Abstract
The behaviour of exposed and copper-jacketed 12.7 mm En8 steel cores impacting against 5 and 9 mm Armox Advance plates was investigated to determine the significance of the jacket during the penetration. The target plates were accelerated into stationary projectiles (a reversed-ballistic configuration) and the impact was monitored using a multichannel flash X-ray system to gain insight into the interaction of the core target. Numerical simulations were also carried out to compare result with the experimental testing. Explicit numerical software LS-DYNA was used to model the behaviour of the target and the projectile during the impact collision. Fragments of the core and target plate were collected post-shot for analysis. A similar penetration behaviour was observed for both plates, although the post-shot core was shorter after impacting against the 9 mm plate, consistent with enhanced erosion behaviour. The copper jacket protected the core, resulting in greater surface defeat and dwell compared to the unjacketed core. Numerical studies agreed on the cases of projectile impacting the 5 mm and 9 mm target. However, the target fracture cannot be captured. This could be caused by the input of material data and strain rate parameter modelling in LS-DYNA was limited, while the impact phenomenon was high velocity impact that the material exhibits a highstrain rate effect. Overall, the ductile jacket appeared to serve two functions: (1) Absorbing reflected energy during impact, hence cushioning the impact and thereby preserving the core, and (2) constraining or confining the core. In this study, the steel core design and copper jacket has a more complex geometry compared to the simplified steel core designs often applied in several earlier ballistic studies. The captured flash X-rays revealed significantly less erosion in the jacketed cores, agreeing with the post-impact core length measurements.
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Acknowledgments
The authors would like to thank Karl Norris, Adrian Mustey, David Wood and Andrew Roberts for help in preparing the targets and supporting the ballistic testing in of the Dynamic Response Group at Cranfield University’s Shrivenham Campus. The authors also acknowledge the Indonesia Endowment Fund for Education (LPDP) which supported both the experiments and the M.Sc. by Research programme. Thanks are due to LSTC for providing academic license on LS-DYNA computational software.
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Denny Lesmana received his B.Sc. degree (Chemistry) at Brawijaya University, Indonesia in 2010 and his M.Sc. degree (Defence and Security) at Cran-field University, UK in 2018. He is currently working as an expert in Ammunition Process and Product Development at PT. Pindad (Persero). His research interests are ammuntion design, warhead system, engineering simulation (CFD and structural analysis), fragmentation, and defeat mechanism.
Faizal Arifurrahman received his B.Sc. degree in Aeronautics and Astronautics at Institut Teknologi Bandung (ITB), Indonesia in 2015 and his M.Sc. degree in Military Vehicle Technology at Cranfield University, United Kingdom in 2017. He is currently working as a junior staff in Faculty of Mechanical and Aerospace Engineering (FTMD), ITB Indonesia. His research interests are mechanics of material, material dynamics, lightweight structures, and vehicle armour protection system.
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Lesmana, D., Arifurrahman, F., Hameed, A. et al. On the importance of the bullet jacket during the penetration process: Reversed-ballistic experimental and numerical study. J Mech Sci Technol 34, 1871–1877 (2020). https://doi.org/10.1007/s12206-020-0408-9
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DOI: https://doi.org/10.1007/s12206-020-0408-9