Abstract
In our work, graded density impactors fabricated from 8 to 40 layers, are specifically designed to generate desired strain rates (on the order of 105~106 s-1) and thermodynamic path(shock loading-ramp loading-release). And experiments on phase transition and strength for metals (bismuth, LY12 Al) have been performed with light gas gun to peak pressure between 30 GPa and 50 GPa. Particle velocity at sample/window interface in these experiments are simultaneously traced by a distance interferometer system for any reflector, and a wave profile analysis is employed to explore the solidification transition and strength behaviour along elevated isentrope.
Highlights
Phase transition and strength of materials under extreme conditions is fundamentally interesting in condensed matter physics, Geophysics, some engineer applications and so on [1, 2]
In order to define the additional information of materials beyond the principal Hugoniot and isentrope, a controlled-path loading method based on graded density impactor (GDI) are employed here
To cause bismuth melting with the initial shock loading generated by the first layer of graded density impactor and solidification with the subsequent ramp loading generated by the other layers of graded density impactor, impedance for every layer was designed with MLEP (Multi-Material Lagrangian Elastic-Plastic) code and the complete equation of state built by Johnson[4]
Summary
Phase transition and strength of materials under extreme conditions is fundamentally interesting in condensed matter physics, Geophysics, some engineer applications and so on [1, 2]. It is important to describe the characteristics of physical processes and provide the thermodynamic properties of kinetics in material for dynamic compression. Observations of phase transition and strength in dynamic compression experiments are frequently made via satisfactory techniques, gas gun, explosive, powerful pulse facilities and so on. Despite kinds of experimental and theoretic methods have been applied to obtain the basic properties of materials, it seems that the existing experimental and theoretical describing characteristics for materials at a wide pressure-temperature-strain rate range are still surprisingly puzzled and give a great variety for model verification, such as the large unexplored region of phase space among Hugoniot, isentrope and static experiments. In order to define the additional information of materials beyond the principal Hugoniot and isentrope, a controlled-path loading method based on graded density impactor (GDI) are employed here. The impactor here we used typically have between 8 to 40 layers of 200 m ~1000 m thick at the diameter from 20 mm to 50 mm
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