Impact initiation of explosives and propellants via statistical crack mechanics

Over the past 20 years, a number of scientists have conducted numerous fundamental investigations based on quantum chemistry theory into various mechanistic processes that seems to contribute to the sensitivity of energetic materials. A large number of theoretical methods that have been used to predict their mechanical and spark sensitivity are summarized in this article, in which the advantages and disadvantages of these methods, together with their scope of use are clarified. In addition, the theoretical models for thermal stability of explosives are briefly introduced as a supplement. It has been concluded that the current ability to predict sensitivity is merely based on a series of empirical rules, such as simple oxygen balance, molecular properties, and the ratios of C and H to oxygen for different classes of explosive compounds. These are valid only for organic classes of explosives, though some special models have been proposed for inorganic explosives, such as azides. An exact standard for sensitivity should be established experimentally by some new techniques for both energetic compounds and their mixtures. © 2013 Wiley Periodicals, Inc.

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“…A general approach has therefore been proposed by Dienes et al [70] to Table 2. The number of doorway modes and atomization energy.…”

Section: Statistical Crack Mechanics Methodsmentioning

confidence: 99%

Theoretical evaluation of sensitivity and thermal stability for high explosives based on quantum chemistry methods: A brief review

Yan

Zeman

2012

Int J of Quantum Chemistry

114

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“…In general, grains experience high stresses and fracture, leading to subsequent frictional interactions across crack surfaces. Frictional dissipation can be the most important source of heating that leads to local temperature rises and to the formation of hot spots (Dienes et al 2006;Barua & Zhou 2011a;Barua et al 2012). The spatial distribution, size and temperature of the hot spots are critical measures for assessing the ignition sensitivity of a PBX (Tarver et al 1996;Menikoff 2004).…”

Section: Introductionmentioning

confidence: 99%

Microstructural level response of HMX–Estane polymer-bonded explosive under effects of transient stress waves

2012

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The effect of transient stress waves on the microstructure of HMX-Estane, a polymerbonded explosive (PBX), is studied. Calculations carried out concern microstructures with HMX grain sizes on the order of 200 mm and grain volume fractions in the range of 0.50-0.82. The microstructural samples analysed have an aspect ratio of 5 : 1 (15 × 3 mm), allowing the transient wave propagation process resulting from normal impact to be resolved. Boundary loading is effected by the imposition of impact face velocities of 50-200 m s −1 . Different levels of grain-binder interface strength are considered. The analysis uses a recently developed cohesive finite element framework that accounts for coupled thermal-mechanical processes involving deformation, heat generation and conduction, failure in the forms of microcracks in both bulk constituents and along grain/matrix interfaces, and frictional heating along crack faces. Results show that the overall wave speed through the microstructures depends on both the grain volume fraction and interface bonding strength between the constituents and that the distance traversed by the stress wave before the initiation of frictional dissipation is independent of the grain volume fraction but increases with impact velocity. Energy dissipated per unit volume owing to fracture is highest near the impact surface and deceases to zero at the stress wavefront. On the other hand, the peak temperature rises are noted to occur approximately 2-3 mm from the impact surface. Scaling laws are developed for the maximum dissipation rate and the highest temperature rise as functions of impact velocity, grain volume fraction and grain-binder interfacial bonding strength.

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“…The simulation betrays this problem as the lateral deformation is effectively underestimated. To introduce this anisotropy, a solution has recently been proposed (Dienes et al, 2006). Some anisotropy of the crack distribution is taken into account as well as coalescence and nucleation of cracks.…”

Section: Resultsmentioning

confidence: 99%

Mechanical characterisation of a viscoplastic material sensitive to hydrostatic pressure

Gratton¹,

Gontier²,

Allah³

et al. 2009

European Journal of Mechanics - A/Solids

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International audienceThe present paper deals with the characterisation of the static mechanical behaviour of an energetic material all along its lifespan. The material behaviour is viscoplastic, damageable and sensitive to hydrostatic pressure. For such materials, existing models have generally been developed in the framework of transient dynamic behaviour. These models are not suitable for a static study. Therefore a specific experimental protocol and an associated model are developed. Characterisation is derived from both uniaxial compressive, tensile tests and tri-axial tests. Plastic behaviour is described by means of a parabolic yield criterion and a new hardening law. Non-associated plastic flow rule and isotropic damage complete the model. The performance of the model is illustrated through the simulation of various loading paths

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Impact initiation of explosives and propellants via statistical crack mechanics

Cited by 159 publications

References 74 publications

Theoretical evaluation of sensitivity and thermal stability for high explosives based on quantum chemistry methods: A brief review

Theoretical evaluation of sensitivity and thermal stability for high explosives based on quantum chemistry methods: A brief review

Microstructural level response of HMX–Estane polymer-bonded explosive under effects of transient stress waves

Mechanical characterisation of a viscoplastic material sensitive to hydrostatic pressure

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