Study On The Structural Design Of NiTi Alloy Peripheral Vascular Stent With High Fatigue Resistance

With the development of interventional therapy,peripheral vascular stent interventional therapy has become one of the most effective means to treat peripheral vascular diseases.This study focused on the structural unit of NiTi alloy peripheral vascular stent with high fatigue resistance.Firstly,NiTi alloy peripheral vascular stent with“Z” type unit was designed by UG and connected by polytetrafluoroethylene membrane.Secondly,the three processes of compression,expansion and service of different types of stents support units were simulated by using finite element analysis,which was designed through orthogonal experimental design method.The influence of structural parameters of support units on their stress-strain or fatigue performance in the three stages was explored.Finally,the structural design parameters of NiTi alloy peripheral blood scaffold with high fatigue resistance were obtained by orthogonal test.The results are as follows:(1)Through the simulation of the stent compression process,it is found that the maximum compression strain and radial resistance of NiTi alloy peripheral blood stent increase with the increase of the diameter of NiTi alloy wire support unit.The analysis of orthogonal test results shows that compared with the effect of the diameter change on the maximum compressive strain of the support,the influence of the structural parameters of the support is greater.The best anti-compression performance can be obtained when the supporting unit length L=7 mm,the connection arc radius R=0.5 mm,the included Angleα=15° and the included Angle β=20°.In contrast,the radial resistance of the compressed support unit is closely related to the diameter and structural parameters of the support.For the "Z" support unit designed in this study,when the diameter of the support unit varies from 0.15 to 0.25 mm,the length of the support unit L=5~6 mm,the radius of the connection arc R=0.3 mm,the included Angle α=10~15°,and the included Angle β=10°,NiTi alloy peripheral vascular stent shows the best anti-compression performance.(2)Through the simulation of stent expansion process,it is found that the radial support force of NiTi alloy peripheral vascular stent after expansion increases with the increase of the diameter of NiTi alloy wire support unit.The results of the orthogonal test show that the radial support force is closely related to the diameter and structure of the support unit.If the diameter of the support unit varies from 0.15 to 0.25 mm,the bracket shows the best radial support performance when the length of the support body L=5~6mm,the radius of the connection arc R= 0.3 mm,the included Angle α=10°,and the included Angle β=10~20°.In addition,the blood vessels in a physiological pulsating cycle load cycle,sustained radial support stability and its body is closely related to the diameter and the change of structural parameters,when the supporting body changes between 0.15 to0.25 mm in diameter,and the supporting body length L=5~6 mm,connecting arc radius R=0.5 mm,the included Angle α=10~15°,the included Angle β= 20°,NiTi alloy peripheral vascular stents shows excellent stability of radial support.(3)Through the simulation of the stent service process,it is found that with the increase of the NiTi alloy support body diameter(0.15~0.25 mm),the fatigue nodes in the service process of the stent will be more divergent,and the fatigue safety performance of the stent will be reduced.By studying the fatigue safety factor(FSF)of structural support units,it is found that when the structural parameters are L=7 mm,R=0.3 mm,α=20 °,β=15 °,the FSF of NiTi alloy wire support unit with a diameter of 0.25 mm is less than 1.The FSFs of other support units are all greater than 1.The results of the orthogonal test show that if the diameter of the support unit varies from 0.15 mm to 0.25 mm,the NiTi alloy peripheral blood vessel stent shows a high fatigue safety factor when the length of the support body L=6 mm,the radius of the connection arc R=0.4~0.5mm,the included Angleα=10~15 °,and the included Angle β=10~20 °.