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.

Solar concentrators increase the amount of usable energy available in solar collection systems by focusing energy through an aperture to which energy is magnified within the area of its trajectory. Design challenges of a solar concentrators for space applications are to make them more lightweight, compact, and exhibit a smooth and consistent reflective surface curvature for optimal performance. Shape memory alloys (SMAs) offer an effective and compact solution to engineering needs, such as solar reflectors, to reduce weight and improve overall energy collection and concentration performance. The one-way shape memory effect can be used for this application, where the SMA is heat treated in a strained designed curvature by forcing the austenite microstructure to “remember” the original shape even after deformation. SMAs are capable of actuating from the stow configuration and into the designed shape after the solar energy exposure induces a phase transformation. In this study, NiTi and NiTiCu SMAs were thermomechanically processed into plates and cut into three sizes of triangular chips for use as reflector components. Standard binary NiTi SMAs was modified with the substitution of Cu for Ni to achieve a narrower hysteresis and better thermomechanical cycling stability. The SMAs were produced from commercially available NiTi SM495 plates by ATI Specialty Alloys and Components (Albany, OR) and custom-melted NiTiCu buttons. Each processing step was comprehensively characterized to monitor microstructural and thermomechanical property changes using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Vickers hardness (HV). The NiTi and NiTiCu triangular chips were shape-set utilizing a custom-made apparatus to attain the intended curved surface with specific dimensions for a reflector component within a solar concentrator.