Carew E O, Talman E A, Boughner D R, Vesely I
Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, OH 44195, USA.
J Biomech Eng. 1999 Aug;121(4):386-92. doi: 10.1115/1.2798335.
The elements of Quasi-Linear Viscoelastic (QLV) theory have been applied to model the internal shear mechanics of fresh and glutaraldehyde-fixed porcine aortic valve leaflets. A novel function estimation method was used to extract the material functions from experimental shear data obtained at one strain rate, and the model was used to predict the material response at different strain rates. In general, experiments and predictions were in good agreement, the larger discrepancies being in the prediction of peak stresses and hysteresis in cyclic shear. In shear, fixed tissues are stiffer (mean initial shear modulus, 13 kPa versus 427 Pa), take longer to relax to steady state (mean tau 2 4,736 s versus 1,764 s) with a slower initial relaxation rate (mean magnitude of G(0), 1 s-1 versus 5 s-1), and relax to a lesser extent than fresh tissues (mean percentage stress remaining after relaxation, 60 versus 45 percent). All differences were significant at p = 0.04 or less, except for the initial relaxation slope. We conclude that shear experiments can complement traditional tensile and biaxial experiments toward providing a complete mechanical description of soft biomaterials, particularly when evaluating alternative chemical fixation techniques.
准线性粘弹性（QLV）理论的要素已被应用于模拟新鲜的和经戊二醛固定的猪主动脉瓣小叶的内部剪切力学。一种新颖的函数估计方法被用于从在一个应变率下获得的实验剪切数据中提取材料函数，并且该模型被用于预测在不同应变率下的材料响应。总体而言，实验和预测结果吻合良好，较大的差异在于循环剪切中峰值应力和滞后现象的预测。在剪切过程中，固定组织更硬（平均初始剪切模量，13千帕对427帕），达到稳态所需的松弛时间更长（平均τ2为4736秒对1764秒），初始松弛速率更慢（G(0)的平均大小，1秒-1对5秒-1），并且比新鲜组织的松弛程度更小（松弛后剩余应力的平均百分比，60%对45%）。除了初始松弛斜率外，所有差异在p = 0.04或更小的情况下均具有显著性。我们得出结论，剪切实验可以补充传统的拉伸和双轴实验，以便对软生物材料提供完整的力学描述，特别是在评估替代化学固定技术时。
