Objective To study biomechanical properties of two types of cylindrical nitinol stent-grafts under working condition of self-expanding, full deployment and bending, and analyze effects of structural change on biomechanical indexes of the grafts by numerical simulation methods. MethodsFirstly, the finite element models of two annular stent-grafts (i.e. stent-graft Ⅰ, stent graft Ⅱ, and a connecting rod was added to each stent unit of stent-graft Ⅱ for reinforcement) and target vessels were built. The stent-graft was transported to target vessel by delivery sheath, which was then removed to self-expand the stent-graft, and the contact between the vessel and the stent-graft was established. Secondly, the arterial pressure of 6.65-19.95 kPa (50 150 mmHg) was applied to inner surface of the stent-graft when the stent graft was fully deployed. Thirdly, the angular displacement was applied to both ends of the stent-graft to bend and deform the stent-graft. Finally, the maximum Von Mises stress (VMS) of the deformed vessel, the maximum principal strain (MPS), the maximum VMS and structural changes of the stent-graft were analyzed. ResultsFor both the stent-graft Ⅰ and Ⅱ, when they were self-expanding, the maximum VMS on the vessel was 0.349 MPa and 0.371 MPa, respectively; when they were fully deployed, the mean strain was 0.086% and 0.053%, the alternating strain was 0.049% and 0.027%, the maximum VMS on the membrane was 2.098 MPa and 2.430 MPa, respectively; when they were bent, the MPS was 0.069% and 0.101%, respectively, with more serious deformation on stent-graft Ⅰ. ConclusionsThe strain and stress of two stent-grafts under each working condition were less than their own material yielding limit. Stent-graft Ⅱ showed larger radial force in self-expanding, smaller strain under arterial pressure and better flexibility in bending deformation due to its connecting rod between each stent unit. These research results would provide an analysis method for structure design and material selection of the stent-graft, as well as a more intuitive and accurate technique guidance for intervention operation of the stent-graft in clinic.