HYDRODYNAMIC RAM

BALLISTIC SIMULATOR

Figure 1: Diagram of the HRAM Ballistic Simulator

A general schematic of the ballistic simulator test arrangement is shown in Figure 4. In this figure a light gas gun is shown as the device used to launch 12.5 mm spherical projectiles that impact and penetrate a target panel. In so doing, the resulting energy transfer creates pressure waves within the tank, as well as producing a liquid spurt that exits the penetration hole in the target plate. Standard 5.56 mm and 7.62 mm ballistic devices are also available. The resulting high velocity flow escaping from the target panel has been captured using a Laser based PIV system and high-speed camera.

Figure 2: Transparent Side of the Ballistic

Simulator Partially Filled With Water

There are many instances where high velocity projectiles impact and penetrate liquid filled containers causing a transfer of the projectile’s kinetic energy (KE) to the liquid. This energy transfer from KE to mechanical energy results in the generation of violent pressure waves which can lead to catastrophic container failure, a phenomenon referred to as Hydrodynamic Ram (HRAM).

In order for ESI to undertake an investigation into the effects of HRAM, a purpose built large liquid filled container was designed and constructed. This container (tank) had to be capable of withstanding ballistic impacts as well as the large reflected pressure waves created by HRAM. In addition the tank had to be instrumented and provide for significant optical access to analyze the processes that arise when HRAM occurs.

This ballistic simulator is capable of holding 1000 gallons (~ 4000 liters) of liquid and is approximately 6 ft x 6 ft x 4 ft (183 cm x 183 cm x 117 cm) in dimensions, Figure 1.

The simulator is fabricated from ballistic steel with optical access being provided by one side wall constructed of a thick acrylic sheet, as well as two relatively smaller windows, arranged at the top and the opposite side wall with similar acrylic sheeting, Figure 2.

Additionally, a 6” x 6” (15.24 cm x 15.24 cm) replaceable target panel holder is located on the front wall of the simulator. This feature allows for target panels, up to 1 “ thick (2.54 cm) to be held in place and withstand being impacted and penetrated by armor piercing projectiles, and enable quick replacement after completion of a test Figure 3.

Figure 4: General Diagram of a Typical HRAM Fuel Spurt Test

Configuration Driven by a Light Gas Gun

Figure 3: Transparent Side of the Ballistic

Simulator Partially Filled With Water

Furthermore, the simulator is also equipped with numerous instrumentation ports on the steel walls, as well as providing a number of different types of probe holders within the interior of the container. Present instrumentation includes high-speed pressure transducers, accelerometers, strain gauges, particle image velocimetry (PIV), and high-speed visualization techniques.

 

To-date, studies have been undertaken on projectiles that have impacted and penetrated this simulator include 5.56 mm and 7.62 mm armor penetrating rounds, 12.7 mm armor penetrating incendiary rounds, and 12.7 mm spherical balls of different materials.

Figure 5 displays an actual test where the simulator is impacted with a spherical ball, penetrates the target plate, and enters the simulator. The pressure field resulting from the projectile is acquired using several high-speed pressure transducers and the motion recorded simultaneously with a high-speed camera.

Figure 5: An HRAM Test Showing a Spherical Ball Entering the Test Section and Pressure Monitored with High-Speed Transducers

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