High strain-rate microstructural spall failure modes in refractory alloys
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The major objective of this investigation is to fundamentally understand and predict how intergranular (IG) and transgranular (TG) fracture modes nucleate and propagate in niobium and tungsten polycrystalline systems due to defects, such as total and partial dislocation densities and grain boundary (GB) structures and misorientations. A dislocation density crystalline plasticity (DCP) formulation based on the evolution and interaction of total and partial dislocation densities was integrated with a recently developed fracture approach to investigate the fracture nucleation and propagation of simultaneous multiple fracture events, including both IG and TG fracture events in refractory alloys subjected to high strain-rates. The validated predictions indicate that dislocation density pileups induce IG fracture, and that TG fracture occurred due to normal stress accumulations, which exceeds the fracture stress along cleavage planes.
