A recent study published in Aerospace combined the projectile breakdown theory and projectile impact model to analyze helicopter fuselage projectile damage. The efficacy of the proposed analysis method was compared to that of the finite element method (FEM).
Study: An Efficient Analysis Method of Aluminum Alloy Helicopter Fuselage Projectile Damage Based on Projectile Breakdown Theory. Image Credit: Wojciech Wrzesien/Shutterstock.com
Background
In modern local warfare at low altitudes, the helicopter fuselage is susceptible to damage from gunfire, and repair during the battle requires rapid assessment of projectile wounds. Thus, the efficiency of analysis directly affects the battlefield's rapid repair efficiency of helicopter fuselage damage.
It is difficult for a FEM to investigate the helicopter fuselage projectile damage in a multi-projectile environment due to the fuselage’s complex shape and structure.
FEM-based numerical simulations focus mainly on residual velocity and damage of simple flat plate models, requiring huge computational time to evaluate a helicopter fuselage injury with complex structures.
Thus, this study proposed an efficient analysis method for helicopter fuselage projectile injury by coupling a projectile penetration theory with a projectile collision calculation model.
The computational results were compared with experimental data to validate the method’s accuracy.
Computational Methods
Firstly, the researchers established an analysis method including projectile penetration theory and projectile collision model to quickly compute the projectile impact coordinates, residual velocity of the projectile body, and the fuselage damage area (fuselage material was aluminum alloy 2A50) under multi-projectile environments.
Subsequently, FEM was used to analyze the helicopter projectile injury process and damage in detail.
A three-dimensional (3D) helicopter model in STL (standard triangle language) format comprising numerous triangular facets was used for projectile collision. The collision of the projectile with the helicopter fuselage was determined by analyzing the intersection points and triangular face pieces in the 3D model.
If the intersection point was within a triangle face piece, it divided the piece into three sub-triangles. The total area of these sub-triangles was equal to the area of the triangle face piece.
Alternatively, if the intersection point was outside the triangle face piece, the total area of sub-triangles was greater or smaller than the area of the triangle face piece.
These calculations provided the projectile strike’s coordinates. Subsequently, the extent of the impact of a projectile injury was analyzed at six collision points. Furthermore, the residual velocity and damage area were calculated at different incidence angles.
The helicopter fuselage’s damage process and configuration at six strike points were further analyzed by coupling the ABAQUS (FEM) software with the proposed method.
Based on the determined six impact points coordinates, the angle of incidence, and the projectile injury features, the projectile and helicopter fuselage were assembled in the assembly module.
Finally, the impact was calculated using ABAQUS/Explicit with a rear fuselage solid support and 1,000 m/s initial velocity as the boundary conditions.
Results and Discussion
The experimental data from previous studies was used to verify the accuracy of the proposed method. The selected experiment used a two-stage air gun system to launch projectiles.
For the same incidence angle and thickness, the projectile residual velocities of the projectiles with different initial velocities predicted by the proposed method agreed well with the experimental data, and the maximum error was 2.3%.
The projectile residual velocity and damage region estimated by the proposed method and FEM were similar.
The percentage differences between the residual velocity determined using these two methods for the six impact points were 3.1%, 2.0%, 2.20, 2.26%, 4.7%, and 3.4%, respectively.
The corresponding percentage differences between the damaged area identified by the two methods were 8%, 5.02%, 5.88%, 9.56%, 4.88%, and 7.97%, respectively. Hence, the proposed method of projectile injury analysis could obtain results approximate to the FEM.
Furthermore, the proposed method could simultaneously analyze the damage of multi-projectile strikes. Notably, the calculation time remained constant despite the increasing number of strikes.
Alternatively, the FEM computational time increased linearly with an increase in the number of strikes. For the analysis of six different strikes, the proposed method consumed 92.1% lesser time than FEM, exhibiting a higher efficiency.
Conclusion
Overall, the proposed analysis method for helicopter fuselage projectile damage combining the projectile penetration theory and projectile impact calculation model, exhibited comparable results to the FEM with 92.1% higher efficiency.
The maximum errors in estimating the residual velocity and fuselage damage area were 4.7% and 9.56%, respectively. In addition, the predicted residual velocities agreed with the experimental data with a maximum error of 2.3%.
The researchers claim that this efficient method can evaluate the actual war situation of a helicopter being hit by multiple projectiles.
It can enable engineers to generate the surrounding multiple-projectile distribution according to the position of the guns on the ground relative to the helicopter. Consequently, the striking point injury and helicopter fuselage damage can be quickly assessed.
Journal Reference
- Xing, X., Tan, J., Yang, Y., Yong, T., Yu, L., & Zhou, Y. (2024). An Efficient Analysis Method of Aluminum Alloy Helicopter Fuselage Projectile Damage Based on Projectile Breakdown Theory. Aerospace, doi: https://doi.org/10.3390/aerospace11060500. https://www.mdpi.com/2226-4310/11/6/500
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.