Bader D L, Kempson G E
Department of Materials, Queen Mary and Westfield College, University of London, UK.
Biomed Mater Eng. 1994;4(3):245-56.
An apparatus and test method were developed to determine the elastic stiffness and damping coefficient of human cartilage in compression. An underdamped, counterbalanced beam applied a sudden compressive force to a full-thickness cylindrical specimen of articular cartilage. The initial oscillatory response decayed to steady state creep after approximately 10 cycles of oscillation. The results were consistent with a Voigt phenomenological model with linear stiffness and damping terms. Standard dynamics analysis of the transient oscillatory response enabled the elastic stiffness to be determined from the frequency and the damping coefficient to be derived from the logarithmic decrement of the decay of the oscillations. The relationship between the mechanical properties and structure of cartilage was determined by treating specimens with two specific proteolytic enzymes. Digestion and removal of proteoglycans alone with cathepsin D caused the damping coefficient to decrease with no change in elastic stiffness. The action of leukocyte elastase on collagen caused a decrease in both damping coefficient and elastic stiffness. It was concluded that the collagen fibrils in cartilage largely control the elastic response while the viscous response is controlled largely by the hydrated proteoglycans. The effects of cartilage thickness was also examined and found to be inversely proportional to the elastic stiffness. It is suggested that this method could be used to uncouple elastic and viscous properties of other viscoelastic materials.
开发了一种用于确定人体软骨压缩时弹性刚度和阻尼系数的装置及测试方法。一个欠阻尼、平衡梁对关节软骨的全层圆柱形样本施加突然的压缩力。初始振荡响应在大约10个振荡周期后衰减至稳态蠕变。结果与具有线性刚度和阻尼项的Voigt唯象模型一致。对瞬态振荡响应进行标准动力学分析，能够根据频率确定弹性刚度，并从振荡衰减的对数减量推导出阻尼系数。通过用两种特定的蛋白水解酶处理样本，确定了软骨力学性能与结构之间的关系。仅用组织蛋白酶D消化和去除蛋白聚糖会导致阻尼系数降低，而弹性刚度不变。白细胞弹性蛋白酶对胶原蛋白的作用导致阻尼系数和弹性刚度均降低。得出的结论是，软骨中的胶原纤维在很大程度上控制弹性响应，而粘性响应在很大程度上由水合蛋白聚糖控制。还研究了软骨厚度的影响，发现其与弹性刚度成反比。建议该方法可用于分离其他粘弹性材料的弹性和粘性特性。
