A Top-Down Characterization of NiTi Single-Crystal Inelastic Properties within Confidence Bounds through Bayesian Inference

The inelastic deformation response of NiTi single crystals involves reversible phase transformation and dislocation slip, which is enhanced by the deformation incompatibility among the phases. The phase transformation–plasticity coupling results in decrease in performance, including reduced work output and early fatigue failure. The characterization of the inelastic properties in this material class is crucial for material assessment/ranking and robust performance predictions. Given that direct mesoscale measurements of (coupled) deformation mechanisms are in many cases impractical, top-down characterization of single-crystal properties from limited macroscopic experiments is mostly employed. Here, Bayesian inference and a micromechanics-based continuum single-crystal model are adopted for determining (i) material property values within confidence intervals that allow for a propagation of the quantified uncertainty onto performance predictions, which can be used toward a more efficient design methodology; (ii) ranking of the relative influence of the various material parameters on the deformation response that can further translate to the respective influence of the various deformation mechanisms conditional on the adopted material model; and (iii) a quantitative evaluation of the importance of the deformation incompatibility among the phases in the overall deformation response.