engleski

An engineering approach to modeling sub-detonative events

Shock or thermal initiation can lead to sub-detonative events such as deflagration or a burning reaction which can grow into a full-fledged steady-state detonation under certain circumstances. Shock-to-Detonation Transition (SDT) being the simplest reaction mechanism which can give rise to detonation occurs when the shock generated by a high-velocity fragment or bullet is sufficiently strong to lead to prompt shock initiation. On the other hand, the likelihood of delayed mechanisms such as Deflagration-to-Detonation Transition (DDT) occurring is very dependent on a myriad of factors such as the initial state of the explosive material, the magnitude of deformation and damage suffered by the material after stimuli and containment. If an explosive is highly confined, detonable and its diameter is greater than its failure diameter, the reaction may undergo an abrupt transition from deflagration to detonation as reaction product gases are produced leading to a rapid rise in pressure, temperature and reaction rate. To account for all the factors leading to DDT is non-trivial, and an ongoing feat for top scientists around the world today. This work presents an engineering approach to model the transition of a low-strength compressive wave resulting from burning or a low-velocity impact to a high velocity detonation wave. The approach involves the incorporation of a user-defined subroutine in the standard hydrodynamics code ANSYS AUTODYN describing an equation of state which switches from a burn model to a reactive burn model when the critical energy criterion is met. The response of an exemplary explosive will be modeled using this approach, and the results are compared qualitatively with published experimental findings. The confinement wall velocity and acceleration profiles are used as criteria of measure for the violence of reaction. The effect of confinement size (wall thickness) and explosives properties are also analysed.

Shock-to-detonation transition ; deflagration-to-detonation transition ; response ; violence ; explosives

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