AEROSPACE ENGINEERING

Abstract

Magnesium (Mg) has received significant consideration as a potential lightweight structural material for automotive, aerospace, railway, and defense applications. Despite the large amount of attention directed towards understanding the mechanical behavior of magnesium, its implementation into industry has lagged. Magnesium’s low-symmetry hexagonal-closed-packed (HCP) structure restricts dislocation motion to specific planes and a select few twinning modes. The activation of this limited set of mechanisms results in a highly complex mechanical behavior. Experimental observations have captured deformation sensitivities to strain rate, temperature, loading orientation, and alloy elements. In many intended applications, structural materials are subjected to high strain rate loading through impact or blast events. When materials are deformed at these high strain rates, local temperature fields can influence the mechanical response through thermal softening further complicating deformation behavior. In this work, a series of experimental techniques are used to address the high strain-rate coupled thermo-mechanical response of magnesium alloy AZ31B. Using a split-Hopkinson (or Kolsky) compression bar and high-speed infra-red (IR) thermography, the temperature evolution of deforming specimens is tracked over the duration of loading (i.e., a few hundred microseconds). Numerical simulations are used to support the experimental effort, providing predictions of deformation mechanisms for a range of loading orientations. Experimental and simulation results are linked to produce the first comprehensive study of magnesium under shear-dominant loading conditions, the first mechanistic approach to the conversion of plastic work to heat (β) in magnesium, as well as provide critical data for modeling efforts directed toward the design of future light-weight structural materials.

Speaker

Dr. Owen Kingstedt

Assistant Professor in the Department of Mechanical Engineering at the University of Utah. Owen earned his B.S. in Mechanical Engineering from Michigan Technological University in 2009, followed by his M.S. and Ph.D. in Aerospace Engineering from the University of Illinois at Urbana-Champaign, in 2009 and 2014, respectively. Prior to joining the U of U in 2016, he was a post-doctoral scholar in the Division of Engineering and Applied Sciences at Caltech. Owen’s current research interests leverage experimental mechanics to investigate deformation processes at high-strain-rates, and at reduced length scales in metallic material systems. He was the recipient of the 2017 M. Hetényi Award for best research paper published in Experimental Mechanics awarded by the Society for Experimental Mechanics.