Sound Velocity Measurements for Shock-Compressed LY12 Aluminum Alloy by Using VISAR Technique

The experimental method to measure the high-pressure sound velocity of shock-compressed LY12 aluminum alloy by VISAR technique is described. Symmetrical plate impact experiments were conducted with the two-stage light-gas gun and at peak stresses about 20, 32, 55 and 71 GPa, respectively. In each shot, a VISAR system with three different fringe-constants was used to measure the particle-velocity profile at the interface between the test sample and the single crystal LiF window. The particle velocity histories deduced from three fringe numbers in each shot coincided with each other excellently. The high signal to noise experimental records also demonstrated that the joint and the treatment of the interface between the sample and the window were very successful. Beside the longitudinal sound velocities at the initial shock stresses, also produced were the sound velocity histories along the release paths, from which the bulk sound velocities at the initial shock stresses were determined by extrapolating the plastic portion of the sound velocity history. These results were consistent with the calculations obtained through Mie-Grneisen equation of state under the assumption that =constant.