Failure of Fluid Dilled Structures Due To High Velocity Fragment Impact

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A series of experimental tests have been conducted to study the failure of fluid filled containers caused by high velocity fragment impact. On penetrating the fluid, the fragment generates high pressure shock waves which on reaching the container walls result in rapid loading of the structure. Commonly known as the hydraulic ram effect, experiments have been performed to study the effect in detail for compact steel fragments of a few grammes mass at velocities between 1 km/s and 4 km/s. High-speed photography has been used to record the projectile motion in the fluid, the growth of the cavity behind the projectile and the propagation of the primary shock wave. Shock pressures in the fluid were measured and show that the duration and magnitude of the primary shock wave increase with increasing projectile velocity. A number of techniques for reducing the damage to the structure by alleviating the shock pressure in the fluid have been studied. The most promising of these techniques rely on interaction with the shock wave and increasing the compressibility of the fluid by introducing collapsible baffles into the fluid and by aeration. Dramatic reductions in structural damage have been obtained with modest levels of fluid loss, < 10%. Future work will involve optimisation of these hydraulic ram alleviation techniques for different projectiles, impact velocities and fluid filled structures.