NUMERICAL MODELING OF STRESS-INDUCED MARTENSITIC PHASE-TRANSFORMATIONS IN SHAPE-MEMORY ALLOYS

Phenomenological models of shape memory behavior are based on either c ontinuum hypothesis (macroscopic) or on volume averages over a represe ntative volume element consisting of several grains. These constitutiv e models attempt to model the shape memory behavior using macro/microm echanics and thermodynamics. In general, these models share a common f eature. They describe the martensitic phase transformation by a parame ter representing the martensite volume fraction, and formulate an evol ution law for the martensite volume fraction. Exploiting the similarit y of these models to elastoplasticity, we describe a finite element fo rmulation of a micromechanics based constitutive model. Several other models can be formulated in a similar way, and the present work can be seen as a testbed approach to study and evaluate the constitutive mod els on a common platform. We present numerical results for Au-47.5at%C d and Ti-50.6at%Ni to validate the finite element formulation. (C) 199 8 Elsevier Science Ltd.