Study On Resistance Of Rigid Flat Projectile Penetrating Into Reinforced Concrete Target

Concrete is a typical multiphase material.Because of the addition of steel bars,it can improve the bearing capacity of concrete and make up for the weakness of its tensile performance.It is widely used in all kinds of buildings.In military warfare,it is a key issue that how to effectively destroy targets or resist precise strikes in the field of weapons and protection.The analysis and characterization of penetration resistance is the basic basis for solving these problems.Therefore,it is of great military significance to analyze the resistance of projectile penetrating into reinforced concrete.In this paper,the rigid flat-headed projectile is taken as the research object,and its penetration speed is less than 800m/s.Based on the bending shear failure of steel bars,the penetration resistance is analyzed from two angles: theoretical and numerical simulation.(1)Based on the theoretical analysis,a dynamic analysis model of penetration resistance is established for the direct collision of projectile body with single bar and multiple reinforcement bars.Based on the theory of penetrating into plain concrete,The relationship between the motion parametersof the projectile and the time is deduced.The penetration depth obtained by using the iterative formula is compared with the young formula,and the validity of the model is verified.Based on the theoretical model,it is analyzed that the effects of different reinforcement ratios and different penetrating position on the penetration of projectile.Under the condition of different reinforcement ratio,it is compared and analyzed that the penetration resistance of projectile body penetrating into different diameters of steel bars(8mm and 30mm),and it is given that the influence of reinforcement ratio on penetration of projectile body.Under the conditions of different penetration positions,in order to ensure that the body’s force is symmetry and trajectory do not deflect,three special penetration positions are considered,such as a rebar mesh,rebars intersection and midpoint of a rebar.By analyzing the penetration resistance of different projectile diameters(100mm and 140mm),the most unfavorable penetration position is obtained.In view of protection,an engineering calculation formula of penetration depth was proposed under the most unfavorable working condition of.(2)In the numerical simulation,LS-DYNA is used to carry out numerical analysis on the process of projectile penetrating into reinforced concrete.Concrete selectes constitutive model of the HJC,and adds two failure parameters of maximum principal strain and shear strain in the setting of material erosion parameters.Steel bars use bilinear follow-up reinforcedmaterial model and add shear strain failure parameters in the setting of material erosion parameters.The reliability of the numerical model is verified by comparing the calculation results of the numerical simulation and theoretical model with the Young formula.It is carried out that the quantitative analysis of the influence of the geometrical dimensions of the projectile on the penetration parameters of reinforced concrete,and the general rule is obtained that the flat head rigid projectile penetrates the reinforced concrete target.The effects of different rebar diameters and mesh on the penetration of projectile under the same reinforcement ratio are analyzed.At the same reinforcement ratio,the resistance to penetration of the projectile is analyzed under the different parameters of steel bar diameter and mesh size.It is obtained that the influence of reinforcement parameters on projectile penetration.