Investigation On The Mechanism Of Mass Erosion Of The High-speed Projectile Penetrating Into Concrete

Based on the use of kinetic energy projectile in the Iraq War, The results show that it can effectively combat the underground target, With the deeper and higher strength of protective facilities, the strike against these facilities require the projectile with higher initial velocity, but it would make the mass erosion of projectile more obvious, which could seriously change the penetration ability of projectile. An intensive investigation on the mass erosion of the high-speed projectile penetrating into concrete is conducted by theoretical analysis and experiment. In order to explore and summarize the physical mechanism of mass erosion, the residual projectiles after penetration experiment are researched through the microscopic analysis, and the mass erosion model based on different mechanism is also built.(1) Based on the microscopic analysis experiments of residual projectiles after penetration experiment, the traces of the mass erosion of residual projectiles surface are investigated. The adiabatic shear band, local cutting traces and the thickness of melt zone on the residual projectile surface are obtained. The physical mechanism of mass erosion is summarized, namely, the mass erosion of projectile is a complex process on the interaction of the projectile material and concrete. The major mechanism, which the projectile material is melt by hot and the projectile material is cutted by the broken particles of concrete or the aggregate, cause the mass loss of projectile, and the most important reason that result in mass loss is that the broken particles of concrete or the aggregate cutting the projectile material, other factors, such as physical or chemical mechanism, are ignored.(2) The dimensional analysis on the mass loss is investigated based on the existing experimental data, and the parameters of the dimensionless number of projectile material strength, projectile mass and initial velocity that impact on the mass erosion is also obtained. According to the results of dimensional analysis and the existing penetration experiment data, the existing semi-empirical mass erosion model is improved, and the effect of the hardness of aggregate and the material strength of prpojectile on the mass erosion and penetration depth is also investigated.(3) Based on the varying friction coefficient considering the adiabatic shear, thermal conductivity and so on, which is built by Klepaczko and so on, the friction force and friction energy in the penetration process is calculated, and the mass erosion model based on the mechanism of projectile material melt by hot is established. The effect of the coefficient of friction on mass loss and motion parameters is also studied, and the results show the influence of the form of friction coefficient on mass erosion is small when the appropriate constant friction coefficient is selected, and the acceleration curve of erosion projectile could be impacted by the varying friction coefficient.(4) The study on the motion parameters of penetration process, in which a varying friction coefficient and a constant friction coefficient is used respectively, is conducted. According to the existing experimental data, a constant friction coefficient and a varying friction coefficient is determined separately, combined with the penetration resistance of projectile based on cavity expansion theory, the motion analysis of projectile is researched, and the results show that a varying coefficient of friction is more appropriate than a constant coefficient of friction in the investigation on the motion parameters of penetration.(5) In order to build a cutting velocity expressing cutting the head surface of projectile, the form of Archard model is modified. Considering the effect of the heat produced by the friction in the penetration process on the cutting coefficient, the mechanism of friction is connected to the mechanism of cutting with the temperature, and the mass erosion model including the two mechanisms is built. In the model, the changing of the head shape of projectile is expressed by the method of node backspacing. The calculated results through this model and the domestic and foreign typical experimental data are compared, and the results confirm that the mass erosion model is valid.