Dr. Marc Meyers

Abstract:

 The solid core of the earth is an iron sphere with a diameter of ~ 2,500 km, at temperature 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 pressures and temperatures 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 mechanisms of plastic deformation and constitutive relationships under laser compression and at the center of the solid core are evaluated analytically and computationally, enabling tentative conclusions. Nabarro- Herring and Weertman creep mechanisms are compared with dislocation glide and PTW predictions. Support: CMEC, NIF, LLNL