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This paper presents an experimental investigation on the perforation behaviour of 5754-H111 and 6082-T6 aluminium alloys. The mechanical response of these materials has been characterized in compression with strain rates in the range of 10 −3 s −1 <ε < 5 • 10 3 s −1 . Moreover, penetration tests have been conducted on 5754-H111 and 6082-T6 plates of 4 mm thickness using conical, hemispherical and blunt projectiles. The perforation experiments covered impact velocities in the range of 50 m/s < V 0 < 200 m/s. The initial and residual velocities of the projectile were measured and the ballistic limit velocity obtained for the two aluminium alloys for the different nose shapes. Failure mode and post-mortem deflection of the plates have been examined and the perforation mechanisms associated to each projectile/target configuration investigated. It has been shown that the energy absorption capacity of the impacted plates is the result of the collective role played by target material behaviour, projectile nose shape and impact velocity in the penetration mechanisms.

The deterministic nature of the fracture location in the dynamic tensile testing of steel sheets

This paper investigates the steady-state elastoplastic fields induced by a pressurized cylindrical cavity expanding dynamically in an anisotropic porous medium. For that task, we have developed a theoretical model which: (i) incorporates into the formalism developed by Cohen and Durban (2013b) the effect of plastic anisotropy using the constitutive framework developed by Benzerga and Besson ( 2001) and (ii) uses the artifical viscosity approach developed by Lew et al. (2001) to capture the shock waves that emerge at high cavity expansion velocities. We have shown that while the development of the shock waves is hardly affected by the material anisotropy, the directionality of the plastic properties does have an effect on the elastoplastic fields that evolve near the cavity. The importance of this effect is strongly dependent on the cavity expansion velocity, the initial porosity and the strain hardening of the material. In addition, the theoretical model has been used in conjunction with the Recht and Ipson (1963) formulas to assess the ballistic performance of porous anisotropic targets against high velocity perforation.

In this paper, we have performed a microstructurally-informed finite element analysis on the effect of porosity on the formation of multiple necks and fragments in ductile thin rings subjected to dynamic expansion. For that purpose, we have characterized by X-ray tomography the porous microstructure of 4 different additively manufactured materials (aluminium alloy AlSi 10 Mg, stainless steel 316L, titanium alloy Ti 6 Al 4 V and Inconel 718L) with initial void volume fractions ranging from ≈ 0.0007% to ≈ 2%, and pore sizes varying between ≈ 6 µm and ≈ 110 µm. Three-dimensional analysis of the tomograms has revealed that the voids generally have nearly spherical shape and quite homogeneous spatial distribution in the bulk of the four materials tested. The pore size distributions quantified from the tomograms have been characterized using a Log-normal statistical function, which has been used in conjunction with a Force Biased Algorithm that replicates the experimentally observed random spatial distribution of the voids, to generate ring expansion finite element models in ABAQUS/Explicit (2016) which include actual porous microstructures representative of the materials tested. We have modeled the materials behavior using von Mises plasticity, and we have carried out finite element calculations for both elastic perfectly-plastic materials, and materials which show strain hardening, strain rate hardening and temperature softening effects. Moreover, we have assumed that fracture occurs when a critical value of effective plastic strain is reached. The finite element calculations have been performed for expansion velocities ranging from 50 m/s to 500 m/s. A key point of this investigation is that we have established individualized correlations between the main features of the porous microstructure (i.e. initial void volume fraction, average void size and maximum void size) and the number of necks and fragments formed in the calculations. In addition, we have brought out the effect of the porous microstrucure and inertia on the distributions of neck and fragment sizes. To the authors' knowledge, this is the first paper ever considering actual porous microstructures to investigate the role of material defects in multiple localization and dynamic fragmentation of ductile metallic materials.