NUMERICAL AND EXPERIMENTAL INVESTIGATION OF COUNTERINTUITIVE DEFLECTION IN BLAST-LOADED METAL PLATES

Thin-walled metal plates are frequently used in engineering applications where weight reduction and structural efficiency are essential. However, when subjected to blast loading, these plates may display counterintuitive behavior (CIB), characterized by final permanent deflection towards the blast source rather than away from it. This phenomenon, known as reverse snap buckling, has been observed under specific conditions where the interaction between elastic deformation, plasticity, and inertial effects leads to an unexpected structural response. Despite prior studies, a thorough understanding of the mechanisms governing CIB remains elusive due to its strong dependence on material properties, strain rate effects, pressure-time history, stand-off distance, and boundary conditions. The transition from an intuitive response (IB) - where the plate deforms outward - to CIB is highly sensitive to these parameters, making predictions particularly challenging. This study investigates CIB in Aluminum Alloy 2024-T3 circular plates through a combined experimental and numerical approach. Blast tests have been conducted on plates under varying boundary conditions and loading scenarios to capture the onset and evolution of CIB. At the same time, finite element simulations have been employed to explore the phenomenon's sensitivity to key parameters, validate experimental findings, and provide insights into the underlying physics. A mapping of the IB and CIB regions has been developed to enhance the understanding of the conditions leading to this peculiar response. The results of this study will aid in developing predictive models for blast-loaded structures and improve design strategies for lightweight metallic components exposed to extreme loading conditions.