Finite Element Analysis And Fatigue Test For The TiNi Vascular Stent

In recent years, the study of fatigue lifetime and structure design of TiNi vascular stent has attracted considerable attention due to its potentially important effect on the clinical therapy. In this paper, the thermal and mechanical expanding processes of two stents with different size were simulated by a finite element software ANSYS. The work condition of the stents was also simulated. The fatigue lifetime of the stents was predicted using the Goodman diagram. Then one stent was selected to test the fatigue lifetime.The results show that maximum stress of TiNi stent increases obviously and the stress of the struts increases slowly during the stent’s expanding process. The wave peaks of the stent are the stress-centred areas. At the same diameter, the stress ofΦ10mm stent is lower than the stress ofΦ8mm stent .The points of the wave parts and the bridge parts are located at the modified Goodman diagram. All the points are under the non-linear criteria curve. This indicates that two stents will not be fractured during the working process.Total 7pcs TiNi stents(Φ10×20mm) were evaluated in accelerated fatigue test simulating physiological conditions to 400 million pulsatile cycles, equivalent to 10 years human time. Three of them were performed 300,000 cycles of bending fatigue testing at the same time. The result shows that TiNi stents can maintain dimension and structural integrity after 10 years human time, no crack, no broken strut, which demonstrates that the stents have a high bending fatigue lifetime and are safe enough for 10 years of real-time use in human.