Stability and fragmentation of ejecta in hypervelocity impact
The present study offers an explanation for the behavior of debris ejected from the back surface of a target impacted by a high velocity projectile. Such debris is observed to expand as a ductile bubble and then fragment through surface instabilities when a critical expansion is achieved. An approximate model of hypervelocity impact developed by Swift et al. (1983), which assumes as expanding spherical shell of matter for the debris cloud, is introduced to motivate the analysis. We then solve for the spherically symmetric motion of, and pressures within, a spherical shell of ideal incompressible fluid subjected to inner and outer pressure boundary conditions. The solution is specialized to the freely expanding spherical shell (no pressure on the inner and outer boundaries). We then specialize further to the thin freely expanding spherical shell. Material response is extended to ideal incompressible plasticity and solutions for the radial and circumferential stress distributions are determined. Experimental results from high velocity impact tests of lead and uranium projectiles on lead and uranium targets using multiple flash radiography diagnostics (Grady et al., 1985) are compared with the theory. Although data are limited and the material and kinematic parameters somewhat uncertain, the comparison supports the physics and analysis put forth in this study. Similar comparisons are made between the analysis and computational simulations of the lead and uranium impact experiments. Again the results support the proposed mechanisms of initial inertial stability followed by plasticity-induced onset of instability and fragmentation. 13 refs., 12 figs.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- DOE/DP
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5296444
- Report Number(s):
- SAND-89-0507C; CONF-891214-14; ON: DE90004087
- Resource Relation:
- Journal Volume: 10; Journal Issue: 1-4; Conference: Hypervelocity impact symposium, San Antonio, TX (USA), 12-14 Dec 1989
- Country of Publication:
- United States
- Language:
- English
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