A Study on Reduction of Friction in Impact Compressive Test Based on The Split Hopkinson Pressure Bar Method by Using a Hollow Specimen Nobuhiko Kii 1,a , Takeshi Iwamoto 2,b , Alexis Rusinek 3,c and Tomasz Jankowiak 4,d 1 Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8527 Japan 2 Institute of Engineering , Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8527 Japan 3 National Engineering School of Metz, 1 route d’Ars Lquenexy, CS 65820 57078 Metz Cedex 3, France 4 Institute of Structural Engineering, Poznan University of Technology, Piotrowo 5, 60-965 Poznan, Poland a m124931@hiroshima-u.ac.jp, b iwamoto@mec.hiroshima-u.ac.jp, c rusinek@enim.fr, d tomasz.jankowiak@put.poznan.pl Keywords: Split Hopkinson pressure bar, Impact compression, Hollow specimen, Reduction of friction coefficient, Johnson-Cook model Abstract. The split Hopkinson pressure bar (SHPB) technique is widely-used to describe the impact compressive behavior of different materials including metals. During the impact test, the specimen deforms in a wide range of impact strain rate from 10 2 to 10 4 s -1 . It is a reason why the method is studied for many years even though the structure of the apparatus based on the SHPB is simple. Actually, the cylindrical specimens are widely used for a compressive test and it is clearly seen that stress measured by the test includes the increment of stress (an error) derived by friction effect between a specimen and pressure bars. Therefore, it is important that the measured stress should indicate similar value as the proper stress of the material by reducing friction effect during not only quasi-static but also the impact test. Various attempts to reduce a friction effect in past have been conducted. A method to reduce friction effect is in general a use of lubricants. However, it is ineffective because it can be considered that this method contributes to an attenuation of the stress wave for obtaining the stress-strain curve under impact loading. Thus, rise time of waves obtained by the experiment becomes longer compared with a case not to use lubricants. Recently, a study can be found using a ring specimen, however, the determined thickness of the specimen is quite thin and it can be considered that a buckling effect cannot be vanished. In this study, a use of hollow specimen is suggested to solve the problem related to reduce the friction effect by decreasing a contact area between a specimen and pressure bars instead of a cylindrical specimen. The compressive experiments at various strain rates are conducted by using a hollow specimen. Applied Mechanics and Materials Vol. 566 (2014) pp 548-553 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.566.548 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 80.185.240.29, National Engineering School of Metz, Metz , France-13/06/14,16:34:07)