High-pressure equation of state of soda-lime glass: shock experiments and molecular simulation
Abstract
Use of soda-lime glass as a component of improved penetration-resistant structures and coatings may depend on knowledge of its stress-strain rate response to pressures above 100 GPa.An integrated family of diagnostics and plate impact experiments can define the thermodynamic state of material at discrete high-P, high-T states. However, a comprehensive equation of state for interpolation and extrapolation also requires a functional form and fitting method. Molecular dynamics simulations, although not completely accurate, can guide the design of such functions,which can then in turn be fitted to a set of experiments. We will combine new shock velocity, temperature and sound-speed measurements on soda-lime glass with development and application of a simulation-guided EOS that is more accurate than current models, which dependon the poorly-motivated (for amorphous materials) Mie-Grneisen approximation.The project work is laid out over two years, expected to include about ten experiments on our two-stage light gas gun. The experiments will emphasize conditions above 100 GPa, extending upwards progressively to the limits of our launching capability (7.6 km s1 with a Ta flyer yields an estimated pressure in soda lime glass of 163 GPa). We will pair thick-flyer shots with pyrometer and PDV diagnostics that yield shock velocity, shock temperature, and free-surface release velocity with thin flyer-shots with pyrometer diagnostic that yieldsound speed of initial release and a duplicate measure of shock temperature. Furthermore, we will deploy a ceramic-coated pickup coil around the target in order to measure electromagnetic signals generated by the shocked material and the high-temperature plume generated by its release. Reflectivity measured by returned PDV signal strength can be converted to as estimate of electrical conductivity and carrier density of the shocked material in its compressed state, whereas induced currents in the coil upon expansion of the release plume will characterize the extent of ionization in the release vapor or plasma.The new dynamic compression data will be assimilated in two ways to calibrate the new post-Mie-Grneisen equation of state. First, the functional form abstracted from the model will be empirically fit to the new and critically reviewed literature data. Second, the parameters of the force field used in the molecular dynamics simulations will be tuned to achieve an optimal match to the experimental data and then further simulations with the new force field will be used to compute a full set of computed state points at all relevant pressure and temperature conditions, and finally the equation of state will be fit to the fullset of simulations.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 17, 2020
- Source ID
- N000142012603
Entities
People
- Paul D. Asimow
Organizations
- California Institute of Technology
- Office of Naval Research
- United States Navy