Collaborative Research: Identifying Hydrogen-Density Based Laws for Plasticity in Polycrystalline Materials

Hydrogen-induced degradation of structural materials is responsible for unexpected component failures across the aerospace, marine, energy, and infrastructure sectors. Similarly, concerns over hydrogen-induced embrittlement are a primary factor hindering the broader adoption of a hydrogen-based fuel economy. Current efforts to prevent these failures are complicated by challenges with accurately predicting hydrogen-related damage and its dependence on hydrogen concentration. This study will use a combined experimental and modeling approach to address these questions, resulting in new fundamental understanding of how hydrogen affects material behavior. This research will also benefit the national welfare in clean energy efforts by enabling the prediction of hydrogen-induced damage under conditions where hydrogen-assisted fracture is of concern. Moreover, in addition to training multiple graduate students, this project will actively engage in educational outreach with middle and high school students through dedicated events, lectures, and laboratory demonstrations. The researched study will establish how hydrogen affects plastic damage accumulation and leverage developed insights to create a hydrogen-sensitive crystal plasticity framework. First, conventional (mechanical testing) and advanced (high-energy X-ray diffraction) techniques will be employed to elucidate the effect of hydrogen concentration on the deformation behavior of pure single crystal and polycrystal Ni under monotonic and cyclic loading conditions. Second, this dataset will be leveraged to derive consistent hydrogen-sensitive laws for crystallographic slip and hardening that incorporate hydrogen effects on backstress development and dynamic recovery, enabling use for a wide range of hydrogen concentrations and loading conditions. Third, these deformation laws will then be integrated into a crystal plasticity framework, which will undergo validation using both experimental mechanical testing data and spatial distributions of microstructure-scale elastic strains via electron backscatter diffraction techniques to demonstrate model efficacy. The researched study will have broad impact as the hydrogen-informed crystal plasticity framework will be critical to supporting a hydrogen-based fuel economy. Additionally, all experimental data from this effort will be made available to the research community. Middle and high school students will get exposure and insight into critical issues for hydrogen embrittlement based on interactive Virtual Labs, case studies, and hands-on laboratory investigations that illustrate hydrogen’s effect on deformation behavior and potential component failure. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.