Advancements in Experimental Impact Dynamics

Abstract

This habilitation thesis addresses advancements in experimental impact dynamics. It identifies several challenges in analyzing dynamic and impact-related phenomena, which have to be overcome to enhance material characterization at intermediate and high strain rates. Specifically, the focus is on complex deformation modes such as penetration and non-linear collapse. The thesis introduces key research topics to address these challenges, including the limited controllability of experiments, issues with signal quality, and the inherent limitations of the split Hopkinson bar method. Additionally, it discusses obstacles in analyzing internal material processes that are difficult to observe in situ. To address these challenges, modifications to the conventional split Hopkinson bar apparatus and the development of new direct impact and penetration measurement techniques are proposed. These innovations aim to minimize the limitations of standard setups. Wave separation techniques are enhanced to enable more accurate and reliable de-convolution of longitudinal strain waves. A specialized device, utilizing linear motors, is designed and commissioned to facilitate highly controllable experiments at intermediate strain rates. Furthermore, highspeed X-ray imaging is used to observe internal material processes, e.g., during dynamic penetration and bending. To support this, two specialized facilities are established: an X-ray facility for intermediate strain rates and a flash X-ray facility for high strain rates. As a result, this thesis presents novel experimental systems and methodologies, demonstrating their capabilities in several advanced applications.