VISAR Applications

By applying the Hugoniot equations in increments using VISAR-measured inputs, VISARs are used to determine entire loading and unloading paths of materials on the pressure-volume plane. The loading/unloading paths indicate material behavior at the high pressures and strain rates of shockwaves, such as dynamic yield strengths, polymorphic phase transitions, shock-induced melting, elastic constants at high pressures, etc. Shear wave effects and spall strengths are also determined by VISARs. By measuring such material equation-of-state behavior, VISARs enable computer specialists to model material behavior for computer solutions of shockwave problems which are not amenable to laboratory experiments, such as an asteroid impact on the earth, for example.

In addition to material equation-of-state measurements, VISARs have been used to measure in-bore accelerations of projectiles as they are launched, a feat which requires a very large depth-of-field but which has nevertheless been done many times. A related VISAR application, but on a micro scale, is the measurement of the velocity histories of thin “flying foils” undergoing acceleration to very high velocities due to the sudden vaporization of a driving substrate. When used as impactors, flying foils produce tremendous shock pressures in specimens, if only for very short times.

The use of flying foil micro-impactors in shockwave research opens the door to less expensive equation-of-state measurements over a wider range of peak shock pressures. However, because such measurements require scaling conventional EOS experiments to micro dimensions, the time scales associated with the experiments are also much smaller, and the 1 to 2 ns time resolutions of conventional VISAR measurements may no longer be sufficient. This problem has been addressed by the development of electronic streak camera methods of recording VISAR data, thus improving the time resolution by at least an order of magnitude.

VALYN VIP, Inc.

301 Solano Drive S.E.

Albuquerque, NM 87108 USA
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