Ricochet quantification using a multiple sensor approach

Abstract

This study investigates the ricochet behaviour of three different small-arms projectile types using a novel ricochet measuring device. The results can be used to estimate the danger potential of ricochets on shooting ranges.A ricochet is the change of direction and velocity of a projectile after impacting an oblique surface. This impact produces strong vibrations on a rigid plate.

During this impact, flexural waves travel radially outwards from the point of impact. These waves are used to determine the properties of the impactor with accelerometers situated on the target surface. With the use of two measurement plates, one can produce a ricochet and detect the velocity at the same time.

Accelerometers are suitable for accurate momentum measurements of single impacts. However, depending upon strike velocity and the impact angle, a ricochet can separate in multiple fragments after being deflected. From the operational safety perspective, these fragments need to be detected, as well. The approach of a coupled sensor concept was chosen to solve this problem.

Thermographic sensors were additionally used to visualise the heat which is produced after penetrating a rubber layer pasted in front of the steel target plate. With this approach one was able to detect the position of impact. The investigations showed that the measurement system performance is better with a multiple sensor design, which includes accelerometers for the velocity, impact strength and partly the position measurement, while the thermographic sensor was used for the position measurement and partly the momentum measurement.

The investigated ammunition showed plausible fragmentation behaviour, and the results can already be used to estimate the danger potential of different ammunition types. Frangible projectiles fragment to small particles already after being deflected under a small angle. However, Full Metal Jacket projectiles with or without a steel core do not fragment under angles which are less than 5°.

The objective of the paper is to demonstrate the possibility of measuring the complex ricochet mechanics of small projectiles using standard accelerometers with the adequate signal processing approach. This measuring system is supported by an off the shelf thermographic camera.