School of Mechanical Engineering, Tel Aviv University, Israel.
J Mech Behav Biomed Mater. 2012 Apr;8:143-53. doi: 10.1016/j.jmbbm.2011.12.008. Epub 2011 Dec 28.
Chitosan hydrogels (CHs) have been considered as a potential implant material for replacement and repair of the Nucleus Pulposus (NP) within the intervertebral disk. The nonlinear mechanical behavior of a CH material is investigated experimentally and computationally in this study. A series of confined and unconfined compression tests are designed and conducted for this hydrogel. Hyperelastic strain energy density functions (SEDFs) are calibrated using the experimental data. A hyperelastic constitutive model is selected to best fit the multi-axial behavior of the hydrogel. Its general prediction ability is verified using finite element (FE) simulations of hydrogel indentation experiments conducted using a spherical tip indentor. In addition, digital image correlation (DIC) technique is also used in the indentation test in order to process the full-field surface strains where the indentor contacts the hydrogel. The DIC test results in the form of top-surface strains compared well with those predicted by the FE model. Results show repeatability for the examined specimens under the applied tests. Confined and unconfined test results are found to be sufficient to calibrate the SEDFs. The Ogden model was selected to represent the nonlinear behavior of the CH material which can be used in future biomechanical simulations of the spine.
壳聚糖水凝胶 (CHs) 已被认为是一种潜在的植入材料，可用于替代和修复椎间盘内的髓核。本研究从实验和计算两方面研究了 CH 材料的非线性力学行为。为该水凝胶设计并进行了一系列有约束和无约束压缩试验。使用实验数据对超弹性应变能密度函数 (SEDF) 进行了标定。选择超弹性本构模型以最佳拟合水凝胶的多轴行为。使用球形压头压痕仪进行的水凝胶压痕实验的有限元 (FE) 模拟验证了其一般预测能力。此外，数字图像相关 (DIC) 技术也用于压痕试验中，以处理压痕器与水凝胶接触的全场表面应变。DIC 试验结果以顶面应变的形式与 FE 模型的预测结果进行了对比，吻合较好。结果表明，在所进行的试验中，检查的样本具有可重复性。有约束和无约束的试验结果足以标定 SEDF。选择了 Ogden 模型来表示 CH 材料的非线性行为，该模型可用于未来脊柱的生物力学模拟。
