Long-time storage effects on shape memory alloy wires

A rich literature studies shape memory alloy (SMA) wires for their potential use in dampers devices able to reduce wind, rain, and traffic-induced oscillations of stayed cables. Restrainers for bridges and improved aseismic devices also exploit alloy components. Thus, SMAs should be regarded as materials susceptible to storage in the yard. In this paper, the authors discuss the evolution of SMA macroscopic behavior as caused by a long-time storage of the product as acquired. The study discriminates between wires of different diameters, because the flat cycles shown by thin wires (i.e., diameter ) and the non-classical S-shaped cycles of thick wires (of diameter 2.46 mm in this paper) answer differently to environmental modifications. The hysteretic behavior of some specimens of wires, of diameter 2.46 mm, is here investigated to mark the unpredictability of the consequence of a long-time storage, which could prevent from the practical exploitation of such alloys in civil engineering.