Its geometry characteristics could be about described by depth and radius. Thinking of the tiny thickness in the target in this work, penetration depth might be just believed to be equal to the thickness of the target. The emphasis here is put around the definition of your radius of the crater although it is actually tough to accurately describe the real radius of a unregular crater surface. Here we propose a procedure to receive the equivalent radius: Step 1: define many connected atoms inside the cutoff distance (rc , here rc is selected equal to nearest neighbor distance, i.e., 0.286 nm) as a cluster, then the atoms inside the bullet and in the target within rc is usually distinguished from the influence region, which is believed as crater surface; Step two: the highest 1000 atoms along the effect direction (z-axis) are chosen as reference points, along with the geometry center of those atoms is often set as the center of a circle; Step 3: a series of gradually growing circles with a step length of 0.3 nm (an empirical parameter) are generated, after a circular ring consists of more than 50 atoms (an empirical parameter), the present radius is often treated as the equivalent radius on the crater. Primarily based around the above process, the radius of the crater Rc and corresponding crater surface at 50 ps are presented in Figure 9. No obvious crater is made in the case of 1 km/s, exactly where the bullet mixes using the target surface ultimately. For the case of 2 km/s, the target is just not penetrated totally, although types a clear crater. With increasing incident velocity, the comprehensive penetration is discovered. The radius shows Nitrocefin site because the bullet has not completely penetrated the target at the case of two km/s, and hence the incident kinetic energy mainly contributes to plastic deformation or partial melt in the influence region, which results in bigger bumps of crater. As incident velocity increases to 3 km/s, its kinetic energy is consumed by penetration along impact path as well as the transverse expansion is somewhat small. The crater surface could be seen in Figure 9b,c, indicating the reasonability of our proposed procedure.Figure 9. Crater surface and cross-section of sample at 50 ps under up of (a) 1 km/s, (b) 2 km/s, (c) three km/s, (d) 4 km/s and (e) 5 km/s at the case of = six; (f) Radius of crater Rc below distinctive up and draw ratio of bullet. Atoms are colored by matter distribution.Fragmentation right after penetration is of concern since it can assist have an understanding of the material shock response. This kind of phenomena may be often observed inside the high-Nanomaterials 2021, 11,ten ofspeed velocity impact field, like micro-ejecta [44], which occurs when the plane shock wave propagates by way of a material-vacuum interface and a mass of tiny fragmentations are emitted in the material surface. The characteristic of fragmentation is related to shock intensity and surface geometry. Another case is impact-induced fragmentation, the higher nearby temperature results in solid-liquid phase transformation along with the intrinsic velocity gradient causes final separation and develops to fragmentation [10]. Spatial distribution and geometry of fragmentation has presented in Figure ten for the case of three and 5 km/s. When incident vel.
