Experimentation Research And Mechanism Analysis Of Fine-grain Tungsten Penetrator

The purpose of the thesis is to develop a new fine-grain stungsten heavy alloy material which may improves the penetration performance of long-rod penetrator. The fine-grain penetrator is prone to adiabatic shear and induces self-sharpening behavior. Conventional tungsten heavy alloy is well known as insensitive to adiabatic shear and such likely to form mushroom head-like during penetration. Refinement of tungsten grain size can increase the boundary area and enhances the strength and hardness and as well as plastic deformation flow speed under high temperature, which is an effective method to promote the mechanics capability and the sensitiveness of adiabatic shear.The residual penetrators of tungsten heavy alloy and the shot holes of45#steel and603steel were performed respectively by microscopical observation. And also the simulations of penetrating into targets by tungsten long-rod penetrator were conducted by LS-DYNA. As a result, a large mushroom head-like formed in the range of3-4mm ahead of penetrator, which has caused by large plastic deformation of W grains that compressed from sphericity to slender body. It was obvious ductile failure for45#steel, the adiabatic shear band has never formed because of uniform deformation. While for the penetration of603steel, the adiabatic band was observed on the position about lmm ahead of the mushroom, and some micro-cracks were also distributed along the shear band. What important that large coronary cracks beneath the crater about1-2mm were also observed except for some adiabatic bands. Those coronary cracks may evolve from the adiabatic bands, another assumption was that caused by tensile stress which has induced by the superposition of rarefaction at some local areas of impacted interface. And that could reveal the microscopical mechanism of the formation of the crater.The adiabatic shear band generally distributes on the direction of maximum shear stress. And all of indicates that it is a mesoscale behavior which affected by internal-structure of materials. Movable cellular Automata method (MCA) was employed to fabricate the interior structure of tungsten alloy, and further investigation of the shear deformation failure behavior considering the meso-structure features such as the influence of grains size on shear mechanics capacity have been also discussed. From simulation, the vortex-morphology would change continually to sustain the global deformation field. Then the consistency of deformation was lost because of micro-damage for stress concentration between local vortexes, which finally results in failure of the material. It was also proved that the fine grain corresponding low critical stress for fracture and premature instability failure.W nanocomposite powders were synthesized by means of improved spray drying, and two steps sintering process were performed to the preparation of fine grain tungsten heavy alloy with series of different composition. The W grains varied10-20μm diameter, which was fine comparatively to conventional tungsten heavy alloy, and the hardness were also improved. The14.5mm and30mm normal projectiles penetrating into defferent armor plates were carried out in order to test the penetration performance of the fine grain tungsten alloy. The results indicats that fine grain tungsten alloy seems more sensitivity to adiabatic shear and self-sharpening behavior, and exhibits better penetration performance.