Spirt A A, Mak A F, Wassell R P
Department of Bioengineering, University of Pennsylvania, Philadelphia.
J Orthop Res. 1989;7(1):43-9. doi: 10.1002/jor.1100070107.
The strain dependence of the intrinsic viscoelastic properties of the cartilage matrix in shear was investigated. Stress relaxation experiments were performed on bovine articular cartilage at shear strains ranging from approximately 3% to 16%. The tissue was found to exhibit nonlinear strain-dependent viscoelastic behavior, with the nonlinearity occurring primarily in the short-time transient during stress relaxation. In addition, the equilibrium stress was found to fit a quadratic relation with strain. This relationship was noted to be nearly linear with strain from 3% to 16%. The instantaneous stress was seen to be highly nonlinear, and followed a cubic relationship with applied shear strain. Fung's quasilinear theory can be used to describe the stress relaxation response over the range of strains examined when a nonlinear regression is performed to determine an "average" normalized relaxation function. Alternately, strain dependence can be incorporated into the model to describe and predict more accurately the strain-dependent stress relaxation response.
研究了软骨基质在剪切力作用下本征粘弹性特性的应变依赖性。在约3%至16%的剪切应变范围内，对牛关节软骨进行了应力松弛实验。发现该组织表现出非线性应变依赖性粘弹性行为，非线性主要出现在应力松弛过程中的短时间瞬态阶段。此外，发现平衡应力与应变符合二次关系。该关系在3%至16%的应变范围内与应变近似呈线性。瞬时应力被视为高度非线性，且与施加的剪切应变呈三次关系。当进行非线性回归以确定“平均”归一化松弛函数时，冯氏准线性理论可用于描述在所研究应变范围内的应力松弛响应。或者，可以将应变依赖性纳入模型，以更准确地描述和预测应变依赖性应力松弛响应。
