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 Vol. 9  No 5 October  2001            

Ballistic Evaluation Technique

Streak Photography augmented with Fibre Optics Cable for Detonics & Shock Dynamics

Optical techniques using fast streak cameras are well established methods for studying shock wave and detonation phenomena. The use of fibre optics cable not only provides multidimensional view to a streak camera but also accesses the information either hidden inside the test specimen or obstructed by explosion debris. Competing with the latest advances in the diagnostic techniques, fibre optic-based experimental techniques have been developed forthe studies of detonics and shock propagation.

Measurement of Detonation Velocity

Streak camera record of detonation wave arrival at 12 pin location each 100 mm apartIn velocity measurement mode, a number of optical pins are fixed at the outer surface of a cylindrical explosive to record the arrival of detonation wave at the pin locations. The other ends of the optical fibre cables are arranged in a straight array for viewing by a high-speed rotating mirror streak camera Distances of the optical pins  from the explosive initiating are marked on the camera record

Measurement of Shock Velocity

Explosive metal assembly with optical pins terminating at different depths. Remote pin arrangement was made in which the fibre collects the light  from a distance and the optical pin does not disturb the motion of the shocked surface.  In remote pin arrangement, a number of flat-bottomed cylindrical holes are drilled at different depths in a test specimen.  Fibre cables are fixed on the specimen's free surface to directly view the shock breakout at  the bottom of holes The distances of the bottom of cylindrical hole from explosive metal interference are marked in the camera record. The depth of the hole determines the time for which the shock luminescence remains visible to the fibre cab.