Confined and unconfined stress relaxation of cartilage: appropriateness of a transversely isotropic analysis
Confined and unconfined stress relaxation of cartilage: appropriateness of a transversely isotropic analysis
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DOI：
10.1016/s0021-9290(99)00105-0
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发表时间：
1999-10-01
影响因子：
2.4
通讯作者：
Stamenovic, D
中科院分区：
文献类型：
--
作者：
Bursac, PM;Obitz, TW;Stamenovic, D
先前的研究表明，小腿尺骨生长板和骨骺软骨的应力松弛行为可以通过线性横向各向同性双相模型来描述。该模型提供了良好的拟合。当面外泊松比设置为零时观察到的无侧限压缩瞬态。该假设基于以下观察结果：在受限压缩和无受限压缩中，轴向平衡应力 (sigma(z)) 相同，这意味着受限压缩中的径向应力 sigma(r) = 0。在我们的研究中，我们进一步研究了横向各向同性模型描述小腿软骨的受限和非受限应力松弛行为的能力。在能够测量 sigma(z) 和 sigma(r) 的位移控制压缩装置中对小腿关节软骨（直径 4.5 mm，类似于 3.3 mm 高度）进行了一系列受限和非受限应力松弛测试。在平衡状态下，有限压缩中的 sigma(r) > 0 且 sigma(z) 大于无侧限压缩中的 sigma(z)。通过线性横观各向同性双相模型拟合每个应变的瞬态数据并估计材料参数。尽管该模型可以很好地拟合无侧限瞬态，但估计参数过高预测了测量的 sigma(r)。相反，如果模型被限制为匹配平衡 sigma(r)，则拟合效果较差。这些发现表明，线性横向各向同性双相模型不能同时描述观察到的小腿软骨的应力松弛和平衡行为。 (C) 1999 Elsevier Science Ltd. 保留所有权利。
Previous studies have shown that stress relaxation behavior of calf ulnar growth plate and chondroepiphysis cartilage can be described by a linear transverse isotropic biphasic model. The model provides a good fit. to the observed unconfined compression transients when the out-of-plane Poisson's ratio is set to zero. This assumption is based on the observation that the equilibrium stress in the axial direction (sigma(z)) is the same in confined and unconfined compression, which implies that the radial stress sigma(r) = 0 in confined compression. In our study, we further investigated the ability of the transversely isotropic model to describe confined and unconfined stress relaxation behavior of calf cartilage. A series of confined and unconfined stress relaxation tests were performed on calf articular cartilage (4.5 mm diameter, similar to 3.3 mm height) in a displacement-controlled compression apparatus capable of measuring sigma(z) and sigma(r). In equilibrium, sigma(r) > 0 and sigma(z) in confined compression was greater than in unconfined compression. Transient data at each strain were fitted by the linear transversely isotropic biphasic model and the material parameters were estimated. Although the model could provide good fits to the unconfined transients, the estimated parameters overpredicted the measured sigma(r). Conversely, if the model was constrained to match equilibrium sigma(r), the fits were poor. These findings suggest that the linear transversely isotropic biphasic model could not simultaneously describe the observed stress relaxation and equilibrium behavior of calf cartilage. (C) 1999 Elsevier Science Ltd. All rights reserved.