Kim Ju Hyun, Kang Tae Jin, Yu Woong-Ryeol
Intelligent Textile System Research Center, Department of Materials Science and Engineering, Seoul National University, 599 Gwanangno, Gwanak-gu, Seoul 151-742, Republic of Korea.
J Biomech. 2008 Nov 14;41(15):3202-12. doi: 10.1016/j.jbiomech.2008.08.005. Epub 2008 Sep 19.
The mechanical behavior of a stent is one of the important factors involved in ensuring its opening within arterial conduits. This study aimed to develop a mechanical model for designing self-expandable stents fabricated using braiding technology. For this purpose, a finite element model was constructed by developing a preprocessing program for the three-dimensional geometrical modeling of the braiding structure inside stents, and validated for various stents with different braiding structures. The constituent wires (Nitinol) in the braided stents were assumed to be superelastic material and their mechanical behavior was incorporated into the finite element software through a user material subroutine (VUMAT in ABAQUS) employing a one-dimensional superelastic model. For the verification of the model, several braided stents were manufactured using an automated braiding machine and characterized focusing on their compressive behavior. It was observed that the braided stents showed a hysteresis between their loading and unloading behavior when a compressive load was applied to the braided tube. Through the finite element analysis, it was concluded that the current mechanical model can appropriately predict the mechanical behavior of braided stents including such hysteretic behavior, and that the hysteresis was caused by the slippage between the constituent wires and their superelastic property.
支架的力学行为是确保其在动脉血管内打开的重要因素之一。本研究旨在开发一种力学模型，用于设计采用编织技术制造的自膨胀支架。为此，通过开发一个用于支架内部编织结构三维几何建模的预处理程序构建了有限元模型，并针对具有不同编织结构的各种支架进行了验证。编织支架中的组成丝（镍钛诺）被假定为超弹性材料，其力学行为通过使用一维超弹性模型的用户材料子程序（ABAQUS中的VUMAT）纳入有限元软件。为了验证该模型，使用自动编织机制造了几个编织支架，并重点对其压缩行为进行了表征。观察到当对编织管施加压缩载荷时，编织支架在加载和卸载行为之间表现出滞后现象。通过有限元分析得出结论，当前的力学模型能够适当地预测编织支架的力学行为，包括这种滞后行为，并且这种滞后是由组成丝之间的滑动及其超弹性特性引起的。
