Increasing data from high rate characterization experiments using optical reconstruction

Uniaxial characterization experiments in tension and compression are widely used to evaluate the mechanical response of materials to applied deformation over a wide range of strain rates. By taking photographs of the specimen as it deforms, it is possible to more fully characterize materials by reconstructing the specimen shape during the deformation process. This allows us to better evaluate the stress and strain in the specimen during deformation, and also provides a more rigorous validation of material models. For many materials, specimens with initially circular cross sections will evolve to a different shape; in particular, hcp metals become elliptical. We have developed a technique whereby images of a specimen during deformation (for example, from a high speed camera) from three different angles are used to reconstruct elliptical cross sections during an experiment. The technique has been applied to tensile Hopkinson bar experiments and Taylor Impact experiments on Zirconium. This paper presents an overview of the technique and the data that it can provide. © 2012 American Institute of Physics