# Double-Bend and Semi-Spherical Energy Deflectors' Blast Load Efficiency--A Comparative Study
## 4 Results and Discussion
### Numerical Analyses of the Double-Bend Deflector
In the case of deflectors with a constant B-dimension, the smallest values of pendulum deflection for all explosive charge distances were obtained for the 80-45 variant, which means that increasing an B-dimension results in an improvement of energy deflector properties. Figure 18 shows the effects of the A-dimension and B-dimension values on the deflections of the ballistic pendulum for the various distances considered. They confirm that an increasing A-dimension results in a deterioration of the deflector's ability to dissipate energy. The critical factor in this regard is the B-dimension, which is of most significant importance, especially for short charge distances from the deflector (the curve in Figure 18 for the 30 cm stand-off is characterized by the steepest slope relative to the other two). Figure 17: Change of the maximum pendulum swing in the function of the stand-off distance; (**a**) constant A-dimension; (**b**) constant B-dimension. The exact results of the obtained deflections of the ballistic pendulum are shown in Table 6.  
Analyzing the deflectors studied so far, it turned out that the A-dimension has the most favorable value of 60 mm, whereas the B-dimension's is 45 mm. For this reason, it was decided to analyze another group of deflectors with an A-dimension equal to 60 mm  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Max. Swing of the Pendulum [mm]**} \\ \hline
**Deflector Size** & **30 cm Stand-Off** & **40 cm Stand-Off** & **50 cm Stand-Off** \\ \hline
60-15 & 54.54 & 51.02 & 45.95 \\
70-15 & 56.23 & 51.78 & 47.03 \\
80-15 & 57.47 & 52.9  
and a varying value of the B-dimension. This group is referred to as 60-series, as opposed to the double-bend deflectors' group with an A-dimension equal to 80 mm, designated in the following as 80-series. The curves representing the course of the ballistic pendulum swing for this group of deflectors are shown in Figure 19. In this variant, the difference between the maximum and minimum values of the pendulum swing for each distance was 10.1% for both 30 and 40 cm and 8.9% for the distance of 50 cm. Figure 19: Swing of the pendulum—60-series double-bend deflector with constant B-dimension. (**a**) Stand-off of 30 cm; (**b**) Stand-off of 40 cm; (**c**) Stand-off of 50 cm. Figure 20a shows a graph of the change in maximum pendulum swing depending on the value of the B-dimension. It shows that although the best results were obtained up to a B-dimension value of 45 mm, the difference between it and the 35 mm value was only 3.5%, 2.3%, and 1.7% for charge distances of 30, 40, and 50 cm, respectively. Figure 20b compares 60-series (solid line), and 80-series (dashed line) deflectors as a function of B-size values for all three considered explosive charge stand-offs in every case considered. Using 60-series deflectors resulted in lower pendulum deflection values than 80-series deflectors. The former is characterized by more ability to dissipate energy. We can see the only deviation from this rule for the stand-off of 30 cm and B-size of 45 cm, wherein a slightly lower deflection was obtained for the 80-45 variant. However, this difference was only 1.2%. It is worth noting that using a 60-25 deflector for a distance of 30 cm results in a very similar result as using an 80-25 deflector, but for a distance of 40 cm. The exact results of the ballistic pendulum deflections for 60-series double-bend deflectors are shown in Table 7.  
Figure 20: Change of the maximum pendulum swing in the: (**a**) function of the stand-off distance; (**b**) function of the B-size for the 60-series (solid line) and 80-series (dashed line) double-bend deflectors.