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2 Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

2 2011

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Simulation of Steel Armour Penetration Using the Johnson-Cook Model

Wiśniewski A., Tomaszewski Ł.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

2011

Vol. 2, Nr 4 (6)

27-36

The numerical simulations were carried out of penetration of 12.7 mm armour piercing projectile into the ARMOX 500 steel armour with the use of the AUTODYN 2D software program applying axis symmetry. The calculations were performed by means of the SPH (Smooth Particle Hydrodynamic) method. A constitutive Johnson-Cook model was used for both the armour and the projectile. The influence of discretization density of the numerical model on the residual velocity vr of the projectile, its wear and time of calculations was studied. An eight times decrease in the distance between the SPH particles in the numerical model causes an over 130 fold increase of the projectile residual velocity and a 960 fold increase in the calculation time. The examined aspects included the influence of armour thickness g and yield stress Re of the projectile material on its residual velocity and manner of the projectile and armour damage. The residual velocity of the projectile decreases together with an increase of the armour thickness and for g = 20 mm is vr = 300 m/s. Together with a decrease of the yield stress of the projectile material its residual velocity also decreases, the wear of the projectile increases, the shape and the dimensions of cross section hole in the armour also change.

Numerical Simulations of Penetration of 9 mm Parabellum Bullet into Kevlar Layers : Erosion Selection in Autodyn Program

Wiśniewski A., Pacek D.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

2011

Vol. 2, Nr 3 (5)

11-20

A numerical model was performed of penetration of 9 mm Parabellum bullet into Kevlar layers, with the use of the AUTODYN software program. Simulations were conducted with a bullet modelled by means of the Smooth Particle Hydrodynamicsmethod (SPH) and with an armour coded by a Lagrange grid. The simulations were performed for 20 layers of Kevlar (one layer: thickness - 0.3 mm, surface density - 220 g/cm²) and for impact velocity of 350 m/s. The comparison included the mean velocity of the bullet (which takes into account the velocities of particles that separated from the part of the bullet penetrating the armour) and the velocities at gauge points established near the axis of symmetry of the bullet. The gauge point representative for velocity of the bullet was indicated. With regard to excessively large deformations of the grid, that caused interruption of the initial simulation, the criteria of erosion (cells removal) were introduced. From effective strains available in the AUTODYN software, the effective instantaneous geometric strain was selected. Influence of the erosion strain (value of strain for which cells are removed) onto the mass of removed cells and the residual velocity of the bullet were investigated. Simulations with neglect and respect to mass of removed cells in further calculations were performed. The erosion criteria for which further simulations should be conducted were indicated.