Miniature Beryllium Split-Hopkinson Pressure Bars for Extending the Range of Achievable Strain-Rates (original) (raw)
Metals
Conventional Split Hopkinson Pressure Bars (SHPB) or “Kolsky” bars are often used for determining the high-rate compressive yield and failure strength of materials. However, for experiments generating very high strain-rates (>103/s) miniaturization of the setup is often required for minimizing the effects of elastic wave dispersion in order to enable the inference of decreasingly short loading events from the data. Miniature aluminum and steel bars are often sufficient for meeting these requirements. However, for high enough strain-rates, miniaturization of steel or aluminum Kolsky bars may require prohibitively small diameter bars and test specimens that could become inappropriate for inferring representative properties of materials with large grain size relative to the test specimen size. The use of a beryllium Kolsky bar setup is expected to enable high rates to be accessible with larger diameter bars/specimen combinations due to the inherent physical properties of beryllium, ...
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Design of Inserts for Split-Hopkinson Pressure Bar Testing of Low Strain-to-Failure Materials
Experimental Mechanics, 2009
In the present study a new insert design is presented and validated to enable reliable dynamic mechanical characterization of low strain-to-failure materials using the Split-Hopkinson Pressure Bar (SHPB) apparatus. Finite element-based simulations are conducted to better understand the effects of stress concentrations on the dynamic behavior of LM-1, a Zr-based bulk metallic glass (BMG), using the conventional SHPB setup with cylindrical inserts, and two modified setups—one utilizing conical inserts and the other utilizing a “dogbone” shaped specimen. Based on the results of these computational experiments the ends of the dogbone specimen are replaced with high-strength maraging steel inserts. This new insert-specimen configuration is expected to prevent specimen failure outside the specimen gage section. Simulations are then performed to validate the new insert design. Moreover, high strain-rate uniaxial compression tests are conducted on LM-1 using the modified SHPB with the new inserts. An ultra-high-speed camera is employed to investigate the changes in failure behavior of the specimens. Additional experiments are conducted with strain gages directly attached to the gage section of the specimens to determine accurately their dynamic stress–strain behavior.
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