Dynamic Hole Closure Experiments on Ti-6Al-4V

The shock induced collapse of holes and pores is of interest across a variety of dynamic research areas, from the compaction of porous/damaged geological materials in planetary impact to the energy absorbing behaviour of porous additively manufactured materials and the collapse of bubbles in fusion science research. Recently, hole collapse experiments have been used to infer the dynamic strength of materials through comparison to hydrocode modelling. Much of the previous work has focused on the collapse of pores with internal micro-jet formation or the uniform closure of the holes without consideration to the effects of shear localization or the potential for cracking to occur. This work looks at the planar shock loading of titanium alloy (Ti64) samples with 1 mm or 2 mm diameter (polymer filled or un-filled) holes parallel to the shock plane. The experiments were undertaken in a full shock recovery geometry with post-shock microstructural analyses. The results of show considerable cracking through grains, implying a highly localized concentration of stress around the holes, with cracks extending away both parallel and perpendicular to the shock loading. The length of these cracks increases with the shock stress and shock duration. Where the hole collapse is restrained by the infill material, cracking is suppressed but still observed.

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