Study on the Phenomena of the Mass Ejection from the Free Surface of Aluminum at Different Dynamic Loading Rates

The relation between the mass-ejection and the dynamic loading rate has been investigated with emphasis on the micro-jetting mechanism. Artificial wedged-grooves were made as the geometrical defects on the free surface, ramp-wave generator technique was employed to control the rate of dynamic loading, and quartz transducer was used to measure the ejected mass quantitatively. It is found that both the ejected mass and the maximum ejected velocity decrease with decreasing the loading rate if the wedged-groove size and the peak stress are fixed, and there is an indication that the ejected mass decreases with decreasing the geometrical defect volume if the dynamic loading condition, including peak stress and loading rate, is fixed. Using HELP code, we have carried out two-dimensional numerical simulation for the experiments aimed at micro-jetting mechanism study. The numerical results are in good agreement with the measured ones.