BIPHASIC CREEP AND STRESS-RELAXATION OF ARTICULAR-CARTILAGE IN COMPRESSION - THEORY AND EXPERIMENTS
BIPHASIC CREEP AND STRESS-RELAXATION OF ARTICULAR-CARTILAGE IN COMPRESSION - THEORY AND EXPERIMENTS
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DOI：
10.1115/1.3138202
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发表时间：
1980-01-01
影响因子：
1.7
通讯作者：
ARMSTRONG, CG
中科院分区：
文献类型：
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作者：
MOW, VC;KUEI, SC;ARMSTRONG, CG
关节软骨是一种双相材料，由固体基质相（约占总组织重量的 20%）和间质液相（约 80%）组成。每个相的固有机械特性以及这两个相之间的机械相互作用使组织具有有趣的流变行为。在这项研究中，固体基质被假设为本质上不可压缩、线弹性和非耗散的，而间质流体被假设为本质上不可压缩和非耗散的。此外，假设唯一的耗散来自相之间相对运动的摩擦阻力。然而，还开发了更一般的本构方程，包括固体基质的粘弹性耗散以及间质液的粘性耗散。假设组织的“平均”渗透率恒定，即与变形无关，并且假设固体含量函数 Vs/Vf（各相的体积比）根据实验确定的重量比随深度变化。这种线性非齐次理论用于通过非线性回归技术描述实验获得的双相蠕变和双相应力松弛数据。根据 10 次蠕变实验确定的固有“聚合”弹性模量为 0.70 ± 0.09 MN/m2，根据 6 次应力松弛实验确定的固有“聚合”弹性模量为 0.76 ± 0.03 MN/m2。组织的“平均”渗透率为(0.76 ± 0.42) × 10−14m4/N•s。我们得出的结论是，渗透率系数的巨大差异是由于假设渗透率与变形无关。我们还得出结论：1）非线性渗透双相模型，其中渗透率函数由实验确定的经验定律给出：k = A（p）exp [α（p）e]，可用于更准确地描述关节软骨的流变特性，2）相对运动的摩擦阻力是控制压缩时组织的流体/固体粘弹性特性的最重要因素。
Articular cartilage is a biphasic material composed of a solid matrix phase (∼ 20 percent of the total tissue mass by weight) and an interstitial fluid phase (∼ 80 percent). The intrinsic mechanical properties of each phase as well as the mechanical interaction between these two phases afford the tissue its interesting rheological behavior. In this investigation, the solid matrix was assumed to be intrinsically incompressible, linearly elastic and nondissipative while the interstitial fluid was assumed to be intrinsically incompressible and nondissipative. Further, it was assumed that the only dissipation comes from the frictional drag of relative motion between the phases. However, more general constitutive equations, including a viscoelastic dissipation of the solid matrix as well as a viscous dissipation of interstitial fluid were also developed. A constant “average” permeability of the tissue was assumed, i.e., independent of deformation, and a solid content function Vs/Vf(the ratio of the volume of each of the phases) was assumed to vary with depth in accordance with the experimentally determined weight ratios. This linear, nonhomogeneous theory was applied to describe the experimentally obtained biphasic creep and biphasic stress relaxation data via a nonlinear regression technique. The determined intrinsic “aggregate” elastic modulus, from ten creep experiments, is 0.70 ± 0.09 MN/m2and, from six stress relaxation experiments, is 0.76 ± 0.03 MN/m2. The “average” permeability of the tissue is (0.76 ± 0.42) × 10−14m4/N•s. We concluded that the large spread in the permeability coefficients is due to the assumption of a constant deformation independent permeability. We also concluded that 1) a nonlinearly permeable biphasic model, where the permeability function is given by an experimentally determined empirical law: k = A(p) exp [α(p)e], can be used to describe more accurately the rheological properties of articular cartilage, and 2) the frictional drag of relative motion is the most important factor governing the fluid/solid viscoelastic properties of the tissue in compression.