Spall fracture of beryllium under shockwave loading

Abstract

We present investigations of beryllium spall fracture with samples of dimensions Ø 65×7 mm, which were made via vacuum hot pressing. Samples were loaded at normal incidence by a detonation wave of the explosive charge of TG 5/5 composition, 7, 14 and 30 mm in thickness, which gave shockwave stresses of 21-25 GPa within the sample. Spall fractures formed as the sample unloading at an air gap. A velocity profile was measured at the free boundary using VISAR laser interferometer, a spall layer thickness was measured with two-frame impulse X-ray radiography, and the shockwave profile was measured via a manganin-based gauge in a fluoroplastic base in the course of deceleration of a spall layer and of a basic part of beryllium. Hugoniot dynamic yield strength (Y HE) and spall strength (σ P) were measure as 0.69-0.73 GPa and 0.85±0.03 GPa, respectively, at a strain rate of ε ∼10 4 s -1 in the unloading part of the incident pulse. A weak dependence between the spall layer thickness and HE layer thickness was recorded in tests. The weak dependence is not described through existing damage models and points to the need to develop more sophisticated models. © 2012 American Institute of Physics.