A method for the in situ measurement of evolving elliptical cross-sections in initially cylindrical Taylor impact specimens

This paper presents a novel approach to the classic Taylor impact experiment using an ultra-high-speed camera and mirror arrangement to measure the elliptical cross-section of a specimen in situ as a function of time. This optical measurement technique is used to quantify the key aspects of material behaviour, such as the area strain perpendicular to the impact direction and the lengths of the semimajor and semiminor axes of the elliptical sample cross-section, which were caused by anisotropic plastic deformation, as functions of time and the axial position. The application of this technique gives access to previously unattainable data on the anisotropic plastic deformation of Taylor impact specimens and therefore has the potential to provide a more rigorous method of validation for anisotropic constitutive material models. To demonstrate the feasibility of the new method, experiments were carried out on cylindrical Taylor impact specimens machined from strongly textured high-purity zirconium plate. The surface geometry of a recovered specimen was measured using a coordinate measurement machine and compared with the optically measured surface geometry reconstructed from post-impact images. Excellent agreement between the two methods was found.