Nose Shape Effects from Projectile Impact and Deep Penetration in Dry Sand

The goal of this study was to demonstrate the role of nose shape on the embedment phase of long rod projectiles penetrating densely packed sand targets. Conical nose projectiles having various apex angles were launched into sand targets at an impact velocity of approximately 200 m/s. A vertical firing range was designed and calibrated for launching projectiles with a diameter of 14.3 mm. Aluminum rod projectiles with conical nose apex angles ranging from 30 to 180 degrees were tested. Soil targets were prepared by means of dry pluviation. Velocity-time histories were resolved using a photon Doppler velocimeter (PDV). High-fidelity velocity-time histories were obtained through measurement of the frequency shift in the laser light wave reflecting from the back of the projectile. Highly reflective retroreflective tape was applied to the back of the projectiles to enhance the intensity of the reflected light. Optical probes were used to collect the reflected light. The results of the experiments revealed that both the magnitude of the peak deceleration and the depth corresponding to peak deceleration were a function of the nose shape. A decrease in the apex angle of a conical projectile led to a reduction in the peak deceleration, with the resulting peak stress occurring later in penetration for projectiles with smaller apex angles. Upon impact on the soil target surface, a near conical-shaped mass of compacted comminuted sand formed on the nose of the projectiles tested. These observations can be used to improve predictions of projectile depth of burial in phenomenological modeling of penetration and depth of burial.