Structure Design And Optimize Of Coronary Magnesium Alloy Stent

Coronary atherosclerosis is one of the major cardiovascular diseases threateninghuman life. At present, the stent is main method for the treatment of coronary arterystenosis, and mainly includes the traditional bare metal stent, drug-eluting stent andbiodegradable stent. The biodegradable stent is the main development direction in the stentfield. It includes biodegradable polymers stent, biodegradable iron stent and biodegradablemagnesium alloy stent. Magnesium alloy stents with good biocompatibility and favored bythe public, but the elongation of magnesium alloy materials is low, lead to the stentoccurred fracture failure problem in expansion and caused seriously restrict thedevelopment of magnesium alloy stent.Stent will experience elastic deformation and large plastic deformation in the couplingprocess. Because of the plastic deformation ability of material is poor, stent appear stressconcentration in the process of deformation and result stent fracture failure. Therefore, toreduce the stent stress and strain is one of the effective means to improve the fracturefailure problem. In order to reduce the stent stress and strain, this study by using the finiteelement method to simulation and analysis stents after change the parameters. Focus on theeffect of initial diameter, strut length and strut number in circumference direction of onestructure of magnesium alloy stent on the expansion properties and mechanics properties ofstent, thus achieve the objective of parameter optimization and find the suitable structurefor magnesium alloy stent. And by using the experimental method to prove the finiteelement simulation result is rationality.The finite element results show, when only to change the parameters of initialdiameter, the max stress and strain of stent are decreases, and the radial recoil rate in thewhole stage and axial elongation rate and crimp inhomogeneity are decreases, the axialshortening rate, expansion inhomogeneity and safety coefficient are increases. When onlyto change the parameters of strut length, the max stress and strain of stent and the axialelongation rate and axial shortening rate are decreases., but the radial recoil rate in thewhole stage, crimp inhomogeneity, expansion inhomogeneity and safety coefficient areincreases. When only to change the parameters of the strut number in the circumferencedirection, the max stress and strain of stent are decreases, and the axial elongation rate, crimp inhomogeneity, axial shortening rate and expansion inhomogeneity are decreases,the radial recoil rate in the whole stage and safety coefficient are increases. When changethe three parameters at the same time, the max stress and strain of stent are decreases too,and the axial elongation rate, crimp inhomogeneity and axial shortening rate are decreases,the radial recoil rate in the whole stage, expansion inhomogeneity and safety coefficientare increases. The results show that no matter to optimize one parameter or multipleparameters of stent all can effectively reduce the max stress and strain, increase safetycoefficient and improve the safety performance.The experimental results show that stress concentration area of stent is consistent withthe finite element analysis results, and the biological mechanics properties almostunanimously. Through the stent in vitro expansion test method to verify the finite elementsimulation results are rationality and reliability, and to provide scientific basis for thestructure design and optimization of coronary magnesium alloy stent.