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(80) Production(s) de GEORGE M.
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Roughness of oxide glass subcritical fracture surfaces
Auteur(s): Pallares Gael, Lechenault F., George M., Bouchaud Elisabeth, Ottina Cédric, Rountree Cindy L., Ciccotti Matteo
(Article) Publié:
Journal Of The American Ceramic Society, vol. 101 p.1279-1288 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01633422_v1
Ref Arxiv: 1711.05040
DOI: 10.1111/jace.15262
WoS: 000419096700032
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: An original setup combining a very stable loading stage, an atomic force microscope and an environmental chamber, allows to obtain very stable sub-critical fracture propagation in oxide glasses under controlled environment, and subsequently to finely characterize the nanometric roughness properties of the crack surfaces. The analysis of the surface roughness is conducted both in terms of the classical root mean square roughness to compare with the literature, and in terms of more physically adequate indicators related to the self-affine nature of the fracture surfaces. Due to the comparable nanometric scale of the surface roughness, the AFM tip size and the instrumental noise, a special care is devoted to the statistical evaluation of the metrologic properties. The 2 roughness amplitude of several oxide glasses was shown to decrease as a function of the stress intensity factor, to be quite insensitive to the relative humidity and to increase with the degree of heterogeneity of the glass. The results are discussed in terms of several modeling arguments concerning the coupling between crack propagation, material's heterogeneity, crack tip plastic deformation and water diffusion at the crack tip. A synthetic new model is presented combining the predictions of a model by Wiederhorn et al. [1] on the effect of the material's heterogeneity on the crack tip stresses with the self-affine nature of the fracture surfaces.
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Mechanical behavior of wheat endosperm. Local measurements by AFM and numerical modeling
Auteur(s): Chichti Emna, Delenne Jean-Yves, Lullien-Pellerin V., George M.
Conférence invité: 5ème journées scientifiques du LabEx Numev (Montpellier, FR, 2016-10-05)
Ref HAL: hal-02019637_v1
Exporter : BibTex | endNote
Résumé: Mechanical behavior of wheat endosperm. Local measurements by AFM and numerical modeling
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The Wheat Grain as a cemented granular material: Nanoscale investigation of its mechanical properties
Auteur(s): Heinze K., Delenne Jean-Yves, George M., Lullien-Pellerin Valerie
Conference: 3. International Conference on Structural Nano Composites (NANOSTRUC 2016) (Aberdeen, GB, 2016-09-12)
Ref HAL: hal-01605556_v1
Exporter : BibTex | endNote
Résumé: The Wheat Grain as a cemented granular material: Nanoscale investigation of its mechanical properties. 3. International Conference on Structural Nano Composites (NANOSTRUC 2016)
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Bottom-up model for understanding the effects of wheat endosperm microstructure on its mechanical strength
Auteur(s): Chichti Emna, Lullien-Pellerin Valerie, George M., Radjai Farhang, Affes Rafik, Delenne Jean-Yves
(Article) Publié:
Journal Of Food Engineering, vol. 190 p.40-47 (2016)
Texte intégral en Openaccess :
Ref HAL: hal-01414119_v1
DOI: 10.1016/j.jfoodeng.2016.06.009
WoS: WOS:000382349300005
Exporter : BibTex | endNote
7 Citations
Résumé: Wheat flours are essential ingredients of daily food products like bread, cookies or pastries. Their quality depends on the milling process and mechanical strength of wheat grains. Although it is well known that the strength and rupture of grains are strongly controlled by the endosperm microstructure, the respective roles of the starch and polymer volume fractions and their adhesion are not yet fully understood. This typical biological microstructure can be modeled as a cemented granular material, where the two size populations of starch granules (large:A-type, small:B-type) are the particles, and the protein matrix, which partially fills the space between granules, plays the role of a cement. This structural model of wheat endosperm is used, together with mechanical characteristics of starch and proteins obtained by means of Atomic Force Microscopy (AFM) measurements, to simulate the mechanical behavior and breakage of wheat endosperm in milling process. We find that the porosity outweighs the effect of other parameters for the elastic modulus, which declines as a nearly linear function of porosity. We also show that the tensile strength is an increasing function of the amount and connectivity of starch granules with increasing concentration of stresses along chains of granules. This effect is more significant at low porosity where stress distribution is mainly controlled by the contact network between starch granules. This effect explains why the protein content is not fully correlated to vitreousness, and samples of similar protein content can be different in vitreosity. Finally, we find that the starch-granule adhesion strongly affects the tensile strength whereas the effect of starch volume fraction appears mainly at high interface adhesion, which is the case of hard type wheat grains.
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Micromechanisms of fracture propagation in glassy polymers
Auteur(s): Ciccotti Matteo, George M., Nziakou Y. K., Fischer Guillaume, Genix A.-C., Bresson Bruno, Roux Stéphane
Conference: Workshop: Chemical and Structural Transformations in Materials under Mechanical Load (Lausanne, CH, 2015-04-01)
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What makes glass break?
Auteur(s): George M.
(Séminaires)
ICG Summer School (Montpellier, FR), 2015-07-08
Résumé: What makes glass break?
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