20 research outputs found
Constitutive modeling of the anisotropic behavior of Mullins softened filled rubbers
No full textOriginal constitutive modeling is proposed for filled rubber materials in order to capture the anisotropic softened behavior induced by general non-proportional pre-loading histo-ries. The hyperelastic framework is grounded on a thorough analysis of cyclic experimental data. The strain energy density is based on a directional approach. The model leans on the strain amplification factor concept applied over material directions according to the Mul-lins softening evolution. In order to provide a model versatile that applies for a wide range of materials, the proposed framework does not require to postulate the mathematical forms of the elementary directional strain energy density and of the Mullins softening evo-lution rule. A computational procedure is defined to build both functions incrementally from experimental data obtained during cyclic uniaxial tensile tests. Successful compari-sons between the model and the experiments demonstrate the model abilities. Moreover, the model is shown to accurately predict the non-proportional uniaxial stress-stretch responses for uniaxially and biaxially pre-stretched samples. Finally, the model is effi-ciently tested on several materials and proves to provide a quantitative estimate of the anisotropy induced by the Mullins softening for a wide range of filled rubbers
Caractérisation expérimentale et modélisation du comportement mécanique d’élastomères chargés sous conditions de chargement cycliques
No full textRubber-like materials are submitted to cyclic loading conditions in various applications. Fillers are always incorporated within rubber compounds. They improve the mechanical properties but induce a significant stress-softening under cyclic loadings. The physical source of the softening is not yet established and its modeling remains a challenge. For a better understanding of the softening, filled rubbers are submitted to cyclic loadings. In order to quantify the effects of the loading intensity and the number of cycles, original methods are proposed to characterize the softening. To study the influence of the material microstructure on the softening, compounds with various compositions are considered.Non proportional tensile tests including uniaxial and biaxial loading paths are applied in order to highlight the softening induced anisotropy. Such unconventional experimental data are used to provide a general criterion for the softening activation. A constitutive modeling grounded on a thorough analysis of experimental data is proposed. The model is based on a directional approach. The Mullins softening is accounted for by the strain amplification concept and is activated by a directional criterion. The model ability to predict non proportional softened material responses is demonstratedLes applications pour lesquelles des élastomères sont soumis à des sollicitations cycliques sont nombreuses. Des charges sont généralement utilisées afin d'améliorer leurs propriétés, cependant, elles induisent également un adoucissement important de la contrainte lors de sollicitations cycliques. A ce jour, les phénomènes physiques conduisant à l’apparition de cet adoucissement ne sont pas clairement établis et sa modélisation demeure une difficulté majeure.Afin d'étudier l'adoucissement, des élastomères chargés sont soumis à des chargements cycliques. Des méthodes de caractérisations originales sont proposées afin de quantifier les effets de l'intensité du chargement et du nombre de cycles. Pour faire le lien avec la microstructure du matériau, plusieurs mélanges de compositions différentes sont utilisés. Des chargements non proportionnels de traction uniaxiale et biaxiale sont appliqués afin de mettre en évidence l'anisotropie induite par l'adoucissement. Ces données expérimentales non conventionnelles sont utilisées afin de définir un critère général pour l'activation de l'adoucissement Mullins. Une loi de comportement fondée sur une analyse approfondie des données expérimentales est proposée. La modélisation est basée sur une approche directionnelle. L'adoucissement Mullins est modélisé en utilisant le concept d'amplification de la déformation et son activation est pilotée par un critère directionnel. La capacité du modèle à prédire les réponses d'un matériau ayant subit un historique de chargement non proportionnel est validé
Someone Called Derrida
No full textA dramatised adaptation
of John Schad’s documentary novel
by Fred Dalmasso & John Schad
Someone Called Derrida is a real-life murder mystery that focuses on not only the famous French philosopher, Jacques Derrida’s complex relationship to Oxford but also the final years in the life of the author’s own father, 1990-1996 - years overwhelmed by dementia, nightmare and memories of, inter alia, the public school at which he had boarded during the Second World War. Every factual detail is, as far as the author can tell, correct; moreover, the voices which surround the author are verbatim: Jacques Derrida’s words come directly from a single book of his called The Post Card (1979); the nightmare-words of the author’s father are as transcribed in the 1990s by the author’s mother; and the words that detail life both in Oxford and at the boarding school all come direct from published accounts. All references for all details and quotations can be found in the book
Influence des paramètres matériaux sur le comportement des élastomères Influence of the material parameters on the mechanical properties of rubbers
No full textLe comportement sous sollicitations cycliques des matériaux élastomères induit un adoucissement, une déformation rémanente et une anisotropie. Le travail présenté portera sur la caractérisation de ces phénomènes d'endommagements afin d'établir des liens avec les propriétés matériaux. The behavior of rubber-like materials under cyclic loading induces softening, permanent stretch and anisotropy. The aim of the presented work is to characterize such damage in order to introduced relation to material properties
Experimental characterization and modelling of the cyclic softening of carbon-black filled rubbers
No full textInternational audienceSeveral carbon-black filled styrene-butadiene rubbers (SBRs) were submitted to uniaxial tension cyclic tests at large strain for investigating filled rubbers cyclic softening. In order to study the effect of the material composition (amount of fillers and crosslink density) and of the stretch intensity, an original method for cyclic softening characterization is proposed. The softening is seen as an amplification of the stretch in the rubber gum, and a stretch amplification factor is then introduced as the softening parameter. The latter is evaluated for various materials and several levels of cyclic stretch intensity. Material softening is shown to increase with the loading intensity, the amount of carbon-black fillers and the decrease of the crosslink density. In terms of modelling, the introduced softening parameter provides access to the entire stress-stretch responses of the softened material for any cycle. Therefore, a model is written for the description and the prediction of the stress-stretch responses of filled rubbers during proportional cyclic tests
Caractérisation expérimentale et modélisation du comportement mécanique d élastomères chargés sous conditions de chargement cycliques
No full textLes applications pour lesquelles des élastomères sont soumis à des sollicitations cycliques sont nombreuses. Des charges sont généralement utilisées afin d'améliorer leurs propriétés, cependant, elles induisent également un adoucissement important de la contrainte lors de sollicitations cycliques. A ce jour, les phénomènes physiques conduisant à l apparition de cet adoucissement ne sont pas clairement établis et sa modélisation demeure une difficulté majeure.Afin d'étudier l'adoucissement, des élastomères chargés sont soumis à des chargements cycliques. Des méthodes de caractérisations originales sont proposées afin de quantifier les effets de l'intensité du chargement et du nombre de cycles. Pour faire le lien avec la microstructure du matériau, plusieurs mélanges de compositions différentes sont utilisés. Des chargements non proportionnels de traction uniaxiale et biaxiale sont appliqués afin de mettre en évidence l'anisotropie induite par l'adoucissement. Ces données expérimentales non conventionnelles sont utilisées afin de définir un critère général pour l'activation de l'adoucissement Mullins. Une loi de comportement fondée sur une analyse approfondie des données expérimentales est proposée. La modélisation est basée sur une approche directionnelle. L'adoucissement Mullins est modélisé en utilisant le concept d'amplification de la déformation et son activation est pilotée par un critère directionnel. La capacité du modèle à prédire les réponses d'un matériau ayant subit un historique de chargement non proportionnel est validéeRubber-like materials are submitted to cyclic loading conditions in various applications. Fillers are always incorporated within rubber compounds. They improve the mechanical properties but induce a significant stress-softening under cyclic loadings. The physical source of the softening is not yet established and its modeling remains a challenge. For a better understanding of the softening, filled rubbers are submitted to cyclic loadings. In order to quantify the effects of the loading intensity and the number of cycles, original methods are proposed to characterize the softening. To study the influence of the material microstructure on the softening, compounds with various compositions are considered.Non proportional tensile tests including uniaxial and biaxial loading paths are applied in order to highlight the softening induced anisotropy. Such unconventional experimental data are used to provide a general criterion for the softening activation. A constitutive modeling grounded on a thorough analysis of experimental data is proposed. The model is based on a directional approach. The Mullins softening is accounted for by the strain amplification concept and is activated by a directional criterion. The model ability to predict non proportional softened material responses is demonstratedVILLENEUVE D'ASCQ-ECLI (590092307) / SudocSudocFranceF
A simple framework for full-network hyperelasticity and anisotropic damage
No full textInternational audienceA formulation of a constitutive behaviour law is proposed for hyperelastic materials, such that damage induced anisotropy can be accounted for continuously. The full-network approach with directional damage is adopted as a starting point. The full-network law with elementary strain energy density based on the inverse Langevin is chosen as a reference law which is cast into the proposed framework. This continuum formalism is then rewritten using spherical harmonics to capture damage directionality. The proposed formalism allows for an efficient (and systematic) expansion of complex non-linear anisotropic constitutive laws. A low order truncated expression of the resulting behaviour is shown to reproduce accurately the stress-strain curves of the exact behaviour laws
Effects of the Amount of Fillers and of the Crosslink Density on the Mechanical Behavior of Carbon-Black Filled Styrene Butadiene Rubbers
No full textSeveral carbon-black filled styrene-butadiene rubbers are subjected to monotonic uniaxial tension tests in order to investi-gate the effects of the amount of fillers and of the crosslink density on their mechanical properties. The Young modulus, the volume changes associated with material damage and the stretch to failure are extracted and discussed. Results compare well to the literature results when exist and quantitative analysis are proposed when possible. Results show that filled rubbers are not incompressible when submitted to uniaxial tension tests and their volume changes are strongly dependent of the amount of fillers but are unaffected by the crosslink density. The latter shows strong impact on the filled rubbers stretch to failure but more interestingly this impact is com-parable to what is encountered in unfilled rubbers. The stretch to failure is improved by the addition of fillers with an optimum for material filled around 30 phr
Micromechanical modeling of the linear viscoelasticity of carbon-black filled styrene butadiene rubbers: the role of the rubber-filler interphase
No full textVersion éditeur : http://www.sciencedirect.com/science/article/pii/S0167663612002190Micromechanics modeling of the linear viscoelasticity of carbon-black filled styrene butadiene rubbers (SBR) shows that a simple representation of a spherical rigid-phase surrounded by rubber gum and embedded in an homogeneous equivalent medium provides access to the effective volume fraction of fillers. This simple representation is successful for a significant range of filler amount, and for materials in the glassy state. For materials in the rubbery state, experimental results support the existence of a filler-rubber interphase with reduced mobility due to confinement. The 4-phase micromechanics model, which accounts for a bounded rubber layer coating the fillers, provides satisfactory estimates of the linear viscoelasticity of filled rubbers from the rubbery state to the glassy state. It also provides access to the filler rubber interphase behavior that appears viscoelastic, and to an estimate of the interphase thickness.ANR MATETPRO AMUFIS
A Mullins softening criterion for general loading conditions
No full textSamples of carbon-black filled styrene butadiene rubbers (SBRs) were submitted to successive nonproportional loadings in order to define a general criterion for the Mullins softening. For this purpose, each sample was initially submitted to uniaxial or biaxial preloadings followed by a cyclic uniaxial tension test. An original experimental analysis aimed at defining the activation threshold for the Mullins softening during cyclic uniaxial loadings. The experimental data provide substantial evidences establishing the surface of the maximum directional stretch undergone by the material as a relevant Mullins softening criterion. The latter was used to successfully predict the Mullins softening surfaces for additional loading cases
