Flyer point

Following the left-going shock in the flyer, the next interaction to occur is the shock with the free surface at the rear of the flyer, [point (2) in the x-t diagram. Figure 19.10]. This interaction is shown on the P-u plane in Figure 19.12. 

Example 19.3 A thick slab of stainless steel has been impacted by a flyer plate. The impact formed a square-wave shock pulse in the steel that traveled to the opposite surface (which was free). The interaction of the shock pulse at the free surface produced a rarefaction wave that is traveling back into the square-wave shock pulse. The shock pressure is 7.5 GPa. When the rarefactions meet they will form a tension. Will the steel spall at this point ... 

This effect is seen quite dramatically in data obtained by both Moulard and Wenograd (Ref. 9). In both sets of tests reported, very long shock pulses were used (the flyers were actually cylinders). Therefore, the data are shown only for pressure, not energy fluence. Each data point represents the 50% pressure for detonation versus nondetonation for different diameter flyers. The explosive targets were Composition B, and the flyers were steel. These results are shown plotted in Figure 22.8. 

In the simplest sense, a convenient method to determine a relationship between two measured properties is to plot one against the other (Fig. 1.2). Such an exercise will provide either a line fit of the points or a spread that may or may not be within the limits of experimental error. The data can then be used to determine the approximate accuracy of one or more points employed in the plot. For example, a point that lies outside the limits of experimental error di flyer) will indicate an issue of accuracy with that test and the need for a repeat determination. 

Figure 4. Profiles of mass velocity, temperature, longitudinal stress, and density as functions of longitudinal position at various times in methane simulation at 25 km/s flyer plate impact speed. The impact point of the flyer plate is at x=0, and the impact time is t=0.

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