Abstract
Three new testing configurations that have been developed since the last DYMAT conference in 2009 are presented. The first is high strain rate testing of Kevlar cloth and Kevlar yarn in a tensile Split Hopkinson Bar (SHB) apparatus. The Kevlar cloth/yarn is attached to the bars by specially designed adaptors that keep the impedance constant. In addition to determining the specimen’s stress and strain from the recorded waves in the bars the deformations are also measured with Digital Image Correlation (DIC). The second testing configuration is a high strain rate shear test for sheet metal. The experiment is done by using a flat notched specimen in a tensile SHB apparatus. The shear strain is measured using DIC within the notch and on the boundary. The third development is a compression apparatus for testing at intermediate strain rates ranging from 20 s −1 to 200 s −1 . The apparatus is a combination of a hydraulic actuator and a compression SHB. The stress in the specimen is determined from the stress wave in a very long transmitter bar and the strain and strain rate is determined by using DIC. The results show clean stress strain curves (no ringing).
Highlights
The Split Hopkinson Bar (SHB), introduced by Kolsky [1] in 1949, is the most commonly used technique for characterizing the deformation and failure of materials at strain rates ranging from about 400 s−1 to 5, 000 s−1
The force applied to the specimen and the average strain in the specimen can be determined from the waves in the bars that remain within the elastic limit during the experiment
Over many years the SHB technique was mostly used for testing specimens that were subjected to a uniform state of stress and deformation
Summary
The Split Hopkinson Bar (SHB), introduced by Kolsky [1] in 1949, is the most commonly used technique for characterizing the deformation and failure of materials at strain rates ranging from about 400 s−1 to 5, 000 s−1. On the other end the actuator of a typical hydraulic machine can move fast enough to deform the specimen at the required strain rate, but results from such tests are noisy with large oscillations (referred to as ringing). This happens because the whole testing machine is not in static equilibrium during the test. The new apparatus for compression testing at intermediate strain rates that is presented here is made up from a hydraulic actuator that can apply dynamic loads for the required duration and a long transmitter bar that can measure the force in the specimen without the effects of wave reflections
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
