Effects of Solid-Solid Phase Changes On Impact Mechanics
Abstract
Stress-wave profiles in vitreous GeO2 induced by planar and spherical projectile impact were measured using piezoresistance gauges in the 4 to 18 GPa shock pressure range. Comparison of the shock data for fused SiO2 with those for vitreous GeO2 demonstrates that range of transformation to a denser, presumably 6-fold coordinated structure in both media are similar. The Hugoniots of GeO2 and SiO2, both initially vitreous, are found to be virtually coincident if pressure in SiO2 is calculated by multiplying the GeO2 pressure by the ratio of the initial densities of vitreous GeO2 to fused SiO2. The volume axes are translated with the specific volumes upon onset and completion of the phase change are aligned. This result, as well as the usual crystal-chemical structural arguments, provides the basis for considering vitreous GeO2 as an analogous material to fused SiO2. Our spherical projectile impact results demonstrate: (1) The supported elastic shock in fused SiO2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. A supported elastic precursor in vitreous GeO2 decays faster with radius than a linear elastic wave; (2) In GeO2 (vitreous) unsupported shock waves decay with peak pressure in phase transition range (4-15 GPa) with propagation radius (r) as infinity r(exp -3.35), close to the prediction of Chen 1999.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1999
- Accession Number
- ADA369953
Entities
People
- C. Liu
- J. K. Knowles
- N. S. Brar
- T. J. Ahrens
Organizations
- California Institute of Technology