# Study on the Interference Process of Liquid Radial Reflux on the Stability of a Shaped Charge Jet
## 4 Experiments and Calculation  
### X-ray Experiment  
X-ray tests were conducted on the process of jet penetration in the LFCS to verify the accuracy of the theoretical model.  
The size parameters of the LFCS used in the test are shown in Figure 15. The LFCS mainly consisted of a metal shell with a cavity, a liquid filler, a cover plate, and a sealing strip, which were connected by screws. Here, the liquid filler was water, while the shell material was steel Q235. The jet tip velocity of the \(\varphi\)56 mm shaped charge used in the test was 6700 m/s, and the tail velocity was 1200 m/s. At 30 \(\upmu\)s, the jet tip radius was 1 mm and the tail was 7 mm. The stand-off was 80 mm.  
The X-ray test was arranged according to Figures 16-18, where the distance between the bottom of the LFCS and the horizontal ground was \(H_{D}\), the magnification factor was \(k_{A}=\frac{a+c}{a}\) and \(k_{B}=\frac{b+d}{b}\), and the light-emitting time of the two X-ray machines was \(T_{A}\) and \(T_{B}\), respectively. Parameters of the X-ray test layout are shown in Table 5.  
The two times of the X-ray machine emission were 60 and 80 \(\upmu\)s. The jet shape captured by the X-ray machine is shown in Figure 19.  
The X-ray images at 60 \(\upmu\)s showed that the tip of the jet was disturbed when the SCJ penetrated the LFCS, and necking and lateral deviation appeared. The undisturbed jet continued to extend over time due to the high velocity and velocity gradient of the SCJ, and the distance between the broken jets also increased. X-ray images at 80 \(\upmu\)s showed that the fracture and lateral deviation of the jet further intensified, while the jet at the back part maintained good continuity and collimation, which is in good agreement with the analysis in this study.  
Figure 16: Schematic of the interaction between projectile and target.  
Figure 17: Schematic of the X-ray experiment layout.  
According to the X-ray images, we can calculate the velocity interval of the SCJ disturbed by liquid radial reflux. Taking the marked lines as a reference, the measured distance between the tip of the jet and the marked line is \(\Delta X_{A1}\) at 60 \(\upmu\)s and \(\Delta X_{B1}\) at 80 \(\upmu\)s, while the measured distance between the tail of the disturbed jet and the marked line is \(\Delta X_{A2}\) at 60 \(\upmu\)s and \(\Delta X_{B2}\) at 80 \(\upmu\)s. Therefore, the distance of the tip of jet movement within the time range \(\Delta T\) is \(\Delta S_{1}\), while the distance of the tail of disturbed jet movement within the time range \(\Delta T\) is \(\Delta S_{2}\), so the velocity of the tip of the jet, \(V_{jx}\), and the tail of the disturbed jet, \(V_{jd}\), can be calculated as  
\[V_{jx}=\frac{\Delta S_{1}}{\Delta T} \tag{27}\]  
\[V_{jd}=\frac{\Delta S_{2}}{\Delta T} \tag{28}\]  
where \(\Delta T=T_{B}-T_{A}\), \(\Delta S_{1}=\frac{\Delta X_{B1}}{k_{B}}-\frac{\Delta X_{A1}}{k_{A}}\), and \(\Delta S_{2}=\frac{\Delta X_{B2}}{k_{B}}-\frac{\Delta X_{A2}}{k_{A}}\).  
Figure 19: X-ray test results.  
Figure 18: Site layout of the X-ray experiment.  
Accordingly, it can be calculated that the velocity interval of the disturbed jet is [3389.9, 5456.7] m/s.