Toward High Strain Rate Inverse Design via Experimental Exploration of High Strain Rate Dynamic Behavior of Materials and Structures
Brianna MacNider, University of California, San Diego
There is a great amount of interest in designing materials and structures for improved dynamic behavior, targeting applications such as impact mitigation and shock tailoring. Advances in computational methods have led to the inversely design of structures for targeted nonlinear properties via topology optimization and machine learning which could be implemented in tailoring structures for such dynamic applications. However, most recent work has focused either on quasi-static behavior, or on low strain rate regimes in which the exploited mechanisms of deformation remain unchanged from the quasi-static regime. Protective applications such as blast and impact mitigation, crashworthiness, and others, take place in higher strain rate regimes (on the order of 103 or greater), and engage effects such as viscoelasticity, fracture, plasticity, liquification, spallation, etc. How best to approach an inverse design problem with such considerations is an ongoing question. In pursuit of better understanding of high strain rate behavior and bridging the gap between low strain rate design tools and high strain rate applications, my residency work focused on several experimental explorations of high strain rate behavior. Experimental X-ray studies at the Advanced Photon Source enabled the first ever in-situ measurement of spallation induced void formation and growth in magnesium, providing insight into the high strain rate failure processes that will help inform damage modeling and design attempts. Furthermore, Hopkinson bar experiments were conducted with the aim of exploring the shifting deformation mechanisms in lattice structures as a function of increasing strain rate. This work focuses on strain rates at the beginning of the transition from low to high strain rate dominated behaviors, providing insight into how the structural deformation mechanisms engaged begin to shift. Both of these experimental investigations are expected to help inform inverse design tools aiming to target high strain rate behavior.