Structure Design And Performance Study Of Ni-Ti Alloy Vascular Stent

As the development of industry and the change of the ecological environment, the incidence rate of vascular disease is increasing, which has affected people’s health seriously. Cardiovascular disease is the first killer of human health and life and the traditional treatment has the shortcomings of high risk, difficult faults, and expensive. The stent implantation, as a professional technology of interventional therapy, has developed rapidly and obtained good effect. Through the finite element analysis technology, we can get the information of vascular stents’ supporting performance and so on, estimated the fatigue life of intravascular stent, guidance to optimize the structure design of the vascular stents, which can greatly promote the process of stents’ development.This topic selected the Ni-Ti alloy vascular stents of wire weave type, plate cutting and laser engraving, the M type and Z type of Ni-Ti alloy vascular stents, Used finite element analysis software to study the supporting performance, resilience and fatigue properties of the stents, which did important guidance value on the product research and development.From the results of finite element calculation, we could find that the support force of plate and tube vascular stents increased as quadratic index and the support force of wire vascular stent increased linearly with the increased of load. Under the same displacement load and sectional area, the main reason of different supporting performance was that vascular stents of wire, plate and tube with different shape of cross section.By analyzing the M type of stents, we could find that the same ratio of h/H structural design, the smaller value of the height H of stents was, the greater the supporting force to be. Fixed the values of the height H, with the ratio of h/H ratio increasing, the supporting force was reduced and the degree turned to be more prominent under the same displacement load. When the h/H=1, the type of M stent transformmed into Z type and the value of supporting force was minimum at this time. The type of M structure with different ratios of h/H designed, the stents’ resilient rate was highly different under different displacement loading, based on h/H=1/2, the resilient rate of the structure with h/H<1/2 was significantly higher than the structure with h/H>1/2.For the type of Z stents, changing the wire diameter and the height of the stents had more remarkable influence on the supporting performance and resilient rate than changing the bend radius. The supporting force and resilient rate of the stents would be optimized either by increasing the wire diameter or reducing the height of support muscle, while, increasing the bend radius of the stent, The supporting force turned to be optimized, but the resilient rate had the opposite effect. What’s more, the result of compressive test through the universal testing machine was consistent with the computed result of finite element analysis, demonstrating the rationality of the finite element model.400 million pulse fatigue test was carried on the chosen stent by the fatigue machine. The result indicated that there was no fracture line in the stent and it was intact, which verified the fatigue properties of the stent met the requirement and the rationality of the geometric parameters.In the process of stents’ design, the appropriate support of stents, high resilience, high fatigue properties and flexibility etc was considered, which demanded us to pay attention to the combination of the parameters when designed stents’ structure. In the clinical application of stents, The stents should be designed according to its structure and performance characteristics, relatively speaking, M type structure was advantageous to stents anchoring and orifice closed, which more suitable for the end of stents; Z type structure was conducive to joint with vessel wall, which more suitable for the central location. The simulation results by finite element analysis about the vascular stents’ supporting performance in this article would contribute to both the future clinical choice and the optimized design of the stent.