Appendix A
EFFECT OF POSITIVE DURATION ON DAMAGE
__ Ay1 GENERAL
_ The study of the effects on damage of positive duration was
undertaken prior to the test in Operation CASTLE and completed during
the time the test was conducted at Pacific Proving Ground.
“For.-drag targets, such as vehicles, much damage will result because ofmotion due to either high acceleration forces or impact with
the ground. The easiest and simplest parameter selected from experimental data for correlation to forces of a blast wave was (Usplaczment.
Displacement of the item is proportional to the dynamic pressure
impulse of the. blast wuve.
calculations were made for displacements of 1/4-ton trucks
exposed to weapons of various yields.
Furthermore, a statistical
analysis was conducted:to determine the relation of displacement of a
vehicle to damage. From this procedure, the quantitative effect on
damage of ~he positive.duration was ovtained.
A.2
CALCULATED DISPLACEMENTS FOR OPERATION CASTLE
In the calculations for’‘aisplacenents performed, the loading
methods developed by Armour Research Foundation (see Reference 5)
were used, These calculations“are for linear displacements assuming
@ constant area and a constant.‘frictional force for 1/4-ton truck
exposed to the long durations expected in Oreration CASTLE. The
calculations involved the computation!of the pressure-time decay
curves for the pressures of interest,:the integration of these curves
and calculations of the displacements’ for various coefficients of
friction. Three values of coefficient of sliding friction
were used, 0.25, 0.5, and 1.0 and three values of yield, 0.125 MI,
1.0 MI and 10 MI burst at surface level. |.
The equations used to describe the decay of the pressure-time
curve was the modified Friedrich's equation, and: the duration for
pressures of interest were obtained from Operation IVY.
The durations
are not considered to be precise. However, three yignificant figures
were used so that the resulting displacement data would form smooth
curves.
The data used for the calculations are listed ‘in Teble A.l.
Fig. A.l and Fig. A.2 present the normalized overpressure and
dynamic pressure decay curves. Three pressures are Plotesd: in each
figure to indicate the decay changes as \ changes.
The calculated values of displacement obtained were plotted
against dynamic pressure and arc shown in Figs. A.3, Ae4, A.5 and A.6.
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