Initiation and propagation in primary explosives

1993 ◽  
Vol 441 (1912) ◽  
pp. 359-375 ◽  
Keyword(s):  
High Speed ◽  
Major Effect ◽  
Lead Azide ◽  
High Speed Photography ◽  
Related Phenomenon ◽  
Reaction Products ◽  
Heat Of Explosion ◽  
Initiation And Propagation ◽  
Void Structure ◽  
Detonation Transition

The initiation and propagation of deflagration and detonation in mercury fulminate, lead azide, mercuric-5-nitrotetrazole and silver-5-nitrotetrazole have been studied using various techniques. Streak and framing high-speed photography were used to observe these events directly. The main aim has been to investigate the factors which affect deflagration-to-detonation transition (DDT) and the related phenomenon of dead-pressing, which may be regarded as a failure of the DDT process at high pressed densities. These factors include the variable properties of pressed density, void structure, confinement and charge dimension and geometry, and also fixed properties (for a given explosive) such as shock and thermal sensitivities, heat of explosion and the quantity and state of the reaction products. The nature and strength of the initiating stimulus also have a major effect on the subsequent reaction.

Behaviors of High Explosive near the Critical Conditions for Shock Initiation of Detonation

2007 ◽  
Vol 566 ◽  
pp. 15-22 ◽  
Author(s):  
Shiro Kubota ◽  
Yuji Ogata ◽  
Yuji Wada ◽  
Tei Saburi ◽  
Kunihito Nagayama
Keyword(s):  
Shock Front ◽  
High Speed ◽  
High Explosive ◽  
Critical Conditions ◽  
High Speed Photography ◽  
Shock Initiation ◽  
Donor And Acceptor ◽  
Inner Diameter ◽  
Detonation Transition ◽  
Reaction Wave

The behaviors of the high explosive near the critical conditions for shock initiation of detonation are investigated by high speed photography and pressure measurements in gap tests. The sample is RDX base explosive, and the inner diameter of donor and acceptor charges is 26 mm. Gap material is PMMA. Near the critical condition, the results under the following conditions have been discussed. 1) Shock to detonation transition (SDT) take place in acceptor, 2) The SDT does not occur, but the reaction wave affects the leading shock front in acceptor, and 3) The gap length in which the effect of the reaction wave to shock front almost disappears. These results are very useful to construct the initiation model for solid explosive.

The role of rapidly compressed gas pockets in the initiation of condensed explosives

1974 ◽  
Vol 340 (1620) ◽  
pp. 113-128 ◽  
Keyword(s):  
High Speed ◽  
Thermal Contact ◽  
Gas Bubbles ◽  
Lead Azide ◽  
High Speed Photography ◽  
Water Tank ◽  
Minimum Volume ◽  
Specific Heats ◽  
Series Of Experiments ◽  
Minimum Volumes

The mechanism of initiation of explosion by the rapid compression of gas spaces has been studied by means of high-speed photography at framing rates up to 10 7 frames s -1 . Single crystals of silver azide, lead azide and PETN were mounted in a water tank and gas bubbles of chosen composition and size (diameter in the range 50 μm to 1 mm) collapsed on to them by water shocks of strength about 0.1 GPa (1 kbar). The gas bubbles collapsed to minimum volumes in times of the order of 1 μs (depending on the initial bubble size). Initiation of fast reaction occurred in the azides within ca . 5 × 10 -8 s of the bubble reaching minimum volume provided the bubble made thermal contact with the explosive. During the collapse, the bubble involuted to form a jet of velocity of a few 100 ms -1 , and after reaching minimum volume, expanded giving an expansion shock. The importance of these phenomena in the initiation of explosion, as well as possible initiation by shock perturbation, was assessed in a series of experiments designed to separate the various possible mechanisms. The conclusion is that adiabatic heating of the gas in the bubble was the prime cause for initiation. Calculations, and experiments with gases such as argon and helium (high value of γ ; the ratio of the specific heats) and butane (low γ ) supported this conclusion. Finally, the relevance to other explosive situations is discussed.

Crack divergence phenomena in tempered glass

2020 ◽  
Vol 13 (3) ◽  
pp. 115-129
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Optimal Design ◽  
High Speed ◽  
Glass Plate ◽  
Acute Angle ◽  
Divergence Angle ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Thick Glass

High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.

Experimental study of hydrodynamic effects in the inverse water hydrocarbon emulsions flow in microchannels

2016 ◽  
Vol 11 (1) ◽  
pp. 30-37 ◽  
Author(s):  
A.A. Rakhimov ◽  
A.T. Akhmetov
Keyword(s):  
High Speed ◽  
Petroleum Industry ◽  
Chemical Compounds ◽  
High Viscosity ◽  
Blocking Effect ◽  
High Speed Photography ◽  
Simple Chemical ◽  
Reported Study ◽  
Dynamic Blocking ◽  
Hydrodynamic Effects

The paper presents results of hydrodynamic and rheological studies of the inverse water hydrocarbon emulsions. The success of the application of invert emulsions in the petroleum industry due, along with the high viscosity of the emulsion, greatly exceeding the viscosity of the carrier phase, the dynamic blocking effect, which consists in the fact that the rate of flow of emulsions in capillary structures and cracks falls with time to 3-4 orders, despite the permanent pressure drop. The reported study shows an increase in viscosity with increasing concentration or dispersion of emulsion. The increase in dispersion of w/o emulsion leads to an acceleration of the onset of dynamic blocking. The use of microfluidic devices, is made by soft photolithography, along with high-speed photography (10,000 frames/s), allowed us to see in the blocking condition the deformation of the microdroplets of water in inverse emulsion prepared from simple chemical compounds.

scholarly journals Prey Capturing Dynamics and Nanomechanically Graded Cutting Apparatus of Dragonfly Nymph

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 559
Author(s):  
Lakshminath Kundanati ◽  
Prashant Das ◽  
Nicola M. Pugno
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Speed ◽  
Prey Capture ◽  
High Speed Photography ◽  
Sensory Organs ◽  
Dragonfly Nymph ◽  
Drag Forces ◽  
Predatory Insects ◽  
Dragonfly Nymphs

Aquatic predatory insects, like the nymphs of a dragonfly, use rapid movements to catch their prey and it presents challenges in terms of movements due to drag forces. Dragonfly nymphs are known to be voracious predators with structures and movements that are yet to be fully understood. Thus, we examine two main mouthparts of the dragonfly nymph (Libellulidae: Insecta: Odonata) that are used in prey capturing and cutting the prey. To observe and analyze the preying mechanism under water, we used high-speed photography and, electron microscopy. The morphological details suggest that the prey-capturing labium is a complex grasping mechanism with additional sensory organs that serve some functionality. The time taken for the protraction and retraction of labium during prey capture was estimated to be 187 ± 54 ms, suggesting that these nymphs have a rapid prey mechanism. The Young’s modulus and hardness of the mandibles were estimated to be 9.1 ± 1.9 GPa and 0.85 ± 0.13 GPa, respectively. Such mechanical properties of the mandibles make them hard tools that can cut into the exoskeleton of the prey and also resistant to wear. Thus, studying such mechanisms with their sensory capabilities provides a unique opportunity to design and develop bioinspired underwater deployable mechanisms.

Droplet transfer behavior of narrow gap laser wire filling welding

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940045 ◽  
Author(s):  
Z. Zhang ◽  
R. Wang ◽  
G. Gou ◽  
H. Chen ◽  
W. Gao
Keyword(s):  
Welding Speed ◽  
High Speed ◽  
Transition Period ◽  
High Speed Photography ◽  
Narrow Gap ◽  
Droplet Transfer ◽  
Transfer Behavior ◽  
Feeding Speed ◽  
Wire Feeding ◽  
Droplet Transition

In this paper, we study the droplet transition behavior of narrow gap laser wire filling welding under the condition of changing welding speed and wire feeding speed, and it was observed by high-speed photography. It was found that with the increase of welding speed, the frequency of droplet transfer was reduced and the transition period was prolonged. With the increase of wire feeding speed, the wire was not fully melted and finally inserted into the molten pool.

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