Pulse shaping techniques for testing brittle materials with a split hopkinson pressure bar |
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Authors: | D J Frew M J Forrestal W Chen |
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Institution: | (1) Sandia National Laboratories, 87185-1174 Albuquerque, NM;(2) Department of Aerospace and Mechanical Engineering, The University of Arizona, 85721-0119 Tucson, AZ |
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Abstract: | We present pulse shaping techniques to obtain compressive stress-strain data for brittle materials with the split Hopkinson
pressure bar apparatus. The conventional split Hopkinson pressure bar apparatus is modified by shaping the incident pulse
such that the samples are in dynamic stress equilibrium and have nearly constant strain rate over most of the test duration.
A thin disk of annealed or hard C11000 copper is placed on the impact surface of the incident bar in order to shape the incident
pulse. After impact by the striker bar, the copper disk deforms plastically and spreads the pulse in the incident bar. We
present an analytical model and data that show a wide variety of incident strain pulses can be produced by varying the geometry
of the copper disks and the length and striking velocity of the striker bar. Model predictions are in good agreement with
measurements. In addition, we present data for a machineable glass ceramic material, Macor, that shows pulse shaping is required
to obtain dynamic stress equilibrium and a nearly constant strain rate over most of the test duration. |
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Keywords: | Hopkinson bar pulse shaping brittle materials high strain rate |
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