Picu R C, Deogekar S, Islam M R
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 e-mail: .
J Biomech Eng. 2018 Feb 1;140(2):0210021-02100212. doi: 10.1115/1.4038428.
Connective tissue mechanics is highly nonlinear, exhibits a strong Poisson's effect, and is associated with significant collagen fiber re-arrangement. Although the general features of the stress-strain behavior have been discussed extensively, the Poisson's effect received less attention. In general, the relationship between the microscopic fiber network mechanics and the macroscopic experimental observations remains poorly defined. The objective of the present work is to provide additional insight into this relationship. To this end, results from models of random collagen networks are compared with experimental data on reconstructed collagen gels, mouse skin dermis, and the human amnion. Attention is devoted to the mechanism leading to the large Poisson's effect observed in experiments. The results indicate that the incremental Poisson's contraction is directly related to preferential collagen orientation. The experimentally observed downturn of the incremental Poisson's ratio at larger strains is associated with the confining effect of fibers transverse to the loading direction and contributing little to load bearing. The rate of collagen orientation increases at small strains, reaches a maximum, and decreases at larger strains. The peak in this curve is associated with the transition of the network deformation from bending dominated, at small strains, to axially dominated, at larger strains. The effect of fiber tortuosity on network mechanics is also discussed, and a comparison of biaxial and uniaxial loading responses is performed.
结缔组织力学具有高度非线性，呈现出强烈的泊松效应，并且与显著的胶原纤维重新排列有关。尽管应力-应变行为的一般特征已得到广泛讨论，但泊松效应受到的关注较少。一般来说，微观纤维网络力学与宏观实验观测之间的关系仍不明确。本研究的目的是进一步深入了解这种关系。为此，将随机胶原网络模型的结果与重构胶原凝胶、小鼠皮肤真皮和人羊膜的实验数据进行比较。重点关注导致实验中观察到的大泊松效应的机制。结果表明，增量泊松收缩与胶原纤维的优先取向直接相关。在较大应变下实验观察到的增量泊松比下降与横向于加载方向的纤维的约束效应有关，且这些纤维对承载贡献很小。胶原纤维取向速率在小应变时增加，达到最大值，在大应变时降低。该曲线中的峰值与网络变形从小应变时的弯曲主导到大应变时的轴向主导的转变有关。还讨论了纤维曲折度对网络力学的影响，并对双轴和单轴加载响应进行了比较。
