Proctor’s correlation cannot be applied to deformation of the bottom head of the vessel, since it is based only on experiments that apply to the radial deformation of cylindrical vessels. Thus, for the bottom head, the following equation by Cole (24) may be used for damage predictions in the axial direction

Impulse = KW°-33(W°-33I Ry (5.14)

where R is the distance from the charge W, fi = 1.05 for a range of under­water explosions and can be put equal to unity for the classical acoustic law with adequate accuracy, and К is an experimental factor.

Table 5.12 shows typical vessel properties that may be used in the evalua-

tion of these equations. The ultimate strain eu should be diminished by a factor of between one-third and one-half to account for vessel irregularities, welds, and nozzles. The dimunition factor is relatively constant for different regularities considered in Proctor’s explosive work (22). Thus for a real vessel

eu (for the calculation) = ej3 (5.15)

One large uncertainty in this type of simple calculation for damage to the vessel wall is just how much the shock is attenuated by the vessel internals. Proctor (23) has shown that the attenuation could be considerable.