Studying Hypervelocity Impact Phenomena


File image: Thiot Ingenierie Shock Physics Laboratory.
Using a Specialised Imaging SIM8 ultra fast framing camera researchers at the Thiot Ingenierie Shock Physics Laboratory have been able study high velocity impacts of aluminium spheres against an aluminum target at velocities in excess of 4000 m/s.
Interest in hypervelocity has traditionally been driven by the military community but is increasingly of interest to the space / aerospace industry for areas of research such as enhancing the survivability of aircraft to in-flight explosions and in protecting valuable space satellites from damage from stellar debris.
To model a hypervelocity impact – Thiot Ingeniere undertook to accurately record a 3 mm ball with a velocity in excess of 4000m/s, just before, at and after impact. To allow the necessary accurate measurements of the projectiles just before impact it was determined that exposure times of 20 nanoseconds or less were required to reduce motion blur to less than the size of a pixel. Consequential to such short exposure times was also the problem of producing adequate light levels to fully define the edges and the corners of the projectile.
Data shown in Specialised Imaging Application Note 9 was produced by Thiot Ingeniere researchers using a SIM8 Ultra fast framing camera programmed for 200,000 frames per second with 20 ns exposures. The 3mm projectile was fired from a fixed 2-stage light gas gun. The event was backlit using a SI-AD500 flash lamp to provide adequate illumination for the complete event.
The high resolution images from the SIM8 clearly show the cloud of ejected material thrown backwards on impact and also demonstrates that even though the projectile disintegrates on impact, the fragments maintain the original projectile shape ahead of the main fragment cloud. The test also showed that the remaining fragments do not have enough energy to penetrate a second aluminum plate when two thin layers were used instead of one thicker layer.
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