Limbert Georges, Middleton John
Biomechanics Research Unit, The Cardiff Medicentre, UWCM, Dental School, Heath Park, Cardiff CF14 4UJ, UK.
Med Eng Phys. 2006 Mar;28(2):99-113. doi: 10.1016/j.medengphy.2005.03.003.
Further to our previous work on the development of a general constitutive framework for transversely isotropic viscohyperelasticity (Limbert, G, Middleton, J. A transversely isotropic viscohyperelastic material. Application to the modelling of biological soft connective tissues. Int J Solids Struct 2004;41(15):4237-60.), we propose a phenomenological constitutive law to describe the anisotropic viscohyperelastic behaviour of the human posterior cruciate ligament (PCL) at high strain rates. The mechanical formulation is based on the definition of a Helmholtz free energy function containing a hyperelastic and a viscous potential. The equations are valid for arbitrary kinematics and satisfy elemental thermodynamic principles. Identification of the constitutive model with experimental data obtained from human PCL specimens was performed and showed the ability of the model to capture accurately the mechanical characteristics of the PCL at various strain rates. Influence of the isotropic and directional viscous stress responses on the global mechanical response are discussed in connection with the modelling hypotheses. This work was motivated by the need to provide an accurate constitutive model of the PCL to be used in finite element analyses of human occupants in car crash simulations. Besides uniaxial tests along the natural fibre orientation of the PCL, additional tests such as equibiaxial, strip biaxial compression-tension and shear tests were also performed in order to assess the physical response of the model in different loading situations. It was found that the model performed as well in these conditions.
继我们之前关于横向各向同性粘弹性超弹性通用本构框架的研究工作（Limbert, G, Middleton, J. 横向各向同性粘弹性超弹性材料. 应用于生物软结缔组织建模. 《国际固体结构杂志》2004年；41(15):4237 - 4260.）之后，我们提出了一个唯象本构定律，以描述人体后交叉韧带（PCL）在高应变率下的各向异性粘弹性超弹性行为。力学公式基于一个包含超弹性势和粘性势的亥姆霍兹自由能函数的定义。这些方程对任意运动学均有效，并满足基本热力学原理。通过从人体PCL标本获得的实验数据对本构模型进行了识别，结果表明该模型能够准确捕捉PCL在各种应变率下的力学特性。结合建模假设，讨论了各向同性和方向性粘性应力响应对整体力学响应的影响。这项工作的动机是需要提供一个准确的PCL本构模型，用于汽车碰撞模拟中人体乘员的有限元分析。除了沿PCL天然纤维方向进行单轴测试外，还进行了诸如等双轴、条带双轴压缩 - 拉伸和剪切测试等额外测试，以评估模型在不同加载情况下的物理响应。结果发现该模型在这些条件下表现良好。
