R. Orhan Yıldırım

Response of Alumina/4340 Steel Laminated Composites against the Impact of 7.62 mm Armor Piercing Projectiles

Laminated composite armors provide significant advantages to the defense systems when considering both the mobility and energy consumption. Among them, alumina faced laminated composite systems have been considered as strong candidates due to their relatively low cost and availability. In this study, the ballistic response of alumina/4340 steel laminated composites was investigated under the impact of 7.62 mm armor piercing (AP) projectiles. The influence of the mechanical properties of the steel backing layer and the areal density on the ballistic performance of these composites was examined. Experimental results showed that the best ballistic protection was found for the composites having the steel backing layer of 40 or 50 HRC (Hardness Rockwell C).

On the drop-weight testing of alumina/aluminum laminated composites

Laminated composites with ceramic front layers and metallic or composite backing layers have gained attractiveness as lightweight armours, as they exhibit the same ballistic performance with lower areal densities as compared to steels. Drop-weight testing (DWT) has potential for evaluating the low velocity impact behaviour of materials. This testing gives significant ideas and information about failure mechanisms and behaviour of materials under low velocity impact. In this study, DWT of alumina/aluminum laminated composites was done in order to investigate the effects of lamination type, density with respect to area and mechanical property of backing material on the low velocity ballistic performance of these composites. The experimental results showed that the laminated composite with ceramic front layer and aged-aluminum alloy as backing layer was the most effective among different investigated specimens against low velocity impact loads.

Effect of Thickness on Deformation of Plates Subjected to Transient High Pressures

Blast loading can induce a substantial amount of damage in structural elements such as, beams and plates, the shape and extent of which is quite difficult to predict. This work investigates the changes in the deformation of a square plate that undergoes a constant weight explosive detonation with changing plate thickness. As a first step, free field explosion is investigated. After the calculation of the pressures and forces acting on the plate, and the positive phase duration of the pulse, the non-dimensional impulse values are found. Plate tearing is predicted by using these non-dimensional impulse values. The same plate is modelled and solved for the numerical prediction of the midpoint deflection. Using this procedure, the effect of the plate thickness is investigated for the deformation of plates. The results of the theoretical and numerical solutions are then compared with the experimental findings.Copyright

Investigation of rain erosion on a brittle material by means of numerical simulation

In this work, the resistance and deformation characteristics of a brittle material against rain erosion are examined by using the non-linear, explicit software LS-DYNA. The water jet with varying speeds impinges at 90° on silica float glass plates with different thicknesses. In the simulations, the Arbitrary Lagrangian Eulerian method is used for modelling of the water. In order to analyse the deformations on the brittle material Johnson–Holmquist–Ceramics (JH-2) is used as the material model. Minimum plate thickness (for constant water jet speed) and maximum water speed (for constant plate thickness), which do not cause any damage to the target, are determined depending on the geometry, boundary conditions and assumed failure strain value for erosion. The results are compared with the water-hammer pressure.

Simulations on concrete penetration of shaped charges

In this paper, the effects of the use of various aluminium materials as liner material in shaped charges for the perforation of concrete slabs are examined with numerical simulations. Using AUTODYN-2D software, formation of the shaped charge jets for seven different aluminium materials are modelled first and then these jets are directed to 35 MPa compressive strength concrete slabs. Those analyses are performed for a constant liner thickness which corresponds to 8% of the shaped charge diameter. Furthermore, the effect of standoff on the penetration of concrete slabs is examined by using shaped charges with the same geometry and liner material (7075-T6). The cone angle of the shaped charge is taken as 100°.

Analytical Solution and Experimental Verification of Shaped Charge Jet Penetration

In the scope of this study a one dimensional shape charge code was developed using analytical and semi-empirical approaches. The penetration part of the code is based on the hydrodynamic theory of penetration. The code is capable of modeling and visualizing of shaped charge liner collapse, jet formation and target penetration. Factors affecting the penetration were investigated by utilizing the developed code. Since the code is based on the solution of some analytical expressions rather than the solution of finite difference equations, the solution cost comes out to be enormously less than those of 2 or 3 dimensional hydrocodes. Some number of experiments was performed by using copper liners on steel target plates. The results were compared with the developed code and a good consistency was obtained.© 2006 ASME