# Double-Bend and Semi-Spherical Energy Deflectors' Blast Load Efficiency--A Comparative Study
## 5 Summary  
The article presents the results of experimental and numerical studies of innovative shapes of energy deflectors. In order to determine the deflector's ability to dissipate energy, a test stand was prepared in the form of a ballistic pendulum, to which energy deflectors were mounted and loaded with a wave of energy from the detonation of an explosive charge (Semtex A1).  
Figure 23: Comparison of the best variants for both double-bend and semi-spherical deflectors. V-shaped deflector added as reference.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**Max. Swing of the Pendulum [mm]**} \\ \hline
**Deflector Size** & **30 cm Stand-Off** & **40 cm Stand-Off** & **50 cm Stand-Off** \\ \hline
10 & 59.04 & 54.31 & 51.34 \\
15 & 58.69 & 54.46 & 50.65 \\
20 & 58.19 & 54.52 & 49.95 \\
25 & 58.62 & 53.76 & 49.57 \\
30 & 57.69 & 53.46 & 49.03 \\
35 & 56.77 & 52.97 & 48.31 \\
40 & 57.15 & 52.01 & 47.79 \\
45 & 56.05 & 51.37 & 47.07 \\
50 & 54.66 & 50.73 & 46.19 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Values of the pendulum maximum swing for all semi-spherical deflector sizes.  
The results of these analyses allowed validation of the created numerical model of the test stand. A series of double-bend and semi-spherical deflectors differing in key dimensions were prepared in the next step. In the case of double-bend deflectors, these were the so-called A-size and B-size, whereas in the case of semi-spherical deflectors, it was the radius of the rounded working part. The dimensions were chosen so that all the deflectors considered had the same height. Tests were conducted for three explosive charge stand-offs: 30, 40, and 50 cm.  
The results of the numerical tests established that:  
* For a double-bend deflector, an increasing A-size results in a deterioration of its energy dissipation capability. An increasing B-size, on the other hand, results in the opposite situation, i.e., the performance is improved;
* Increasing the A-size from 60 mm to 130 mm results in a 7.4% deterioration in effectiveness for a 30 cm stand-off. When the distance is increased, the deterioration in effectiveness increases slightly to 8.9%;
* The deflector effectiveness increases by as much as 15.6% for a 30 cm stand-off, increasing the B-size from 15 mm to 45 mm. For greater distances, the effectiveness increase decreases to 10.5%;
* Using semi-spherical deflectors is more effective, by up to 5%, than a typical V-shaped deflector, whereas for double-bend deflectors, the difference increases to 14.5%  
Conceptualization, M.K. and R.P.; methodology, R.P.; validation, M.K. and A.J.; formal analysis, M.K. and R.P.; investigation, M.K. and A.J.; resources, R.P.; data curation, M.K.; writing--original draft preparation, M.K.; writing--review and editing, R.P. and A.J.; visualization, M.K. and A.J.; supervision, R.P.; project administration, R.P. All authors have read and agreed to the published version of the manuscript.  
The article was written as part of the implementation of the university research grant No. 22-769 of the Military University of Technology.  
Not applicable.  
Data availability StatementData is unavailable due to privacy restrictions.  
The authors would like to thank [PERSON] from the Institute of Mechanics and Computational Engineering of the Military University of Technology for his help in conducting material tests on 41 Cr4 steel.  
The authors declare no conflict of interest.