Simultaneous transformation and plastic deformation in shape memory alloys

This paper discusses the 3-D numerical modeling of irrecoverable inelastic strain generation in shape memory alloys (SMAs), which is becoming increasingly important as more complicated engineering applications of SMAs are designed. Such behavior, although often rate-independent, can be rate-dependent at high temperatures. This work primarily addresses the modeling of rate-independent inelasticity in SMAs. A material behavior of particular interest occurs when plastic slip and martensitic transformation are occurring simultaneously and the influence of irrecoverable inelastic strain formation on phase transformation is considered. Motivated by experimental results obtained both from the laboratory and the literature, an SMA model which additionally captures the formation and evolution of plastic strains is proposed. The model is implemented into a 3-D finite element method framework and analysis results for two different boundary value problems are discussed. These problems include pre-working of an SMA beam actuator and micro-indentation of SMA thin films.