Penetration And Perforation Mechanism Of Rigid Projectile Into The Concrete Target

In this dissertation, the normal penetration of rigid projectile into the concrete target and reinforced concrete target, the oblique penetration, normal and oblique perforation of rigid projectile into the concrete target were studied by using the analytical model, experimental research and numerical simulation.The primal contents and conclusion in this dissertation are as follows:1) The process of normal penetration of the rigid projectile into the semi-infinite thick concrete target was studied. The concrete material in the comminuted region (plastic region) was supposed to be described by the Griffith strength theory. On the basis of the Griffith strength theory, the corresponding static and dynamic cavity expansion models were established. Based on the dynamic cavity expansion theory, the analytical model of normal penetration of a rigid projectile into a concrete target was developed. The validation of this analytical model was done through a comparison of results from the analytical model with the experimental results published in the literature. The normal penetration experiments into the concrete targets were conducted with the kinetic projectiles. The corresponding finite element simulation models were also constructed. The predictions from the analytical model which was based on the Griffith strength theory are in agreement with the results form experiments and simulations.2) The process of normal penetration of the rigid projectile into the semi-infinite thick reinforced concrete target was studied. The post-test failure characters of the steel bars were analyzed. Two structure response models:bending plus shearing failure and bending plus end tension fracture were used to simplify the failure models of the steel bars. On the basis of the failure theory of beam, the direct resistance of steel bar for the process of the projectile passes through the middle of the reinforcement was analyzed. The difference computational model for normal penetration into the reinforced concrete target was developed based the normal penetration resistance model for the concrete material which was supposed to be described by the Griffith strength theory. The validation of this computational model was done through a comparison of results from the computational model with the experimental results published in the literature. The normal penetration experiments into the reinforced concrete targets were conducted with the kinetic projectiles. The predictions from the analytical model were compared with the post-test penetration depth-time history, penetration velocity-time history and penetration deceleration-time history. Comparative results show that the influence of steel bar is local for the penetration process. The penetration resistance of concrete material is the main component of the penetration resistance of the reinforced concrete medium.3) The process of oblique penetration of the rigid projectile into the semi-infinite thick concrete target was studied. Based on the geometric relation between the projectile attitude and the fictitious horizontal plane, the actual dimension of the projectile stress surface at different time was analyzed. The projectile stress surface was partitioned into a series of element sides by using the method which was developed from the equal division method for the projectile stress surface. With this method, the accumulating ranges of the axial and circumferential coordinate of the starting points of the element sides were obtained. The analytical model of the distance from the spherical centre to the elastic region superficies externals of the finite sphere (the horizontal plane of the target) was developed based on the geometry relation between the projectile attitude and the horizontal plane of the target. The value ranges of the axial and circumferential coordinate of the starting points of the element sides which were affected by the free surface of the target (the horizontal plane of the target) were obtained. The analytical model of the modified radial Cauchy stress component over the element side of the projectile stress surface was derived by introducing the finite spherical cavity expansion theory. The transformation method for the integral models of the resistance and resistance torque over the projectile stress surface and the accumulation models of the resistance and resistance moment over the element sides was analyzed. On the basis of the planar motion difference equation using the time as increment, the difference engineering computational model for the oblique penetration into the concrete target with the projectile (hemi-spherical nose projectile and ogive-nose projectile) was developed. The experiments of oblique penetration of the kinetic projectiles into the concrete targets were conducted. The predictions from the difference engineering computational model are in agreement with the results from experiments.4) The perforation process of the rigid projectile into the finite thick concrete target was studied. Based on the penetration resistance theory for arbitrary nosed projectile, the analytical model of penetration resistance was developed by introducing the finite spherical cavity expansion theory. The difference computational models for the normal perforation process were developed based on the modified ballistic limit velocity theory and the analytical model of reducing stress surface which was based on the finite spherical cavity expansion theory. The analytical model of the distance from the spherical centre to the elastic region superficies externals of the finite sphere (the two free surfaces of the target) was developed based on the geometry relation between the projectile attitude and the two free surfaces of the target (the horizontal plane and rear surface of the target). The computational model of the modified radial Cauchy stress component over the element side of the projectile stress surface was also derived by introducing the finite spherical cavity expansion theory. The analytical model of the reducing stress surface for the oblique perforation concrete target with projectile was developed based on the reducing stress surface model for the normal perforation process. On the basis of the difference computational model for oblique penetration process, the difference computational model for the oblique perforation of concrete target by the projectile (hemi-spherical nose projectile and ogive-nose projectile) was developed. Multi-group finite element models of the concrete targets subjected to projectiles perforation at different oblique angles were constructed. The predictions from the difference computational model for the oblique perforation process are in agreement with the results from simulations.