Characterization, Modeling and Performance Evaluation of a Variant of Insensitive Munition

Abstract

The idea of Insensitive Munitions (IM) originated about 40 years ago. The unplanned initiation of the munitions and subsequent occurrence of the accidents put the challenge for the munition developers to manufacture such energetic materials that do not respond violently when subjected to accidental initiation stimuli. The properties of IM can change due to aging and they may become considerably less safe for storage and use. The thermal conditions, an environmental condition of storage and the compatibility with other energetic materials utilized affect the aging process of Insensitive Munitions. The effect of aging on IMs can result in the degradation of IMs' properties, thereby increasing the risk of accidents by reducing the expected life cycle of IMs. The use of Insensitive Munitions in military devices is inevitable as the safety of military personnel is extremely important. The main use of IMs is in shaped charges and explosively formed projectiles (EFPs) for penetrating against hard targets. A shaped charge generally consists of a conical metal liner, which on explosive ignition is converted into a jet of metal traveling at hypersonic velocity. Various Insensitive Munitions including HMX-based (PBXN-110), TATB-based (PBX-9502) and RDX-based (8701) have been used in the shaped charge simulations employing ANSYS Autodyn Hydrocode at three different liner obliquities including 42°, 60°, and 70°. Flash X-Ray radiography (FXR) is used to capture the events taking place at the supersonic speed. The FXR experimental method was used to capture the jet formation at 30 μsec and 50 μsec. The jet velocity for 42°, 60° and 70° has been determined through FXR experiments. The simulation results for jet velocity matched reasonably well with the experimental results for RDX-based 8701 explosive. The penetration performance of shaped charge was determined by conducting depth of penetration (DOP) experiments. DOP measured from the simulation is in fair agreement with experimental results. The underwater-ammunition neutralization is a great challenge nowadays. The main aim is to neutralize underwater ammunition without being detonated. The explosively formed projectile has the potential to neutralize underwater ammunitions safely and without detonation. Simulations have been performed using Oxygen-free high thermal conductivity (OFHC) copper liner. Euler/Lagrange coupling method was used to avoid the interaction problems. The ix simulation results showed that the velocity of the EFP is retarded quickly as it enters the water. The EFPs penetration depth against the steel target immersed in water has been measured using simulation studies for a standoff distance of 3CD (charge diameter) in air and 3CD in water. The depths of penetration experiments were conducted for the same stand-off distance as used in simulation to compare both studies. The simulation and experimental results are in reasonable agreement with each other. EFP jet formation was captured using FXR technique. The EFP jet velocity for 120° conical liner has been calculated using images obtained from FXR method. The calculated jet velocity agrees well with the jet velocity determined by simulation. A comparison has been made among three Insensitive Munitions on the basis of jet velocity, jet length and energy ratio and penetration capability against steel targets vis-a-vis depth of penetration measurements and it is observed that RDX-based 8701 explosive provides a good guideline to understand the effectiveness of IMs and has the better performance as compared with other existing Insensitive Munitions and can be used in the battlefield with greater safety and reliability. Besides other new aspects studied and reported in the ibid research work, the nutshell result of this study is the underwater response of EFPs using RDX-based IM (8701) that has been carried out for the first time to the best of our knowledge which provides an insight in understanding these munitions.