Catastrophic collisions: Laboratory impact experiments, hydrocode simulations, and the scaling problem

Details Catastrophic collisions: Laboratory impact experiments, hydrocode simulations, and the scaling problem Catastrophic collisions: Laboratory impact experiments, hydrocode simulations, and the scaling problem

Aug 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt.........4r&link_type=abstract

Ph.D. Thesis Arizona Univ., Tucson.

Astronomy and Astrophysics

Astrophysics

5

Collisions, Fragmentation, Impact Tests, Mathematical Models, Scaling Laws, Collision Parameters, Ejecta, Projectiles, Size Distribution

Scientific paper

The catastrophic fragmentation of finite targets is examined both in the laboratory and using a numerical hydrocode. The objective of the empirical study was to gain some insight into the collisional process, specifically, how impact conditions affect collisional outcome. The hydrocode allows us to investigate the fragmentation of large bodies, and to determine how target size influences the impact event. Nearly 150 experiments were performed. Impact velocities ranged from 50-5700 m/s; target material/structure as well as projectile type were varied, and the effect on fragment mass and velocity distributions was documented. Several factors were found to influence the result of a two-body collision: specific energy, momentum, target strength and internal structure, and projectile type. Velocity data showed that average fragment speeds are on the order of 10's of meters per second. Energy partitioned into ejecta kinetic energy is about 1.2 percent for high velocity collisions and more than 10 percent for low velocity impacts. Our two-dimensional hydrocode successfully reproduced fragment size distributions and mean ejecta velocities from laboratory impact experiments using basalt, and weak and strong mortar as target materials. It also reproduced size distributions from explosive disruption and applied external pressure experiments which used targets composed of weak mortar and weak basalt grout. Using this hydrocode, how target size influences the amount of energy (Q*) required for fracture is analyzed. Q* was found to decrease with increasing target size in the strength regime; in the gravity regime where incoming stress waves must overcome both material bonds and self-compression, Q* increased with increasing target size. The Q* dependence on target size was found to be much stronger than predicted from scaling law theory.

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