Design And Mechanical Behavior Analysis Of Coronary Stents

Coronary stent is an important device used in Percutaneous Transluminal Coronary Angioplasty (PTCA), which is usually implanted to support the stenosed artery. Stents include three main deformation processes from manufacture to application, which are the crimped mechanical behavior to the balloon, expansion behavior depending on inflating of balloon and the resistance behavior to compressing happening while the balloon is retrieved. These three main deformation characteristics correspond to and afect different mechanics technical specification of stents separately.According to the stent designs conception, two kinds of connection strut and the nonuniform amplitude strut are used to design a new stent, which is named coronary stent with nonuniform amplitude wavelike structure. Three-dimensional (3D) finite element emulational models of stents with 316L stainless steel and L605 were constructed by a 3D software Pro/Engineering and a finite element analysis (FEA) software ANSYS. The crimped mechanical behavior to the balloon, expansion behavior, the resistance behavior and flexibility of the stent were calculated, and correlative experimental validations were done to investigate the influence of different factors included design of stent, different materials and soon.The results show that the mechanical behaviors of stents depend greatly on the material used. In the crimped mechanical behavior, the recoil of Co-Cr stent is about 40% larger than that of 316L stainless steel stent. And the factors else are little of influential. In expansion behavior, the internal pressure needed for L605 stent to expand and recoil of L605 stent is larger than that of 316L stainless steel. Increasing strut width or thickness can improve the critical internal pressure needed for stent to expand fast. And the internal pressure of L605 0707-stent (both width and thickness of strut are 0.07mm) is equal to 316L stainless steel 1010-stent (both width and thickness of strut are 0.10mm). The change of stent length while expanding is only associated with its structure and final dilatation state. The foreshortening is just 5.64% when expanding diameter is 3.0mm. The resistibility to compressing of L605 stent is better than 316L stainless steel stent obviously. The number of stent's crowns and the dimension of stent's strut can also influence the resistibility to compressing. The stent's flexibility that depends greatly on the material used is improved with the reducing of the strut's width or thickness. The flexibility of L605 0707-stent is better than 316L stainless steel 1010-stent. The flexibility of stent with "S" form struts is better than stent with straight struts.Analyzed by FEA and experiment, the design stent has high radial strength, small foreshortening, appropriate and even metal covering and outstanding flexibility. In conclusion, FEM can quantify some mechanical behavior of stent and help designers to optimize stent system.