Development of a Simple Model of “Hot-Spot” Initiation in Heterogeneous Solid Explosives

2002 ◽  
Author(s):  
N. J. Whitworth
Keyword(s):  
Simple Model ◽  
Hot Spot ◽  
Solid Explosives ◽  
Heterogeneous Solid

A Simple Model for Calculating Transformer Hot-Spot Temperature

2009 ◽  
Vol 24 (3) ◽  
pp. 1257-1265 ◽  
Author(s):  
Dejan Susa ◽  
Hasse Nordman
Keyword(s):  
Simple Model ◽  
Hot Spot ◽  
Spot Temperature

Hot-spot reaction under transient pressure conditions

1987 ◽  
Vol 413 (1845) ◽  
pp. 329-350 ◽  
Keyword(s):  
Hot Spots ◽  
Hot Spot ◽  
Thermodynamic Description ◽  
Exothermic Reaction ◽  
Pressure Change ◽  
Variable Pressure ◽  
Transient Pressure ◽  
Physical Mechanisms ◽  
Solid Explosives ◽  
Condensed Phase Explosives

The initiation of condensed-phase explosives is often caused by hot spots; that is, localized regions of high temperature created by a variety of physical mechanisms, particularly in solid explosives. Once the hot spots are created, further temperature change is governed by (i) self-heating due to chemical reaction, (ii) heat loss by conduction and radiation, and (iii) adiabatic effects due to pressure and specific volume variation. The last effect includes both self-induced pressure change due to thermal expansion against the surroundings, and externally generated pressure change when initiation is attempted by mechanical impact. This paper presents a thermodynamic description of exothermic reaction under conditions of variable pressure and volume. The reaction rate is assumed to be a function of temperature only. The effect of variable pressure enters through its influence on temperature. It is demonstrated that the effects of self-induced pressure change are small. In the case of externally generated pressure change, explosion times can be affected drastically. These results are discussed in terms of initiation by shock waves of finite duration.

scholarly journals Initiation of solid explosives by impact and friction: the influence of grit

1949 ◽  
Vol 198 (1054) ◽  
pp. 337-349 ◽  
Keyword(s):  
Melting Point ◽  
Hot Spots ◽  
Hot Spot ◽  
Threshold Value ◽  
Maximum Temperature ◽  
Melting Points ◽  
Solid Explosives ◽  
Lower Melting Point ◽  
Determining Factor ◽  
Spot Temperature

This paper describes an experimental study of the initiation of solid explosives, and in particular the effect of artificially introducing transient hot spots of known maximum temperature. This was done by adding small foreign particles (or grit) of known melting-point. The minimum transient hot-spot temperature for the initiation of a number of secondary and primary explosives has been determined in this way. It is shown that the melting-point of the grit is the determining factor , and all the grits which sensitize these explosives to initiation either by friction or impact have melting-points above a threshold value which lies between 400 and 550 ° C. Grit particles of lower melting-point do not sensitize the explosives. The same explosives initiated by the adiabatic compression of air required, for initiation, minimum transient temperatures of the same order as the threshold melting-point values. The results provide strong evidence that the initiation of solids as well as of liquids by friction and impact is thermal in origin and is due to the formation of localized hot spots. There is evidence that in the case of the majority of secondary explosives which melt at comparatively low temperatures, intergranular friction is not able to cause explosion and the hot spots must be formed in some other way. With the primary explosives which explode at temperatures below their melting-points, hot spots formed by intergranular friction can be important.

scholarly journals Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

2019 ◽  
Vol 45 (2) ◽  
pp. 295-315 ◽  
Author(s):  
David E. Kittell ◽  
Cole D. Yarrington ◽  
Jeremy B. Lechman ◽  
David L. Damm ◽  
Melvin R. Baer
Keyword(s):  
Shock Waves ◽  
Stochastic Processes ◽  
Solid Explosives ◽  
Heterogeneous Solid

scholarly journals The response to a hot spot in a combustion problem

1981 ◽  
Vol 23 (1) ◽  
pp. 95-102 ◽  
Author(s):  
K. K. Tam ◽  
M. T. Kiang
Keyword(s):  
Steady State ◽  
Simple Model ◽  
Initial Value Problem ◽  
Initial Temperature ◽  
Hot Spot ◽  
Steady State Solution ◽  
Initial Value ◽  
Multiple Steady State ◽  
Steady State Solutions ◽  
Combustion Problem

AbstractA simple model for a problem in combustion theory has multiple steady state solutions when a parameter is in a certain range. This note deals with the initial value problem when the initial temperature takes the form of a hot spot. Estimates on the extent and temperature of the spot for the steady state solution to be super-critical are obtained.

scholarly journals Ribosomal DNA Replication Fork Barrier and HOT1Recombination Hot Spot: Shared Sequences but Independent Activities

2000 ◽  
Vol 20 (13) ◽  
pp. 4948-4957 ◽  
Author(s):  
Teresa R. Ward ◽  
Margaret L. Hoang ◽  
Reeta Prusty ◽  
Corine K. Lau ◽  
Ralph L. Keil ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Simple Model ◽  
Ribosomal Rna ◽  
Ribosomal Dna ◽  
Replication Fork ◽  
Hot Spot ◽  
Replication Forks ◽  
Nontranscribed Spacer ◽  
A Site ◽  
Replication Fork Arrest

ABSTRACT In the ribosomal DNA of Saccharomyces cerevisiae, sequences in the nontranscribed spacer 3′ of the 35S ribosomal RNA gene are important to the polar arrest of replication forks at a site called the replication fork barrier (RFB) and also to thecis-acting, mitotic hyperrecombination site calledHOT1. We have found that the RFB and HOT1activity share some but not all of their essential sequences. Many of the mutations that reduce HOT1 recombination also decrease or eliminate fork arrest at one of two closely spaced RFB sites, RFB1 and RFB2. A simple model for the juxtaposition of RFB andHOT1 sequences is that the breakage of strands in replication forks arrested at RFB stimulates recombination. Contrary to this model, we show here that HOT1-stimulated recombination does not require the arrest of forks at the RFB. Therefore, whileHOT1 activity is independent of replication fork arrest,HOT1 and RFB require some common sequences, suggesting the existence of a common trans-acting factor(s).

scholarly journals Birth and growth of explosion in liquids and solids initiated by impact and friction

1949 ◽  
Vol 198 (1054) ◽  
pp. 350-372 ◽  
Keyword(s):  
Hot Spot ◽  
Time Lag ◽  
Mass Movement ◽  
Striking Similarity ◽  
Time Lags ◽  
Low Velocity ◽  
Viscous Liquids ◽  
Low Viscosity ◽  
Solid Explosives ◽  
First Moment

The birth and growth of explosions initiated by mechanical and thermal means have been studied. Liquid and solid explosives show a striking similarity. The point of initiation is always located at a source of local high temperature, for example, a hot wire, an electric spark, an impacted grit particle, or at a gas pocket suddenly compressed during impact. There is an appreciable time lag between the first moment of impact and the first appearance of light from the explosion. With secondary explosives the time lag depends on the conditions of impact (it could be varied from 60 to 150 μsec.), but for all the explosives studied the delays under similar conditions are approximately the same. For the primary explosives the time lags are usually much shorter, indicating that a different mechanism of initiation may be operative. The first stage of explosion in liquids is a burning which begins slowly and accelerates to speeds of 500 or even 1000 m./sec. This speed may represent, in the main, a mass movement of the gas products away from the centre of explosion. In most solid explosives (both primary and secondary) the first stage is again a slow burning which accelerates to speeds of several hundred metres per sec. A second stage of constant velocity detonation then sets in. The detonation velocity (which varies from 1100 to 2300 m./sec. according to the explosive and the physical conditions of the layer) may be identified with the low-velocity detonation in large charges, and the correct order of velocity has been explained on hydrodynamic grounds. It is suggested that the continued propagation of the low-velocity detonation stage in a liquid is made possible by the rapid breaking up of the explosive by the detonation shock front, particularly if the liquid has a low viscosity. In more viscous liquids and solids propagation is possible only if hot-spot sources are present in the explosive. The hot spots may be developed by rapid compression of gas pockets, or, if the solid has a high enough meltingpoint, by intercrystalline friction.

Chaos and secular cycles in a structurally simple model society

2012 ◽  
Author(s):  
Alexander Medvinsky ◽  
Alexey Rusakov
Keyword(s):  
Simple Model
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