Elastic-Plastic Properties of Iron

Abstract

Smooth bore cannons were used to produce plane collisions between plates of Armco iron. Projectile velocities ranged from 60 to 400 m/sec. Time resolved measurements of the target free-surface velocities indicate that the dynamic yielding process is time dependent on a submicrosecond time scale. The shape of the Hugoniot curve in the pressure-volume plane up to 80 kbars shows that true hydrostatic equilibrium has not yet been established behind the elastic wave. On the other hand the substantially constant free-surface velocities behind the plastic front indicate that the material cannot be far from equilibrium after a short time. Some data on the rarefaction sound speed in the high pressure region are interpreted to imply a value very near 6 km/sec.