Gurney velocity

The Gurney velocity V of a metal plate, projected by a slab of detonating expl that is initiated simultaneously along its air (or vacuum) face is given by (See Eqns (B-4) (B-6))... 

Fig 17 Computed Gurney velocity, [2(E0—Ej)], as a function of the characteristic velocity, [1.44po0] (mm/jusec), for C—H—N—0 explosives at various initial loading densities. Least squares fit to calculated values is shown. Also shown are experimental values of Gurney velocity (Ref 10), /2Eg, for maximum loading density for six pure explosives and three mixtures... 

One of the big unresolved problems in detonation physics is that of the isentropic expansion of detonation products ie, there exists no completely acceptable relationship between expansion volume and pressure. Henry (quoted in Ref 27) assumed that detonation products expand radially with a linear velocity gradient. He also assumed a polytropic EOS with 7 = 3 (T in our notation) and that a cylindrically-loaded steel casing bursts at R/R0 = 1.2. At large R the casing approaches its full Gurney velocity, which... 

Of the above assumptions, only the last can be verified directly by comparison with exptl data. However, since that comparison will be correct at the end of detonation and since the other assumptions are made consistent with the observed Gurney velocity at the end of casing expansion, he suggests that the casing motions in between will also be fairly well represented... 

Therefore, we can conclude that for shaped charges the loading density of the high explosive and its detonation velocity (or to be more precise the Gurney velocity, see Ch. 7.3) are relevant performance parameters. 

The chemical detonation energy of the explosive is changed into kinetic energy, until the fragments have a steady-state velocity (Fig. 7.19), from which the Gurney velocity can be calculated. 

The constant JlE is the so-called Gurney velocity (in km s ), which is dependent on the nature of the explosive. 

The Gurney velocity 2E is decisive for the performance of the explosive used. As we already saw in Ch. 3, Kamlet and Jacobs introduced the parameter which relates the detonation velocity and the detonation pressure for CaHbNcOd explosives with the heat of detonation Q (in cal g 1), where M is the molecular weights of the gaseous detonation products (in g mol-1) and N is the number of moles of... 

To approximate the Gurney velocity, Hardesty, Kamlet et al. have suggested the following relationship ... 

It was only in 2002 that A. Koch et al. could show that the Gurney velocity J2E and the detonation velocity (D = VoD) of an explosive can roughly be described using the following simple relationship ... 

Therefore, there is a simple approximation for the Gurney velocity yJlE for either a pure explosive or for an explosive formulation, when the charge density p and detonation velocity are known (Tab. 7.4). 

Tab. 7.6 Dependence of the experimentally determined Gurney velocities yj2E on the cylinder material used.

A very simple approach to approximate the Gurney velocity for CaHbNcOd explosives (density p, in g cm-3) was introduced in 2008 and is based on the following equation ... 

Of course, the Gurney velocity can also be determined experimentally by using the measured fragment velocity V. It can be concluded that the relationship discussed above provides a good approximation, but that the Gurney velocity is also dependent on other factors including, for example, the material of the confinement used (in particular its density). This can be seen in Table 7.6. 

Figure 7.21 also shows that the Gurney velocity for a specific explosive, with a particular charge density, is only constant when the surface density (in g cm 3) of the cylinder walls is above a critical value of approx. 1 g cm 2. 

The most recent work, which has mainly been reported by Joe Backofen, shows that the Gurney velocity is not only dependent on the explosive, the mass of the... 

Example Calculation of the Gurney Velocity for a General Purpose Bomb... 

Gurney velocity as being cylindrical. The total mass of the MK84 is 907 kg and the mass of the HE is approximately 430 kg. 

Fig. 7.21 Dependence of the Gurney velocity on the surface density (in g cm of the cylinder walls for Composition B (p = 1.71 g cm ).

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