Investigation On The Mass Abrasion And Motion Of The Projectile Non-normal Penetrating Into Concrete

The non-normal penetration/perforation of rigid/eroding projectile into concrete wasinvestigated through theoretical analysis, numerical simulation and experiments. After theconfirmation for the applicability of the cavity expansion theory for different targetmaterials, the penetration model considering shank friction was constructed. Jones massabrasion model and Warren free surface model were improved. The trajectory predictionmodels for rigid projectile non-normal penetrating into semi-infinite targets andrigid/erosion projectile non-normal penetrating into finite thickness targets were established.The influence factors of penetration trajectory, axial/lateral deceleration of projectile werestudied. The research results are available for the estimating of the penetrating ability, theanalysis of the structural response, the optimizing of the structure and the choosing of thematerial for the high velocity non-normal penetrator.(1) The effect of the target inertia term of rigid projectiles’ penetration resistance wasinvestigated using dynamic finite element analysis code LS-DYNA. It is found that formetal targets, the penetration resistance during steady penetration can be treated asconstant; but for brittle targets, like concrete, there is a critical velocity, higher thanwhich the effect of inertia term in penetration resistance is obvious. The cavityexpansion theory are available for brittle targets. The damage number of target can beused to measure the influence of the inertia term. The smaller the damage number is,the less influence the inertia term has.(2) Based on cavity expansion theory, the penetration model considering shank frictionwas constructed. The influence rule of shank friction on penetration was researched.When the initial velocity is in the range of800~1300m/s, a deviation of at least10%onthe penetration depth would occur if shank friction is neglected.(3) The influence of projectile material on mass abrasion of the projectile was investigatedby experiments and theoretical analysis. The Jones mass abrasion model was modified.A method, which can estimate the variation of the nose shape, was developed.Compared with the experimental data, it is shown that the modified model is available for softer and harder material in the calculation of mass loss, penetration depth, noseshape variation, et al.(4) The trajectory for rigid projectile non-normal penetration into semi-infinite target wascalculated based on differential area force law, cavity expansion theory, and modifiedfree surface model. Wake separation and reattachment effect was also considered in thecalculation. The comparison with the experimental data indicates that the trajectorycalculation method proposed in this paper can be used to predict the attitude angle, theaxial/lateral deceleration and corresponding displacement of the projectile. Theinfluence factors of penetration trajectory, axial/lateral deceleration of projectile werestudied. Some optimized design schemes for the high-velocity penetrators were givenfor decreasing the trajectory offset and the axial/lateral deceleration of the projectile.(5) Based on the modified mass abrasion model and trajectory prediction model for rigidprojectiles’ non-normal penetration into semi-infinite targets, the trajectory predictionmodel for eroding projectiles penetrating into finite thickness targets was constructedby introducing the free surface effect for the back of the target. The influence ofasymmetrical erosion on the penetration process was studied. The comparison with theexperimental data indicates that the theoretical model can accurately predict the massloss amount and the penetration path well. At the beginning of the penetration, theaxial/lateral deceleration, the vertical/transverse displacement, the angular accelerationand the angular velocity of the erosion projectile is bigger than that of the rigidprojectile. The final vertical/transverse displacement as well as the attitude angle wouldless than that of the rigid penetration, when asymmetrical erosion is considered.(6) The trajectory predicition model for rigid projectile non-normal penetration/perforationinto finite thickness targets was constructed. The comparison with the experimentaldata indicates that the theoretical model can make an accurate prediction of thevertical/transverse displacement and the attitude angle of the projectile during thevertical/non-normal penetration, and the residual velocity, the change of the attitudeangle during the vertical/non-normal perforation process.