Speaker
Description
Phase-transforming solids, including shape memory alloys (SMAs), represent a class of multifunctional materials renowned for their remarkable thermo-mechanical properties, such as superelasticity and shape recovery. These materials undergo microstructure evolution during stress- and temperature-induced phase transformations between austenite and multi-variant martensite. The energy dissipation associated with these transformations gives rise to hysteretic behavior under thermo-mechanical cyclic loading. Notably, experiments have revealed a rate-independent response under quasi-static conditions, with hysteresis loops maintaining a finite width even at extremely low loading rates. The phase-field method has become a powerful tool for modeling complex interface topologies that evolve during phase transformations. Despite numerous important contributions addressing the continuum mechanical description of SMAs, see [1] and the references therein, many existing phase-field models employ rate-dependent dissipation formulations, limiting their ability to accurately replicate the thermo-elastic hysteresis loops observed under quasi-static conditions. This work focuses on a recently developed thermomechanically coupled and variationally consistent phase-field approach that addresses these limitations [2]. The study provides a comprehensive guide for implementing phase-field models capable of capturing the rate-independent hysteretic behavior of phase-transforming solids. The approach integrates rate-independent and rate-dependent driving force formulations while incorporating temperature-dependent local energetic minima to reflect experimentally observed behaviors, such as sigmoidal undercooling hysteresis and microstructural evolution. The practical applicability of this approach is demonstrated in two-dimensional finite element simulations, which includes studies of microstructure formation in twinned martensite and the evolution of remanent microstructure under cyclic loading conditions. The influence of driving force thresholds is examined, and it is shown how model parameters can be calibrated using experimentally observed martensite start and finish temperatures. Finally, the work outlines future extensions of the framework to multi-phase and multi-variant alloy systems. This methodology provides a deeper understanding of the complex microstructural properties and behavior of SMAs, facilitating the design of SMA-based devices.
References
[1] L. Xu, T. Baxevanis, D. C. Lagoudas, 2019, Smart Mater. Struct. 28(7), 074004.
[2] O. El Khatib, V. von Oertzen, S. A. Patil, B. Kiefer, 2022, Proc. Appl. Math. Mech. 23(2), e202300273.
