Study On Armor Steel-concrete Composite Structure Against Projectile Penetration And Explosion

Under the background of protective structure against the prototype projectiles,systematic tests and numerical simulations on typical protective material,i.e.,concrete and steel,and high resistance protective structure,i.e.,armor steel-concrete composite structure were conducted.The main content and innovation are as follows:(1)For the penetration and explosion calculation method of prototype projectiles,by summarizing and analyzing the existing test date of geometric similarity projectile penetrating concrete and mortar targets,the major factor accounting for the scaling effect in depth of penetration is that the size of coarse aggregate does not scale with the size of the projectile accordingly.Aiming to reduce the influence of scaling effect,total five shots 100-203 mm-caliber scaled projectile penetration test on concrete target was conducted and a practical finite element method for predicting the depth of penetration of large caliber projectile into concrete was proposed.Furthermore,the depths of penetration of typical five prototype projectiles into concrete with different strength grades were predicted.The applicability of empirical and semi-empirical formulas was further evaluated.Considering the combined effect of penetration and explosion of prototype projectiles,a dynamic damage constitutive model was established to describe the dynamic resistance,damage evolution,and cracking behavior of concrete under the penetration and explosion.Based on the conducted combined penetration and explosion test of 105 mm-caliber projectile on the semi-infinite concrete target and existing prefabricated hole charge explosion test on the finite concrete plane,a finite element method was proposed for the perforation and scabbing failure of protective structures.The above work can provide reference for the design of protective structure.(2)The armor steel has the superior strength-to-weight ratio and application potential in protective structures.Firstly,the static and dynamic mechanical test,including quasi-static tensile test at room temperature,quasi-static tensile test at elevated temperature,high strain rate test and quasi-static tensile test of notched specimens,of the two new armor protection steels(NP450 and NP510 developed by Nanjing Iron and Steel Co.,Ltd.)and the projectile steel(30Cr Mn Si Mo VE developed by Zhongyuan Special Steel Co.,Ltd.)were carried out.Based on the test data,the full parameters of Johnson-Cook(J-C)constitutive model of three types of high strength steels were further calibrated.Finally,the Taylor bar impact test and corresponding numerical simulations were carried out to verify the reliability of the constitutive model parameters.The relevant test methods in this chapter can provide reference for parameter determination of similar high-strength steels,and the verified constitutive model parameters can be used for the subsequent armor structure design.(3)Aiming to comprehensively evaluate the ballistic behaviors of armor steels,firstly,total 25 shots 15 mm-caliber projectile impact armor steel plate test was conducted.The full-field strain and displacement responses of the target plate during the whole impact process were obtained using the high-speed 3D digital image correlation(DIC)technology.The accuracy of the calibrated J-C constitutive model parameters of two armor protection steels was verified by comparing the simulated residual velocity of projectile and out-of-plane displacement time-histories of target with test data.Furthermore,the failure modes of two armor protection steel plates under the identical initial impact velocity were compared.The results show that both the ductile hole enlargement and petal formation occurred on NP450 armor steel with low strength and high ductility,while the shear plugging failure occurred on NP510 armor steel with high strength and low ductility.Using the typical finite element method and smoothed particle Galerkin(SPG)method,the projectile impact test was simulated.The comparison results show that the traditional finite element method is recommended for the target failure mode concerned,and the SPG method is recommended for the quickly prediction of projectile residual velocity.Finally,considering the demand of protective structure against prototype projectiles,a staggered seam splicing armor steel shield structure was designed and produced.The penetration resistance was examined by conducting 203 mm-caliber projectile impact test.By comparing with the concrete shield,it is proved that the designed armor steel shield has the advantages of light weight and high resistance,and can be quickly replaced and repaired after being impacted.(4)As for the high resistance protection structure against combined effect of penetration and explosion,firstly,total 12 shots penetration test of 30 mm-caliber projectile was carried out to quantitatively evaluate the resistance of armor steel-UHPC composite target.Based on the ballistic efficiency factor,it is proved that the NP510-UHPC composite target exhibits better penetration resistance than the single UHPC target and the NP450-UHPC composite target.Furthermore,a combined penetration and explosion test of 105 mm-caliber projectile on NP510-UHPC composite target was carried out.The comparison results with normal strength concrete show that the NP510-UHPC composite target has excellent resistance against penetration and explosion of large-caliber projectile,and the total damage depth and crater diameter are reduced by 74.6% and 77.2%,respectively.Based on evaluation of ballistic efficiency factor,it is pointed out that the combined effect of penetration and explosion of the projectile should be considered in the design of the armor steel-UHPC composite target,rather than the single penetration.(5)For the demands of protective structure,firstly,the armor steel-concrete composite structure with high resistance was designed based on the conducted test and numerical simulation of armor steel and armor steel-UHPC composite target.Then,the resistances of scaled composite structure against once and twice projectile impact were validated by conducting four shots combined penetration and explosion test of large caliber scaled projectiles.Finally,based on the numerical simulation,the applicability of the composite structure design method was validated,which can provide a reference for the composite structure design against various prototype projectiles.The results show that the designed armor steel-concrete composite structure has the advantages of light weight,high resistance and prefabrication,and can be quickly repaired by replacing the armor steel plate in shield after being impacted.