Spherical Equivalency of Cylindrical Charges in Free-Air
SOUTHWEST RESEARCH INST SAN ANTONIO TX
Pagination or Media Count:
Few experimental investigations can be found in the literature in which free-air blast parameters from cylindrical charges have been measured. As part of the work to update the DOETIC Manual 11268, Prediction of Blast and Fragment Loadings on Structures, these free-air blast data were reviewed and analyzed. One of these sets of experimental data was used to develop graphs of equivalent spherical weights for cylindrical charges with length-to-diameter ratios of 14, 11, and 41. The actual peak side-on overpressure and impulse data from Pentolite cylindrical charges initiated at one end were scaled to standard sea level conditions using Sachs scaling factors and the charge weights converted to equivalent TNT values based on Pentolite spherical charge test data. Then, equivalent spherical weights were determined using the standard air blast curves for spherical TNT detonations in free-air. Side-on pressure and impulse data measured along eight radials at 22.5 degree increments and at scaled distances of about 3 to 15 ftlbsup 13 were used to develop the equivalent spherical mass ratios. These results show the significant difference a cylindrical charge geometry has on the free-air blast loads as compared to spherical charges. To demonstrate further this difference, impulse amplitude ratios for one cylindrical charge versus a spherical charge were computed and applied to the reflected impulse loads on a flat surface from a free-air burst.