Nonlinear dynamics of a pseudoelastic shape memory alloy system-theory and experiment

• Published in: Smart materials and structures 2014-08, Vol.23 (8), p.1-17
• Main Authors: Enemark, S, A Savi, M, F Santos, I
• Format: Article
• Language: English
• Subjects: Constants; Dynamical systems; Dynamics; Exact sciences and technology; Helical springs; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mathematical models; Mechanical instruments, equipment and techniques; model validation; Nonlinear dynamics; Physics; Shape memory alloys; Springs (elastic)
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/0964-1726/23/8/085018

In this work, a helical spring made from a pseudoelastic shape memory alloy was embedded in a dynamic system also composed of a mass, a linear spring and an excitation system. The mechanical behaviour of shape memory alloys is highly complex, involving hysteresis, which leads to damping capabilities and varying stiffness. Besides, these properties depend on the temperature and pretension conditions. Because of these capabilities, shape memory alloys are interesting in relation to engineering design of dynamic systems. A theoretical model based on a modification of the 1D Brinson model was established. Basically, the hardening and the sub-loop behaviour were altered. The model parameters were extracted from force-displacement tests of the spring at different constant temperatures as well as from differential scanning calorimetry. Model predictions were compared with experimental results of free and forced vibrations of the system setup under different temperature conditions. The experiments give a thorough insight into dynamic systems involving pseudoelastic shape memory alloys. Comparison between experimental results and the proposed model shows that the model is able to explain and predict the overall nonlinear behaviour of the system.