Dr. Rubén Rosales

We introduce (and present the results of) a new model for the solid to solid phase transitions that result from shock loading. This model introduces (essentially) a single free "viscosity" parameter, which we adjust to fit the experimental measurements. We are currently exploring the possibility that this process can be turned around, and be used as a way to measure the wave dissipation that occurs in materials at very high pressures (e.g. deep below the Earth surface). The solid-to-solid phase transitions that result from the shock loading of certain materials, such as the graphite-to-diamond transition, and the $\alpha$-$\epsilon$ transition in iron, have been the subject of a substantial theoretical and experimental literature. Recently a model for such transitions was introduced which, based on a Critical Stress condition (CS). The CS model, without the use of fitting parameters, accounts quantitatively for the main features of the existing observations in a number of systems. However, disagreements in some details between the predictions and experiment do exist. In this work we present a new version of the CS model, the viscous CS model (vCS), as well as a numerical method for its solution. The combination of the new model and solver results in a much improved overall modeling capability.

Trabajo en colaboracion con J. Weatherwax, D. Vaynblat, and O. Bruno