A Study on the Thermomechanical Properties of Shape Memory Alloys-based Actuators used in Artificial Muscles

Shape memory alloys (SMAs) are a class of smart material having the unique ability to return to a predefined shape when heated. These materials are employed in a variety of emerging applications, and may potentially be used to avoid traditionally voluminous and heavy prosthetic actuators. The primary focus of this article is to convey the design and evaluation of a compact, lightweight, and high-strain SMA ribbon-based artificial muscle for use in such biomimetic applications. A key factor in the design of such an actuator is a thorough understanding of the thermomechanical response of the shape memory material. As such, a review of the relevant constitutive models is included. A selected hysteresis model is evaluated for potential application to ribbon type elements. The proposed actuator achieves strains of 31.6%; a marked improvement over previously documented SMA-based actuators.