Modifications and Applications of the HERMES model: June - October 2010

Reaugh, J E

Lawrence Livermore National Laboratory

关键词: Fragmentation;    Velocity;    Ignition;    Surface Area;    Modifications;   

DOI  :  10.2172/1016979
RP-ID  :  LLNL-TR-462751
RP-ID  :  W-7405-ENG-48
RP-ID  :  1016979

美国|英语

来源: UNT Digital Library

【 摘 要 】

The HERMES (High Explosive Response to MEchanical Stimulus) model has been developed to describe the response of energetic materials to low-velocity mechanical stimulus, referred to as HEVR (High Explosive Violent Response) or BVR (Burn to Violent Reaction). For tests performed with an HMX-based UK explosive, at sample sizes less than 200 g, the response was sometimes an explosion, but was not observed to be a detonation. The distinction between explosion and detonation can be important in assessing the effects of the HE response on nearby structures. A detonation proceeds as a supersonic shock wave supported by the release of energy that accompanies the transition from solid to high-pressure gas. For military high explosives, the shock wave velocity generally exceeds 7 km/s, and the pressure behind the shock wave generally exceeds 30 GPa. A kilogram of explosive would be converted to gas in 10 to 15 microseconds. An HEVR explosion proceeds much more slowly. Much of the explosive remains unreacted after the event. Peak pressures have been measured and calculated at less than 1 GPa, and the time for the portion of the solid that does react to form gas is about a millisecond. The explosion will, however, launch the confinement to a velocity that depends on the confinement mass, the mass of explosive converted, and the time required to form gas products. In many tests, the air blast signal and confinement velocity are comparable to those measured when an amount of explosive equal to that which is converted in an HEVR is deliberately detonated in the comparable confinement. The number of confinement fragments from an HEVR is much less than from the comparable detonation. The HERMES model comprises several submodels including a constitutive model for strength, a model for damage that includes the creation of porosity and surface area through fragmentation, an ignition model, an ignition front propagation model, and a model for burning after ignition. We have used HERMES in computer simulations of US and UK variants of the Steven Test. We have recently improved some of the submodels, and report those developments here, as well as the results of some additional applications.