Use the Force: Review of High-Rate Actuation of Shape Memory Alloys

Abstract

Typical shape memory alloy actuators provide a unique combination of large stresses and strains that result in work-per-volume larger by more than two orders of magnitude than all other actuation methods that are based on active materials. High-rate actuation of shape memory alloys can provide improved energy efficiency, and shorter response and total actuation times, along with large travel-per-wire-length, with respect to slow-rate SMA applications. In this article, we review the different aspects of high-rate actuation of shape memory alloy wires in the high-driving-force regime. We briefly survey previous experimental results about the kinetics and thermodynamics of the phase transformation in view of its practical implications. New experimental results, regarding energy efficiency, total actuation time, repeatability, and fatigue, are presented and discussed. The paper provides general design guidelines for obtaining high actuator performance, as well as guidelines for selecting the source of the electric pulse and its parameters. Finally, we construct and solve detailed simulations of actuator response that can serve as accurate design tools.

A review on shape memory alloys and their prominence in automotive technology

“…The resistivity and surface-area-to-volume ratio, which affects the heating and cooling rate of the wire, is also dependant on the cross-sectional area of the wire (Dana et al, 2021). The rate of heating (H) experienced by the wire can be expressed in terms of current passing through the wire (I), the electrical resistance of the wire (R), and heating time (t), using equation ( 3),…”

“…Where, “U” is the heat transfer coefficient, “A sf ” is the surface area, “ΔT” is the temperature difference between the wire and the atmosphere, and “t cool ” is the time taken for the wire to cool (Dana et al, 2021; Nizamani et al, 2017).…”

High-Power Shape Memory Alloy Catapult Actuator for High-Speed and High-Force Applications

“…The activation scheme in this demonstrator aims at full SMA wire contraction with maximum velocity and thus generating an acceleration of a mass. Even though the mechanical stress-strain behavior of SMA wires is highly non-linear and hysteretic (Figure 1, [27]), in this specific case the only constraint is to reach the fully austenitic branch (2) from resting position (1) as fast as possible. This means, no further control of the actuator is needed or intended, the only goal is maximum power release upon activation.…”

“…The content of this paper deals with combining both topics in a descriptive way, resulting in a mechatronic system for technology demonstration purposes. Dana, Vollach and Shilo give an overview of these high-rate SMA applications [27], which can be used for the development of quick release mechanisms in safety applications [26] or contactors as prominent practical examples. In both cases, the SMA actuator must provide high forces in the range of several micro-or milliseconds to either pull a safety pin and activate a brake-/blocking mechanism or disconnect/break a highvoltage and high-current electrical circuit.…”

Estimation of heat transfer model parameters by using recursive least square (RLS) method for a shape memory alloy wire

“…Enhancement of the actuation response of an SMA wire through its thermo-mechanical properties is still a common and current research subject (Dana et al, 2021). Recently, applications such as reinforcement by SMA wire embedded with secondary materials to create composite structure designs have gained popularity (Bhaskar et al, 2020; Kang et al, 2018).…”