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Simulation on Structural Response and Development of a Vulnerability Analysis Method for Complex Systems Subjected to Impact Force

Simulation on Structural Response and Development of a Vulnerability Analysis Method for Complex Systems Subjected to Impact Force
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A vulnerability assessment procedure for combat systems under impact loading was proposed in this dissertation. Local impact simulations were performed to predict the impact forces generated by a high velocity projectile and blast pressure using AUTODYN. The resulting penetration behavior of a steel panel was analyzed for various projectile velocities, sizes, and panel thicknesses. Three-layer panels with Kevlar as the core material were simulated to understand the effects of structural layering on the reduction of the impact force. The forces acting on the panel in the longitudinal and transverse directions were calculated from the obtained stress distribution in the local deformation model. The impact forces caused by blast pressure were also obtained from the local impact simulation. Using the estimated force input, the vibration resulting from high velocity projectiles impacting on a structure was simulated for complex structures. The structural behavior of a three-dimensional structure subjected to impact forces was predicted using the spectral element method. The Timoshenko beam function was applied to simulate the impact wave propagations induced by a high-velocity projectile at relatively high frequencies. The interactions at the joints were analyzed for both flexural and longitudinal wave propagations. The effects of rigid body mounted on the structure on the wave propagations were also investigated by considering the mass-stiffness interaction. Transient longitudinal and flexural wave propagations were calculated to analyze the radiation of the impact energy along the structural span. The impact responses of the complex structures calculated by using the spectral element method were compared to the results obtained using the finite element analysis and the impact test results for validation. Finally, simulations of the impact energy transfer through the three-dimensional combat vehicle model were performed, and the sound pressure radiating from the vibrating structure was also calculated. The results were used to directly assess the combat vehicle’s vulnerability to the impact loading. The system configurations of a combat vehicle were first defined for vulnerability analysis. The kill probabilities of the crucial components for an operating system were calculated as a function of the predicted acceleration amplitudes, according to the acceptable shock response spectrum. The vulnerabilities of a specific system were obtained from the assumed fault trees representing mission kills on a logical basis. The impact-induced vulnerability of the combat system was then calculated and compared with different impact conditions. Following the proposed vulnerability assessment procedure, the vulnerable positions of a three-dimensional combat vehicle with high possibilities of damage generation of components due to impact loading were identified from the estimated shock response spectrum. The effects of several design parameters, such as the impact direction, the projectile velocity, the number of hits, the allowable acceleration level, and the support stiffness of the component on the system failures were discussed for the purpose of vulnerability reduction. The proposed vulnerability analysis method requires less computation time compared to the conventional method to calculate the system vulnerability for various impact conditions. Furthermore, the proposed method is applicable for assessing the vulnerability of a wide variety of combat systems, and for developing shock reduction materials and structures.
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