考虑尺寸效应的聚合物血管支架力学性能

Mechanical Properties of Polymeric Vascular Stents Considering Size Effect

目的研究考虑尺寸效应的聚合物血管支架力学性能,分析支架结构对支架力学性能和支架变形过程中尺寸效应的影响规律,为支架的结构设计提供理论依据。方法建立考虑尺寸效应的聚乳酸的Cosserat理论模型,并结合有限元法,通过三点弯曲和平板压获得支架抗弯刚度和径向刚度,进一步分析支架筋厚和筋宽、支撑单元曲率半径和轴向间距对支架径向支撑性能和尺寸效应的影响规律。结果聚合物血管支架在弯曲和压缩过程中均存在明显的尺寸效应现象;支架径向刚度与支撑单元曲率半径和轴向间距均呈负相关,与筋厚和筋宽均呈正相关;支撑单元曲率半径、轴向间距以及支架筋厚和筋宽越小,聚合物血管支架压缩过程中的尺寸效应越大。结论支架的径向支撑性能主要由结构的刚度决定,并受支架变形过程中尺寸效应的影响;支架几何结构的特征尺寸越小、支架弯扭变形的程度越大,则尺寸效应越明显,对支架径向支撑性能的增幅越大。

Objective The mechanical properties of polymeric vascular stents considering size effect were investigated,and the influence laws of stent structure on mechanical properties of the stents and size effects during stent deformation were further analyzed,so as to provide the theoretical basis for structural design of the stents.Methods The Cosserat theoretical model of poly lactic acid(PLA)considering size effect was established,and combined with the finite element method,the bending stiffness and radial support stiffness of the stents were obtained by three-point bending and flat plate compression,and the influence laws of rib thickness and rib width of the stents,radius of curvature and axial spacing of the support unit on radial support performance and size effect of the stents were further analyzed.Results There was a significant size effect on the polymeric vascular stent during bending and compression.The radial support stiffness of the support unit was negatively correlated with the radius of curvature and axial spacing,and positively correlated with the rib thickness and rib width,and the smaller the radius of curvature and axial spacing of support unit,rib thickness and rib width of the stents,the larger the size effect during compression.Conclusions The radial support performance of the stent is mainly determined by the structure stiffness,and affected by the size effect during stent deformation.With smaller characteristic dimensions of the stent geometric structure and greater bending and torsional deformation of the stent,more obvious size effects will be obtained,which leads to a greater increase in radial support performance of the stent.