International Journal for Research in Applied Science & Engineering Technology (IJRASET)

ISSN: 2321-9653; IC Value: 45.98; SJ Impact Factor: 7.538

Volume 11 Issue III Mar 2023- Available at www.ijraset.com

The numerical results corresponding to residual velocities of different configurations (0.5/0.5, 0.67/0.33, 0.33/0.67) and span diameters (68, 100, 150 and 200 mm) of the shells have been presented in Table 2 against ogive nosed projectileimpact. The predicted residual velocity for 1 mm thick monolithichemispherical shell was quite close to actual residual velocity. Further, the graphical representation of similar results has been shown in Fig. 3 for direct comparison of the monolithic target with different layered configurations of 68, 100, 150 and 200 mm span diameter. All double-layered hemisphericalshell configuration offered larger drop in the residual velocitythan the monolithic hemispherical shell. Moreover, the double layered configu ration with equal thickness 0.5/0.5 showed highest decrease in the re sidual velocity followed by the0.67/0.33, 0.33/0.67 and the single layered target, respectively.The maximum deviation in between the experimental and thenumerical results was found to be 10.43 m/s for 200 mmdiameter. The influence of target configurations was muchsignificant close to ballistic limit which subsequentlydecreased with increase in the incidence velocity of theprojectile, see Fig. 3. Similar trend was found for plastic deformation of the shell with incidence velocity of the projectile. The deviation of numerically predicted results fromactual experimental results was quite small.

The ballistic limit velocity(V50) was obtained toquantify the per formance of the target against the ogivenosed projectile. It was obtained through the average of themaximum projectile velocity, at which target couldn’t getperforation and the minimum projectile velocity and thevelocity at which the target completely perforated. Theballistic limit velocities of different span diameter withvarying configurations have been shown in Table 3 which wasfurther represented in Result showed that the ballistic limit ofthetarget was increased with increasein the span diameter ofthehemispherical shell. Moreover layering of the hemispherical shell enhanced the ballistic resistance of theshell. How ever, the double layered target (0.5/0.5) showedthe highest ballistic limit followed by the (0.67/0.33),(0.33/0.67), and 1 mm monolithic target.

The ballistic limit of the layered hemispherical shell 0.5/0.5, 0.67/ 0.33, 0.33/0.67 for 68 mm diameter was 16.8%, 9.54% and 6.55% higher than the monolithic hemispherical shell, for 100 mm span.

B. Test Procedure

The following is the standard test procedure with proper safety

1) Configure/Set up test fixture

2) Turn on helium pressure in trailer

3) Turn on power to electromagnetic coils and data acquisitionsystem

4) Ifnecessary, set up high speed video

5) Close trigger ball valve

6) Insert projectile into gun barrel

7) Ifnecessary, set up gun barrel wire trigger

8) Set regulator on nitrogen bottle

9) Ifnecessary, turn on lights for high speed video

10) Close and lock all test area doors

11) Chargehelium bottle to desired test pressure

12) Turn weapon keylock to “weapon ready”

13) Press “system ready” button

14) Arm data acquisition system

15) Press “test” button

16) Press “arm” button

17) Activate siren

18) After 5 second audible count down, press “fire” button

19) Press “endtest” button

20) Turn weapon keylock to safe position andremove

21) Ifnecessary, turn off lights for high speed video

22) Ifnecessary, save high speed video recordings

23) Record projectile velocities from data acquisitionName:

24) Close valves on nitrogen cylinder andhelium trailer

25) Remove specimen from test fixture