No abstract

We conducted shock wave experiments on iron carbide Fe3C up to a Hugoniot pressure of 245 GPa. The correlation between the particle velocity (up) and shock wave velocity (us) can be fitted into a linear relationship, us = 4.627(±0.073) + 1.614(±0.028) up. The density‐pressure relationship is consistent with a single‐phase compression without decomposition. The inference is further supported by the comparison of the observed Hugoniot density with the calculated Hugoniot curves of possible decomposition products. The new Hugoniot data combined with the reported 300‐K isothermal compression data yielded a Grüneisen parameter of γ = 2.23(7.982/ρ)0.29. The thermal equation of state of Fe3C is further used to calculate the density profile of Fe3C along the Earth's adiabatic geotherm. The density of Fe3C was found to be too low (by ~5%) to match the observed density in the Earth's inner core, and Fe3C is unlikely a dominant component of the inner core.

No abstract

We investigate spallation of polycarbonate under plate impact loading. The Hugoniot equation of state up to ∼1.3GPa (corresponding to a peak particle velocity ∼380m/s) is obtained, and spall strength and corresponding strain rates are determined at peak shock stresses up to ∼2.4GPa (corresponding to a peak particle velocity ∼600m/s). With increasing shock strength, the transition from strain-hardening to softening at shock states occurs as a result of shock heating; spall strength remains approximately constant, followed by a rapid drop upon strain softening. Release/tensile melting occurs at higher impact velocities. Three-dimensional void configurations of the postmortem samples are obtained via X-ray computerized tomography. The small voids are flat and curved for low-speed shots but become ellipsoidal for high-speed shots, and their coalescence leads to different shapes likely due to different damage mechanisms.