Dr. Marc Meyers
Seminar Information
Zoom link https://ucsd.zoom.us/j/8425066501?omn=97140479247
The solid core of the Earth is an iron sphere with a diameter of ~ 2,500 km, at atemperature of ~5,000K and pressure of ~350 GPa. This temperature far exceeds iron's melting point at ambient pressure but it is solid because of the Clausius Clapeyron equation. The mechanical properties and microstructure of the solid core are virtually unknown because of the impossibility of reaching it. Experiments at the National Ignition Facility of Lawrence Livermore National Laboratory on iron using high-powered pulsed lasers have reproduced the pressure and temperature in the range of the Earth core, albeit at a strain rate that is many orders of magnitude higher (10 6 s -1 ). This is enabled by the observation of the growth rate of Rayleigh- Taylor instabilities on the surface of iron, which are dependent on the strength. The
calculated strength are in ~10-20 GPa range; polycrystalline and monocrystalline iron and Fe-30%Ni were subjected to high amplitude ramped laser-generated pulses. [001] orientation crystal were found to be slightly stronger than the [111]
orientation, in contrast with quasistatic results. The predictions of the Preston-Tonks- Wallace were compared with measured strengths and were found to be lower. This constitutive equation does not have a grain-size parameter. Molecular dynamics calculations and observations indicate that the grain size is on the order of 20 -40 nm. A correction in the equation leads to much closer results. A relationship between strain rate and grain size is applied, based on the Derby-Ashby analysis. The grain size is found to increase to the meter range in the solid core of the Earth. The mechanisms of plastic deformation and constitutive relationships under laser compression and at the center of the solid core are evaluated analytically and computationally Nabarro- Herring, Coble, Harper-Dorn, and Weertman creep mechanisms are compared with dislocation glide and predictions from the Preston- Tonks-Wallace constitutive equation.
This research was supported by CMEC and is being conducted in collaboration with
LLNL NIF researchers.
Marc André Meyers is a graduate (Mechanical Engineering) of the Federal University of Minas Gerais, and earned his doctorate at the University of Denver. He held university positions at the Military Institute of Engineering (Rio de Janeiro), South Dakota School of Mines and Technology, and New Mexico Institute of Mining and Technology, prior to joining the University of California, San Diego where he is Distinguished Professor. Dr. Meyers’ effort at unifying dispersed activities through the fundamental physics and chemistry principles relevant to high strain rate deformation have given rise to the field of dynamic behavior of materials. He has also contributed to nanocrystalline materials, synthesis and processing, and
mechanical properties in general. In recent years he has turned his curiosity and effort to biological, biomedical, and bioinspired materials and, in particular, how they derive their mechanical properties in terms of their hierarchical structure/architecture. His work in this area, whether associated with abalone shells, toucan beaks, fish scales or teeth, among many other biological materials, has been an inspiration and has generated worldwide interest in terms of the complex structure/property relationships that they portray and the complicated nano/micro-mechanisms that underlie their mechanical performance. His work, is published in over 500 articles (google scholar HI: 120) and is widely cited (65,000 citations). In the educational area, he advised 56 doctoral dissertations and authored or co-authored four textbooks translated into Chinese and Portuguese. He organized four summer schools in mechanics and materials with leading scholars and students recruited globally.
Dr. Meyers is a Fellow of TMS, APS, ASM International and the Brazilian Academy of Sciences. He has received numerous awards, including the APS George Duvall Shock Compression Award, the European Dymat Society's Rinehart Award, the TMS Mehl Award, the Morris Cohen Award, the Weertman Education Award, the German
Materials Society (DGM) Heyn Medal, the ABM Colpaert Award, and the Chinese Institute for Metal Research Lee Hsun Award. He is also recipient of the German Humbolt Senior Scientist Award, the Luxembourg Institut Grand Ducal's Grand Prix en Sciences, the Acta Materialia Hollomon Award and Gold Medal. He also writes fiction and retraced the 1914 Roosevelt Rondon expedition to the Amazon