Quantification of ejecta from shock loaded metal surfaces

Mass ejecta from shock-loaded surfaces with finite disturbances were calculated for different elastic-perfectly plastic metals with the Mie-Gruneisen equation of state and with varying disturbance amplitudes (h ₀), wave numbers (k), and geometric shapes. In our simulations, the disturbance extends periodically in the transverse direction and the perturbed free surface is subjected to a single normal shock. The total ejected mass was found to depend on kh ₀ (the product of the wave number and the initial amplitude of the disturbance) and (P/Y ₀) ^1/2 (where P is the shock pressure and Y ₀ is the metal yield stress). For specific shapes of the disturbance, there seems to be a unique relation between the ratio of the total ejected mass and the mass removed by the disturbance. In addition, we found the cutoff condition (kh ₀) _c below which no ejecta can be produced. Generally, the amount of mass ejected increases with kh ₀. However, a striking feature near the ejecta cutoff is the existence of a finite region (kh ₀) _c ≤ kh ₀ ≤ (kh ₀) _T where the ejected mass decreases with kh ₀. For all the metals and shock conditions we have considered, the ejecta production increases monotonically for the range of kh ₀ values we have computed above (kh ₀) _T This effect and the global behavior of mass ejecta will be discussed.