Abstract
To investigate the cratering effects of hypervelocity rod projectile impacting on rocks, a two-stage light gas gun was used to carry out 10 groups of small-scale experiments, whose velocity ranges from 1.5 km/s to 4.1 km/s. After each experiment, the morphology and size of the hypervelocity impacting crater were accurately obtained by using a device for image scanning. According to the morphology of the final crater, the impact crater can be divided into crushing area, spallation area, and radial crack area. Based on the experimental results of steel projectile vertical impacting on granite targets, the relationship between the depth and the diameter of the crater is analyzed, i.e., h/D≈0.1∼0.2; it shows that the depth of the crater is much smaller than the diameter of the crater, and the crater seems to be a shallow dish. The relation between the kinetic energy of the projectile and the size of the crater was discussed. With the increase of the projectile kinetic energy, it is uncertain whether the depth of the crater increases, but the volume of the crater will increase. Lastly, dimensionless analysis of the impact crater was carried out. Specifically, the limitations of point source solutions to hypervelocity rod projectile impact cratering have been proved, and there is no essential difference to calculate the final crater by using the energy scale or the momentum scale.
Highlights
To investigate the cratering effects of hypervelocity rod projectile impacting on rocks, a two-stage light gas gun was used to carry out 10 groups of small-scale experiments, whose velocity ranges from 1.5 km/s to 4.1 km/s
Less success had been achieved in predicting the final crater size. e author found that the excavation flow velocity was a small fraction of the particle velocity, which was sensitive to the constitutive equation of materials
It was difficult to calculate cratering by simplistic constitutive equations. erefore, experimental investigation based on the physical model and dimensional analysis is necessary to study the problem of hypervelocity impact cratering
Summary
A two-stage light gas gun (Figure 1) was used, which can accelerate a projectile whose weight in grams to 3 to 5 km/s. The residual projectile and the target are recovered. E projectile penetrates the target after the sabot is decorticated by the shelling device. E target material of all experiments is granite. E parameters of granite measured before the experiment are density, elastic P-wave velocity, uniaxial compressive strength, ultimate shear strength, shear modulus, and Poisson’s ratio. E target is made of granite with a density (ρt) of 2670 kg/m3, a longitudinal wave velocity (ct) of 4900 m/s, a uniaxial compressive strength (fc) of 150 MPa, a ultimate shear strength (τs) of 1.0 GPa, a shear modulus (G) of 27.0 GPa, a Poisson’s ratio (]) of 0.2, and Hugoniot elastic limit (H) of 2.36∼2.63 GPa. e cross section of the target is a square with a side length of 600 mm and a total thickness of 800 mm. No residual projectile was found; erosion damage of projectiles occurred. ere were no tensile cracks on the edge of the rock target, which indicated that the target was large enough to be considered as a semi-infinite target without being affected by the boundary reflection wave
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