Failure diameter

Critical Diameter (Failure Diameter). A brief discussion is given in Vol 3 of Encycl, pp C560-R C561-L... 

Zel dovich, ZhPriklMekhan i TekhnFiz 1963 (6), pp 59-65 CA 60, 14325 (1964) (Onedimensional instability and attenuation of detonation) 10a) Mary L. Pandow et al, "Studies of the Diameter-Dependence of Detonation Velocity in Solid Composite Propellants. II. Prediction of Failure Diameters , 4thONRSympDeton(1965), 102-06 11) C.G. 

Detonation, Failure Diameter in. Same as Critical Diameter in Detonation... 

Accdg to Ref 66, p 166, Manson Guenochg proposed (Ref 46b) that the decrease of deton vel with diam exhibited by gases is due to the inhibition of the chem reaction in the neighborhood of the wall over a layer of thickness 8. Then they made four assumptions (expressed by equations 5.6.1 to 5 6.4 incl of Ref 66) and came to the conclusion that the wave vel at a given diam is determined by the ideal C-J velocity and the failure diameter... 

The problem that remains is the study of the interaction of a shock with a matrix of holes in three-dimensional geometry. The basic two-dimensional processes involved in the failure of detonation, the failure diameter of explosives, and the sputtering initiation observed for density discontinuities near the critical size have been described. The three-dimensional study of the interaction of numerous failures and reignited detonations which is necessary for a complete numerical description of these problems must await new computing hardware ... 

The crysts of TNT in cast expls may vary from microscopic size to a substantial fraction of the size of the charge, depending upon casting conditions and procedure. The approach known as cream casting results in very fine crysts. In mixed expls, which usually are cast in the form of slurries, the solid particles tend to inhibit cryst growth, although TNT crysts sometimes apparently grow around the particles of the slurry. The effects of particle size on initiation sensitivity, failure diameter, and performance characteristics also have been observed to apply to crystal size in cast TNT... 

Failure Diameter. The minimum diameter below which propagation of detonation does not take place. Also known as critical diameter... 

Akhimova Stresik (Ref 17) studied the detonation characteristics of Ammonium Perchlorate (AP) mixed with various fuels . They were primarily interested in the failure diameter (critical diameter) of these mixts, but they do report some detonation velocity measurements at the critical diameter of the mixts... 

If the brass plate were completely incompressible, the failure thickness so determined would be half that of an unconfined infinite sheet. The failure thickness of an unconfined sheet is less than the failure diameter of a cylinder because rarefactions in a cylinder enter from all sides of the charge and influence the detonation. Thus, the failure diameter may be several times the failure thickness and may vary from one expl to another. More complete details are given in Ref 3... 

XTX-8003 (eXTrudable explosive). Los Alamos National Scientific Laboratory (LASL) designation for an extrudable expl contg PETN (80 wt% 69.9 vol %) coated with a low-temp vulcanizing silicone resin, Sylgard 182 (20 wt % 30.1 vol %) atomic compn Ci. 8<>H3.64N , 0103 3 jSi0.27 white putty curable to rubbery solid d, TMD 1.556g/cc, nominal 1.50-1.53g/cc mp 129-135°. XTX-8003 is used in special applications that require expls with small detonation failure diameters... 

SSg/cc mp 200° decompn hardness S5S. XTX-8004 is used in special applications that require more thermal stability than XTX-8003 (see above) can give. The detonation failure diameter is slightly greater than that of XTX-8003 Manufacture. Same as XTX-8003 Chemical Properties (Ref 2) ... 

Failure in detonation of coal mining expls 4 D347 Failure diameter 6 FS... 

Electrostatic Sensitivity 50% pt, Joules Explosion Temp in 5 secs, °C Failure Diameter, cm Friction Sensitivity at 440kg-cm Friction Test (Sliding Rod)... 

H. N. Presles and C. Brochet, Induction Delay and Detonation Failure Diameter of Nitromethane Mixtures, in Gasdynamics of Detonations and Explosions, vol. 75 of Progress in Astronautics and Aeronautics, J. R. Bowen, N. Manson, A. K. Oppenheim, and R. I. Soloukhin, eds.. New York American Institute of Aeronautics and Astronautics, 1981, 282-295. 

We are interested in reaction-zone length because it appears to be the major parameter controlling detonation velocity in the nonideal detonation region. It appears that explosives with thick reaction zones have a larger effect on detonation-velocity/diameter and failure diameters than explosives with thin reaction zones. 

The same mechanism, side losses that cause steady-state detonation velocity to decrease in the nonideal region, eventually become so dominant with decreasing diameter that a point is reached where steady-state detonation cannot be maintained. At this point detonation fails it either suddenly slows down to below the sound speed in the unreacted explosive or stops altogether. This point is called the failure diameter, D, it is also called the critical diameter, Dent- Failure diameter is strongly affected by confinement, particle size, initial density, and ambient temperature of the unreacted explosive. Failure diameter can be roughly correlated to the velocity-diameter constant a, as seen in Figure 21.7. 

Figure 21.7 Rate constant a plotted versus failure diameter (Ref. 8).

Figure 21.8 Failure diameter of nitroglycerine and liquid TNT as a function of temperature (Ref. 5).

Figure 21.9 Failure diameter of TNT as a function of initial density (Ref. 7). I. Pressed or powder Grains ize (I) 0.01-0.05 mm (b) 0.07-0.2 mm. 2. Cast (a) Poured clear (b) creamed (c) creamed with 10% powder added.

Data for both groups of explosives are given in Table 21.5, which includes notes explaining the particular confinement and/or temperature conditions at which the data were obtained. Some failure diameters were shown previously in Table 21.4. 

Figure 21.10 Failure diameter versus initial density for AN-fuel (peat) explosives at different grain sizes (Ref. 7).

Figure 21.11 Failure diameter for detonation of AP as a function of initial density. Average grain size, 10 m (Ref. 7).

The failure diameter is deduced from Fig. 8, and is approximately equal to 100 A. All the results presented so far the existence of a failure diameter, the curvature of the front and the variation of the detonation velocity with the cylinder radius, are consistent with continuum theory. Nevertheless, the necessary condition to get a steady detonation wave is the existence of a sonic point that isolates the reaction zone from the rarefaction waves coming from the back. This is investigated in the case of a planar detonation wave (using periodic boundary conditions in 3D). 

In detonation wave applications, the model has successfully calculated embedded gauge, laser interferometric metal acceleration, failure diameter, corner turning, converging, diverging, and overdriven experiments [57,61-63,67]. Figure 9 shows the measured and... 

A detonation refers to a shock wave in an energetic material that runs at a steady velocity driven by chemical reactions initiated at the shock front [38,39]. Due to damping at edges and surfaces, the detonation state can occur only if the sample is larger than the critical failure diameter [3]. With a few exceptions, the critical diameter is typically in the nun to cm range, so detonations are associated with macroscopic loads of energetic materials and are extremely powerful. For HMX, the detonation velocity is 9.1 km/s, the pressure is 39 GPa,... 

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