2 research outputs found
Shock and Release Temperatures in Molybdenum
Shock and release temperatures in Mo were calculated, taking account of
heating from plastic flow predicted using the Steinberg-Guinan model. Plastic
flow was calculated self-consistently with the shock jump conditions: this is
necessary for a rigorous estimate of the locus of shock states accessible. The
temperatures obtained were significantly higher than predicted assuming ideal
hydrodynamic loading. The temperatures were compared with surface emission
spectrometry measurements for Mo shocked to around 60GPa and then released into
vacuum or into a LiF window. Shock loading was induced by the impact of a
planar projectile, accelerated by high explosive or in a gas gun. Surface
velocimetry showed an elastic wave at the start of release from the shocked
state; the amplitude of the elastic wave matched the prediction to around 10%,
indicating that the predicted flow stress in the shocked state was reasonable.
The measured temperatures were consistent with the simulations, indicating that
the fraction of plastic work converted to heat was in the range 70-100% for
these loading conditions
Explanation for Anomalous Shock Temperatures Measured by Neutron Resonance Spectroscopy
Neutron resonance spectrometry (NRS) has been used to measure the temperature
inside Mo samples during shock loading. The temperatures obtained were
significantly higher than predicted assuming ideal hydrodynamic loading. The
effect of plastic flow and non-ideal projectile behavior were assessed. Plastic
flow was calculated self-consistently with the shock jump conditions: this is
necessary for a rigorous estimate of the locus of shock states accessible.
Plastic flow was estimated to contribute a temperature rise of 53K compared
with hydrodynamic flow. Simulations were performed of the operation of the
explosively-driven projectile system used to induce the shock in the Mo sample.
The simulations predicted that the projectile was significantly curved on
impact, and still accelerating. The resulting spatial variations in load,
including radial components of velocity, were predicted to increase the
apparent temperature that would be deduced from the width of the neutron
resonance by 160K. These corrections are sufficient to reconcile the apparent
temperatures deduced using NRS with the accepted properties of Mo, in
particular its equation of state.Comment: near-final version, waiting for final consent from an autho