D. Lagoudas, D. Hartl , Texas A&M University , College Station , TX
Modeling of the martensitic transformation in Shape Memory Alloys (SMAs) has allowed for the analysis of fully-recoverable inelastic deformations in devices composed of this material and used in the medical, aerospace, and other fields. In the past, however, the analysis of irrecoverable deformations has rarely been addressed. This work discusses a new class of SMA constitutive model that considers both phase transformation and the evolution of irrecoverable viscoplastic strains exhibited when these materials are subjected to sufficiently high temperatures, such as during shape-setting. To date, shape-setting, when analyzed, has been modeled by imposing a spatially-homogeneous elimination of internal stresses within a deformed body. In this work, it is shown that an accurate and new transformation-viscoplastic constitutive model, implemented in a finite element analysis (FEA) framework and calibrated using NiTi creep data, can provide more valuable insight into the response of constrained SMA structures exposed to elevated temperatures.
