Simulation of cubic to monoclinic-II transformations in a single crystal Cu–Al–Ni tube

Motivated by recent unusual experimental results [Šittner, P., Hashimoto, K., Kato, M., Tokuda, M., 2003. Stress induced martensitic transformations in tension/torsion of CuAlNi single crystal tube. Scripta Materialia 48, 1153–1159] indicating a strong coupling between axial and torsional deformations in single crystal monoclinic-II shape memory alloy tubes, various computational aspects of numerically modelling the observed behavior in monoclinic-II materials are discussed. As a necessary first step, the shape strain computations in monoclinic-II systems are examined. It is found that ambiguities regarding the lattice parameters and proper unit cell in the existing literature have implications for the macroscopic constitutive theories of such alloys. This is demonstrated in the context of a detailed numerical investigation of the experimental problem of interest, wherein it is found that numerical simulations demonstrate proper quantitative response, a strong axial → torsional coupling given a biasing initial condition, and the observed lack of torsional → axial coupling. Implications of the findings are discussed with regard to both the further development of numerical models and future avenues for experimental research.