Experimental Investigations of the Superelastic Impact Performance of Nitinol 60

Nitinol 60 (NiTi60) is a nickel–titanium alloy that has a unique combination of properties such as high hardness, low elastic modulus, and superelasticity. Recent studies of static indentation tests on prestressed samples demonstrated a considerable load capacity increase, which led to the current experimental work. The coefficient of restitution (COR) is measured for two NiTi60 spheres of different diameters (0.635 and 1.270 cm). This work shows that mechanically stressing NiTi60 spheres enables them to achieve a normal COR greater than 0.9 when colliding with NiTi60 landing. This is one of the highest ever reported COR values for self-mated crystalline metal alloys at moderate impact velocities. Consequently, it is believed that this material may be a potential candidate for use in applications requiring highly resilient and wear-resistant metallic materials. A well-known analytical formulation for the coefficient of restitution is used to gain insight and to elucidate some of the COR results presented.