High-pressure Oxygen-free Copper Uninstall

Two experimental methods were used to investigate the isentropic release properties of OFHC copper at 116-148 GPa and 12,18.5GPa shock compression states. Off-Hugoniot data have been measured and discussed in this dissertation.Method I: Calibrated release measurement. High energy explosive was used to create a powerful and planar shock wave for accelerating flyer plate to high velocity, and high pressure was produced when flyer impacting with the sample. In the experiments, the impactor was Brass and target was OFHC copper. By measuring the shock wave velocities of HR2 steel, high-density glass, aluminium alloy (LY12/LF6), magnesium-aluminium alloy(MB2), polymethyl methacrylate and air, shock pressure and release isentrope of OFHC copper have been obtained. (Note: Hugoniot parameters C₀ λ of the materials used were known previously).Results indicate that with the approximation of γ₀ρ₀ - ργ Grtlneisen equation of state is usable to describe the release isentrope of OFHC copper in the present pressure range. In addition, the difference (W-2u) becomes greater with the increase of shock pressure, where W is the measured particle velocity at the final release state (1 atm) and 2u is computed from the mirror line of Hugoniot. Thermodynamic computation indicates that copper melt at the final release state (1 atm) in the shock pressure range from 148GPato 219GPa.Method 2: Lagrange wave speed measurement. Light gas gun was used to create shock pressure. Staged samples, cuneiform window with aluminium coat on the reflecting surface and VISAR(Velocity Interferometer System for Any Reflector) were employed in the experiments. Polymethyl methacrylate and OFHC copper were assembled as the impactor to impact staged samples. Due to the release by the rarefaction wave from the rear of copper impactor , and with the measurement of the velocity at the interface of sample and window, the release path was detected. Lagrange wave speed in the release process was computed from the measurement, and result shows a good agreement with the data in literature. Furthermore from the Lagrange wave speed, the stress-strain relationship in the release process was calculated using the impedance match solution. Comparison of the stress-strain with the fluid elastic-plastic model indicates that OFHC copper exhibits a clear work-harden behavior during the release. Numerical simulation also confirm this analysis that the fluid elastic-plastic model can approximately describe the shockcompression and release process of OFHC copper in the teens GPa range, but for precise description, especially in the initial release stage, more detail constitutive model is needed.