Effect of Aspect Ratio and Boundary Conditions in Modeling Shape Memory Alloy Nanostructures with 3D Coupled Dynamic Phase-Field Models

TL;DR

This paper introduces a fully coupled 3D phase-field model for SMA nanostructures that captures thermo-mechanical behavior, boundary condition effects, and dynamic phase transformations, validated through simulations matching experimental observations.

Contribution

The paper presents a novel 3D coupled thermo-mechanical phase-field model for SMA nanostructures, incorporating isogeometric analysis and strain-based potentials for realistic microstructure prediction.

Findings

Disappearance of out-of-plane martensitic variants in high aspect ratio domains

Boundary conditions significantly influence microstructure morphology

Higher strain rates and lower aspect ratios increase yield stress and phase transformation stress

Abstract

The behavior of shape memory alloy (SMA) nanostructures is influenced by strain rate and temperature evolution during dynamic loading. The coupling between temperature, strain and strain rate effects is essential to capture inherent thermo-mechanical behavior in SMAs. In this paper, we propose a new fully coupled thermo-mechanical 3D phase-field model that accounts for two-way coupling between mechanical (or structural) and thermal physics. The 3D model provides a realistic description of the properties of SMAs nanostructures. We use the strain-based Ginzburg-Landau potential for cubic-to-tetragonal phase transformations. The variational formulation of the developed model is implemented in the isogeometric analysis framework to overcome numerical challenges. We have observed a complete disappearance of the out-of-plane martensitic variant in a very high aspect ratio SMA domain as well as the presence of three variants in equal portions in a low aspect ratio SMA domain. The sensitive dependence of different boundary conditions on the microstructure morphology has been examined energetically. The tensile tests on a rectangular prism nanowires, using the displacement based loading, demonstrate the shape memory effect and pseudoelastic behavior. We have also observed that higher strain rates, as well as the lower aspect ratio domains, resulting in high yield stress and phase transformations occur at higher stress during dynamic axial loading. The simulation results using the developed model are in qualitative agreement with the numerical and experimental results from the literature.