ME Professor Sam Daly and her student Kyubum Kim have received the 2013 Hetényi Award from the Society of Experimental Mechanics, for the best research paper published in the journal Experimental Mechanics in 2011: “Martensite strain memory in the shape memory alloy Nickel-Titanium under mechanical loading”, K. Kim and S. Daly, Volume: 51 Issue: 4 Pages: 641-652 Published: 2011. This award was established in 1967 for the best research paper published in Experimental Mechanics. It was named in honor of Dr. Miklos Hetényi.
The abstract for the paper reads as follows: this paper describes an experimental study of stress-induced martensitic phase transformation in the SMA Nickel-Titanium. The rich local thermo-mechanical interactions that underlie transformation are examined using three-dimensional Digital Image Correlation (strain fields) and infrared imaging (thermal fields). We quantify the complex local interactions between released/absorbed latent heat and the extent of transformation, and explore the characteristics of the phase fronts and the evolution of martensitic volume fraction. We also quantify a strong strain memory in the martensite that forms in the wake of the phase transformation front. The accommodated strain in the martensite will remain constant during loading, even as the existing phase front propagates. There also exists a remarkable strain memory in the martensite that persists from cycle to cycle, indicating that the local elastic stress fields in the martensite are driven by a dislocation structure and martensitic nuclei that largely stabilize during the first loading cycle.