Scaling of the Shaped Charge Jet Break‐Up Time

Abstract

Since the formula for the shaped charge jet break-up time was published on 1979 many attempts were made to interpret it and to make its use more efficient. It is shown herein that the V pl parameter depends on the ratio of the liner thickness to the charge explosive diameter by the formula: 1/V pl ¼ 13.9 À 101 · (T L / CD), where T L is the liner thickness, CD is the explosive charge diameter and the numbers are for a published set of measurements with an OFE copper liner driven by COMP-B explosive. To find how the numbers used in this formula change with the liner material and its metallurgical state and with the type of explosive, measurements should be made as prescribed herein. An attempt to begin explaining this formula is made in the discussion.

Breakup Time of Zirconium Shaped Charge Jet

“…The calculated velocity difference between the zirconium jet fragments is compared with that of the copper material measured by Hirsch 4, as shown in Figure 3. It shows that the zirconium material has lower V PL values in the range of the studied T L /CD values, which means that the zirconium jet has a longer time of elongation before its breakup.…”

“…The breakup time proposed in Ref. 4 has the same physical meaning of the breakup time in an one‐dimensional homogeneous ductile metal undergoing a very high strain‐rate deformation.…”

“…2. Among these three approaches, the semi‐empirical formula presented by Hirsch 3, 4 has demonstrated its reliability and efficiency for the prediction of the breakup time of a shaped charge jet element. Hirsch 4 determined the breakup time t b using …”

“…Pugh‐Eichelberger‐Rostoker or PER model 5). V PL is a characteristic plastic velocity representing the average velocity difference between the neighboring jet segments 4. The breakup time proposed in Ref.…”

“…The reciprocal of V PL (i.e. 1/ V PL ) represents the specific breakup time of a certain liner material 4. Experimentally, V PL can be measured using multiple flash X‐ray units, where the position, the length, the radius, and the velocity of each jet segment are determined, based on which the velocity difference between each pair of neighboring jet segments can be determined.…”