Penetration of limestone targets by ogive-nosed VAR 4340 steel projectiles at oblique angles: experiments and simulations

Trajectory instability and convergence of the curvilinear motion of a hard projectile in deep penetration

“…the trajectories of titanium alloy projectiles penetrating into soil targets at nearly normal impact. 9 These experimental results further confirmed the L-C-L movement transition in a curvilinear trajectory. …”

“…Studies showed that the free-surface effect may influence the target resistance only under certain circumstances. For brittle target (concrete or rock), free-surface effect needs to be considered for long-rod penetration, especially when the impact oblique angle is large and penetration depth is shallow [9,12,22]. However, free-surface effect is minor for ductile and soft targets (e.g.…”

“…A projectile may hit a target with oblique, pitch and/or yaw angles, as reported in experimental and numerical studies for their effects on penetration process [7][8][9][10][11][12], which introduced non-axisymmetrical resistance on the surface of the projectile and led to the curved (or curvilinear) projectile trajectory. Early research on projectile trajectory in soil target showed that the projectile trajectory with initial oblique angle may become curvilinear and may even move toward the target surface [13].…”

Hard projectile penetration and trajectory stability

“…Bernard and Creighton(1979), Bless et al (1999), Warren et al (2004), Li and Chen(2003),]. Freesurface effects are important under certain conditions, e.g., brittle target medium (concrete or rock), long-rod projectile penetration [Bless et al (1999)], large impact oblique angles [Warren et al (2004)], and shallow penetration depth [Liu et al (2009)]; however, for the target medium used in this investigation (soil), free-surface effects are less significant since soils are more ductile than brittle in behaviour [Bernard and Creighton (1979)]. Because this study will focus on deep penetration problems, it is legitimate to ignore the free surface effects.…”

Engineering models of high speed penetration into geological shields

“…For non-rock soils (sand, clay, loam) cavity expansion approximation approach for plastic medium and assumption about steplike dependence of compressibility were used, while for rock and concrete shields empirical relationship between local normal stress at the surface of the impactor and instantaneous velocity was employed. Warren et al [65]; Longcope et al [66] took into account the influence of the free surface. To this end, they used spherical cavity expansion models and assumed that radial stress vanishes on some sphere that was viewed as the "free surface".…”