Coalescence Behavior of Voids during One-Dimensional Strain Spallation

The spallation behavior of the ductile metals is a process involving nucleation, growth and coalescence of voids, and the coalescence of voids is difficult to directly observe experimentally. In this paper, the finite element analysis method was used to study the coalescence behavior and competition mechanism among the voids in the process of the ductile metal spallation. Influences of the initial ligament distance, the void diameter, and the void location distribution on the void coalescence were discussed. Through the real-time statistics of the change in diameter during the growth of the voids, the starting time of the coalescence of the voids was quantitatively analyzed. Results show that when the initial ligament distance increases from 20 μm to 50 μm, the initial time of coalescence among the same voids increases continuously, and the accelerations of the diameter increase decreases from about 1.717 Gm/s² to 0.602 Gm/s². When the coalescence occurs between voids with different aperture ratios, small voids preferentially aggregate to big voids. Voids with an angle of 45° have the largest diameter growth acceleration about 3.179 Gm/s² in the growth stage, and the earliest coalescence occurs. For the coalescence among three voids, the calculation results show that the same voids with the same initial ligament distance aggregate and penetrate almost simultaneously, and the starting time of the coalescence between the voids increases with the increasing of the initial ligament distance. The aggregation of big voids to nearby small voids start later. Calculations in this paper reveal the mesoscopic physical process of void growth and coalescence, which is difficult to observe in spallation experiments, and have important reference value for the entire physical process and nature of the material spallation.