In this paper, the effects of temperature and strain rate on the plastic deformation behavior of 5052 aluminum alloy were investigated by quasi-static tensile test and split Hopkinson pressure bar (SHPB) experiments. Meanwhile, the stress-strain relations obtained through these experiments were employed for calibrating Johnson-Cook (J-C) plastic flow constitutive parameters of 5052 aluminum alloy. The results show that the strain rate sensitivity of 5052 aluminum alloy is insignificant in the range of 0.001s-1~3000s-1, while temperature has a great effect on the material plastic behavior. The experimental data are basically consistent with the predicted outcome of J-C constitutive model.
Aim at the problem of Ansys/LS-DYNA software simulating in the shaped charge modeling, this paper studies the influence of calculating gridding size on the multimode penetrator forming. It can be found that when the gridding size is 0.028 times the charge caliber or less, the formation of penetrator can be good with the trail result. It obtained the change curve of the model nodes and the calculating time of certain computer with the size of gridding. When the gridding size is from 0.022 to 0.028 times the charge caliber, the model nodes diminish 30.8%, and the calculating time decreases 42.9%. It obtains the effects of calculating gridding size on the multimode penetrator formation parameters, such as velocity and length-diameter ratio. The simulation results were validated through X-ray imaging experimentation. Both results are in good agreement.
Algorithms for generating and distributing random 3D sphere coarse aggregates were proposed. The 3D finite element mesoscale concrete model, which consists of mortar matrix and coarse aggregates, was established based on the theory of background element and material identification. The interfacial transition zone was simplified as a kind of contact between elements. Based on this model, continuous finite element code was used to simulate the process of rigid projectiles perforating concrete targets and the effect of 3 different coarse aggregate types on residual velocities was analyzed. This work indicates that the strength and density of coarse aggregates affects the residual velocity under lower and higher impact velocity respectively.
This work compares the pure copper (T2 copper)’s stress-strain relationship at different strain rates in the uni-axial tension test and Split Hopkinson Pressure Bar (SHPB) test. Small samples were utilized in the high strain rate SHPB test in which the accuracy was modified by numerical simulation. The experimental results showed that the T2 copper’s yield strength at high strain rates largely outweighed the quasi static yield strength. The flow stress in the stress-strain curves at different strain rates appeared to be divergent and increased with the increase in strain rates, showing great strain strengthening and strain rate hardening effects. Metallographic observation showed that the microstructure of T2 copper changed from equiaxed grains to twins and the interaction between the dislocation slip zone grain boundary and twins promoted the super plasticity distortion in T2 copper.
Using the LS-DYNA software, this paper studied the penetration phenomenon that the long rod armour-piercing projectile with the material of Wf/Zr metallic glass composites and tungsten-alloy penetrating into target. It found that the 93W alloy projectile has a clear mushroom head, and the Wf/Zr metallic glass composite projectile has an acute head and appears “self-sharping” effect obviously. It studied the variation law of the penetration results parameters of the two materials at different penetration initial velocity, and found that the “self-sharping” effect of the Wf/Zr metallic glass composite projectile change to more obvious with the increasing of penetration velocity. It also obtained the change law of the projectile head shape with the penetration velocity.
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