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a b s t r a c tIn this paper a study is presented on the experimental and numerical analysis of the failure process of mild steel sheets subjected to normal impact by hemispherical projectiles. The experiments have been performed using a direct impact technique based on Hopkinson tube as a force measurement device. The tests covered a wide range of impact velocities. Both lubricated and dry conditions between specimen and projectile have been applied. Different failure modes for each case were found. For lubricated conditions a petalling was observed, whereas for dry conditions a radial neck along with a hole enlargement reduces the formation of petalling. The perforation process has been simulated by the application of 3D analysis using ABAQUS/Explicit FE code. The material behavior of the circular specimen was approximated by three different constitutive relations. The main task was to study the influence of the material definition on the response of the sheet specimen with special attention to the failure mode.

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In this paper, a numerical study of normal perforation of thin steel plates impacted by different projectile shapes is reported. The numerical simulations of this problem have been performed using a finite element code, ABAQUS Explicit with a fixed and an adaptive mesh for the plate. To define the thermoviscoplastic behaviour of the material constituting the plate, the Johnson Cook model has been used. This homogeneous behaviour has been coupled with the Johnson Cook fracture criterion to predict completely the perforation process. Three kinds of projectile shape (blunt, conical and hemi spherical) have been simulated with a large range of impact velocities from 190 to 600 m/s. The analysis considers the influ ence of adiabatic shear bands, plastic work and the gradient of temperature generated in the plate. The numerical results predict correctly the behaviour projectile plate in agreement with experimental data published by other authors.

Investigation of mechanical impact behavior of short carbon-fiber-reinforced PEEK composites, Composite Structures (2015), doi: http://dx.Abstract. This paper describes the results of an experimental and numerical investigation of the impact behavior of short carbon fiber reinforced polyether-ether-ketone (SCFR PEEK) composites. The biocompatibility of PEEK and its short fiber composites, their rapid processing by injection molding and suitability for modern imaging have supported technological advances in prosthetic implants used in orthopedic medicine. Surgical implants, including hip and cranial implants, can experience clinically significant impact loading during medical installation and useful life. While the incorporation of short fibers in a thermoplastic matrix can produce significant improvements in stiffness and strength, it can also cause a marked reduction in ductility, making study of their energy absorption capability essential. In this work, the mechanical impact behavior of PEEK composites reinforced with polyacrylonitrile (PAN) short carbon fibers 30 % in weight is compared with unfilled PEEK. The perforation tests conducted covered an impact kinetic energy range from 21 J to 131 J, equivalent to the range observed in a fall, the leading cause of hip fractures. Energy absorption capability, damage extension and failure mechanism have been quantified and reported. A numerical modeling that includes homogenization of elastic material and 1 anisotropic damage is presented and validated with experimental data. At all impact energies, SCFR PEEK composites showed a brittle failure and their absorption energy capability decreases drastically in comparison with unfilled PEEK.

In this work, a study has been made of the effect of the adhesive layer thickness on the efficiency of alumina/aluminium armours. Full-scale tests were made shooting armour piercing projectile against panels thick enough to arrest the projectile and also close to the ballistic limit. The adhesive layer, of different thickness, was of the toughened epoxy resin. The fire tests revealed the influence of thickness on the response of the lightweight protection. Numerical simulations were performed to analyse the experimental results. The anaysis showed an optimum adhesive layer thickness for the best performance of the lightweight protection considered.

a b s t r a c tIn this paper a physical based constitutive relation for defining the thermo viscoplastic behaviour of FCC metals with dependence on strain on thermal activation processes is presented. The model, based on previous considerations reported by Rusinek