VAPORIZATION WAVE TRANSITIONS
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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A vaporization wave analogous to the unsteady simple wave in an expanding gas is proposed to account for phenomena observed in the evaporation of superheated metals. The vaporizing model is visualized on thermodynamic grounds as carrying the liquid metal through a continuous succession of states either on or near the liquidus line in the two-phase region. On this line, the adiabatic sound speed for wet vapor will limit the rate of propagation of the vaporization front into the liquid. Experimental data for wire explosions of Al, Ag, Cu, Au, Pn, and Hg frozen are analyzed for wave speeds. While the influence of thermal expansion of the liquid can be accounted for theoretically, insufficient thermal data are available for the metals to permit correction of the wave speeds for this effect. The experimentally derived wave speeds are compared with theoretical values of the adiabatic sound speed in the wet vapor obtained from a modified van der Waals equation of state. At low velocities, the agreement is satisfactory but higher values deviate considerably from theory.
- Physical Chemistry
- Properties of Metals and Alloys
- Ammunition and Explosives