MULTISCALE MODELING OF HYDROGEN-AFFECTED CRACK TIP DAMAGE USING FULLY COUPLED CHEMO-MECHANICAL CRYSTAL PLASTICITY FRAMEWORK FOR AUSTENITIC STAINLESS STEEL

Hydrogen embrittlement is a long-standing issue in engineering structural applications with a multitude of competing hypotheses and theories. Despite advances in experimental and computational capabilities, common understanding of contributing phenomena has not yet been achieved. Accordingly, models are varied and limited in scope, even for a given material system. A more complete understanding of hydrogen-related damage across multiple length and time scales is still an open challenge. In the present report, lower length scale simulations and arguments are used to motivate a mesoscale crystal plasticity model that can inform crack tip field evolution and fatigue crack growth rates. The fully coupled chemo-mechanical framework describes and simulates the complex interplay between hydrogen, hydrogen traps, vacancies, dislocations, vacancy complex stabilization by hydrogen, and damage in the form of nanovoid sheets. The model is implemented at a crack tip using a finite element framework to simulate the influence of hydrogen on deformation and fatigue damage development of face-centered cubic (FCC) austenitic stainless steel 316L (SS316L), a structural material important in energy applications. Accounting for hydrogen and hydrogen-related damage across multiple length scales in this way facilitates study of hydrogen embrittlement that can be related to experimental observations and historical attributions of hydrogen effects on deformation and damage in FCC metals and alloys.