Stress-strain curve for nitinol stent

The figure shows a stress-strain curve for a nitinol stent based upon an 8 mm balloon. When the stent is released into the vessel, it expands from B until it is stopped by the vessel wall at point C. The continuing opening force directed toward the vessel wall or "chronic outward force" remains very low (from point C to point A). However, the forces generated by the stent to resist compression or radial resistive force increase rapidly until a plateau stress is reached (point C to point D). The radial resistive force is determined by the loading plateau of the stress/strain curve, while the chronic outward force is given by the unloading plateau.