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  • 2005-2009  (2)
  • 1
    Online Resource
    Online Resource
    The Royal Society ; 2007
    In:  Journal of The Royal Society Interface Vol. 4, No. 13 ( 2007-04-22), p. 277-282
    In: Journal of The Royal Society Interface, The Royal Society, Vol. 4, No. 13 ( 2007-04-22), p. 277-282
    Abstract: The molecular mechanisms for plastic deformation of bone tissue are not well understood. We analysed temperature and strain-rate dependence of the tensile deformation behaviour in fibrolamellar bone, using a technique originally developed for studying plastic deformation in metals. We show that, beyond the elastic regime, bone is highly strain-rate sensitive, with an activation volume of ca 0.6 nm 3 . We find an activation energy of 1.1 eV associated with the basic step involved in the plastic deformation of bone at the molecular level. This is much higher than the energy of hydrogen bonds, but it is lower than the energy required for breaking covalent bonds inside the collagen fibrils. Based on the magnitude of these quantities, we speculate that disruption of electrostatic bonds between polyelectrolyte molecules in the extrafibrillar matrix of bone, perhaps mediated by polyvalent ions such as calcium, may be the rate-limiting elementary step in bone plasticity.
    Type of Medium: Online Resource
    ISSN: 1742-5689 , 1742-5662
    Language: English
    Publisher: The Royal Society
    Publication Date: 2007
    detail.hit.zdb_id: 2156283-0
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  • 2
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2009
    In:  Journal of Materials Research Vol. 24, No. 2 ( 2009-02), p. 421-429
    In: Journal of Materials Research, Springer Science and Business Media LLC, Vol. 24, No. 2 ( 2009-02), p. 421-429
    Abstract: Irreversible or plastic deformation in bone is associated with both permanent plastic strain as well as localized microdamage. Whereas mechanisms at the molecular and mesoscopic level have been proposed to explain aspects of irreversible deformation, a quantitative correlation of mechanical yielding, microstructural deformation, and macroscopic plastic strain does not exist. To address this issue, we developed and applied a two-dimensional image correlation technique to the tensile deformation of bovine fibrolamellar bone, to determine the spatial distribution of strain fields at the length scale of 10 μm to 1 mm in bone during irreversible tensile deformation. We find that tensile deformation is relatively homogeneous in the elastic regime and starts at the yield point, showing regions of locally higher strain. Multiple regions of high deformation can exist at the same time over a length scale of 1 to 10 mm. Macroscopic fracture always occurs at one of the locally highly deformed regions, but the selection of which region cannot be predicted. Locally, strain rates can be enhanced by a factor of 3 to 10 over global strain rates in the highly deformed zones and are lower but always positive in all other regions. Light microscopic imaging shows the onset of structural “banding” in the regions of high deformation, which is most likely correlated to microstructural damage at the inter- and intrafibrillar level.
    Type of Medium: Online Resource
    ISSN: 0884-2914 , 2044-5326
    RVK:
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2009
    detail.hit.zdb_id: 54876-5
    detail.hit.zdb_id: 2015297-8
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