Energetic Materials by Manoj K. Shukla Veera M. Boddu Jeffery A. Steevens Reddy Damavarapu & Jerzy Leszczynski

Author:Manoj K. Shukla, Veera M. Boddu, Jeffery A. Steevens, Reddy Damavarapu & Jerzy Leszczynski
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

6 Charge B Modeling and Experimentation

After having established the crucial parameters of the model, Charge B shown in Fig. 1 was designed to maximize the total number of lethal fragments generated. Upon fabrication, the performance of the new charge was tested in a series of experiments including flash radiography, high-speed photography, and sawdust fragment recovery.

The flash radiography tests were performed using two 150 kV x-ray heads located approximately 74 in. in front of the round. Shortly after initiating the round, each of the two x-rays heads were flashed at the separate prescribed times and intervals several microseconds apart. Two flash radiography tests were conducted. Each test resulted in two dynamic images of the expanding fragmented steel shell, both images superimposed on the film.

The high-speed photography tests were performed employing Cordin Framing Camera Model No. 121 capable of recording up to 26 high-speed exposure frames with time intervals between individual frames of less than 1 μs apart. In the experiments, the round was placed on a test stand in front of a fiducial grid, surrounded with four Argon gas light bombs, all enclosed in a white paper tent. A total of two high-speed photography tests were conducted, each test resulting in over 20 dynamic images of the expanding and fragmenting shell, approximately one microsecond apart.

Figure 7 shows a comparison between the CALE code predictions and the images of the expanding and partially fractured shell obtained from the flash radiography and high-speed photography experiments. The figure shows that the model resulted in an accurate prediction of the shape of the expanding hardened steel shell, including the early break out of the detonation products through the joint between the fuze and the main charge. After the shell breaks up and the detonation products start moving through the air, the discrepancy between the position of the edge of the detonation products cloud observed from the high-speed photography and that from the CALE code simulations is relatively large and needs to be commented. The discrepancy is mainly due to modeling approximations in applying the idealized three-dimensional axisymmetric geometry assumption, the Steinberg-Tipton failure algorithm, and the JWLB equation of state to simulate a complex physical phenomenon of shell fracture coupled with high-rate high-pressure-gradient flow of detonation products through cracks into relatively low pressure regions of air surrounding the shell. Given an excellent overall prediction of the shape of the expanding fragmenting shell evident from flash radiographic images, the final impact of these modeling errors is minimal.

Fig. 7CALE code modeling and experimentation. Charge B

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