Experimental And Numerical Simulation Study On The Penetration Of Hypervelocity Tungsten Alloy Long Rod Projectile Into Granite Target

Hypervelocity kinetic energy projectile has become one of the hot issues in the military field due to the powerful destructive capacity to the ground medium,and it is significant in the military and civil fields to study the process of hypervelocity penetration.Most of the scholar focus on the medium and high velocity research due to the limitation of test equipment and technical method,but less to the study to the hypervelocity penetration.In this paper,the penetration depth,cratering mechanism and damage of granite driven by long-rod tungsten alloy projectile under at super-high speed(1.6～3.85 km/s)was studied by testing.In addition,the LS-DYNA finite element software was used to further analyze to the process of penetration.The main contents and results are as follows:1.The uniaxial compression test and ultrasonic test was carried out to obtain some granite parameters,such as density,uniaxial compressive strength,modulus of elasticity,P-wave velocity,etc.The above work provides references and bases for experimental design and numerical simulation of hypervelocity penetration.2.The experiment of the tungsten alloy long rod projectile(length-diameter ratios of 10:1)hypervelocity penetrating granite was performed on the two-stage light-gas gun to analysis the vertical penetration depth,maximum crater diameter and macroscopic damage law of granite target under different projectile velocities.The test found that the penetration depth shows "three-stage" rule with the projectile velocity and the penetration depth abrupt decrease at 2.32km/s;the granite target shows two kinds of cratering patterns due to the influence of reflected tensile wave and target boundary and the length and number of target cracks along with the velocity increased;the different tensile and compressive strength of granite led to radioactive crack and crater on target surface in the test.3.The commercial finite element software LS-DYNA and a new FEM-SPH adaptive coupling algorithm was used to simulate the damage and stress wave evolution under different penetration velocities.It is found that the faster speed of the projectile caused its kinetic energy decrease and the mass loss rates of target also decrease;the stress wave in the granite spreads with spherical and the stress wave strength decreases with the increase of penetration time.In addition,the stress wave reduces with increase in distance away from the top of the target,and the pulse width becomes shorter gradually.The initial stress wave strength under different projectile velocity increases exponentially.4.The influences of the length-diameter ratio,projectile density,attack angle,as well as the target boundary condition,the composite target of granite on the penetration process are studied based on numerical simulation method.Although the large aspect ratio of projectile can improve its penetration ability,the penetration efficiency was reduce;the penetration depth and the mass loss rates of target was increased with the increase of the projectile density,and the time of complete erosion of projectile decreases;the projectile with different incident angles has different crater shape,and the penetration depth decrease with the increase of angle of attack,the target mass loss accord with the quadratic polynomial function decline law;the damage was more sensitive to the boundary conditions,and the target had less of the cracks due to the unloading effect of the reflection boundary,particularly at the bottom of the target;the damage area,target kinetic energy,penetration depth and crater diameter decrease with the increase of concrete protective layer.