Research On The Performance Of Projectile Penetration And Perforation Into Concrete Target

The concrete structure is a common layout of protective engineering in the cut-and-cover works.Advance concrete materials are developing rapidly,so it is more important and urgent to study the interaction between the projectile and concrete target.Most of research is still concentrated on the normal incident cases;the research of oblique penetration is relatively littered.The research of ballistic deflection and collapse of projectile non-normal penetration and perforation into of finite thickness concrete target needs to go future.Focused on this key issue,the normal and oblique penetration,normal and oblique perforation of projectile into the concrete target were studied by using the analytical model,experimental research and numerical simulation.The research results can provide theoretical basis for the prediction of penetration capacity,structural response analysis,structural optimization and material selection of non-normal penetration.The primal contents and conclusion in this dissertation are as follows:1)The process of oblique penetration of projectile into the semi-innfinite thick concrete target was studied.The penetration characteristic of crater zone was analyzed by using the stress wave surface damage theory.The crater mechanism was explained based on spallation due to the reflection of the stress wave.The stress formula of the projectile surface oblique penetration was given considering the target surface crack effect and the rigid body kinematics theory.The calculation model was successfully established for different target pose,and different nose shape of projectile penetrating concrete target.The penetration experiments into concrete target were carried out.The experimental data of penetration depth and deflection angle of projectile were obtained to verify the theoretical model.The experimental results were in good agreement with the theoretical calculations and verified the reliability of the oblique penetration model based on the mechanism of spallation.2)Ballistic deflection and ricochet of oblique penetration into concrete were studied.First dimensional analysis of projectile structure on ballistic deflection was carried out,and oblique penetration simulation model was established under different nose-shapes.The ballistic deflection effect was given.The ballistic deflection was simulated with different oblique angles and yawed angles.The results show that the deviation angle of the truncated ogive projectile is small,the anti-ballistic ability of deterioration is strong,penetration ballistic is relatively good,concave and ogive projectile second;penetrating ability of projectile nose with high density and high hardness tungsten alloy is stronger,ballistic deflection angle smaller;the negative attack angle may reduce the deflection of penetration trajectory,and the positive attack angle may enlarge its deflection..Then the ricochet was analyzed.Experiments of ricochet were carried out and simulation model of ricochet was built.Numerical simulation of ricochet during oblique penetration into concrete target was produced,and the numerical simulation results and experimental results and the theoretical calculated values were compared to verify the correctness of theory analysis model.Finally,the qualitative study of various factors through the orthogonal test was analyzed to identify the ricochet.The results show that the critical angle of ricochet increase with the length of nose sharp increase.The material,and the nose shape,and the velocity of projectile are influence factors of overturning moment.The order of factors affecting the ricochet from big to small is the shape of the nose,the material of the projectiles and the penetrating velocity respectively.3)The perforation process of projectile into the finite thick concrete target was stuied.The normal perforation process of concrete targets with different thickness was described and crater of concrete target based on layer crack mechanism was qualitative analyzed.The model experiments of the finite thickness concrete target were conduct,and the typical failure model of the target plate and the residual velocity after penetration were obtained.The perforation process of the target plate correspond to experiment results was simulated,and the physical process of the occurrence of the concrete target was described.The dimensionless relation of each parameter influence on impact damage effect was obtained by dimensional analysis,and curve fitting of the experimental data was given by least square method.The residual velocity formula was derived and was good aggrement using the three methods.Based on the target free surface layer crack mechanism and plugging failure assumption,introducing the nose shape factor and impact function,engineering model of oblique perforation of the finite thickness concrete target was established.The model was divided into three stages of crater section,and reaming section,and shear punch slug.The calculated values of the residual velocity and rotation curve were obtained.The numerical simulation of the projectile oblique perforation into the concrete target was built and compared with the oblique penetration process model.The results show that:theoretical and simulation results are in good agreement with,the model can provide a reference for the penetration mechanism of finite thickness target.4)Equivalent study of concrete target structure was carried out.The theoretical analysis of projectile penetrating the boundness concrete target was given.Based on the theoretical analysis,numerical simulation of ogive nose projectiles penetrating into cylindrical target was done under the free boundary and non-reflecting boundary with different velocity.The relationship between target diameter size and the velocity when target side constraints can be neglected was getten.Numerical results were given under different boundary conditions effect on the penetration of the target body to equivalent semi infinite target.The influence of restrained steel plate on the penetration depth was analyzed.According to different diameter of target and projectile,the equivalent boundary constraints were given.The concrete target was designed in order to achieve the purpose of penetrating semi infinite target of different sizes according to the requirements of the different test,thereby greatly reducing engineering test cost.To establish the equivalent of anti-penetration behavior of reinforced concrete and plain concrete,experiment research on two medium is carried out using 25 mm smoothbore gun,some parameters are obtained,such as velocity,penetration depth,crater diameter and target destruction shape parameters.The results show that penetration depth decreases slightly with the increase of reinforcement ratio,the addition of steel bars is beneficial to improve the penetration resistance of concrete.LS-DYNA software was used to simulate at the same vertical velocity penetration and perforation of concrete and reinforced concrete,the equivalent relation of thickness was obtained.The research can provide theoretical basis and data reference for constructing equivalent target.