Abstract
Experiments have shown that the shock sensitivity of a single crystal pentaerythritol tetranitrate (PETN) has a strong dependence on the crystal orientation. The ignition and growth (I & G) model has been widely used in studies of the shock initiation of energetic materials while the model is independent of the direction of compression, and thus it is impossible to address anisotropic sensitivity of such material. In this paper, we base our new model in the recently proposed reactive flow concept that incorporates an anisotropic ignition mechanism that depends on both strain and strain rate which are given in the general tensor notation. A multi-dimensional simulation is performed in order to illustrate the strain dependence of the initiation of a PETN pellet. The model is applicable to any anisotropic energetic material subjected to a shock impact, not limited to single crystal PETN.
Highlights
Experiments have indicated that pentaerythritol tetranitrate (PETN) demonstrates an anisotropic sensitivity to the mechanical shock loading.[1,2,3] For instance, the pressure threshold for initiation of detonation for PETN crystals along the direction is at least 4 times that of direction.[4]
The ignition and growth (I & G) model has been widely used in studies of the shock initiation of energetic materials while the model is independent of the direction of compression, and it is impossible to address anisotropic sensitivity of such material
We have described a multi-dimensional anisotropic detonation rate model for impact ignition behavior of a single crystal PETN
Summary
Experiments have indicated that pentaerythritol tetranitrate (PETN) demonstrates an anisotropic sensitivity to the mechanical shock loading.[1,2,3] For instance, the pressure (or mean stress) threshold for initiation of detonation for PETN crystals along the direction is at least 4 times that of direction.[4]. Both the and directions are shown to be sensitive to impact, even at a relatively low pressure of 8.6 GPa while and directions exhibit insensitivity to stresses up to a Chapman-Jouguet (C-J) pressure of 31 GPa. The microscopic mechanism behind the anomalous characteristics observed in experiments have been explained by the steric hindrance effect.[2] The steric hindrance model consists of dislocation and preferred slip planes induced by the microstructure of PETN. The anisotropic reactive response of a two-dimensional PETN crystal subjected to an external shock impact is presented, which enhances the fidelity of the current state of direction sensitive detonation simulation from a granular to a continuum scale
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