Document Type : Original Article
Authors
- Pooya Pirali 1
- Mohsen Heydari Beni 1
- Sajjad Nourbakhsh Shabanlou 1
- Jafar Eskandari Jam 1
- Majid Eskandari Shahraki 2
1 Faculty of Materials and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran.
2 Department of Aerospace Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
Abstract
In real-world scenarios, projectile impacts on targets rarely occur at perfectly normal angles. This study employs the finite element software LS-DYNA to numerically investigate the oblique penetration and ricochet behavior of the 7.62 mm APM2 armor-piercing projectile against AA6082-T4 aluminum alloy targets. The material behavior was modeled using the modified Johnson-Cook constitutive model, with failure assessed via the Cockcroft-Latham criterion. The model was validated against experimental data, showing good agreement with exit velocities. A central focus was to evaluate the common simplification of neglecting projectile rotation. Parametric analyses revealed that the critical ricochet angle (θc) increases with impact velocity, rising from 62° at 830 m/s to 80° at 1800 m/s for a 20 mm target. Crucially, while axial rotation was found to have a negligible effect on θc (variation < 1°), it significantly reduced the projectile's residual velocity by 5–15% and influenced its trajectory. Additional analyses showed that target thickness and projectile nose shape are also dominant factors; for instance, θc decreased from 74° to 65° as thickness increased from 10 mm to 30 mm. The results demonstrate that while rotation can be ignored for estimating the critical angle, neglecting it leads to substantial inaccuracies in predicting residual velocity and energy, and is therefore not recommended for high-fidelity simulations. These findings provide critical insights for optimizing armor design and improving the accuracy of ballistic simulations.
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