glass transition temperatures are non-uniform in the HLW package). A damage behavior within the frame of Continuum Damage Mechanics is also used to predict the glass cracking surface area.

Journal of Dynamic Behavior of Materials, Jan 25, 2016

Nuclear Engineering and Design, Aug 1, 2020

Soiling of PV modules is influenced by environmental parameters., both instantly and cumulatively... more Soiling of PV modules is influenced by environmental parameters., both instantly and cumulatively over time. Field measurement of dust accumulation at a minute time-scale, using an outdoor soiling microscope, was used to study the effect of time-of-day and exposure period on soiling of a surrogate glass coupon in Doha., Qatar. It was found that dust accumulation was much greater at night than during the day, principally because of lower nocturnal wind speed and higher humidity. Also, detachment of dust particles from the surface decreased markedly as exposure time increased., possibly due to cementation by moisture. The results suggest that tilting PV modules at night may be a simple yet potent way to decrease their soiling in suitable locations.

Renewable & Sustainable Energy Reviews, Sep 1, 2017

HAL (Le Centre pour la Communication Scientifique Directe), 2012

Materials Today Communications

Stem Cells and Regenerative Medicine, 2021

Orthodontic fixed appliances are used to correct dental malocclusions by optimizing tooth movemen... more Orthodontic fixed appliances are used to correct dental malocclusions by optimizing tooth movement and associated bone remodelling. Currently, orthodontic archwires made of shape memory alloys (SMAs) are widely used to initiate these treatments. We conduct experiments on SMA wires in pseudo in-vivo conditions, complementary to ISO standards, to assess the influence of temperature and humidity and to highlight their expected mechanical behaviour for clinical use. For this, an in-house built measurement device was developed to carry out experiments at controlled temperatures (21°C and 35°C) and in dry or wet conditions (artificial saliva). The dental arch was reproduced by 3D printing. The results show that the temperature has a major influence on the delivered forces whereas wet or dry conditions seem to have less impact. Also, we emphasize that at 35°C (in mouth conditions), in wet or dry conditions, SMAs superelasticity is only effective for displacements up to about 3 mm when an e...

Concepts in Magnetic Resonance Part A, 2019

The present work compares intravenous (IV) and subcutaneous (SC) routes for contrast-enhanced MRI... more The present work compares intravenous (IV) and subcutaneous (SC) routes for contrast-enhanced MRI (CE-MRI) in mice. For that purpose, we selected two contrast media used in clinical practice. MRI acquisitions were performed at 1.5 T on five adult mice (Swiss, 41 g +/- 3 g). On each animal, four acquisitions were achieved with IV and SC administration of either Gd-DOTA or MS-325 (1 acquisition per week). For each route, 0.1 mL of NaCl and 0.1 mL of contrast agent were injected. For each acquisition, 200 T1-weighted images were acquired in a 2 h 34 min time lapse. For each route and contrast medium, dynamic contrast enhancement (DCE) curves were obtained. Time-to-peak (TTP), uptake, and washout constant-time values and contrast-to-noise ratio (CNR) were extracted. IV route TTP value was 4.9 min with Gd-DOTA and 5.4 min with MS-325. SC route TTP was 43.3 min with Gd-DOTA and 45.0 min with MS-325. Despite slower uptake constant-time, we show that SC is a potentially valuable alternative...

Journal of Cellular Immunotherapy, 2018

Высокомолекулярные соединения. Серия А, 2008

Journal of Dynamic Behavior of Materials, Jan 25, 2016

Nuclear Engineering and Design, Aug 1, 2020

Renewable & Sustainable Energy Reviews, Sep 1, 2017

HAL (Le Centre pour la Communication Scientifique Directe), 2012

Materials Today Communications

Stem Cells and Regenerative Medicine, 2021

Concepts in Magnetic Resonance Part A, 2019

Journal of Cellular Immunotherapy, 2018

Polymer Science Series A, Jan 1, 2008

Journal of Materials Science, Jan 1, 2012

Journal of Engineering …, Jan 1, 2011

Polymer Degradation …, Jan 1, 2012

Polymer, Jan 1, 2005

The mechanical response of solid amorphous polymers is strongly dependent on the temperature and ... more The mechanical response of solid amorphous polymers is strongly dependent on the temperature and strain rate. More specifically, the yield stress increases dramatically for the low temperatures as well as for the high strain rates. To describe this behavior, we propose a new formulation of the cooperative model of Fotheringham and Cherry where the final mathematical form of the model is derived according to the strain rate/temperature superposition principle of the yield stress. According to our development, the yield behavior can be correlated to the secondary relaxation and we propose an extension of the model to temperatures above the glass transition temperature. For a wide range of temperatures and strain rates (including the impact strain rates), the predicted compressive yield stresses obtained for the polycarbonate (PC) and the polymethylmethacrylate (PMMA) are in excellent agreement with the experimental data found in the literature.

Journal De Physique Iv, Jan 1, 2003

Three molecular theories are used to predict the yield behavior of amorphous polymers for a wide ... more Three molecular theories are used to predict the yield behavior of amorphous polymers for a wide range of temperatures and strain rates. These include the state transition theory of Ree-Eyring, the conformational change theory of Robertson and the disclinations theory of Argon. For each of these models, the yield stress behavior of polymethylmethacrylate (PMMA) is described over a wide range

Polymer Testing, Jan 1, 2004

The polymer processing conditions used in injection moulding strongly influence mechanical proper... more The polymer processing conditions used in injection moulding strongly influence mechanical properties of materials in the solid state. This investigation presents an experimental method for measuring the local Young’s modulus and its application to polyoxymethylene (POM), polyamide 66 and glass fibre-filled polyamide 66 test pieces. An inverse method allowing local longitudinal Young’s moduli to be estimated from local natural flexural frequencies has been evaluated. The results obtained reveal a large variation in the local Young’s modulus over the thickness of an injection moulded piece, in particular in the outer skin zone. The influence of the various operational parameters has been evaluated.

Journal De Physique Iv, Jan 1, 2006

Journal of Materials Science, Jan 1, 2004

The small strain (below yielding) tensile loading-unloading tests were carried out on the low-den... more The small strain (below yielding) tensile loading-unloading tests were carried out on the low-density polyethylene (LDPE) and polypropylene (PP) at low strain rate and room temperature. The experiments unambiguously indicate to a remarkable decrease in residual strains in comparison with those predicted by conventional viscoelastic models. These deviations cannot be explained without taking into account structural transformations of semi-crystalline polymers. As long as small deformations cannot result in significant change in content and texture of crystalline and amorphous components, it was assumed that such transformations should include disintegration of connectivity in crystallite clusters. This structural rearrangement is supposed to be caused by the strain-induced decrystallization of narrow (and thus highly stressed) “bridges” connecting domains of conjugated crystallites or inside crystallites. A simple 1D modelling of the deformation processes supports this expectation. The disconnection in polymer morphology is simulated by small portions of amorphous ligaments appearing between neighbouring crystallites in the course of deformation. In spite of simplicity of the model a precise fitting of the stress-strain diagram is obtained along with small variations in structural and material characteristics (crystallinity degree, effective rigidity and plastic ability) of the concerned polymers.

Composites Science and Technology, Jan 1, 2005

The simulation, by traditional uni-dimensional rheological models, of viscoelastic unloading to z... more The simulation, by traditional uni-dimensional rheological models, of viscoelastic unloading to zero stress after tensile testing of short glass fiber-reinforced polyethylene and its pure matrix is poor. The models significantly underestimate recovery rates, even with small amounts of strain. The use of a finite number of relaxation times does not sufficiently increase recovery rates during unloading when models are generated from the responses of materials under load. Similar results and observations are obtained using rate jumps in loading and unloading. 3D models developed using local state methods require that an additional recovery potential should be used. This observation seems to prove that it is necessary to take into account the evolution of the polyethylene microstructure while the stress is applying, thus justifying the existence of the additional potential. The similar situation that exists for pure polyethylene means that the phenomenon must not be confused with material damage.

Polymer, Jan 1, 2005

In many applications, polymer materials undergo a large variety of mechanical loading conditions,... more In many applications, polymer materials undergo a large variety of mechanical loading conditions, wherein the influences of temperature and strain rate are of prime importance. Mahieux and Reifsnider [Mahieux CA, Reifsnider KL. Polymer 2001;42:3281. [19]] have proposed a statistical model to describe the stiffness variation of polymers over a wide range of temperatures. However, this model does not consider any frequency/strain rate dependence of the stiffness modulus. Starting from this consideration, we propose here to transform this latter model into a robust physically based model for the prediction of the stiffness modulus for a wide range of temperatures and frequencies/strain rates. This new formulation has been successfully validated for two amorphous polymers, polymethylmethacrylate (PMMA) and polycarbonate (PC), using dynamic mechanical analysis and uniaxial compression testing. Good agreement has been found between theory and experiment for the non-linear behavior of the initial Young's modulus, at the very high strain rates.

Polymer Science Series A, Jan 1, 2006

A general approach to the description of the mechanical properties of materials whose deformation... more A general approach to the description of the mechanical properties of materials whose deformation is accompanied by considerable structural rearrangements is developed. As in the case of classical simulation of the deformation behavior of viscoelastic and elastoplastic bodies, the concept of basic structural-mechanical element that reflects the properties of a fragment of a continuous medium is introduced. The simplest version of two alternative structural states is considered. Equations that define the kinetics of transition between these states and the mechanical properties of the base structural-mechanical element include expressions for elastic strain, plastic flow, and structure evolution. It is assumed that structural transitions and plastic flow are effected by the thermofluctuation mechanism. It is shown that the array of elements characterized by an appropriate set of parameters can describe the specific features of deformation behavior and structure evolution for a wide range of materials, in particular, polymers and composites, at their early deformation stages.

Polymer Science Series A, Jan 1, 2008

Journal of Engineering Materials and …, Jan 1, 2011

Depos 20 Du 8 au 10 mars 2006 Obernai, Jan 1, 2004

Comptes Rendus Mécanique, Jun 6, 2012

Surgical and Radiologic …, Jan 1, 2012

Journal of the mechanical behavior of biomedical materials, 2013

Effective elastic properties of arthropod endocuticle using a multiscale approach.Step by step ho... more Effective elastic properties of arthropod endocuticle using a multiscale approach.Step by step homogenization technique.Effects of homogenization technique.Effect of interfaces (interphases) at different scales of the microstructure.In this paper the mechanical response of the arthropod cuticle is evaluated by means of a multiscale approach including interface effects. The cuticle's elastic behavior is modeled at the nano and the micro scales by mean-field homogenization techniques. With respect to the work of Nikolov et al. (2011), the idea has been extended to study, at different scales of the structure, the effect of the used homogenization technique as well as the interface effect on the global elastic properties. First results revealed the sensitivity of the used homogenization technique on the global predicted elastic properties of the arthropod cuticle. To account for the interface between the fillers and the matrix of the composite structure of the arthropod cuticle, interphases are assumed at different scales of the structure with the same shape and topological orientation as the fillers. The approaches are based on few parameters directly related to the mechanical properties, the volume fraction and the morphology of the interphase. Results of the predicted elastic properties using the multiscale model including interphases are in good agreement with the experimental results. We show that the introduction of interphases leads to an improvement of the global elastic response in comparison to the multiscale model without interphases.

Journal of the mechanical behavior of biomedical materials, 2013

The purpose of the present work is to propose a new multiscale model for the prediction of the me... more The purpose of the present work is to propose a new multiscale model for the prediction of the mechanical behavior of vein walls. This model is based on one of our previous works which considered scale transitions applied to undulated collagen fibers. In the present work, the scale below was added to take the anisotropy of collagen fibrils into account. One scale above was also added, modeling the global reorientation of collagen fibers inside the vessel wall. The model was verified on experimental data from the literature, leading to a satisfactory agreement. The proposed multiscale approach also allows the extraction of local stresses and strains at each scale. This approach is presented here in the case of vein walls, but can easily be extended to other tissues which contain similar constituents.

Computer Methods and Programs in Biomedicine, Jan 1, 2010

Computer methods in biomechanics and biomedical engineering, 2013

Journal of Mechanics of …, Jan 1, 2012

In this paper we present a new method to predict in real time from a preoperative CT image the in... more In this paper we present a new method to predict in real time from a preoperative CT image the internal organ motions of a patient induced by his breathing. This method only needs the segmentation of the bones, viscera and lungs in the preoperative image and a tracking of the patient skin motion. Prediction of internal organ motions is very important for radiotherapy since it can allow to reduce the healthy tissue irradiation. Moreover, guiding system for punctures in interventional radiology would reduce significantly their guidance inaccuracy. In a first part, we analyse physically the breathing motion and show that it is possible to predict internal organ motions from the abdominal skin position. Then, we propose an original method to compute from the skin position a deformation field to the internal organs that takes mechanical properties of the breathing into account. Finally, we show on human data that our simulation model can provide a prediction of several organ positions (liver, kidneys, lungs) at 14 Hz with an accuracy within 7 mm.

Prediction of abdominal organ positions during free breathing is a major challenge from which sev... more Prediction of abdominal organ positions during free breathing is a major challenge from which several medical applications could benefit. For instance, in radiotherapy it would reduce the healthy tissue irradiation. In this paper, we present a method to predict in real-time the abdominal organs position during free breathing. This method needs an abdo-thoracic preoperative CT image, a second one limited to the diaphragm zone, and a tracking of the patient skin motion. It also needs the segmentation of the skin, the viscera volume and the diaphragm in both preoperative images. First, a physical analysis of the breathing motion shows it is possible to predict abdominal organs position from the skin position and a modeling of the diaphragm motion. Then, we present our original method to compute a deformation field that considers the abdominal and thoracic breathing influence. Finally, we show on two human data that our simulation model can predict several organs position at 50 Hz with accuracy within 2-3 mm.

Progress in Biophysics & Molecular Biology, Jan 1, 2010

Prediction of abdominal viscera and tumour positions during free breathing is a major challenge f... more Prediction of abdominal viscera and tumour positions during free breathing is a major challenge from which several medical applications could benefit. For instance, in radiotherapy it would reduce the healthy tissue irradiation. In this paper, we present a new approach to predict real-time abdominal viscera positions during free breathing. Our method needs an abdo-thoracic 3D preoperative CT or MR image, a second one limited to the diaphragmatic area, and a tracking of the patient’s skin position. First, a physical analysis of the breathing motion shows it is possible to predict accurately abdominal viscera positions from the skin position and a modelling of the diaphragm motion. Secondly, a quantitative analysis of the skin and organ motion allows us to define the demands our real-time simulation has to fulfill. Then, we present in detail all the necessary steps of our original method to compute a deformation field from data extracted in both 3D preoperative image and skin surface tracking. Finally, experiments carried out with two human data show that our simulation model predicts abdominal viscera positions, such as liver, kidneys or spleen, at 50 Hz with an accuracy within 2–3 mm.

Bridging veins are frequently damaged in traumatic brain injury. These veins are prone to rupture... more Bridging veins are frequently damaged in traumatic brain injury. These veins are prone to rupture in their subdural portion upon head impact, due to brain-skull relative motion, giving rise to an acute subdural hematoma. To understand the biomechanical characteristics of this hematoma, we take into account the periodical distribution of bridging veins in the sagittal plane. This allowed the use of the method of homogenization by asymptotic expansion to calculate the homogenized elastic properties of the brain-skull interface region. The geometry of this zone was simplified and a representative volume element was developed comprising: sinus, bridging vein, blood circulating inside them, surrounding cerebrospinal fluid and tissues. The heterogeneous elementary cell is transformed to an anisotropic homogenous equivalent medium and the homogenized elastic properties were calculated. The macroscopic homogenized properties resulted from the current study can be incorporated into a finite element model of the human head at macroscopic scale. The main results of this homogenization theory are the calculation of the local stress field into the elementary cell, as well as its homogeneous anisotropic properties at the macroscopic scale.

… and Clinical Applications, Jan 1, 2012

Composites Science and Technology, Jan 1, 2010

Effective conductivity of polymer composites, filled with conducting fibers such as carbon nanotu... more Effective conductivity of polymer composites, filled with conducting fibers such as carbon nanotubes, is studied using statistical continuum theory. The fiber orientation distribution in the matrix plays a very important role on their effective properties. To take into account their orientation, shape and distribution, two-point and three-point probability distribution functions are used. The effect of fibers orientation is illustrated by comparing the effective conductivity of microstructures with oriented and non-oriented fibers. The randomly oriented fibers result in an isotropic effective conductivity. The increased fiber orientation distribution can lead to higher anisotropy in conductivity. The effect of fiber’s aspect ratio on the effective conductivity is studied by comparing microstructures with varying degrees of fiber orientation distribution. Results show that the increase in anisotropy leads to higher conductivity in the maximum fiber orientation distribution direction and lower conductivity in the transverse direction. These results are in agreement with various models from the literature that show the increase of the aspect ratio of fibers improves the electrical and thermal conductivity.

Composite Structures, Jan 1, 1987

This paper deals with tridirectional composite material mechanical behaviour. The different const... more This paper deals with tridirectional composite material mechanical behaviour. The different constituents of the composite material are fibre-yarns, matrix and their respective interfaces. The mechanical behaviours of these constituents are built up for each of them. They are characterised by some parameters from the elastic domain, up to the rupture. These parameters are identified by using classical and original tests on a tridirectional carbon-carbon composite.Micro-macro mechanical relationships are then given. They derive from simple physical ideas and are founded on damage notion and homogenisation theory.This approach completes another mechanical model of the homogeneous behaviour for this material.Comparisons between the theoretical and experimental results are given.

Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule B-mecanique Physique Astronomie, Jan 1, 1998

On met en évidence un endommagement spécifique localisé au voisinage du bord d'une structure comp... more On met en évidence un endommagement spécifique localisé au voisinage du bord d'une structure composite, lorsque celle-ci a subi un frottement intense de type freinage. La mesure de cet endommagement est rendue délicate à la fois par la géométrie particulière de ces structures, mais aussi par l'hétérogénéité et la porosité habituelles des matériaux utilisés, les plus performants pour résister aux températures élevées. On identifie cet endommagement par meso-dureté et à des profondeurs successives dans le voisinage de la surface de contact.Evidence is presented of specific damage localized at the edge of carbon-carbon structures submitted to high tribological solicitations like braking. The measurement of this damage is more difficult on account of the geometry of braking structures, but also because of the heterogeneity and porosity typically displayed by the composites used, which are extremely resistant to high temperature. Evaluation of damage is based on meso-hardness at various depths under the braking surface.

This paper deals with the measurement of subsurface damage of composite materials after braking s... more This paper deals with the measurement of subsurface damage of composite materials after braking situations. Several carbon–carbon composites materials have been studied and tested under industrial braking conditions. Two damage measurement methods were used to estimate the braking effects on the mechanical behaviour of these materials. In particular, a meso-hardness test has been adapted to the heterogeneity of carbon–carbon composite and to their macro-porosity. Depending on the type of material, the results show that meso-hardness is a good indicator of local behaviour at a small depth under the surface. For one C–C composite, reinforced with long random fibers, we measure the evolution of damage as a function of the distance of the braking surface. Another original compression-bending test was also used, which confirms this damaged subsurface effect before wear occurs.

CR JNC11, Arcachon, Jan 1, 1998

Composites science and technology, Jan 1, 2005

... Auteurs : Alain Berthoz, Jean-François Caron, Marie-Florence Grenier-Loustalot, Charles-Yanni... more ... Auteurs : Alain Berthoz, Jean-François Caron, Marie-Florence Grenier-Loustalot, Charles-Yannick Guezennec, Pierre Letellier, Claude Lory, Denis Masseglia, Nicolas Puget, Isabelle Queval, YvesRémond, Fabien Roland, Jean-François Toussaint et Jean-Luc Veuthey. ...

The global mechanical behaviour of a 4D carbon–carbon (C– C 4D) composite material is described. ... more The global mechanical behaviour of a 4D carbon–carbon (C– C 4D) composite material is described. Designed for aeronautic applications and particularly for the brake discs of heavy air craft, this material is a layered composite reinforced in three directions in the plane (−60°, 0°, 60°) to which the fourth direction of reinforcement is perpendicular. Having ascertained the compliance matrices in the plane to which the braking surface is parallel, we have determined the engineering constants of an elementary ply from the basic assumptions of the classical laminations theory (CLT). Finally, to construct both linear-elastic and elastoplastic constitutive equations of the C– C 4D, we propose a thermodynamic model that accurately characterises the behaviour of this material. This simple model can be identified from simple mechanical tests.

Mechanism and Machine Theory, Jan 1, 2009

We propose hereafter a unified model of epicyclic gear trains, based on a primitive parametric ke... more We propose hereafter a unified model of epicyclic gear trains, based on a primitive parametric kernel, which contains all usual gear train formulations of any compound gear train. We show that the nested and the Ravigneaux gear train derive from a unified model, which permits to obtain the formulation of ratio and efficiency. Therefore the conception of a gear train if the kinematics or dynamics are fixed can be solved with an analytical resolution.

Journal of Materials Processing Technology, Jan 1, 2009

A transient three-dimensional finite element model is developed to simulate the phase transformat... more A transient three-dimensional finite element model is developed to simulate the phase transformation during the selective laser sintering process; taking into account the thermal and sintering phenomena involved in this process. A bi-level structure integration procedure is chosen, in which the temperature dependent thermal conductivity, specific heat, and density are integrated at the outer level then used as material constants for the integration of the heat equation in the inner level. Results for temperature and density distribution, using a polycarbonate powder, are presented and discussed.

Comptes Rendus de l'Academie des …, Jan 1, 1999

Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule B-mecanique Physique Astronomie, Jan 1, 1999

La description cinématique d'un système donné de solides rigides (résolution du problème direct) ... more La description cinématique d'un système donné de solides rigides (résolution du problème direct) ne permet pas d'aborder le problème de son invention. Le problème inverse, c'est-à-dire l'obtention du concept si la cinématique est fixée (entrée-sortie) n'a jamais été abordé de façon analytique. On propose, à partir d'une approche paramétrique, une formulation permettant de résoudre le problème inverse pour tout train épicycloïdal à deux étages. En outre, pour ces mécanismes, on met en évidence une théorie unifiée dont le noyau primitif est une fonction homographique de tous les paramètres du système.The calculation of a given gear train (solution of the direct problem) is never really difficult, but does not give one any idea how it was invented. Since the inverse problem (i.e. obtaining the concept if the kinematics are fixed) has never been approached in an analytical way, we propose, from the general formula of the ratios, a single equation which enables one to resolve the inverse problem for every two-level gear train, and suggest new unified kinematic and dynamic formulations.

Materials Science Forum, Jan 1, 2007

Journal of Mechanical Design, Jan 1, 1999

ABSTRACT

Bulletin-Institut de l'engrenage et des …, Jan 1, 1997

Bulletin-Institut de l'engrenage et des …, Jan 1, 1996

Computational Materials …, Jan 1, 2012

Physics Letters A, Jan 1, 2012

Solid State …, Jan 1, 2011

Journal of Engineering …, Jan 1, 2012

... Majid Baniassadi, Akbar Ghazavizadeh, Yves R??mond, Said Ahzi, David Ruch, Hamid Garmestani. ... more ... Majid Baniassadi, Akbar Ghazavizadeh, Yves R??mond, Said Ahzi, David Ruch, Hamid Garmestani. ... Baniassadi, M., Addiego, F., Laachachi, A., Ahzi, S., Garmestani, H., Hassouna, F., Makradi, A., Toniazzo, V., and Ruch, D., 2011, ???Using SAXS Approach to Estimate Thermal ...

Supplemental …

... Majid Baniassadi&#x27;&#x27;2, Akbar Ghazavizadeh3, David Ruch&#x27; ... more ... Majid Baniassadi&#x27;&#x27;2, Akbar Ghazavizadeh3, David Ruch&#x27; ,Yves Rémond2, Said Ahzi2, Hamid Garmestani4 &#x27;Centre de ... University of Aveiro, 3810-193, Aveiro, Portugal &quot;School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Dr. NW Atlanta ...

Journal of Engineering …, Jan 1, 2012

ABSTRACT In this study, a hierarchical multiscale homogenization procedure aimed at predicting th... more ABSTRACT In this study, a hierarchical multiscale homogenization procedure aimed at predicting the effective mechanical properties of silica/epoxy nanocomposites is presented. First, the mechanical properties of the amorphous silica nanoparticles are investigated by means of molecular dynamics (MD) simulations. At this stage, the MD modeling of three-axial tensile loading of amorphous silica is carried out to estimate the elastic properties. Second, the conventional twp phase homogenization techniques such as finite elements (FE), Mori-Tanaka (M-T), Voigt and Reuss methods are implemented to evaluate the overall mechanical properties of the silica/epoxy nanocomposite at different temperatures and at constant weight ratio of 5%. At this point, the mechanical properties of silica obtained in the first stage are used as the inputs of the reinforcing phase. Comparison of the FE and M-T results with the experimental results in a wide range of temperatures reveals fine agreement; however, the FE results are in better agreement with the experiments than those obtained by M-T approach. Additionally, the results predicted by FE and M-T methods are closer to the lower bound (Reuss), which is due to lowest surface to volume ratio of spherical particles. [DOI: 10.1115/1.4005419]

Mechanics of Materials, Jan 1, 2010

Continuum damage mechanics is used to model the damage induced by a thermal shock to the R7T 7 gl... more Continuum damage mechanics is used to model the damage induced by a thermal shock to the R7T 7 glass, the French borosilicate glass used for nuclear waste vitrification. A finite element model of the thermal shock is developed in which the elastic constitutive equations are coupled with an anisotropic stress-based damage evolution law. The Weibull distributions of strength measured at various temperatures by biaxial flexural tests are used to identify the parameters of this damage evolution law. Vibration tests are conducted to identify the elastic properties of the glass and to determine the effect of thermal shock-induced damage on the glass residual stiffness. The residual stiffness predicted by the damage model agrees with that measured experimentally. The fractured surface in the glass after a thermal shock is estimated, assuming that all the elastic energy associated with the stresses that are higher than a pre-determined threshold is dissipated in the creation of new surfaces. Comparison between the predicted and experimentally-measured fractured surface is performed. The model is shown to capture the saturation of the crack network density for severe thermal shocks; whereas this is not the case if damage is not accounted for in the constitutive equations.

Journal of Engineering …, Jan 1, 2012

Journal of nanoscience and nanotechnology, 2010

Thin Solid Films, Jan 1, 2010

In this paper, we present numerical simulations of the residual stresses developed between diamon... more In this paper, we present numerical simulations of the residual stresses developed between diamond coatings and Ti-6Al-4V substrates when using chemical vapour deposition technique. The large difference in thermal expansion coefficients of diamond and titanium alloys results in high residual stresses in the diamond film. This could lead to interfacial cracking and material failure. The finite element method was used to simulate the cooling process of diamond films at various thicknesses and deposited at temperatures ranging from 600 °C to 900 °C. The influence of different parameters such as temperature, film thickness, material characteristics, geometry and edge effects are investigated for different case geometries. The film debonding and cracking is discussed and numerical results are compared with existing experimental and numerical results. Finally, some propositions are made to enhance the experimental process in order to reduce the residual stress intensities and the possible material degradation.

Physica E: Low-dimensional Systems and …, Jan 1, 2012

Despite the success of surgical implants such as artificial hip, materials used in these procedur... more Despite the success of surgical implants such as artificial hip, materials used in these procedures still do not satisfy the demands of human life time functioning. Currently used materials such as titanium alloys, ceramics and polymers are degraded after about a dozen years of use. Diamond coating technology has proven to be efficient in the performance of human joints. In this study, we have investigated the deposition of diamond thin films on Ti6Al4V using a new developed time-modulated Chemical Vapour Deposition (TMCVD) method. Finite element simulations were used to analyse the development of residual stresses. Micro Raman spectroscopy was also used to evaluate the residual stresses and compare with numerical models.

Materials & Design, Jan 1, 2010

In the present work a mesh free method is used to study the effect of interfaces on the crack pro... more In the present work a mesh free method is used to study the effect of interfaces on the crack propagation path in multilayered like Solid Oxide Fuel Cells (SOFCs) materials. The partition of unity principle was introduced to model the crack tip singularity. The penalty method is used to model the materials discontinuity along the interfaces. The stress intensity factors (SIF) were computed using the interaction integral. The mesh free method is implemented and verified using results from the literature. A parametric study of crack propagation in mono-layer and bi-layer material is conducted. Finally an application to SOFC unit shows that crack initiated in the anode propagates towards the anode/electrolyte interface.

Statistical correlation functions are a well-known class of statistical descriptors that can be u... more Statistical correlation functions are a well-known class of statistical descriptors that can be used to describe the morphology and the microstructure-properties relationship. A comprehensive study has been performed for the use of these correlation functions for the reconstruction and homogenization in nano-composite materials. Correlation functions are measured from different techniques such as microscopy (SEM or TEM), small angle X-ray scattering (SAXS) and can be generated through Monte Carlo simulations. In this book, different experimental techniques such as SAXS and image processing are presented, which are used to measure two-point correlation function correlation for multi-phase polymer composites.

Higher order correlation functions must be calculated or measured to increase the precision of the statistical continuum approach. To achieve this aim, a new approximation methodology is utilized to obtain N-point correlation functions for multiphase heterogeneous materials. The two-point functions measured by different techniques have been exploited to reconstruct the microstructure of heterogeneous media.

Statistical continuum theory is used to predict the effective thermal conductivity and elastic modulus of polymer composites. N-point probability functions as statistical descriptors of inclusions have been exploited to solve strong contrast homogenization for effective thermal conductivity and elastic modulus properties of heterogeneous materials. Finally, reconstructed microstructure is used to calculate effective properties and damage modeling of heterogeneous materials.

The Journal of chemical physics, 2014

Journal of The Mechanics and Physics of Solids, Jan 1, 2009

The strong-contrast formulation is used to predict the effective conductivity of a porous materia... more The strong-contrast formulation is used to predict the effective conductivity of a porous material. The distribution, shape and orientation of the two phases are taken into account using two- and three-point probability distribution functions. A new approximation for the three-point probability function appropriate for two-phase media is proposed and discussed. Computed results for the effective conductivity using the strong-contrast formulation are compared to the Voigt and the Hashin-Shtrikman upper-bound estimates. These results show that the predicted effective conductivity is lower than both Voigt and Hashin-Shtrikman bounds. Compared to previous results using the weak-contrast formulation, the strong-contrast formulation seems to provide a better estimate for the effect of the microstructure on the conductivity.

International Journal of Solids and Structures, Jan 1, 2009

Statistical continuum theory based approaches are commonly used for the computation of the effect... more Statistical continuum theory based approaches are commonly used for the computation of the effective properties of heterogeneous materials. Statistical distribution and morphology of the microstructure are represented by n-point probability function. One-point probability function statistical representation of the microstructure leads to volume fraction dependent homogenization. However, second and higher order probability functions include the information of phase distribution and morphology. Most statistical based homogenization methods are limited to two-point probability function due to the lack of simple approximation of higher order probability functions that can be easily exploited. In this paper, a new approximation of the three-point probability function is proposed and discussed. The new approximation results are compared to existing approximations from the literature and to the real probability functions calculated from a computer generated two-phase micrographs.