- Journal
- INTERNATIONAL JOURNAL OF IMPACT ENGINEERING
- Année
- 2020
- Volume
- 135
- Article
- 103388
- Mois
- JAN
- DOI
- 10.1016/j.ijimpeng.2019.103388
Abstract
Impact tests were performed from 4 to 5.77 km/s of 3.0-cm-diameter aluminum spheres impacting 2024-T351 aluminum targets. This data was compared to previously published data for smaller scale impactors (0.1588 cm to 1.27 cm). It was seen that there are no size-scaling effects for the crater depth. The slight size-scaling effect in the crater diameter directly correlated with the nonlinear size-scaling effect in the ejecta mass. There is a qualitative change in the ejecta mass somewhere in the vicinity of 1.27-cm-diameter impactors, in that impactors with diameters less than this have ejecta mass showing a strong diameter dependence while for impactors larger than this diameter there is little size dependence and the ejecta mass scales only with impact velocity squared. A strain-rate-dependent failure model is developed based on a mechanical model of shear-band slip over a characteristic finite length. The underlying mechanical model is nonlocal, but, through certain assumptions, leads to a failure strain expression that depends on the equivalent plastic strain rate to the 2/3rds power. This failure model was implemented in the hydrocode CTH and showed excellent agreement with experimental ejecta mass data. It can explain the origin of the size scale dependence in the ejecta mass as well as the observed saturation. The saturation in the ejecta mass is due to the static failure properties of the material. The new data also shows that the 0.45 power dependence on the projectile diameter for the momentum enhancement 13 continues up through the 3.0-cm-diameter sphere impactors. This size scaling behavior of the momentum enhancement is surprising in that there is not a change in the momentum enhancement scaling behavior even though there is a qualitative and quantitative change in the ejecta mass scaling behavior. The new damage model does not predict the experimentally-observed momentum enhancement size-scaling behavior, even though it does predict the ejecta mass behavior.