Volokh K Y
Faculty of Civil and Environmental Engineering, Technion-I.I.T., Haifa 32000, Israel.
J Biomech. 2008;41(2):447-53. doi: 10.1016/j.jbiomech.2007.08.001. Epub 2007 Sep 18.
Two approaches to predict failure of soft tissue are available. The first is based on a pointwise criticality condition, e.g. von Mises maximum stress, which is restrictive because only local state of deformation is considered to be critical and the failure criterion is separated from stress analysis. The second is based on damage mechanics where internal (unobservable) variables are introduced which make the experimental calibration of the theory complex. As an alternative to the local failure criteria and damage mechanics we present a softening hyperelasticity approach, where the constitutive description of soft tissue is enhanced with strain softening, which is controlled by material constants. This approach is attractive because the new material constants can be readily calibrated in experiments on the one hand and the failure criteria are global on the other hand. We illustrate the efficiency of the softening hyperelasticity approach on the problem of prediction of arterial failure. For this purpose, we enhance a bi-layer fiber-matrix microstructural arterial model with softening and analyze the arterial failure under internal pressure. We show that the overall arterial strength is (a) dominated by the media layer, (b) controlled by microfibers and (c) increased by residual stresses.
有两种预测软组织失效的方法。第一种基于逐点临界条件，例如冯·米塞斯最大应力，这种方法具有局限性，因为仅将局部变形状态视为临界状态，且失效准则与应力分析相分离。第二种基于损伤力学，其中引入了内部（不可观测）变量，这使得该理论的实验校准变得复杂。作为局部失效准则和损伤力学的替代方法，我们提出一种软化超弹性方法，通过应变软化增强软组织的本构描述，应变软化由材料常数控制。这种方法具有吸引力，一方面新材料常数可以在实验中轻松校准，另一方面失效准则是全局性的。我们通过动脉失效预测问题说明了软化超弹性方法的有效性。为此，我们对具有软化特性的双层纤维 - 基质微观结构动脉模型进行增强，并分析内部压力下的动脉失效情况。我们表明，动脉的整体强度（a）由中膜层主导，（b）由微纤维控制，（c）由残余应力增加。
