Finite Element Analysis On Mechanical Behaviors Of AZ31 Magnesium Alloy Coronary Stent

Magnesium alloys has recently been studied as biodegradable coronary stent material for its good biocompatibility and biodegradability. However, compared with stainless steel, magnesium alloy as the coronary stent material has lower tensile strength, yield strength, elongation and poorer plastic deformation ability, which cause magnesium alloy stent to emerge higher radial recoil rate, lower radial force and non-uniform stress and strain (stress concentration) and other poorer mechanical properties. In consideration of the premises, this paper studied about optimization design of magnesium alloy stent structure in order to cover the shortage of material property itself. The group self-developed AZ31 magnesium alloy stent has been studied to optimizing structure using the finite element method. By means of changing length, width, radial and other structure parameters of coronary stent unit, the sensitivity factor of stent radial resilience, radial force and the stress and strain distribution was researched by sensitivity analysis method.. The results show that the structure parameters is an important factor of stent properties. The different stent performance were impacted by different sensitivity to different structural parameters. Through simulation analysis, the radial recoil rate, radial force and stress and strain distribution is concerned. For the radial recoil rate, the main factors affecting its performance is variable length, wire width, radius and wall thickness, according to the order of the influence. For the radial force, the main factors affecting its performance is variable length, wire width and wall thickness. For the stress and strain distribution, the main factors affecting its performance is variable length, wire width and radius. In all of these factors, respectively, the significant impact on three performance factors are the length and wire width variable. Changing the radius of stent units can cause a great impact on both radial recoil and maximum principle strain, but less impact on the radial force; Changing the wall thickness of stent units can affect the radial force and radial recoil, but less impact on the maximum principle strain. The influence of structure parameter is important to designing the coronary stent.According to the actual experimental on self-developed stent, it was found that stent structure is non-uniform after the deformation process, mainly due to "V"-shaped beam opening angle is different while the support ring-shaped is unfolded. This is the case, the stent assembly with balloon was were dynamically simulated by changing the structure of the stent, balloon wings and balloon thickness under different circumstances. From the simulation results, the number of balloon wings, the compatibility of stent and balloon, the number of connected muscle and the balloon itself thickness were highly impact on non-uniformity of stent expansion.Specifically, the symmetry of Stent and balloon closer, more uniform stent expansion, in practical cases, the number of balloon wings and the number of stent easiest repeat element of the axial should be the same; more thin balloon thickness, more uniform stent expansion, and in the choice of balloon, the thin-wall balloon should be selected to expand; in the meantime, more symmetrical connected muscle structure and more the number of connected muscle, more uniform stent expansion, in the choice of reinforcement bracket, the number of connect tendons can not to reduce in excess, connect tendons should be symmetrically distributed. Therefore, these initiatives are conducive to improved stent symmetry.