High Strain-Rate Testing of Brittle Materials Using Miniature Beryllium Split-Hopkinson Pressure Bars

Split-Hopkinson Pressure Bars (SHPB) or “Kolsky” bars are often employed for determining the high-rate compressive failure strength of high-strength brittle materials. However, experiments generating very high strain-ratesHigh strain-rate demand miniaturization of the setup for appropriately measuring decreasingly short loading events. Miniature aluminum and steel bars are often sufficient for this. However, for high enough strain-rates, miniaturization of these bars may require prohibitively small test specimens that can be inappropriate for inferring representative properties of materials with large grain size relative to the specimen size. The low Poisson’s ratio of beryllium relative to aluminum and steel is expected to minimize the effect of elastic wave dispersionDispersion on the measurable strain-rates in Kolsky barKolsky Bar experiments. For these reasons, we have developed a Be Kolsky barKolsky Bar apparatus, and, in this paper, we experimentally determine the dispersionDispersion characteristics of these bars and compare the results with those of similarly size setups made from aluminum and steel. The results show no appreciable dispersionDispersion in the data from the beryllium Kolsky barKolsky Bar setup, demonstrating its advantage over aluminum and steel.