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We present a combined experimental and numerical study on the strain rate effect of closed-cell Al-Si-Ti foams having different relative densities fabricated using the powder metallurgy foaming technique. The high strain rate tests were conducted with split Hopkinson pressure bar technique at 800 to 2500 s−1. Two-dimensional mesoscale finite element models were created from tomographic images of the homologous foam. The rate sensitivity of the foam originates mainly from that of its parent material, increasing with increasing relative density. Stress elevation due to other effects, such as micro-inertia, shock wave, and gas pressure in individual cells, is negligible. [ABSTRACT FROM PUBLISHER]

Abstract Density-graded metallic foam projectiles are proposed for shock loading simulation, with special focus placed upon designing pressure pulses having specific shapes. Experiments are performed to explore the potential of density-graded foam projectiles in generating shock loadings of various pulse shapes. Subsequently, three-dimensional Voronoi foam models with varying gradient profiles along the length direction are constructed for finite element (FE) simulations, which are validated against the experimental data. Then, FE simulations of density-graded foam projectiles impacting a stationary rigid wall are conducted to quantify the effect of density gradient on the shape of the pressure pulse generated and explore the physical mechanisms underlying such effect. It is demonstrated that density gradient affects significantly local crushing stress and local density within the shock front when it propagates from the impact end to the other end of the foam projectile. Inspired by the FE simulation results and the classical Taylor impact model, one-dimensional theoretical model for density-graded foam projectiles is developed to predict the contact force between the projectile and the fixed rigid wall. Finally, the theoretical model is employed to determine the geometry, density gradient, and firing velocity of foam projectiles needed to generate shock loadings with prescribed pulse shapes. Graphical abstract Unlabelled Image Highlights • Density-graded metallic foam projectiles can be used to simulate shock loadings with varying pulse shapes. • The local crushing stress and local density within the shock front are key factors altering the pulse shapes. • By considering pulse shapes, the shock loading simulation technique can be expanded to broader applications. [ABSTRACT FROM AUTHOR]

• A novel composite projectile for simulating combined blast and impact loading has been proposed. • The composite-projectile-based approach is proved to be valid in simulating combined loadings from cased explosives under certain conditions. • Based on the experimental approach, a new synergetic effect of combined blast and single fragment impact loading is found. • The proposed approach provides a chance to investigate ballistic impact of deforming target experimentally. A novel composite projectile is put forward to simulate combined blast and single fragment impact loading, which is comprised of a cylindrical aluminum foam projectile embedded with a fragment simulation projectile (FSP). Comparison between cased explosive and composite projectile in terms of the generated combined loading shows that the composite projectile technique is theoretical feasible. Experimental tests for normal impact of the composite projectile on clamped plates are carried out. Results show that the proposed composite projectile can induce both blast-induced deflection and fragment-induced perforation on the clamped plate. The arrival time interval between blast and fragment has significant influence on the extent of induced damage on the plate and the residual FSP velocity. Numerical simulations with the method of finite elements are carried out to provide further insight into the interaction between the composite projectile and clamped plate, and to explain observations and measurements in experiments. The present study reveals a new synergetic effect of combined blast and single fragment impact loading on clamped plate: arrival time interval between blast and impact loading affects significantly the residual velocity of the FSP. [ABSTRACT FROM AUTHOR]