Intrinsic differences between thinner and thicker wires in NiTi SMA

Abstract

The civil engineering equipment, such as the bridges, were located outside the laboratory equipment and were subject to the direct effect of the external temperatures. In moderate climates, the summer and winter temperatures vary between −10°C and 40°C, but in northern Europe or Canada, the cold temperatures can easily reach −50°C or lower. The temperature modifies the SMA behaviour by the action of the Clausius-Clapeyron thermodynamic equation. The analysis performed in this work focuses on the similarity, suitability and guaranteed behaviour of NiTi SMA wires with different diameters. In particular, the study establishes the effects of the summer-winter temperature variation on the SMA. It was found that the external temperature has a negative effect on the thinner wires in comparison with the valuable behaviour of thicker wires. The particular effects of the diameter are enhanced when the samples are submitted to strain-aging.