A Three-dimensional Constitutive Model for Polycrystalline Shape Memory Alloys Under Large Strains Combined With Large Rotations

Shape Memory Alloys (SMAs) are described as high-energy-density actuators that can enable active, smart morphing structures. The abstract notes that many SMA constitutive models assume infinitesimal strains, but some SMAs can produce transformation strains around 8–10%, where that assumption may fail. It also highlights that real industry use may involve large rotation deformations, so a constitutive model built on a finite deformation framework is needed. The work proposes a three-dimensional SMA constitutive model that uses logarithmic strain to support a consistent finite-strain formulation. The model introduces martensitic volume fraction and a second-order transformation strain tensor as internal state variables to represent the inelastic response of polycrystalline SMAs. The authors state the formulation and numerical implementation could be extended later to include other inelastic effects such as transformation-induced plasticity, viscoplasticity, and creep under large deformations.