A Manual for Conducting Image-Based Inertial Impact (IBII) Tests

Abstract

For brittle and low wave speed materials testing, with the split-Hopkinson pressure bar is difficult at high strain rates. This has led to the increasing use of full-field measurements for high strain rate testing applications. With the advent of ultra-high speed imaging (> 1 Mfps) it is now possible to image elastic strain wave propagation in materials. This capability has in turn led to the development of the Image-Based Inertial Impact (IBII) test. The IBII test uses full-field measurements of an inertially impacted sample (edge-on impact) to extract material properties using the Virtual Fields Method (VFM). The key idea is that the full-field displacement measurements encode the strain information in space and the stress information is encoded in time through the acceleration field. This report gives a detailed description of the IBII test method. The intention is that this report can be used by researchers in the experimental mechanics community to implement the IBII test themselves while avoiding some common pitfalls. This report is divided into three section covering the main aspects of the IBII test method: 1) design of a purpose-built gas gun impact rig for IBII testing, 2) practical implementation of the experimental method and 3) VFM theory and data processing for IBII tests. A data repository is provided at the end of this report that contains all necessary information to conduct IBII tests from plans for the gas gun impact rig through to a data processing code which can be used to analyse IBII data.