Numerical Simulation And Experimental Research On Degradation Behavior Of Magnesium Alloy Vascular Stents

Biodegradable magnesium alloy stents(MAS)have broad application prospects in the treatment of coronary heart disease due to their good degradability,biocompatibility and mechanical properties.However,the rapid degradation rate of MAS in physiological environment restricts its clinical use,and at present,there is no generally agreed research on the degradation mechanism of MAS.Therefore,it is of great significance to study the degradation behavior of MAS.In this paper,the degradation process and mechanical behavior of MAS are studied by combing experiment and finite element analysis.The main research contents and results are listed as follows:(1)The degradation model of MAS was established.The corrosion mechanism of pure magnesium and magnesium alloy was analyzed.Based on the theory of continuum damage mechanics,the degradation model combing pitting corrosion and stress corrosion cracking was established,which integrates the characteristics of inhomogeneity and local severity.The method of establishing degradation model in finite element software was described in detail.(2)Based on the degradation and tensile test,the material parameters and degradation model parameters were determined.The degradation and tensile experiments were carried out on magnesium alloy dumbbell foil as well as the degradation and tensile simulation.Model parameters were corrected by matching the experimental results with the simulation results to prepare for the later stent simulation.(3)The finite element analysis of implantation process,degradation process and radial force test of MAS were completed.The stent-balloon coupling system was established and the model parameters calibrated above-mentioned were used to simulate the whole process.The mechanical behavior,mass loss and radial strength change of stent were analyzed.(4)The effects of geometric parameters of stent on degradation performance were investigated.The stent model was established by changing the ring width,the ring radius,angle of ring and type of bridge,respectively.The changes of mass loss and mechanical properties of the stent with different geometric parameters during degradation process were simulated.The effects of different parameters on stent degradation were compared and analyzed,and suggestions were put forward for stent structure design.