The stent bending force (bending force) is defined as the peak tensile force generated when the middle point is raised 2 mm upward. The measurement method refers to the standard ASTM-E8-04 (Figure 4-5): Two parallel round bars of 8 mm diameter are separated and fixed with a center distance of 16 mm; the round bars form the two end points in the three-point bending test. A metal hook with a diameter of about 3 mm is fixed on the chuck of the universal material testing machine (CMT4105, MTS Industrial Systems, China), and a vertical upward pulling force is applied from the middle point of the bracket (as shown in Figure 4-5). The stents used in the test are Zn-Cu stents and 316L SS stents without delivery system, unexpanded, and all models are 3.0*20. The sample size of the experimental group and the control group are both 6. The bending force of the Zn-Cu stent is 0.14±0.02 N, and the bending force of the 316L SS stent is 0.54±0.12 N. The bending force of the Zn-Cu stent is only 25.9% of that of the 316L SS stent. The bending force of the stent can affect the difficulty of the stent passing through a curved blood vessel: the easier it is to bend, the easier it is for the stent system to pass through the curved blood vessel, and the less damage is caused to the blood vessel wall in the process of passing through the blood vessel. On the other hand, the bending force of the stent can reflect to a certain extent the stent tension on the vascular segment after the stent is implanted in the curved blood vessel. The bending force of the Zn-Cu stent is smaller, so it can follow the curved blood vessel contour better than the 316L stent, and it will bring less stimulation to the blood vessel segment (Figure 4-19).
