Shape Memory Alloy Actuation Device Design Tool

Abstract Shape memory alloys (SMAs) are a novel solution to reducing the actuating system weight and mechanical complexities which consequentially comes with integration challenges. Some of these challenges are due to limited production accessibility and often need reengineering. A materials model turned into analytical routines would allow empirical data to predict the structural behavior of SMAs. An SMA design tool would bridge material science and engineering practices by guiding the users through an iterative design approach to improve integration efficiency for actuating devices. A user-friendly first-order approximation model was developed by the Consortium for the Advancement of Shape Memory Alloy Research and Technology (CASMART) to capture the macroscopic effects of forward and reverse transformation for various actuator types such as wires, springs, and torque tubes. This tool allows quick changes and iterations throughout the design process, which is particularly helpful in comparing actuator types. Although it is convenient to use, the ability to capture the SMA nonlinear and complex inelastic response is limited. Phenomenological-based models have been developed by incorporating classical theory of plasticity and by relating martensite volume fraction to the laws of thermodynamics. The phase transformation can be characterized as a rate-independent plasticity using the volume of martensite to govern the change in material properties between austenite and martensite. The development of the model itself incorporates other characteristics such as the degradation of performance due to plastic strain and the change in transformation strain during partial cycling. The challenge with these models is the complexity for the user. The starting point to create a user-friendly SMA design tool involved combining a phenomenological-based model with Finite Element Models (FEM). Integrating a complex 3D constitutive model with ABAQUS Finite Element Analysis (FEA) encompasses both conventional material parameters and unique shape memory alloy parameters.