Projectile penetration into sand: Relative density of sand and projectile nose shape and mass

• Published in: International journal of impact engineering 2017-05, Vol.103, p.29-37
• Main Authors: Chian, Siau Chen, Tan, Beng Chye Vincent, Sarma, Anand
• Format: Article
• Language: English
• Subjects: Ballistic impact; Ballistics; Barriers; Compacts; Design engineering; Dilation; Energy absorption; Granular materials; Impact tests; Nose shape; Noses (forebodies); Penetration; Projectile; Projectiles; Sand; Shear loading
• ISSN: 0734-743X; 1879-3509
• DOI: 10.1016/j.ijimpeng.2017.01.002

•Out of the projectile nose shapes studied (flat, hemispherical, conical and ogival), the pointed conical head projectile had the lowest ballistic limit, whereas the blunt flat head projectile required the highest ballistic energy to defeat the sand block.•The mass of projectile has a significant influence on the amount of absorbed energy. The effect is more dominant than the nose shape of the projectile.•A strong linear correlation between projectile nose shape, mass and ballistic impact energy was established, which allows quick estimates of the requirements in designing sand barriers to defeat a range of predetermined projectiles at impact energy.•The average penetration resistance of the projectiles follows a linear correlation with the square of striking velocity. A heavier mass projectile produces a steeper slope due to the fact that heavier mass projectiles have higher average velocity inside the target.•The back-calculated drag coefficients of the projectiles are within the range of conventional values. Although some projectiles have different nose shapes, the extended length of the body could have alter the flow pattern, leading to similar drag coefficients. In addition, drag coefficients do not appear to be influenced by projectile mass.•Sand has shown to possess good absorption of impact energy with unique mild reduction in absorption effectiveness over a wide range of velocities. This was proven with various shape and mass of projectiles. Compacted granular materials, like sand, have a tendency to dilate and expand under shear loading. Such tendency of dilation is beneficial to inhibit projectile penetration. Furthermore, the higher the striking velocity of a given projectile, the higher is the peak strength of the sand sample. Different nose shapes (spherical, flat, hemispherical, conical and ogival) and mass (7g, 15g and 20g) of projectiles were fired into sand samples of relative densities ranging from medium dense to very dense state (60%, 75% and 90%). Results showed that the pointed ogival head projectile had the lowest ballistic limit, whereas the blunt flat head projectile required the highest ballistic energy to defeat the sand block. Despite visible effect of nose shape, the mass of projectile has a larger influence on the amount of absorbed energy. On the other hand, initial compaction of the sand alters the depth of penetration marginally. This is attributed to the projectile impact which compacts the sand as the projectile penetrat