Further Study On The Penetration And Perforation Of Metallic Targets Struck By Long Rods

Further study is conducted in this thesis on the penetration and perforation of metallic targets struck by long rod penetrators at high speeds. The crater formed in semi-infinite metallic targets is analyzed and the geometry of the rod head during the penetration process examined by combined experimental and theoretical methods. A theoretical model for the perforation of finite metallic targets by long rods is proposed; Based on the recently suggested ID theory of long rod penetration, Phase three penetration mechanism is investigated and an equivalent density model is suggested to predict the depth of secondary penetration; The effect of material compressibility on the penetration of long rods into semi-infinite targets at high velocities is considered; Plastic wave models are proposed for the plugging failure of intermediate and thick metallic plates struck by flat-ended cylindrical projectiles. The main contents and results of the thesis are as follows:Two analytical models are presented to predict the diameter of crater in semi-infinite metallic targets struck by long rod penetrators. One of models is constructed by using the laws of conservation of mass, momentum, energy, together with the u-v relationship of the newly suggested ID theory of long rod penetration; and another by using the balance of forces exerted on the eroded rod debris which flows around the mushroom head. The shape and diameter of the mushroom head in the second model was suggested based on numerical analysis and experimental investigations. It is demonstrated that the model predictions are in good agreement with available experimental data.Secondary penetration is examined in the present thesis due to the fact that the eroded rod debris forms a tube which can penetrate the target further if the density of rod is greater than that of target and the impact velocity is high enough. A critical condition for secondary penetration is obtained and an equivalent density model proposed to study the depth of secondary penetration. Models for predicting the penetration depth and crater diameter in semi-infinite metallic targets by long rods are extended to jacketed rods in co-erosion mode. It transpires that the present model predictions are in good agreement with the experimental observations for EN24steel jacketed tungsten alloy long rods penetrating semi-infinite armor steel targets in terms of crater diameter and penetration depth.An analytical equation is presented to predict the penetration depth of semi-infinite metallic targets struck normally by long rods at high velocities based on energy balance method. It is assumed that the kinetic energy loss of a long rod is related to the energy dissipated by the plastic deformations in the target, the energy consumed by the long-rod penetrator itself and the energy carried by the eroded rod debris. The present analytical equation is found to be in good agreement with the experimental data for a wide range of impact velocities.The perforation of a finite metallic target struck by a long rod at high speeds is examined based on the newly suggested1D theory of long rod penetration,the adiabatic shear plugging model and the assumption that the perforation processcan be divided into three stages:(1) initial penetration into the plate;(2) plug formation;(3) plug sliding and separation. A theoretical model is proposed to predict the ballistic limit, residual velocity and residual length of the rod. It is found that the model predictions are in good agreement with experimental observations in terms of ballistic limit, residual velocity and residual length of the rod.The effect of material compressibility on long rod penetration is investigated based on the A-T model. The Murnagham equation of state is employed in the present model, where the effect of ordinary p-v work and shock waves are considered. It transpires that the density and pressure near the interface between target and rod increases with increasing impact velocity.Plastic wave models are suggested for the plugging failure of intermediate and thick metallic plates struck by flat-ended cylindrical projectiles. Three cases are examined i.e. rigid projectiles, deformable projectiles and erosive projectiles. A two-stage model is employed to describe the width of the shear band, where the simple shear band will be transformed into adiabatic shear band. The widths of simple shear and adiabatic shear band were theoretically derived by Bai et al. The rod plastic deformation, residual velocity and residual length of the rod, the diameter and length of the plug were investigated. It transpires that the present model predictions are in good agreement with the experimental data for metallic plates struck normally by flat-ended cylindrical projectiles.