ASTM F2606 "Standard Guide for Three-Point Bending of Balloon Expandanble Vascular Stents and Stent Systems" provides guidelines for quantitatively characterizing these products. It provides data that can be used to compare the flexibility of different products by direct comparison of load-deflection curves and by comparison of calculated slopes of the curves.
The standard calls for a specific
three-point bend fixture. The upper load applicator and the lower static supports must have a radius of 6.35 mm. It is recommended that they are designed to minimize friction by using low-friction materials (like Delrin) or by allowing support rotation through bearings. The fixture shown at the right is our standard miniature three-point bend fixture, which is not manufactured using any special materials or bearings for friction reduction. However, these materials can be modified and changed to a customer's specific needs.
Further, if testing in a bath is required, which would be the case if the specimens are sensitive to temperature change from ambient to 37° C or to hydration, then the fixture can be supplied in stainless steel to prevent rust. The fixture can be easily adapted to our standard BioPuls™ Bath, which can maintain physiological conditions of 37° C +/- 1° C.
We recommend Bluehill® Software with the
TestProfiler Module to load and unload the specimen, and to obtain a typical hysteresis curve. The software can provide for the load-deflection data on both segments of the curve, as well as a variety of additional calculations, such as slope, that will allow for direct comparison of a variety of different specimens.