Confined and Unconfined Alumina Bar-on-Bar Impact Experiments for Improved Material Models

Unconfined and confined (in steel sleeves) alumina bar-on-bar (1-d stress) experiments are performed to extend uniaxial strain deformation states imposed in flyer plate impact experiments. A number of investigators engaged in modeling the bar-on-bar experiments have varying degrees of success in correctly simulating the measured in-situ axial stress or free surface velocity histories. Axial velocity of the far end of the unconfined and confined AD998 bars was measured using a VISAR in a series of unconfined and confined alumina bar-on-bar impact experiments at impact speeds from 100 m/s to 500 m/s. A high speed camera was used to photograph impactor and target bars during impact. Velocity history data from an unconfined bar-on-bar impact at 100 m/s show the material response as elastic. Velocity history data on unconfined bars at higher impact velocities of 200 m/s and 300 m/s suggest an inelastic material response. Velocity histories from four shots at impact velocities of 203 m/s, (two at) 293 m/s, and 511 m/s on confined alumina bars exhibit inelastic material response. Axial velocity history data on confined and unconfined bars clearly suggest that confinement marginally enhances the compressive strength of alumina in the 1-d impact configuration.