Investigation Of Finite Cavity Expansion And The Mechanism Of Confined Concrete Against Penetration

On the background of new technology in shielded structure, and for the potential advantages of confined concrete used in shielded structure and severe insufficient of related studies, this paper investigated the analytical solutions 、 experiments and numerical simulations of confined concrete unit impacted by 12.7mm armor piercing projectile(APP). Great emphasis was laid on the mechanism and the anti-projectile performance of penetration into confined concrete filled steel tube. All those will provide the basis for the in-depth study and application of confined concrete used in shielded structure. The innovative contents and work include:(1) Improved the existant incompressible Finite Spherical/Cylindrical Cavity Expansion in elastic-plastic materials. This paper considered the effects of compressibility and boundary displacement to propose the compressible Finite Spherical/Cylindrical Cavity Expansion models. And the results show that: when the elastic wave doesn’t reach the boundary, the model is identical with the infinite cavity expansion; when the elastic wave reaches the boundary, the target is in elastic-plastic stage, the effect of boundary displacement is subtle which can be neglected; when the plastic region reaches the boundary, the boundary displacement is large and the effect of boundary displacement should be considered.(2) Proposed the Finite Spherical/Cylindrical Cavity Expansion models of confined concrete targets and gained analytical solutions on the cavity stress. And the results show that: At the beginning of cavity expansion process, the lateral confinement effects slightly, then with the proceeding of expansion, the confinement improves significantly the cavity stress; the small lateral confining rigidity improves slightly the cavity stress while the large lateral confining rigidity improves significantly; the increment of cavity stress caused by confinement will descend with the increasing confined rigidity, therefore, there exists proper confining rigidity and target radius.(3) Carried out the experiments of concrete filled steel tube impacted by 12.7mm armor piercing projectile(APP), then gained the failure modes and main failure indexes. The results show that: the confined concrete filled steel tube impacted at high velocity(above 800m/s) will develop crater on proximal face、hoop cracks on side face and slippage on distal face; the confined concrete filled steel tube is 15% better than the infinite concrete targets in anti-projectile performance; the confined concrete filled steel tube works well against multi-impact.(4) Combined the ballistic experiments、numerical simulations and Finite Cavity Expansion models, this paper analyzed the mechanism and anti-projectile performance of penetration into confined concrete filled steel tube. The results show that: confined concrete filled steel tube is better than infinite concrete in anti-projectile performance, the confinement of steel can effectively reduce the damage of concrete which is helpful for multi-impact; increasing the lateral confining rigidity can improve the anti-projectile performance of confined concrete filled steel tube and a proper small target size can utilized the lateral confinement effectively and reduce the damage of concrete.