Description of “Hot Spots” Associated with Localized Shear Zones in Impact Tests

Coffey, Charles S.; Armstrong, Ronald W.

doi:10.1007/978-1-4613-3219-0_20

Cited by 26 publications

(6 citation statements)

References 10 publications

(14 reference statements)

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“…Based on the concept of dislocation theory presented by Coffey et al, a dislocation avalanche released from a blocked slip band pile-up configuration may lead to more significant localized heating at crystal slip planes. 51 As shown in Fig. 7, the rod-shaped DNTF crystals accumulate tightly on the microscale.…”

Section: Sensitivitymentioning

confidence: 88%

Crystal morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in a solvent system: molecular dynamics simulation and sensitivity study

Liu

Li²,

Zeman

et al. 2016

CrystEngComm

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Herein, the attachment energy (AE) model was employed to study the growth morphology of 3,4-bisĲ3nitrofurazan-4-yl)furoxan (DNTF) under vacuum and solvent conditions by molecular dynamics simulation.The DNTF crystals were cultivated in H 2 O/acetic acid (AcOH) and H 2 O/EtOH solvents by natural cooling.The calculated results show that the (0 1 1) and (0 0 1) faces have large morphological importance in these two solvent systems, and the predicted DNTF morphologies agree qualitatively with those of the observed experimental results. Radial distribution function (RDF) and diffusion coefficient analyses were performed to explore the adsorption and diffusion behaviors of solvent molecules on DNTF surfaces. Furthermore, the impact and friction sensitivities of different crystal morphologies of DNTF were also tested and discussed.Results suggest that crystal morphology is an important impact factor for controlling the sensitivity of explosives.

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Section: Sensitivitymentioning

confidence: 88%

Crystal morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in a solvent system: molecular dynamics simulation and sensitivity study

Liu

Li²,

Zeman

et al. 2016

CrystEngComm

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“…Baker [15] enhanced this continuum interpretation for thick disk deformation by applying sliding friction models to better match experimental observations that had supported the assertions of Afansev and Bobolev. Coffey et al [16,17] suggest that highly localized shear zones generated due to dislocation growth (avalanche pileup) offered a micromechanical explanation of localized heating that has some resemblance of the mesoscale description proposed by Afanasev [12]. In both cases, the ignition event would occur early in the compaction phase due to adiabatic shear banding that dissipated heat early in the flow development of the sample.…”

Section: Introductionmentioning

confidence: 99%

Influence of Anvil Properties on RDX Thin Layer Ignition Behavior

Yakaboski

Kumar

2017

Propellants Explo Pyrotec

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We report on a drop‐impact protocol that arrests sample radial flow to isolate how anvil properties influence ignition in a thin layer of RDX powder. To eliminate sliding friction as a probable heating mechanism, flow arrestment was provided by a waxed weighing paper that shielded the RDX layer from direct contact with the impact surfaces. RDX reaction sensitivity under bare and shielded conditions for the standard O1 hardened steel anvil was compared with that for two deformable anvil types: 1018 steel and C110 copper. Profilometer measurements of anvil deformation and paper impressions quantified anvil plastic work and final radial flow displacement. Post‐test particle analyses correlated particle size distribution to ignition results. Experiments indicated that the impact energy absorbed by the anvils was varied and inhibited ignition accordingly. For the standard anvil, ignition was not inhibited under flow arrestment, suggesting that significant radial sliding or flow is not essential for thin layer ignition.

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“…However, the very earliest work of Tresca proved that high temperature increases were occurring and thus the model of Eshelby and Pratt must be incomplete. This issue was re-examined by Coffey and Armstrong [19] on the basis of further accumulated evidence that appreciable temperature rises were being evidenced in shear banding experiments. A model favorable to shear banding was envisioned of isothermal stress build-up of stored energy in a dislocation pile-up, then leading to sudden obstacle collapse, and rapid dissipation of the stored energy by very localized plastic work in an earthquake-like dislocation avalanche.…”

Section: Strain Concentration and Adiabatic Shear Bandingmentioning

confidence: 99%

Strain concentrations in tensile, fatigue and fracture behaviour

Antolovich

Armstrong

2014

Strength, Fracture and Complexity

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A critical survey has been made of tensile, fracture, shear banding and fatigue measurements and their interpretations reported for different types of materials and test conditions. The mechanical properties of the materials are shown to be largely determined by microscopic plastic strain concentrations which depend on the inhomogeneity of the material microstructure, especially including importantly inhomogeneity of the dislocation substructure. Understanding this inhomogeneity is shown to provide a number of connections between seemingly disparate phenomena. The evolution of the dislocation substructure and its relationship to crystallography and various levels of microstructure are critically important. Professor Cottrell made seminal contributions to understanding the fundamental mechanisms involved in determining such strain concentrations. His work continues to provide clarity and guidance to current research accomplishments.

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Description of “Hot Spots” Associated with Localized Shear Zones in Impact Tests

Cited by 26 publications

References 10 publications

Crystal morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in a solvent system: molecular dynamics simulation and sensitivity study

Crystal morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in a solvent system: molecular dynamics simulation and sensitivity study

Influence of Anvil Properties on RDX Thin Layer Ignition Behavior

Strain concentrations in tensile, fatigue and fracture behaviour

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