Studies of Shell Fragment Mass Distribution

This report gives fragment mass distribution data requested by the Bureau of Ordnance for the Navy 350 A.A. projectiles, Mk. 27-3 and Mk. 31-1. Part II CSRD Report No. 5606 gives similar data for the 350 A.P. projectile, Mk. 29-2. Part III OSRD Report No. 5608 contains a preliminary investigation of the effect of booster size upon the fragment mass distribution. The experimental procedure for fragment recovery at this laboratory is described. The fragments are caught in sawdust and recovered by a magnetic separator. Methods of analyzing the data are reviewed. No attempt has been made at this time to examine the physical theory of shell break-up but the results have been described in terms of Motts semi-empirical exponential distribution law. Physical tests made upon samples from a single lot, Lot No. 1350 of Mk. 27-3 3 A.A. projectiles showed that the shell were by no means uniform in such properties as hardness and tensile strength. It appeared that a simple hardness test could be used to eliminate sub-standard shell without rendering them unfit for use. A set of ten shell selected for uniform hardness did indeed give satisfactorily reproducible fragment mass distribution data when fragmented with cast TNT fillings. At least one additional shell from the same lot but showing subnormal hardness gave a fragment mass distribution significantly coarser than the others.