Design And Optimization Of The Structure Of Biomedical Magnesium Alloy Stents

Biomedical magnesium alloys have tremendous application potential in the field of biomedical devices for their good biocompatibility and biodegradablity. Therefore, they are attrcting more and more attention. However, magnesium alloys have two main shortcomings being used as coronary stent materials, the shortage of strength and fast degradation speed, and this makes stents failure before achieving the predetermined supporting effect. So it is no time to delay to improve the corrosion resistance and radical strength of magnesium alloy stents. At present, the methods to improve theses disadvantages of magnesium alloy stents are as follows: the design and improvement of magnesium alloy compositions, the improvement of processing technology of magnesium alloy tubes, the design and optimization of magnesium stents, the improvement of surface modification techniques and so on.In this paper, we simulate the crimping process, the self-expansion process, the balloon expansion process and flexibility of V-link stent, S1-link stent on the base of orthogonal test method and principle of continuum damage model, using ANSYS workbench and ABAQUS simulation softwares. Then we verify the mechanical properties of the two stents by real experiment. Basing on the experimental and simulated data, we optimize and design the supporting units and links of the stent structures combining the features of magnesium alloy tubes and laser cutting properties of magnesium alloys, then we achieved S-link stent and Line-link stent. On this basis, we conduct the same simulations and experiments to the the two stents. After that, we explore the influence of structure parameters on the mechanical properties of stents. The result shows that the holistic mechanical properties of the already optimized stent structures are superior to those haven’t optimized ones. The shape and quantity of links have a great influence on the flexibility of stents, the stronger of the deformability of links, the better flexibility of the stent. Therefore, the flexibility of the S-link stent is superior to the Line-link stent, and the less links in the circumferential direction, the better flexibility a stent owns. The shape and width of supporting units have a great influence on the radical deformability and radial force of stents, however, they have little influence on the flexibility of stents. The thickness of stents greatly affects the radical deformability and stress distribution after deformation, the larger the thickness is, the worse of the radical deformability is. And there exists an optimal thickness, in which a stent can achieve the most uniform stress distribution after deformation.