Thermomechanical characterisation of a shape memory alloy for numerical modeling of its actuation response

Abstract

Shape memory alloys (SMA) show the exceptional phenomena of shape memory effect, which is particularly interesting for an active functionalisation of lightweight structures and thus for the realisation of smart structures. To enable a simulation-based design and dimensioning process of such smart structures, the application of sophisticated material models in combination with a comprehensive material understanding is necessary. In this work, the thermomechanical material behaviour of a Nickel-Titanium-based SMA wire material is first experimentally characterised via Differential Scanning Calorimetry technique and an extensive tensile testing campaign under specific temperature conditions. Then, a novel constitutive material model for SMA wire material is proposed to model the temperature-dependent SMA behaviour in terms of the resultant force due to thermal activation. On the basis of experimentally derived model parameters, a strategy is presented for calibrating non-physical model parameters. The results show that the chosen model can reproduce the thermally activated structural behavior of the SMA wire material under consideration of the pre-stretch with a high level of agreement with the experiments. The proposed parameter identification methodology enables the promising material model to be used for the first time at a structural level for the design of adaptive structures.