S4E11

Abstract

The rapid drive towards faster, efficient, and smarter technology has pushed our knowledge of fundamental material behavior to its limits. Consequently, the response of materials to high-amplitude external stimuli at short time scales (microseconds and lower) have exciting future opportunities in fundamental research. Addressing the origins of material behavior at these extreme conditions involves a mechanism-based approach, wherein we probe physical mechanisms at short length and time scales simultaneously. During this webinar, we will discuss this problem primarily in the context of the strength of magnesium at high strain rates. With a density of 1.74 g/cc (two-thirds that of aluminium), magnesium has been sought after as the next major industrial structural metal. Using high-speed microscopy data, we will observe the kinetic evolution of specific volume defects named ‘deformation twins’ – ubiquitous across multiple material systems – during plastic deformation under high-strain-rate loading of magnesium single crystals. The effect of loading rates on these defect kinetics and subsequent material strength will be evident. We will then briefly discuss a generalized approach that combines high-resolution, multi-scale experiments with theory to better understand short-time-scale multi-physical phenomena in materials – followed by some exciting open questions in the area of ferroic material systems and energy conversion. These material systems exploit a strong coupling between thermal, electrical, and mechanical fields to exhibit fascinating multi-functional behavior – albeit, with a rate-dependence very similar to our previous thermo-mechanical problem. Finally, I will present a personalized general perspective on the future of mechanics research – specifically the role of experimental mechanics – towards understanding material behavior at the extremes.

Introduction of speaker

Vignesh completed his undergraduate degree in production engineering from the National Institute of Technology, Tiruchirappalli, India. In December 2018, he completed his doctoral degree in mechanical engineering from the Johns Hopkins University in Baltimore, U.S.A., specializing in the mechanics of materials. Vignesh’s doctoral research, under the mentorship of Prof. K. T. Ramesh, focused primarily on understanding plastic deformation mechanisms in magnesium and their effects on material strength under high strain rate impact. He then moved to the ETH Zürich for his post-doctoral research with Prof. Dennis Kochmann, where he studies the electro-mechanical behavior of ferroelectric materials and develops experimental tools to characterize the static and dynamic behavior of 3D-printed architected metamaterials. Vignesh is primarily an experimentalist, who continues to seek the unification of experiment and theory in our understanding of multi-scale material phenomena at the extremes. When not in the laboratory, you might find him watching south-Indian comedy, or injuring himself on the badminton court and more recently in the mountains.