Understanding the spectrum of dynamic response in structural materials in extreme environments with statistical confidence requires the development of novel high-throughput experiments and analyses. We conducted laser-driven micro-flyer impact experiments on thin niobium foils with a simple body-centered cubic (bcc) structure to investigate its dynamic and shock-induced mechanical response. These experiments, executed in a high-throughput manner, focused on strain rates ranging from 10^5 to 10^6 1/s. Utilizing photonic Doppler velocimetry (PDV), we measured the particle velocity of the target back free surface, revealing spallation events above a critical impact velocity. The analysis of the shock tests revealed an increase in the spall strength with respect to tensile strain rate and shock stress, surpassing values obtained in previous plate impact experiments.
We assess the experimental results in the context of theoretical models of dynamic failure in ductile metals subjected to rapid loading rates and high tensile pressures. The experimental results are consistent with the predictions from theoretical models. Microscopic analysis (electron microscopy, EBSD, EDS, TEM) provided additional insights into the spall failure mechanisms, distinguishing intergranular, transgranular, and mixed-type cracks. Post-mortem characterization of impact sites revealed that dynamic deformation in niobium was governed by dislocation slip, proliferation, and intersection, which ultimately led to the formation of deformation cells and grain refinement. Molecular dynamic simulations corroborated the prevalence of these mechanisms, enriching our understanding of niobium’s dynamic behavior under extreme conditions.
2025-04-09 09:00:00
