EPJ Web of Conferences
Volume 94, 2015DYMAT 2015 - 11th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading
|Number of page(s)||6|
|Published online||07 September 2015|
Two-wave photon Doppler velocimetry measurements in direct impact Hopkinson pressure bar experiments
SMF Fracture and Shock Physics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK
a Corresponding author: firstname.lastname@example.org
Published online: 7 September 2015
Direct impact Hopkinson pressure bar systems offer many potential advantages over split Hopkinson pressure bars, including access to higher strain rates, higher strains for equivalent striker velocity and system length, lower dispersion and faster achievement of force equilibrium. Currently advantages are gained at a significant cost: the fact that input bar data is unavailable removes all information about the striker impacted specimen face, preventing the determination of force equilibrium, and requiring approximations to be made on the sample deformation history. Recently photon Doppler velocimetry methods have been developed, which can replace strain gauges on Hopkinson bars. In this paper we discuss an experimental method and complementary data analysis for using Doppler velocimetry to measure surface velocities of the striker and output bars in a direct impact bar experiment, allowing similar data to be recorded as in a split bar system, with the same level of convenience. We discuss extracting velocity and force measurements, and improving the accuracy and convenience of Doppler velocimetry on Hopkinson bars. Results obtained using the technique are compared to equivalent split bar tests, showing improved stress measurements for the lowest and highest strains.
© Owned by the authors, published by EDP Sciences, 2015
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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