The decay coefficient can be evaluated:
A/Wf = fragment form factor, the ratio of the presented area of
fragment (in2) to the fragment weight (oz), which is taken
as 0.78/(Wf)1/3 for random mild steel fragment produced
by the detonation of a cased charge
[rho]a = density of air
CD = air drag coefficient of fragment, which from Healey's
report is equal to 0.6 in the supersonic region (velocity
> 1,125 fps)
The resulting expression for the striking velocity is as follows:
The variation of primary fragment velocity with distance is shown in Figure 26.
c. Fragment Mass Distribution. Reliable estimates of the mass
distribution of fragments from the casing of an explosive container can be
obtained from the basic equation developed by Mott in A Theory of
Fragmentation and by Gurney in The Mass Distribution of Fragments from
Bombs. Shells and Grenades.