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Uniaxial strain, reverse-ballistic impact experiments were performed on wrought 17-4 PH H1025 stainless steel, and the resulting Hugoniot was determined to a peak stress of 25 GPa through impedance matching to known standard materials. The measured Hugoniot showed evidence of a solid–solid phase transition, consistent with other martensitic Fe-alloys. The phase transition stress in the wrought 17-4 PH H1025 stainless steel was measured in a uniaxial strain, forward-ballistic impact experiment to be 11.4 GPa. Linear fits to the Hugoniot for both the low and high pressure phase are presented with corresponding uncertainty. The low pressure martensitic phase exhibits a shock velocity thatmore » is weakly dependent on the particle velocity, consistent with other martensitic Fe-alloys.« less

The high-pressure dynamic response of titanium dioxide (TiO₂) is not only of interest because of its numerous industrial applications but also because of its structural similarities to silica (SiO₂). We performed plate impact experiments in a two-stage light gas gun, at peak stresses from 64 to 221 GPa to determine the TiO₂ response along the Hugoniot. The lower stress experiment at 64 GPa shows an elastic behavior followed by an elastic–plastic transition, whereas the high stress experiments above 64 GPa show a single wave structure. Previous shock studies have shown the presence of high-pressure phases (HPP) I (26 GPa) andmore » HPP II (100 GPa); however, our data suggest that the HPP I phase is stable up to 150 GPa. Using a combination of data from our current study and our previous Z-data, we determine that TiO₂ likely melts on the Hugoniot at 157 GPa. Furthermore, our data confirm that TiO₂ is not highly incompressible as shown by a previous study.« less

Here we describe how the capability for statically pre-compressing fluid targets for Hugoniot measurements utilizing gas gun driven flyer plates has been developed. Pre-compression expands the capability for initial condition control, allowing access to thermodynamic states off the principal Hugoniot. Absolute Hugoniot measurements with an uncertainty less than 3% on density and pressure were obtained on statically pre-compressed fluid helium utilizing a two stage light gas gun. Helium is highly compressible; the locus of shock states resulting from dynamic loading of an initially compressed sample at room temperature is significantly denser than the cryogenic fluid Hugoniot even for relatively modestmore » (0.27–0.38 GPa) initial pressures. Lastly, the dynamic response of pre-compressed helium in the initial density range of 0.21–0.25 g/cm3 at ambient temperature may be described by a linear shock velocity (us) and particle velocity (u_p) relationship: u_s = C₀ + su_p, with C₀ = 1.44 ± 0.14 km/s and s = 1.344 ± 0.025.« less