Novel measurements of material properties at high rates of strain using speckle metrology

Abstract

The application of speckle metrology to high strain rate materials characterisation, through the use of appropriate high-speed photography, provides an exciting opportunity for measurements to be performed on materials, and in loading configurations, which were not previously possible. In particular, a full understanding of the mechanical properties of inhomogeneous materials such as composites, geological and biological materials at high strain rates, requires more data than has previously been provided by the split Hopkinson pressure bar, which only gives a measure of average specimen response. Following from a separate paper by Siviour and Grantham describing the application of speckle metrology to the Hopkinson bar, this paper discusses recent experiments in which this application was used to make previously unobtainable measurements of specimen response. Results are presented from experiments performed on a polymer bonded explosive simulant and long polymer rods. These experiments were designed to evaluate the technique in a number of different configurations, as well as providing useful experimental data on these materials. In addition, we revisit the use of speckle metrology in the high strain rate Brazilian test.

Keywords:

• SPLIT HOPKINSON PRESSURE BAR
• SPECKLE METROLOGY
• PBX
• HIGH-SPEED PHOTOGRAPHY